Testing Exhaust Cutouts on Big Block Chevy! | Engine Masters | MotorTrend

On this episode of Engine Masters, we see how exhaust cutouts stack up against a full exhaust and a header extension behind our heavy-breathing 598-cubic-inch Big Block Chevy.
#enginemasters #motortrend #davidfreiburger
MotorTrend is the ultimate streaming destination for gearheads coupled with the latest automotive research and news.
Get a fast, simple, and free car quote today ➡️ quotes.motortrend.com
Start your MotorTrend Streaming Free Trial today!
Follow MotorTrend for the latest!
MotorTrend News: www.motortrend.com
MotorTrend App: www.motortrendondemand.com
Facebook: / motortrend
Instagram: / motortrend
Twitter: / motortrend
TikTok: / motortrend

[@jameshall4385]

Now you should do that test with the electric cutouts. See if the flapper valve causes a restriction

[@philking7805]

Good question - You would actually think the flapper valve might divert the gases better than them just finding the route with least back pressure

[@mgmjferg89]

i like the way you think

[@bennyboyy7]

The difference would be like 3 HP at most. The exhaust is just going to leave where it feels like so putting a different style cutout is just a exhaust relief. If too much pressure is killing your power, then opening it electronically or manually is just going to show its relieving back pressure. Mostly sound but it's not like putting a 1000 CFM carb in place of a 300cfm. Or a 4 inch exhaust in place of 2 inch you'd see more difference on a boosted car with a cutout. For best efficiency you need a valve that closes off the regular exhaust and directs the exhaust rather than just blocking it off. But just do the same old carb tricks to a electric cutout like shaving the tiny screws holding the butterfly valve in place, rounding it all so it's smooth but these are going to be such small changes that air temperature difference would make gains or losses look more dramatic.

[@rattyratstuff7125]

I'd think definitely. I bet using 2 cutouts, 1 forward 1 back, to route around mufflers would be perfect. Remove the plates and install pipe and boom. Better way of doing it imo than an electric if you don't mind getting dirty

[@rattyratstuff7125]

Oh or maybe one that cuts out on both sides. Hmmmm

[@Sjackson2369]

this is exactly the thing I come to watch engine masters for. I have been considering doing this on my truck for a little while now, and this just gives me all the more reason.

[@hydrocarbon8272]

I've been doing cutouts & quiet mufflers on all my modded street cars for years, it's fantastic. Now I use vacuum-actuated cutouts, they're fast, reliable, and can be controlled via solenoid with a switch or the EMS.

[@mxguy2438]

I do the same. And since mine makes up to 20 ft-lb more under 3500 rpm with them closed and up to 15 ft-lb more above 3500 with them open, I let my ECU control them with a mac valve and keep them closed until 3500 RPM.

[@Nismo-gy3wz]

@@mxguy2438 AES

[@ChefofWar33]

​@mxguy2438 Meh. I'd like to have a switch that keeps it quiet no matter what. That way I can pass cops and not worry about it.

[@SparkyWrench]

I have a twin turbo and was thinking about dumps. Will this cause the turbos to overheat? And where do you put the dumps on a car that relies so much on the tuning? UPDATE: I installed them and put car on dyno. +20 HP at the wheels with them open. No issues otherwise other than the floor gets hot if left open too long.

[@theprojectproject01]

@@SparkyWrench Are dumps the same as wastegates? Sorry to seem dim, I just don't have a lot of experience with forced induction.

[@Black70Fastback]

I think it would be even better if the full mufflers were built on the angled outlet and the cutouts let it go straight through.

[@JuanFlores-gy5ze]

I've been saying and thinking that for years. The flow is not redirected.

[@lifeonadime4703]

Absolutely. I think that is the optimal route to run em.

[@TheGforcead]

Not just that but knowing the muffler is restrictive it makes common sense to run it out the side, when you uncorrrk you want straight shot cut to where the heat signature stops..

[@8BWN]

X pipe, install the cutouts on the rear you can take advantage of the X and have them built/ orientated for straight flow out the sides when opened up.

[@YZFoFittie]

@@8BWN this is exactly what we did on my Vette...

[@CLAYTONTHEBRAIN]

I have electric cutouts installed and wondered if they helped. This is a great test, it shows the cut outs are worth every penny.

[@mikeyfourbarrel8473]

Good lord. That BBC is a monster. The test is very cool and informative but I’m just in awe of that engine.

[@gumballer133]

Yep, and there are guys getting 1000hp out of the same size engine on pump gas too! My 516 turned out good, but not enough cam so it's very sensitive to low octane fuel. Needs 100octane to run properly.

[@mikelaumaillier9271]

Great comparison. Should have tried the test with the 18" extension on the headers and then the cutout. Thanks for all the great videos. Regards - Mike

[@kern_yak_angler]

same here I was gunna do 12inch extensions then cut outs but i dont have the room so just gunna bolt up the cutouts to the headers like they did

[@CarsandCats]

I used to run cutouts on my blower car because it was WAY easier to uncap them than to drop the entire exhaust. But I did a test once at the track and with the entire exhaust removed it only picked up 5 hundredths and I think that was because of taking off 30lbs of exhaust!

[@stevezurek5826]

I have a Corsa Captains Call exhaust on my boat. Cut outs w solenoids... it def makes a difference on my Mercruiser Mag 350....

[@mickangio16]

I believe that it's all about WHERE in the pipe that you interrupt the pulse with the cutout the same way that an optimum collector length does AND the relief of back pressure created by the mufflers and the rest of the exhaust system. The open header example used 18" long collectors. The cutout equipped example had the cutouts merging into the pipe at about half the length of the 18" collectors effectively making the collector length half of the 18" length. I believe that's the only reason the power was down a bit. The only part that is a bit confusing to me, though, is the closed cutout vs the no cutout example. I think maybe the extra volume of the cutout tube reduced exhaust flow velocity at lower engine speed.

[@davemrak]

I'd like to see if there is a difference in placement? Maybe post H or X pipe to see if it will still take advantage of the exhaust scavenge!

[@thefinalgrind]

There's no need. If it's happening at the beginning, it'll happen anywhere else in the system at some point in the power curve due to all things thermodynamical..thermodynamical. lol. Which I don't think is actually a word but looked more funny than thermodynamics The only thought I had would've been if the cutouts themselves were X piped to dump.

[@bobbygetsbanned6049]

You want them as close to the header collector as you can get. The least resistance the better.

[@karenthomson9749]

No the x pipe h pipe represents a restriction.

[@ChefofWar33]

Interesting test actually. The guys at MotoIQ say that the closer you get them to the headers the better. In fact, it not only increases power, but it makes the engine sound better and less thrashy.

[@burtvincent1278]

Always seemed to work back in the 60s. Some of us used gas tank filler tubes. Winding the engine out with the gas caps on usually resulted in their hands off removal. Relieving that much back pressure obviously helped.

[@paullaverty3038]

This was an outstanding comparison, so happy to see these results. And this test thanks for doing it, love your show.❤😊

[@flamzy150]

I’ve got mine setup so the cutouts are straight and I notice a big difference in not only power but engine is much happier with the cutout open

[@jameshathaway5117]

I always thought these things were made kinda backwards. The dump should be on the easier flowing pipe with the muffler taking the angle pipe. I bet your setup would achieve closer power to straight headers than theirs did. I'm helping my friend weld in a set of vacuum actuated cutouts at the bend where the exhaust bends to go to the y pipe. It all lines up to where the exhaust will go straight back out of the header and out the valve with no bends. We are considering getting the valves that close under vacuum and just plumbing them direct to manifold vacuum. When you are off the throttle the vacuum stays high and the valve stays shut. Under load at full throttle the valves will open automatically.

[@Orygunner67]

Very informative video. I figured there would be exhaust turbulence at the y also but higher exhaust flow/ exhaust pressure would take care of that at high RPMs. And it did!

[@TimothyRaz727]

If I remember correctly, the max wedge exhaust, had a straight shot to the collector, that dumped out behind the front wheel. When capped, the exhaust would back up, then flow out the tailpipe. The max wedge configuration, when uncorked, flowed like open headers, with a straight shot.

[@philking7805]

I've seen rods with a similar arrangement - look like open pipes but the exhaust actually runs in a hidden pipe that links to mufflers under the car... at least until the cap is removed

[@justinsmeltzer2295]

I'm glad I came across this video. I was really deciding on if I was going to put these on my builds. Thank you

[@jackschumacher8472]

Thank you for doing that test. I have been wondering the same thing for a long time. Keep up the great work.

[@AdamOpheim]

The capped off part is backwards on that cutout. You want to plumb the exhaust system off the kick out and have the cap on the straight through part inline with the exh flow so it doesn't have to change directions.

[@weekendgarage3299]

I was on the same wavelength as Freiburger. But wow! Great results.

[@jdmmike7225]

"I'm ordering 3 sets right now." LMFAO 🤣😆

[@johnbehneman1546]

GREAT VIDEO DAVID!!!!! I WONDERED ABOUT EXHAUST CUR OUTS AS WELL. WELL, THE FACTS SPEAK FOR THEMSELVES!!!! SOMETHING TO CONSIDER!!!!! GREAT VIDEO AND THANKS FOR SHARING!!!!

[@daviddavid5880]

Whoa. I had no idea. Totally going to order up a cutout now. Thanks, guys.

[@MrTheHillfolk]

They're a hoot. Ive got one to make noise ,and for some reason I have a Spidey sense to tell me to close it. I close it,round the curve and there's a cop 😄 It's saved me a lot of money in tickets. I recently installed one with a key fob remote ,but it's a project car so I haven't officially used it yet 😄

[@phlodel]

What would happen if you put the cap on the straight sectin of the cut out and hooked the mufflers up to the Y?

[@roadwolf2]

Hmm. That’s actually a good question.

[@mylanmiller9656]

It works Better I run that setup and run the same time slips at the strip as with open headers.

[@phlodel]

@@mylanmiller9656 Stands to reason. The Y itself is a restriction.

[@jbrownjetmech-4783]

Same as open header, but more difficult to set up and probably a little less hp when capped.

[@henrymeynier5072]

Fb always pidgeon holes parts he doesnt like in tests

[@MrUltraworld]

I have mine after the X pipe, that LS sounds glorious with them open.

[@r.d.riddle2068]

We used to swap the cut-out side and weld the flange to the straight through . The theory was since flow was already compromised, may as well take full advantage of the cutout. 50 or so years ago. 2-1/2 inch pipe.

[@DarcyFerrier]

this was one of the most interesting episodes of engine masters ever!

[@UnpopularOpinion314]

My favorite show. I watch every episode religiously

[@terrybaltimore1542]

Great video guys...

[@michaelparadisis4076]

Great episode/test.

[@SixBarrel]

Engine masters the Best of the shows 🍻👍🏻

[@rw9495]

Good to know this works so well!

[@rattyratstuff7125]

The 86 in my pic had a straight pipe with "race muffler" and it was ungodly loud and buzzy. Now I have 2.25 all the way header back, feels super restricted. I'm definitely gonna have to do a cutout that routs around the muffler and resonator for track days. Right on dudes!!!!!!!

[@roadrash6565]

I bought a set of cut outs 2 years ago when I built my truck and decided not to install them at the time. Now I gotta get an appointment to get it done.

[@tedbear631]

Love this show

[@Kh.J.]

Best engine testing show ever

[@pleite567]

I think you should an X pipe and see the difference because now its basically an H and i can recall from previous episodes that it does make a difference

[@davegerrard6857]

Wont change what the cut outs do.

[@freemansgarage]

I think you're onto something. I bet you're right.

[@propdoctor21564]

That would be a good idea to try

[@chrisr897]

You’re saying an x pipe changes what concerning the cutouts?

[@65283impala]

@@chrisr897 I had cutouts exiting straight after the x pipe, no angle there, just on the natural path of exhaust gases. Don't know if it makes any significant difference though.

[@Playermex2]

Always wondered the same, time too watch this vid

[@vk56datty]

I had an e cutout with dual butterflies that opened opposite to each other, so when one opens, the other closes. Great idea, but I lost power all around LMAO. Sounded cool for a bit and that was it. It most likely needs a tune for both opened and closed. I guess the best option, in my opinion, is getting a tune for a vacuumed operated e cutout/muffler so that it's quiet when at low rpms and goes full boar above 3k rpms

[@TheSamplebridge]

That's pretty cool. I'll have to put cutouts on my skylark now

[@mylanmiller9656]

I had a1966 289 mustang back in the 1960's I run cut outs but caped the straight out the back pipe. This run the same time at the strip as a true open header, Then run the Exhaust threw a 2' pipe out the side Of the Header extension for the street!

[@trentcostello4358]

Good to know thanx my friend

[@MrBluGruv]

I know in most real-world applications it would likely be infeasible to build it in such a way in many cases, but I would be curious if the few HP drop over open-header from having the cutouts open could be regained from having the cutout dump be the portion of the split be in-line with the header collectors vs. having them split off away from the straight piping (in other words, perhaps run the main exhaust piping whatever 20-30 degrees inboard instead of straight back so the cutout dump is pointed directly to the back of the car).

[@hybridssuck]

Excellent test!!! I think it’d be neat to do it again only with a mild small block, just to see the loss difference when you knock it down in cubic inches. I’d think that style exhaust wouldn’t kill as much hp on a 400hp 383 small block just as an example.

[@hydrocarbon8272]

TBH 6-7 hp/tq on that combo is 1%, that's within the margin of error on a dyno. As in, there's no noticeable difference.

[@18BIG78]

Man give us old school or some credit we knew it worked lol but it is awesome seeing it on a graph with the digital statistics thanks guys

[@6lik6]

i have a crown vic that i’d love to get some dyno numbers for. it’s tuned with cuttouts where the h pipe would be deleting it. i have 4.10 gears and a bunch of techs told me i would lose power but when they are open it feels significantly faster. only way to truly know is to get some test results

[@noampitlik2332]

And remember you can mount the cut-out or plate on the straight side of the "y," also.

[@SpeedyBoyy]

This video was really good!! I just wish they test the cutouts in multiple location ! what about the cutouts before the mufflers ? or after an H or X pipe

[@shinismoove]

Yeah that's what I was hoping to see too. I wanna know if running the exhaust a little longer into an X pipe would increase horsepower or not

[@jeremysgarage498]

I have cutouts on my 11' challenger classic r/t 6 speed, sounds amazing 😁

[@ianscarantino2117]

Would have been interesting to see a comparative with actuated cutouts. I recently obtained a pair of n.o.s. Warshawsky & Co 2¼" cutouts and they use a little lever with a metal flap inside the pipe to instead either allow the gasses through without creating a high pressure area in the vent pipe, or directly guiding the gasses out the open side.

[@donaldcombs]

66 chevelle 1972 w/ 396 4 speed . Put a y pipe in and welded a pipe water cap threads on it . Picked a target to race at the local hangout and set a time at our road we raced on by a rifinery . I would make an excuse to check tire pressure etc and take the cap of both pipes and pop off the air cleaner . Maybe it was me but I believe it was worth a half second .

[@malkhamm.1666]

I'm curious to see what the other two styles of cutouts would do, theoretically they would do better than the Y. There's the oval ones that come straight off the side Less in line with the flow but what little to no turbulence closed. Then there's the diverter style like No Weeds that changes the direction of flow entirely for the mufflers but dumps straight out for the cutout.

[@heathdelzell9547]

Excellent!

[@AmericanHmongPatriot]

Had this on my kseries. It is nice to drive on a quiet exhaust car.

[@Elver_Galarga_jugo]

I'd like to see if you could get all of the power back by attaching the exhaust to the turned section and putting the block off plate on the straight section. Not that 6hp is enough to matter much on a 790hp big block, but still curious.

[@donalddarbonne779]

The other test is the angle of the cut out. When I installed them, I put the muffler to the angle. When you took the cap off, it was straight flow. I found more power.

[@stanmack1]

Stuff like this makes me wish I had my own dyno and flowbench to test on. They never changed the position of the cutout to see if that mattered. Or clocking them so the exhaust doesn't have to make a turn to go out.

[@propdoctor21564]

Awesome episode and a excellent test !! I think the ultimate setup would be some sort of adjustable cutouts either operated by air or electricity or hydraulically to be able to open and close them on the fly just like they have in performance boats which is called a captain's call exhaust system

[@TJPDmember]

They already exist and have been for the last 10 years at least.

[@vintagetractorsaustralia]

There are a number of them available on the market

[@evcass69]

Any opinions which cutout kit offers the best long term flapper seal? I'm tired of the electric motor flaps not sealing and causing a exhsut leak noise.

[@exothermal.sprocket]

Should have put an atmospheric velocity meter on both ends (normal end and cutout end) and compared the ratio of flows. That's more detail, but it would have been very useful. Also with a ton of newer vehicles running electronic butterfly exhaust valves these days (connected to operating modes), this sort of thing is becoming more relevant.

[@tmolne117]

Forget the engine noise. That 90s racing game menu music was killer

[@ronaldbertin9455]

Good info

[@evcass69]

If you tune the engine for a stock-style closed exhaust, then add a cut-out some place between the collectors & muffler(s), is it beneficial to re-tune fueling or timing?

[@obbyjep7597]

Makes me wonder if quarter wave resonators have much affect on power. They do work for sound at certain rpm good. Those cutouts are kinda like short resonator s.

[@Trikekid84]

I bet the placement of the y pipe makes a difference like collector extension length. I think they nailed it but in a car it might be hard to get right.

[@DerptimeTV]

I put a 3 inch electric cut out to bypass the muffler but still ran a pipe beyond the rear axle on my 94 tbi 350 and picked up 3/4 of a mpg in city and highway. Its already payed itself off in one year. And the truck doesn’t feel as lethargic as it once did.

[@mustanggarland24]

Awesome my cut outs are going to stay😊

[@SightsNjunk]

If you are going for performance, you will want the cutout on the straight part of the pipe, and the muffler on the pipe that is welded on. That way when uncapped, it will have a straight thru flow.

[@ShadowtheRotarygod]

That actually makes a ton of sense. I'd love to see that tested and compared on the same engine and dyno.

[@faisalsaidi3720]

Great episode, you almost answered all my questions… although i have one more question, if i have one of these cutouts on my truck open and i try to cross a small body of water how do you think it would affect the engine (if any) since its located somewhat close to it?! Keep it up guys, always coming up with great videos, big thumbs up

[@celuler22]

It will make some back pressure but won't kill the motor unless it's really deep dont shut the motor off or it may suck water into the exhaust

[@theprojectproject01]

Depends a lot on your cam, reversion is something that boat engines have to deal with continuously. I know the duration and separation numbers are pretty well established, I just don't keep that info inside my head.

[@plusdaddyyt]

I would want to see if you moved cutout to the rear right before mufflers .. seen couple people do it .. I’m sure the cutout closer to the front will be better but be interested seeing compared to test B and C

[@jesseduke694]

This test brings me more questions. And questions about how you guys set up the exhaust. Shouldn't your H pipe be moved farther forward? And maybey the cutouts come after the H pipe? What did difference would that do??

[@georgecrawford4067]

Great test sequence. Since most folks dont have a nearly 600 cu in street engines, what would happen on a high lerformance 383 stroker street/strip set up, more typical for some of us, with a 3 inch exhaust system? Why not situate the open end of the cutout exactly at 18 inches from end of headder collector, or as close to that as practical?

[@jesseduke694]

I also wonder what the effects would be with a 400hp engine instead of a 800 hp engine. It's not really relatable for me. I get we might see some of the same effects just on a lesser scale, but I also wonder about the H pipe being so far back? I think move it closer to the engine & put the cutouts behind the H pipe?

[@tomdavis4050]

Can you guys do a show on header coating? Jet hot, swain tech, cerakote coating, powder coating, and ceramic coating. I know a few of these are to protect your headers. A lot us fight the temperatures under the hood. Thanks guys

[@texmextu2]

This is exactly what I needed to see .. I have electric cut out but don’t like them .. they rattle and the motors go out .. I need the old school one .

[@skip0110]

At high rpm with the mufflers and the corked Y, the entire exhaust system is pressurized so less turbulence. A slug of air gets trapped in the Y and can't get out, it just gets squeezed.

[@blown572hemi]

Max wedge car's have a bend that directs the exhaust straight into the cut out. I imagine power would be down everywhere until uncorked. Then the design really boosts power output.

[@mikebolliger2898]

have u tried with the y fliped straight pipe for cut outs and the y to the mufflers so when u un cap it it is a straight shot out the pipes ? would like to see this test done . thats how i have mine set up

[@GeoTrashPanda]

Fluid dynamics ftw!

[@ludicrous7044]

On some late model high performance cars the sound is adjustable. Run a dyno on one and tell us how it works!! When I get a new car the first thing I do is cut the mufflers off and weld a piece of tubing in the gap!! Never cut the catalyst off obviously!! The sound is nice with less weight!! I have.bad memories with cutouts. Couldn’t afford a trailer so I drove my car to the strip!! Crawl under and open em. Hope it don’t rain or back under in the MUD!😡 We couldn’t leave with open pipes or slicks!! Sometimes the wrecker would lift the back so we could stand up and do both!😊 Later I extended the cutout pipe where I could reach them and aimed them toward the slicks so it would blow the burnout smoke into the stands!!😁 I later bought “cheater” slicks (legal for the street) so no more MUD!! I see burnout cars using my smoke blowing today fifty years later!😼

[@ronthepainter3313]

I've often wondered why the exit for the cutout is on the branch tube instead of the straight part of the pipe. I understand ease of access but if you're at the track you probably have time to crawl further under the car to open them.

[@BigUnk85]

Good Info

[@MrShakotan]

I wonder if you had the cut out straight threw and the muffler path to the side if it would make and difference. Maybe even a modified ball valve? Rather then a cap.

[@northmanlogging2769]

Now what happens if you put the cut out, after the crossover, but still before the muffler?

[@Nismo-gy3wz]

AES

[@benalcorn9661]

I have always felt my QTP cutouts have increased performance dramatically especially at highway speeds.

[@12hullc]

What if you mounted the cut off backward? Faced the capped end toward the motor? Would this increase air flow through the entire exhaust system using the venturi principal?

[@pilsnerfamilymotorsports3275]

i wonder if someone makes a cutout where the cap is on the straight end, you might get all your power back when its open that way, tho it would only work in cases where you have quite a bit of room for your exhaust

[@alcarey8084]

Back in the day (1980s) they had cast iron cutouts with cable operated flappers in the JC Whitney catalog. Some of us knew the truth, even back then.

[@stillhavecommonsense6875]

I'd like to see the cut outs installed backward.... and then further down the exhaust. Cool test

[@AlphanumericCharacters]

I wonder if the affect is different with a lower power small block. Perhaps 400hp. Obviously compared in percentage of loss/gain.

[@denisiwaszczuk1176]

WOW. I used to build them . In the Eighties . They work Big tick. Ha cheers guys.

[@Danger_mouse]

Would love to see the full set of tests done again, but with the full exhaust on the Y, and the cut out cap on the straight through. Then you should have all the power back with the cap removed 👌

[@heavyhitter2655]

Please do a header comparison of shorty, long tubes, mid length, and tri-y on a mild build. A setup that's mainly a typical run of the mill street build. Ohh, and you could even do that same set of tests on a 500+hp setup to show how those choices would matter that much more for best power. The main goal would be to figure out if the claimed attributes of each style of header is true, if the difference between them is noticeable, and if "longtubes vs shorties" and so on is worth the extra dough. Please up vote, folks. I'm sure more people than me want to know if their butt dyno is accurate or if it's a placebo effect..

[@adambatchelder4121]

Did the afr change from open header to full exhaust? Or did you re tune for both ?

[@Monte1970SS]

I didn't need a dyno for this...I found out by putting into practice lol. My car would run 10.9 at 126 ish full exhaust, open electric cutouts and it'll drop to low 10's at 130+.....so alot of horsepower was left on the table with full exhaust haha

[@user-ie9zo5ft4z]

Nice 👍👍👍👍👍 cutout give more power the engine

[@trm4life]

I'd like to see a test like this on a low power engine or even a 4 cylinder. See if it's only a more significant loss on a high power engine.

[@mylanmiller9656]

A small engine can't afford the power loss as much as a big one, it should help the small engine even more!

[@myscreamnbanshee]

I'd like to see you guys do this test with a set of exhaust diverters. Instead of cutouts. As they are similar but completely different to cutouts.

[@INFLICTEDPAIN213]

I'd of thought you would have the "cutout" short side on the "priority" in the y pipe for better flow with cutouts open and then force it round the bend of the y for full exhaust system

[@Circlotron]

Is it possible that the problem is not actually flow, rather the long pipes after the collectors are simply detuning the header/collector combination? And the cutout partially restores the correct length and tuning?

[@voltronlebron]

Comment 6 I think lol You guys are awesome!

[@andykowalski2020]

If going for power then have the muffler be the off to the side hook up and cut out at end of straight pipe.