The Epic C4 Corvette ZR-1 LT5 Engine of the 90's

With the release of information regarding the 2023 C8 Corvette Z06 and its LT6 DOHC flat plane crank engine, I figured it would be a good time to take a closer look at the original Corvette DOHC LT5 engine that was installed in the C4 corvette ZR-1 from 1990-1995.
Watch as a I give a brief description of the development of this engine by Lotus in conjunction with GM, with final casting and assembly by Mercruiser in Stillwater, Oklahoma.
I also go into further detail of the major components of this engine, and remove the upper plenum, fuels rails, and injector housing to illustrate how unique and forward thinking this design was for an engine developed in the mid 80's and how the new LT6 compares to the original LT5 DOHC engine Chevrolet.
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Thanks for watching👍

[@vettematt]

I had a 1991 ZR-1. The LT-5 loves to breathe. With just intake porting, exhaust and a tune, these engines will make 500 crank hp. Mine surprised alot of modern musclecars.

[@VetteSource]

It is amusing to have somebody roll up on an "old" C4 and see the utter look of surprise on their face when you embarrass them in front of their friends😁.

[@howabouthetruth2157]

The legendary LT5 engine was designed and extensively tested & punished by Lotus. GM owned Lotus at the time. During research & development, Lotus ran these engines on the dyno's from peak torque to red line and back to peak torque, to go back to redline, repeated over and over and over again FOR 200 HOURS NON-STOP, AND THE LT5 LIVED & STILL RAN JUST FINE. And yes, the C4 ZR1 with this LT5 engine STILL holds the world records for 24 hr high speed endurance ( 175.7 mph average due to pit stops that had to be included ) and 5,000 mile high speed endurance ( 173+ mph average ). That's like TEN Daytona 500 races back to back to back non-stop, without any caution periods. The only stops were quick stops for fuel, tire changes and driver changes. Mercruiser ( Mercury Marine ) was chosen to mass produce the LT5 due to their extensive knowledge, experience, and success with complicated aluminum casting techniques and the fact that they were also capable of keeping the incredibly close tolerances that the LT5 was designed with. Mercury actually built an entirely new facility for the sole purpose of mass producing the LT5 engine for Chevy. Because of all of the above, I am convinced that the Chevy/Lotus/Mercury LT5 is the most durable V8 ever produced in history for running long and hard. I believe this is true due to the fact that NO other auto maker has broken those records that the LT5 equipped C4 ZR1 still holds to this very day.

[@VetteSource]

Excellent write-up with some great information. I agree that this engine is probably one of the best "alternative" specialty engines from that era and the one that re-started the horsepower wars. Thanks for sharing👍.

[@howabouthetruth2157]

Thank you for the kind words. Actually, the LT5 still stands up to the modern high performance normally aspirated engines, and will outperform most of them in power delivery. Sure, there are a few that can run quicker and faster, but when it comes to running flat-out for an extended period........no one can deny that the LT5 is STILL the King of the Hill.......because no one else has broken the 2 high speed endurance records that the LT5 still owns. No one else is even willing to try it, ( or they have tried in secret, and failed, because had they been successful, the whole world would know about it ) and that includes the engineers at Chevorlet. They stated that it's far more difficult than most people realize, and when you run an engine that hard for that long, things start to deteriorate. @@VetteSource

[@julianneale6128]

This is very interesting reading! Did the C4 ZR1 ever do the 24 Hours of Le Mans? I only ask, because it sounds like the perfect candidate for a class win...

[@blackice7408]

Lexus 5 litre v8 in the ISF, lc500?

[@howabouthetruth2157]

@@blackice7408 Has anyone used the Lexus 5 liter V8 ( or any other engine for that matter ) to break both of the 24 hr and 5,000 mile ( approximately 28 hrs ) high speed endurance records that are still held to this day by a FACTORY STOCK 1990 C4 ZR1 Corvette with it's bespoke LT5 engine developed entirely by Lotus? The answer is NO. And until someone does, there's no way to prove if any other engine can handle such high speed/high rpm punishment like the Lotus/Chevy LT5 has. Ford, Porsche, Audi, and even Mercedes have all tried to break these records, and all of them FAILED miserably. Hardly anyone has even dared to attempt breaking these records ( at least not publicly........if they've tried, they did it in secret, so no one would know they failed, and if they were successful, they would let the whole world know ) because running over 7,500 rpm's at 190 mph non-stop for 24 hrs and/or 5,000 miles ( 28 hrs ) utterly destroys engines. The ONLY modifications that were done to the LT5 engine in the 1990 C4 ZR1 Corvette used to shatter both of those records, was headers & open exhaust. NOTHING ELSE was changed on that engine for breaking those records. They even used the factory suspension with the killer adjustable Bilstein shocks. Per SCCA rules, they had to use race-approved wheels & tires, and install a full roll cage inside the car of course. It's one thing to have an engine as an every day driver that can easily surpass 500,000 miles.......and Toyota certainly has a few engines that do this ( the legendary 2.7 liter 3RZ engine in my 2000 Tacoma 4x4 is one of those engines ) .........but running ANY engine at such crazy high rpm's & speeds is a whole different story. When asked if they would like to try to break their own records, even the Chevy engineers decline, because they know just how difficult it is to do. For at least 60 years, Lotus has been engineering & developing race winning engines that at one time or another, have won every road course event. That's a hell of an accomplishment. Lotus has also CO-developed race-winning engines for other auto makers over the years. The legendary all-aluminum double overhead cam LT5 engine was installed ONLY in the C4 ZR1 Corvette. When Chevy replaced the C4 with the C5 Corvette, they stopped using the uber-expensive Lotus LT5 engine and replaced it with the LS1. Hell, to this very day, the C4 ZR1 with it's LT5 engine can still out-run nearly all new normally aspirated V8's found in modern super cars........and definitely OUT-LAST them if ran wide-open for long periods of time.

[@spenceair1972]

It’s was designed by lotus but built by Mercury marine I think.

[@VetteSource]

Yep, exactly

[@IncomeWithEnergy]

Great video. Just bought my '91 1-owner ZR-1 a month ago and am truly enjoying its provenance, uniqueness and collectibility... it's been a hit at the local shows.

[@VetteSource]

Thanks, glad you enjoyed it. They do tend to create a stir once the hood is raised. The younger crowd isn't very familiar with them.

[@gordocarbo]

@@VetteSource 20 yrs ago Id have 50 yr old guys take a peek under the hood look at the fender and say "oh its those slow tpi pos". Ok buddy.

[@trip5003]

great job explaining the LT5 . I own a 1995 . Removed the Plenum a few times now . Easy by the third time lol . Replaced Starter , 16 new injectors , new FPR now called an Improved Fuel Pressure Regulator or IFPR , new Plugs , new fuel pumps , there are 2 fuel pumps on this car , new fuel filter , new Ignition coils , 5-8 coil had failed so changed all of them .

[@VetteSource]

Thanks Trip, glad you enjoyed it. Some of the normal maintenance for an LT5 engine seems extreme compared to other engines, but oh boy how fun they are to drive👍. I've always loved the last year 95's with the 405HP engine. Great performers with the updated interior design. Do you happen to have one of the Competition Yellow Z's?

[@trip5003]

@@VetteSource mine is Polo Green with black dash and beige interior . The Ronald McDonald ZR-1 is a Competition Yellow with a red interior lol . But it was the McDonald car so it had to have those colors . No idea where that car is now . I also have the Marc Haibeck Chip in my car so it adds another 10 HP so mine it is 415 hp .

[@VetteSource]

Yep, I saw the Ronald McDonald Z and the one off Admiral Blue with Red interior Z. I believe they were both 94 models. The Polo Green is a really nice color as well.

[@gordocarbo]

@@trip5003 Why guys drool over that Im clueless. Oh...rare. Fn redicluous looking I Think. Remember the dealer by my house had a white top red gut GS for a yr couldnt give it away all the staff called it a clown car. Now the vette guys drool over it cause rare, lol

[@emilianocruz11]

One of the Best Corvette engines of all the Time

[@VetteSource]

I do like this one quite a but, very exotic and what a sound when it's running through the higher RPM ranges.

[@24theMoney]

Lotus really knows how to design an engine.

[@VetteSource]

Yea, it is one unique piece of machinery👍.

[@shorts116]

Just bought an Ultima Sport that has an LT5 in it,, think it's a 96 motor and is brand new, only done a few miles ie under 25 miles. Car has a long history and was even lost for 7 years. Watching vids to find out about the motor as not many in the UK! Thanks very interesting video.

[@VetteSource]

Thanks, glad you enjoyed it👍. That seems like a pretty interesting car you've discovered with what is probably an interesting history.

[@gordocarbo]

90-95 only. COuld have been an over the counter piece

[@cheezyrider1111]

My mans got 2 lt5’s? Jeez bro. Last one I saw was selling for like 15k. Love the lt5 but it makes my lt1 look very simple lol

[@VetteSource]

Simple isn't always that bad, my friend. I'll take the LT1 or LT4 any day when it comes to changing the oil or any of the engine driven accessories. Of course driving the LT5 makes up for it😁.

[@gordocarbo]

Had 2 when I owned mine. Kinda had to just in case. Had almost 0 miles it only sold for a couple grand on ebay. Days of getting 15k are long gone unless maybe its stil in a crate

[@phyllisdorsey1880]

There is a Pcv system on my 1991 ZR - 1 . Actually, there are 2 pcv valves

[@VetteSource]

That is correct, I misspoke. Forgot about the two valves installed underneath the plenum. I may be misremembering since i haven't torn one down in many years, but I seem to recall something about the oil ventilation system being rather inadequate with the DOHC which necessitated the cylinder case box setup to recurculate oil fumes back into the plenum. Thanks for keeping me straight👍.

[@dukeman7595]

I thoroughly enjoyed your tutorial of this engine, you are extremely attentive to accuracy and detail. Thank you.

[@VetteSource]

Thanks Dalton, glad you enjoyed it. I appreciate the positive feedback👍

[@DJones476]

@Dalton: Even by today's standards, the performance still stands up. You won't have to worry about being overtaken by an EV driven by some dipshit with a man bun! 😜

[@jeffflanagan2814]

Great video, thank you!

[@VetteSource]

Thanks, glad you enjoyed it👍.

[@supremevettes1443]

Awesome channel love all the c4 corvette content 💯

[@VetteSource]

Thanks for the feedback, glad you're enjoying it👍.

[@WarriorsPhoto]

Good video and thank you for sharing so much about the LT5. I will always remember the day I saw a V8 with DOHC under the hood of Corvette. I have respected GM ever since then. (:

[@VetteSource]

Yep, I remember the excitement when I first heard I was going to be produced. For a teenager of the 80's it was one of the most incredible things to see.

[@WarriorsPhoto]

@@VetteSource DOHC isn’t new but it was a first for the Corvette. I hope this new DOHC, flat plane crank, V8 sticks around as well. (:

[@WydGlydJim]

One thing you might find interesting, is that on your second engine, the little girl that installed the secondary vacuum actuators, bless her heart had no real mechanical ability of understanding, and she installed them 180 degrees out. This caused the arm from the actuator to have an angled configuration over to the linkage. It was designed to be installed so the arm was parallel to the linkage. This never caused an issue, and was not caught on many many LT-5s. The diaphragms never failed although I would never change one to the correct orientation, as it has been “ran in” in the wrong configuration. 😋

[@VetteSource]

Now that's an interesting bit of trivia. Where can I find out more about it?

[@gordocarbo]

@@VetteSource FSM, Have it all on a CD.

[@jasonbear1336]

I had a 1986 and 1988 Corvette with L98 engine. I loved the torque on those cars, but would have love a ZR-1!

[@VetteSource]

For sure, the TPI provides a unique stop light to stop light experience, but the LT5 in the ZR-1 is a completely different animal👍

[@gordocarbo]

Had both for dailies....long term, cost/ease of ownership keep driving the TPI cars.

[@bonosimic532]

magnificent ! the C4 Zr1 is a very historic and significant super sportscar, restore and bring it back to full glory asap pls!

[@VetteSource]

For sure, luckily it looks a little rougher than it actually is. It's suffered more from being disassembled for several years. I'm hoping to start getting it back together shortly.

[@lonerider5982]

Love the concept. Would like to put in a classic C3, sort of a "resto mod"

[@VetteSource]

Yep, seen quite a few of them over the years. They always draw a crowd due to the unique nature of the LT5

[@WarriorsPhoto]

@@VetteSource The LT5 or the resto mod?

[@VetteSource]

Pretty much the presence of an LT5 in a restomod since it's such an unusual engine.

[@WarriorsPhoto]

@@VetteSource Yeah I know what you mean. I’ve seen em twice only.

[@emilianocruz11]

Dear Brian i hope one video of how to dissamble a lt5 dohc 32 valvs from a c4 zr1 please

[@VetteSource]

I'll see what I can come up with👍.

[@gordocarbo]

That will probably never happen. Complex engine and some original gaskets are about impossible to get

[@davedavis775]

The record was broken in the 2000's by a Volkswagon that was pretty much a race car . Not a street car with a production engine. They did change the 3.45 gears in the ZR1 to a 3.07 unit to help keep the engines revs down. They were running at 75 % throttle . The drivers got in and put the pedal to the floor . Still it was one hecht of a record . They also ran a L98 Corvette producing around 350 horsepower along with the ZR1 . Both cars set records. There is a video about the record run and it also can be found here on KZbin. The LT5 responds well to modifications like long tube headers and a free flowing exhaust system. The 90-92 system steals some power . They fixed this on the later cars . They also used the better mufflers on the 96 LT1 and LT4 Corvettes. You can bring the 375 h.p. 90-92 LT5 up over 400 h.p. with long tube headers and better exhaust system than the factory one. If you do full engine porting of the plenum , injector housings , and cylinder heads you can be over 500 h.p. . Porting is done per the engines displacement. The next upgrade would be to go with larger pistons and cylinder liners . A popular upgrade is the 368 displacement . Next is to stroke the LT5 but this gets expensive . The big motor use to be a 415 making over 600 h.p.. Now some are well over that like 441 cubic inches. Lingenfelter with Lotus' Graham Behan was adding twin turbos for whatever power you wanted 700+ or even beyond 800 , 900, even over 1000 . Check out the ZR1 specialist , Marc Haibeck has been doing these cars for many years now. Another LT5 builder is Corey Henderson . Also check out the ZR1 net registry website. Marc did my 91 . It's a stock 350 cubic inch LT5 making 528 h.p. at the crank. This included full engine porting for a 350 , larger throttle body, bigger injectors, long tube headers, Corsa 2.5 exhaust, fidanza lightweight flywheel , Marc's custom chip for the combo, short throw shifter, and one of his secondary deletes . It runs on all 16 injectors all the time. The fuel economy isn't hurt much at all by this mod . Currently it still has the stock 3.45 gears but I have a 4.10 Dana 44 center section to go in. You can run any gear you like 3.70 , 3.90, 4.10 , or even 4.30 . The 4.10's make the tall 6th gear more usable on the highway . With stock 3.45 gears you would only use 3 gears at the drag strip. 4.10's you would be shifting into 4th just about the time you reach the trap. The 4.10's give you more torque in all gears . You need good sticky tires like a drag radial though.

[@VetteSource]

Dave, thanks for the thorough writeup. Lots of good information you shared there. Just out of curiosity, is anyone still making headers for the LT5? I know the aftermarket likes to move on from what they believe is old tech, but it would be cool to still be able to source some aftermarket exhaust goodies for them.

[@Airwolf1971]

@@VetteSource Last I checked Stainless Works was still making a complete exhaust system for C4 Zr1s.

[@VetteSource]

Excellent!. I'll have to look into their systems to see what's available when I begin the reassembly on this one. Thanks for the lead👍

[@IncomeWithEnergy]

@@VetteSource OBX has headers and Maximizer maybe for less than Stainless Works just not to sure on fitment and quality.

[@VetteSource]

Cool, I'll check them out and see what they have to offer.

[@Z06-viper]

Thank you for the info!!!!

[@VetteSource]

Any time, my friend!

[@emilianocruz11]

One of the Best Corvette engines ever made beacuse its still my favorite Corvette engines ever made AND remember that.years lingefelter Made a monsters zr1 engines in 1993 to 1995 and made a unique zr1 in 1995 called the lingefelter zr1 twin turbo Lt5 with 800hp

[@VetteSource]

Yep, I remember those well. Lingenfelter and Calloway produced some really awesome Corvettes during the late 80's and 90's

[@DelEast740]

This engine really reminds me of a V8 version of the GM Quad 4 H.O. I had a 90 grand am le with a quad 4 h.o. thing screamed for a n/a 4 banger.

[@VetteSource]

Yea, the Qauad 4 seem liked it was the half LT5 engine. Definitely a potent little 4 banger, but not without its share of issues.

[@holeshot1721]

A guy in my town had one and he said he went to 5 shops to get a clutch done and nobody wanted to touch it! So of course we took the job on seeing that we could barely keep the lights on. To be frank we were scared going in it sat for a 2 weeks before we even attempted. Bro we banged that clutch job out in prbly 3.5 hours with 2 guys. Def a before lunch or after lunch job. Wasnt that bad after we finished. We looked at each other like did that just happen. Yeah what a cool car that nobody knows about.

[@VetteSource]

Awesome story, man. Thanks for sharing👍.

[@bobbycarbajal4460]

Loved this video!!! Your a library of knowledge on this engine! Thanks!!!!

[@VetteSource]

Thanks Bobby, appreciate the positive feedback👍.

[@kenqv3481]

You had a Lot of the details wrong.. it does have PCV and the secondary valving is actually INSIDE the heads- but still a cool video

[@VetteSource]

Thanks, glad you enjoyed it👍

[@Mr.Vazquez]

You have c4s for days love it!! Finally got a home and two car garage where my 91 currently seats awaiting fine touches engine and trans out re wire etc. Do you sell c4 parts?

[@VetteSource]

I do sell them as a matter of fact. My contact information is ony "About Me" page, and through my social media links.

[@Tate_Cunningham]

Wasn’t expecting that much information. Wish I could like the vid twice

[@VetteSource]

Thanks Tate, glad to hear you enjoyed it👍.

[@aaronlevine9623]

@VetteSource, there most certainly is a PCV system on the LT5. In fact there are 2 PCV valves. You're looking right at them at 6:40 in this vid. Not in the typical valve cover location, but they are there.

[@VetteSource]

Hey Aaron, that is correct. I addressed it in one of the earlier comments you may have not seen. Thanks for clarifying for everyone👍

[@neal6473]

I think Tim Allen, the actor, put an LT5 on his 1996 Chevrolet Impala ss car.

[@VetteSource]

He sure did. I was just telling my kids about that car the other day. Wonder if he still has it?

[@neal6473]

@@VetteSource Yea, Tim Allen still has the car, and it was on one of the Jay Leno classic cars show channel on KZbin.

[@VetteSource]

That's 😎. I figured he would keep it long-term👍.

[@howabouthetruth2157]

This was very interesting. Thank you!!!

[@VetteSource]

Glad you enjoyed it!

[@beaches2mountains230]

MAIN REASON THIS OG DOHC CORVETTE DIDNT SELL GOOD WAS BECAUSE OF THE 100K PRICE TAG AS WELL AS THE FACT THAT DESPITE THE UPGRADED SUSPENSION AND WIDER STANCE, IT DIDNT LOOK ANY DIFFERENT THAN A REGULAR OL CORVETTE. IM SURE WE COULD EASILY TELL THE DIFFERENCE BUT IT WAS EXTREMELY SUBTLE TO NOTICE THE DIFFERENCE IN WIDTH.

[@VetteSource]

Yep, there was definitely some.of that price gouging going in back then just like there is today. Personally, I prefer the 90 Z's over the 91-95's due to there being more obvious differences in the body styles.

[@gordocarbo]

True that was what made them cool they were unsuspecting to most guys Mine was 58k new.

[@robertmcwhinney4596]

Mopar's and other's was called 3 duce's set up or 6 pack! Your right they looked awesome!😉👍

[@VetteSource]

That's it👍. Love the look of the triple dueces.

[@taproom113]

Had a 1970 T/A Challenger, Plum Crazy on Black with the 340 "SIX PAK". Awesome car ... wish I'd Never sold it! Still have my Black on Red 1991 ZR-1 ... it's Not for sale ;-) ^v^

[@geneyus6411]

Awesome video, seeing this Unique Unicorn 🦄

[@VetteSource]

Yep, very cool engine

[@geneyus6411]

@@VetteSource I hope you keep the best one for yourself!👍

[@VetteSource]

For sure, I have one hiding around here that I haven't highlighted yet.

[@darrylrichardson1997]

These engines are expensive and I was trying to figure out why but kinda make sense theses seem underrated engine

[@VetteSource]

Hey Me, I'm assuming you're too young to remember when the C4 ZR-1's came out. At the time, they were one of the most badass cutting edge pieces of technology that was available and were in high demand, just like the current C8 Z06. They were referred to as the "Corvette From Hell" on one magazine cover. Very few cars could hold a candle to them, and even today, a ZR-1 will leave a look of utter astonishment on the face of many racers as they get walked on by one of these. The problem lies in the inevitable passage of time. As the generations mature, what was new becomes old and forgotten with the exception of the most fervent diehards. Then, all of a sudden, something will jog the collective memory of the group, and they are popular again. With the ZR-1, even though they have somewhat faded into obscurity, they maintain a relatively high value because the people that know understand what a monster of a car it is.

[@darrylrichardson1997]

@@VetteSource lol 😂 yeah I’m only 26 I was born in 97

[@VetteSource]

That's ok, at least I know the younger generation still knows a good piece of machinary when they see one😁.

[@gordocarbo]

@@VetteSource When my nephew was 10 he knew right away what my Z was when I pulled up. It was on his video games

[@TheMrmmkkpro]

#2822 sitting in my garage. Still holds the 24 hour world top speed endurance record 5000 km top speed record 5000 mile top speed record. Still "King of the Hill" And yes it still holds the records for a domestic production vehicle. Great video.👍👍🏁🏁

[@VetteSource]

Hey Michael, good to see you got the old boy up and running. Enjoy the rest of your weekend👍.

[@bobolulu7615]

#1781 sitting in mine!

[@DeFreshS10]

great video

[@VetteSource]

Thanks, glad you enjoyed it👍

[@asken021]

Great video, congratulations, but could you tell me where the engine identification number is? I have one here in my workshop in Brazil and I needed to find this number so we can get the car's documentation

[@VetteSource]

Hi Asken, glad you enjoyed it. The VIN number for the LT5 engine is stamped into the passenger side rear of the engine block. You will need to get underneath the car to see it. An inspection mirror/flashlight helps. It is located on the vertical face of the block directly adjacent to the transmission dowl pin in front of the bellhousing.

[@vkhken1966]

I read till 1993 all major repairs to the LT5 were done by Mercury marine. Engines were removed and shipped to Mercury. Even gave the option for a new engine instead of repair. After 1993 GM took control of repairs.

[@VetteSource]

I think I remember seeing that in the book that came about detailing the LT5 engine. If I'm remembering correctly, GM didn't feel that the dealer technicians had the advanced training or special tools needed to properly reassemble the major subassemblies like you mentioned.

[@gordocarbo]

@@VetteSource THey were a pain in the azz to work on unless they were out, too.

[@robertnelson5204]

Mercury made these man.

[@VetteSource]

Yep, designed by Lotus/GM and cast and assembled by Mercury Marine in Stillwater, Oklahoma.

[@stevemoyers5693]

I had a 94 Z and you can remove the alternator without removing the plenum. Not a lot of fun though.

[@VetteSource]

Hey Steve, thanks for the information👍. Like you said it looks possible, but a tight fit to get it away from the plenum/throttle body/extension housing. That's one item I've ever had to remove from a running Z car over the years. Just shows how reliable the alternators have become over time.

[@stevemoyers5693]

@@VetteSource i hear you….I had to do the job twice as the first rebuild of the alt they installed a bad bearing. Didn’t know it untill i fired it up! There was a learning curve so the second time was a bit easier but still….

[@iturbo5733]

Was that a 3400 DOHC engine behind the LT5? I'd love to see a similar video on that too!

[@VetteSource]

Good eye, man. In the year since I posted this video your the first person that recognized the 3400 DOHC. It is waiting it's tuen to be installed in a 1994 Olds Cutlass Convertible that I've had on the back burner for awhile. I'll have some videos highlighting it this coming year.

[@Gotmath8]

Lots of amazing cars there. Do you resto them? Part them? Or are they all to keep as projects? Wish we were neighbors. :)

[@VetteSource]

Actually a little bit of everything. My primary business is parting out the ones that can't be saved, light resto for the ones that can see the road again, and future projects for the ones I hope to get to some day😁.

[@gregs_garage]

um... is that really how the secondary intake works? like the tiny hole in the throttle body is the only opening in the "normal" key setting? and the big plates don't open until "Full" key? Something seems off about that.

[@VetteSource]

yep, as odd as it sounds, that was the primary source for air flow. I remember the first time I saw it I couldn't wrap my head around it because I was used to the throttle blades of the L98. Here's a general operation description - A large, forward mounted air cleaner would feed a cast-aluminum throttle-body assembly with three throttle blades - a primary blade of 0.87-inch diameter and two larger, secondary blades measuring 2.32 inches across. The injection system of the LT5 actually operated in three, progressive stages. In the “first stage” mode, air would be drawn into the throttle body and past the primary throttle blade to the plenum, from which it was distributed to the eight primary ports. During this stage, the secondary throttle blades remained closed below 80 degrees (approximately) of the primary blade opening, which equated about 70 miles per hour on the road. During the “second stage” mode, the secondary throttle blades would open to add air to the eight secondary runners and ports, providing that the ECM was satisfied that full power would be required. In that event, the ECM would trigger the vacuum actuator to open the secondary runner throttles. The third “mode” of the LT5 engine was commonly referred to as the “Valet Mode”. Because the engine management system operated in stages that were mechanically controlled, the second stage performance could literally be locked out with a key. The actuator could be manually disabled via a mechanism in the center console, engaging the “valet” mode, which inhibited full-power operation when handling the car over to parking-lot attendants or other vehicle operators who might otherwise not be trusted with the car.

[@anondale5635]

@@VetteSource thats not technically correct. the small tb mid bottom opens first and the larger ones open soon after irregardless of the power key. power key activates the vacuum actuated secondary throttle plates under the inj housings.

[@VetteSource]

Ok, that makes sense. I was aware of the progressive opening of the larger throttle blades under increased speed/acceleration, kind of like the vacuum pods on the #1 and #3 carburetors on a TriPower, but wasn't familiar at what speed/throttle position they began to come into play. Thanks for clarifying👍.

[@tjmoneybags]

@@anondale5635 I had a 91 Zr1 and I agree. I thot it was the secondary throttle blades in the 8 of 16 intake tunnels that resulted in the added power. If it could make 210 hp on that tiny primary hole of air then they proved restrictor plates are unnecessary! haha

[@desireehill8779]

My husband is in need of a part for his Vette, how can he reach you?

[@VetteSource]

Desiree, he can reach me through DM @VetteSource on FB or IG and also find my direct contact information.

[@bobolulu7615]

Youre not quite right about the throttle body. The one you showed at the front of the engine is just a standard throttle body. One of each of the intake valves for each cylinder had its own vacuum operated thottle butterfly and it would open when the ecu requirements were met. That small vacuum pump operates 2 actuators that are under the intake manifold. 4 of the intake butterflies are connected together on eac side with a vacuum servo to pull them open. Each intake valve has its own fuel injector. Also under the intake manifold is the ignition coils and coil amplifier and right down the bottom in the V is the Denso starter motor. I have one of these and havevhadvthe intake off maby times sorting vacuum leaks and a buggered starter.

[@VetteSource]

Thanks for the detailed description. I'm aware of the secondary throttle system and how it operates, but didn't want to get that in depth for this video. I will have another video out later showing the system in greater detail once I fire up another long-term stored 1990 ZR-1 I have laying around here somehwere😁.

[@nuke_ratt]

Can you point me to any additional detail on the secondary throttle system and on an EGR delete?

[@VetteSource]

Murray, I am planning a follow up video for the LT5 shortly. Were you looking for a video that takes a deeper dive into the secondary throttle system and EGR system?

[@nuke_ratt]

@@VetteSource that would be very helpful. It’s the first time we have utilized this motor - tired of seeing LS swaps and wanted to do something unique with this motor. Lots to learn. Was looking into a possible EGR delete as well as trying to understand the throttle system as there are the two cables off the throttle body and I believe the secondary throttle system utilizes vacuum to open. Have the supplemental book specific to this motor on order. Thanks much for the help. Great video - I’ve watched multiple times.

[@VetteSource]

Great, glad it has been helpful. You're on the right track ordering the FSM for the LT5. Be on the lookout for that video soon👍.

[@georgesantiago6005]

You can delete those valve, refreshing the engine. Nice engine looks like the TPI engine.

[@VetteSource]

Hey George, I agree. It always looked like a TPI on steroids to me. Plus that crazy DOHC makes it sound very distinctive in comparison to the SBC engines.

[@makosharkcnc7730]

i like the engine/ but i think i would not want it cause there weren't that many made, i will stick with my LT1 i would mind a LS too

[@VetteSource]

Yea, that has become the problem as they've aged. If you can wrench on your own cars, it's not that bad, but God help you if your depending on a general mechanic shop to repair and source parts for the LT5

[@gordocarbo]

@@VetteSource if you need parts the go to place is the zr1net registry. Good group o guys there .Otherwise bend over! lol One reason I decided to sell mine .Loved it but having to hoard parts extra engine "in case" soured me. DIdnt need them but still..

[@mcmc1863]

Uk vette fan here, im lookin at a '90 with 187 miles...yes, 187 miles....up for 60k sterling, are there probs with the '90? Great vid 👍

[@VetteSource]

Thanks MC, appreciate the feedback. No problems with the 90s other than the normal maintenance issues that will arise with the high-tech features from the early computer cars from non-use. I would perform a very through inspection of the car you are considering to see which if any of these items are inoperable, and price your offer accordingly from there. Sounds like a phenomenal car👍.

[@mcmc1863]

@@VetteSource guessing none use isnt to good on the LT-5?

[@VetteSource]

That's with any car, but as long as it's been properly stored it can be brought back out of hibernation.

[@TechScottBrown]

The Multec injectors were infamous for electrically shorting. Upgrading the 16 injectors to a Bosch design will bring true proper engine operation. Here’s a link to a video I shot many years ago walking through diagnosing a shorted injectors on the “secondary” side: kzbin.info/www/bejne/iJyul6J3bLGGiJo

[@gordocarbo]

90 Z or an L98?

[@yeanlingsoda359vortexcars8]

Could you put this engine in a older 1981 camaro? Im interested for my car

[@VetteSource]

It's definitely a swap that can be accomplished, but a little more complex due to the custom wiring harness and specialized engine fitting that will be required. If you do a Google search, you'll be able to find some cars that have an LT5 swap to give you some ideas.

[@gordocarbo]

Sure can. Wont be cheap youll need the electronics, have to figure your fuel system (used 2 pumps). Doable but not a weekend swap BEtter get one complete as possible cause little parts will cost a fn fortune

[@Jmonster68]

I want it

[@VetteSource]

Come on, I got a good price for ya😁

[@nicklouallen4784]

Do the engines make a different sound when secondary key is turned on?

[@VetteSource]

That's a good question. I've never noticed a difference in the timber or exhaust note between the two settings. Most of the distinctive sound of the LT5 comes from the overhead cams when pushing it into the higher RPM ranges.

[@gordocarbo]

Youll definitely hear it

[@gotuzzo71]

Do you have an lt5 available for sale?

[@VetteSource]

Hey Gus, this was the last spare LT5 I had and sold it a few months back. I have one more, but it's still installed in my 90 Z. Are you looking for one to put in a hot rod?

[@gotuzzo71]

@@VetteSource yes, building a custom truck on a C5 chassis. I thought a 32v would be cooler than an LS

[@VetteSource]

Yep, that would be a unique build. I'll check my contacts and see if anyone has an LT5 they would be willing to sell.

[@JJ-gz9ts]

すごく良い動画です🎉 日本で1994年のc4 zr-1に乗っています。😊

[@VetteSource]

素晴らしい、楽しんでいただけてよかったです! あそこのZR-1はあまり一般的ではないでしょう。 あなたのZR-1は何色ですか？

[@JJ-gz9ts]

シカゴで作られた。 BLACKです！ とても良い車です♬

[@flagcityparts]

I recently found a 92 z-51 in a barn that hasn't ran in 7 years. I bought it because it was cheap 2k$ but didn't know it was a z51 car until i ran the vin at the dealership. the hood also didn't open. should I sell the motor and ls3 swap it or just sell the whole car as a project?

[@VetteSource]

Hey Flagcity. Is it a Z51 or ZR-1? Lots of difference as one is a suspension package and the other a completely different Corvette with a unique VIN number and 1 of only 502 produced in 1992. With that being said, it would be a mistake to break apart a ZR-1 for an LS swap. Just let me know what your working with and I can give you some further ideas.

[@flagcityparts]

@@VetteSource today I received a message back from a local corvette restoration company and there interested in buying the car off of me, there offered me 9600 for the car. I'm waiting for proteam corvette to make a offer on the car so i can see who's fare. I do alot of ls swaps so moving it to someone who will restore it. it is better than having it sitting a year waiting on parts

[@VetteSource]

Yep, that's the best option. Definitely a car you want to keep together for somebody to put it back on the road in its original condition. What color was it by the way?

[@flagcityparts]

@@VetteSource red ext. red int. black strip down the middle of the car

[@VetteSource]

Yep, red on red is a cool combination. Good luck with the sale, and let me know how it goes. I may have people down here that would be interested in it if you don't find a buyer in your area.

[@ronstowe8898]

Mercury marine group actually built the engine for Chevrolet.

[@VetteSource]

That's correct, thanks for sharing the info👍

[@mikewest9033]

Mopar called them 6 packs

[@VetteSource]

Yep, exactly. Six Pack on the Mopars, Tripower for GM, and I think Ford just referred to it as the 6V.

[@lasvegaslife5770]

Can u break down the l98 vs lt1 c4 power (all stock)???? Lt1 has 50 more hp !! Thats alot!!! But 0 to 60 times are basically the same??? So from dead stop to top end at what point and at what MPH does the lt1 50 extra horse power kick in and pass the l98??? This is all me and my c4 friends talk about!!!! End that battle cause no body is gonna race past 60 round here !!!

[@VetteSource]

That's an excellent idea👍. Having both a TPI and LT1 here, I'll see if I can put together something that can address those questions for you guys.

[@lasvegaslife5770]

@@VetteSource awesome!!!!! Looking forward to it!!

[@herkloader34]

The L98 has more low end torque than the LT1, but past 60, the LT1 runs away from the L98 with that 50 extra horsepower.

[@lasvegaslife5770]

@@herkloader34 L98 had 350 tourqe the lt1 had 340.. so those 2 cars 0-60 should be about the same .. after that lt1 pulls ahead due to its 50 extra hp. Even the ls1 c5 0-60 is about the same 0-60.. and after that the ls1 pulls ahead due to its extra horse power. I'm trying to get people to realize 0-60 times are not that different for example. 5.7 vs let's say 4.8 0-60.. in real life they gonna be close 0-60

[@gordocarbo]

Thats due to the short tunner intake of the LT1 it pulls more rpm where the L98 maxes out thats all.

[@scruffy7443]

I would replace my lt1 in my trans am for this LT5 engine

[@VetteSource]

Now that would be an awesome upgrade. I'll bet somebody has tried it somewhere, but it would definitely take some custom modification.

[@scruffy7443]

@@VetteSource This was where GM failed the f-body owners like me, if they would have ported this LT-5 motor to the 93-97 f-bodies instead of using the mechanics nightmare the LT1 with having to replace the opti-spark when failed and change of the hard to get to spark plugs from time to time it would have been reliable imo, if you look at how the LT5 spark plug and distributor are placed on this motor, it's not a money pit like the old LT1 seriously, let me tell you, when i first bought my 95 trans am, i did not do any research, first time i wanted to change my spark plugs, i literally cried under the cars, well my eyes watered like WTF! i pay $300+ to $500+ for a mechanic to change what i mentioned, I live in Cali, and also those LT1s hardly pass smog here with the dreaded DMV emission dyno test just to let you know.

[@gordocarbo]

@@scruffy7443 Believe me the LT1 is the engine you wanna have in that car Dont even know if it would fit under the cowl .If it did good luck servicing it. BUild your lt1 plenty of good parts to make it fast

[@rugbyguitargod]

15:11 I cringed when that aluminum fuel rail (w/injectors still in) fell on the concrete floor. Not exactly cheap parts to either replace or repair either, i'm assuming? :|

[@VetteSource]

Yea, that one got away from me. Food thing is they are much more sturdy than they look, but like you said LT5 parts VERY difficult to find. Thanks for watching👍.

[@rugbyguitargod]

@@VetteSource good thing they overspec'd EVERYTHING on these engines, right? lol

[@VetteSource]

That's for sure.

[@garymathews4042]

the newer vette engines have direct injection ,which helps with power

[@VetteSource]

Hey Gary, good point. I forgot to mention that when I made the video. Thanks for the comment👍.

[@rslyrick5315]

Hey VetteSource, love your videos ! One question, is it worth investing in a C4 ZR-1 if some parts can't be found anymore for that LT5 ? Even if you invest in a very good one vette, well cared over the years, at some point, there might and will be a thing. I would be ok paying a decent amount of money for some parts because the car definitely deserves it but not being able to find them is just a show-stopper... :/ what's your opinion about it ? Is that a question that nobody want to hear or should i stop worring about such thing and go for it ? :)

[@VetteSource]

Thanks RS, glad you're enjoying them👍. That's a good question that gets asked fairly often. I tend to think that for the immediate term, even cars with more difficult to locate repair parts can be thoroughly enjoyed. In the event something unique to the car/drivetrain needs replaced, there are always going to be vendors like myself that trade and sell the unique items, such as the LT5 engine components and ZR-1 specific body parts. Personally, I dont think there's any reason to deny yourself the enjoyment of the car for something that's a possibility and not an inevitability. The trick is to perform your due diligence when making the investment to buy the best car, low or high mileage, you can. With regular exercise, maintenance, and care you'll have a ZR-1 that will last for many decades. Let me know if you need any further guidance.

[@rslyrick5315]

​@@VetteSource Thank you for you answer! Do you mind if I contact you via your business e-mail for further questions, not strictly related to this video, but still about Vettes ?

[@VetteSource]

For sure. My information is on my YT "About Me" page, or you can send me a DM through FB or IG @VetteSource

[@IncomeWithEnergy]

I just bought my ZR-1 and had the same concerns but I just dove heart first and figured it out as I went... turns out that after 30 years there is a genuinely committed and huge support, resources and cult following for the car that ANYTHING that could possibly be wrong with the car or engine hat already been figured out. This LT5 has truly become an adventure of discovery for me and enjoyable learning experience that I didn't expect. Additionally, it's still shares at least 80% of parts with the other base Corvettes so common C4 parts are readily available and those that aren't there usually a work around.

[@gordocarbo]

No these arent investments especially a Z Sure they are rare and all but most younger guys have 0 interest in them, they find out parts are tough to come by and $$ and not just anyone can work on them. Crowd is aging out as it is. Only investment grade vettes imo are pre 71

[@MexicanGhost2013]

I thought the LT5 was made by Mercury Marine, not Lotus.

[@VetteSource]

Designed and tested by Lotus, manufactured by Mercury Marine for their expertise in dealing with complex sand castings of aluminum engines.

[@MexicanGhost2013]

@@VetteSource makes sense thanks for sharing the knowledge!

[@VetteSource]

Not a problem, glad to do it. Thanks for watching👍.

[@BB-019]

LT5s have Forged Aluminum Cylinder liners- Nicosil Coated, not Steel,, they have Hydraulic lifters, (lt6 is a solid lifter engine), and the only secondary butterflies are in the other 8 of 16 plenum tubes, not the dual throttle body's, (those are coupled together). Keep up the videos, but please try to give correct info. Aren't these LT5 engines BITCHEN!!!!! WAY AHEAD OF THEIR TIME!!!

[@VetteSource]

Yep, I seem to remember the cylinder liners being aluminum now that you mention it, but its been so many years I forgot that detail. I don't believe I indicated that the LT5 had solid lifters, or that the secondary throttle butterflies weren't in the plenum tubes. My videos are usually done in a stream of consciousness, so it's possible I misspoke without realizing it. I'm not a spring chicken anymore and the older I get I realize there's way too many details to remember regarding the different generations of Corvettes.😂. I do however, recall pointing out the plenum secondary butterflies in the last half of the video. Maybe you missed that section. Thanks for your recommendations, I'll take them into consideration in the future. Appreciate you watching and commenting👍 And I agree, the LT5 is still in my mind one of the most wicked Corvette engines out there.

[@dukeman7595]

@@VetteSource You did 'not' indicate that the LT5 had solid lifters or the the other issue he complained about.

[@VetteSource]

Yea, that was kind of puzzling to me that he heard it that way.

[@gordocarbo]

@@VetteSource Everyone wants to be a corvette car expert online. lol

[@mikes.1882]

Anybody put one of these in a gen 4 camaro?

[@VetteSource]

The 4th generation F-Bodies have such a deep firewall, I'm not sure if this bad boy would fit in there, but that would be an interesting build for sure.

[@km6832]

Push rod engines make more torque?

[@VetteSource]

Do they?

[@km6832]

@@VetteSource do they? Was a question

[@VetteSource]

You mean you were asking me if push rod engines make more torque?

[@km6832]

@@VetteSource yes. What makes you say that

[@VetteSource]

I'm gonna have to go back and watch my own video to get the proper context of what I was actually saying😁.

[@randybills3848]

those are very cool and what a tech leap for the age but man what a maintinance headache

[@VetteSource]

Hey Randy, I definitely agree. These are incredibly cool engines and so much fun to drive, but kind of like working with a 3000 piece jigsaw puzzle😁

[@randybills3848]

@@VetteSource yeah man but would still take it lol

[@VetteSource]

For sure, wouldn't kick it out of my bed😁

[@dukeman7595]

@@VetteSource Even if it ate crackers! Awesome piece of engineering.

[@gordocarbo]

Not really. EVerything is under the plenum no need to do anything else. Even water pumps arent bad

[@hunnterful1]

If you know you know

[@VetteSource]

That's it👍

[@brianbiro9094]

Thought it had 405hp 🤔👊👍✌️🦅🇺🇸🦼

[@VetteSource]

That's correct. It was 405 HP in 1993-1995. 1990-1992 was 375 HP👍

[@skip741x3]

Dohc yes, but it was a crossplane... the old dohc sounds nothing like the newest z06 flatplane one for that reason.....very cool engine though! I'd love to own one of those zr1's!

[@VetteSource]

Crossplane, thank you. That was the terminology I was looking for when making the video and couldn't remember it to save my life while shooting. The C4 ZR-1 is definitely a car to experience firsthand, it will make a convert out of you.

[@wall4xxx]

Back in day there’s was real engineering making engine from ground up with creativity not copies off other just real creativity lol today we copied everything from sole’s to sock 🧦 we have become lazy parasites humans hopefully one day this will stop lol

[@VetteSource]

Yea, I have to admit I don't see much in the way of original design anymore. Most engines seem to be cookie cutter generic pieces with very few unique features.

[@The-carpenter-420]

Seems like chevy threw away the ohc 32 valve with ford picking it up and ford throwing away the pushrod and picking up the ohv. The basic design of the ls is ford design. Oiling, cooling, firing order, basic geometry of it was ford.

[@VetteSource]

Yea, they dropped it like a hot potatoes after the 90's were over and done. Funny that they have swung back around to this design in the new Z06 engine.

[@gordocarbo]

LS was a clean sheet design has nothing in common with Ford. Esp the heads

[@louiszuech5436]

Mercury marine in Stillwater Oklahoma. Overly complicated for soso power output.

[@VetteSource]

Yep, that is correct. I'm not so sure I would agree on the so-so power output. Maybe you've never ridden in one😁.

[@louiszuech5436]

@@VetteSource just compared to today's vettes.

[@gordocarbo]

@@louiszuech5436 That makes 0 sense Like comparing something made in 2050 to a new one today. The 90s could rip off 12.90s with great mpg in the right conditions. Wasnt til the Z06 came out that time could be matched or beat

[@louiszuech5436]

@@gordocarbo you make zero sense I love the old cars but 385 HP is average gm make a 3.6 high option single turbo that makes 455 HP 30 + mpg!

[@gordocarbo]

@@louiszuech5436 ANy car can make power with a turbo .did they have that in 90, no . Comparing anything newer than the car in the vid is what makes 0 sense .

[@ztwntyn8]

Make sure you read comments and don’t go with all of this info. Some is good though

[@VetteSource]

Wow, tough crowd on this video. After looking back at my FSM's and technical notes it's obvious I mixed up a few things most likely due to my advanced age and the useless Corvette trivia stuffed in my brain all these years😁. You guys have given me a good idea though. So we can clear the record and make sure no misinformation is getting put out there, I'll make another video describing the LT5 secondary throttle system in detail so I can correct the errors in this presentation. I'll do my best to make sure you don't have to shake your head from me making stuff up next time. Just remember if you're going to comment to keep the swearing out of it. This is a family friendly channel and I automatically delete comments with curse words👍.

[@IncomeWithEnergy]

@@VetteSource the vette nerds really came out play on this one huh...

[@damianbrennan2258]

What's the big deal FORD had the camer i

[@VetteSource]

I'm guessing you were born after the LT5 was produced😁.

[@damianbrennan2258]

@@VetteSource No I'm older than u long live the 427 sohc as far as chefs go that's the best motor they made

[@VetteSource]

Ok, now I'm clicking. For some reason I thought you were referring to the modular engines from the late 90s/00s. Like you, the Big Blocks of the 60's are my favorites for power and pure sound. The best expression I ever heard about a solid lift cam/high compression big block was that each cylinder sounded like it was living it's best life while idling. Definitely something that can't be replicated with today's engines.

[@gordocarbo]

HOw many yrs was the cammer in production? Longevity mpg? Those 2 arent even in the same solar system.

[@howabouthetruth2157]

I believe peak torque for the LT5 is at 4800 rpm. But I'm told that the LT5 pulls like crazy throughout it's entire rpm range.

[@VetteSource]

I think that is correct, but would have to go dig through my reference books.

[@herkloader34]

My '91 Z pulls hard through 7,000 rpm and sounds amazing with the resonator and muffler delete with H-pipe exhaust.

[@gordocarbo]

@@herkloader34 They are gonna get thier best time by shifting waaay before that ..they are only making heat and noise at 7k got the time slips to prove it. SOmewhere!

[@gordocarbo]

They do...its seamless power not likea pushrod engine When you get the secondaries open you can feel it..kinda like hitting an old double pump carb. Cool analog feel to it.