Differance between a LZ9 3900 and LZ4 3500 plenum

[@Spiritof_76]

I just realized that the 3900 variable intake is a modern twist on the old Weiand dual port intakes they used to make. Two runner paths for the air to enter the heads. I had a 3900 Monte, and it was a fun car for a midsize. It was weird to hit the top speed limiter and feel the engine "wanting" to rev higher.

[@modeverything1]

It should be fun in a smaller car, considering how well they move the vans around!

[@ethanlindsey]

Can the LZ4 upper plenum be rotated so the throttle body is on the accessory belt side of the engine for RWD applications? I realize that the throttle body might be in the way of the belt just by looking at pictures of the LZ4/LZ9 engine so the belt routing may need to be modified in some way. So does the manifold physically bolt down and work assuming the accessory drive was modified in a way to get it out of the way? I'm thinking maybe LZ9 bottom end + F body accessories + LZ4 intake turned around + 5.3 throttle body + LNJ cam + Microsquirt.

[@modeverything1]

The plenum will bolt on facing the front of the engine, but not with the factory accessorie drive. The RWD timing cover will bolt up, but the bolt holes in the ends of the heads are different and you have to make a custom coolant crossover/remote thermostat set up to get everything to work. Check out the DOT motorsports channel, they did this setup in their s10 road race truck!

[@ethanlindsey]

@@modeverything1 I have a 1997 5 speed dodge Dakota I was thinking about putting the LZ9 into. I wonder if I could just build a riser plate for the plenum to space it over the FWD accessories and have a "ghetto holley high ram" :) I would guess there is enough hood clearance in a Dakota. The AX15 5 speed trans that comes in the 4 cylinder Dakotas actually has a 60 degree v6 bellhousing pattern. I've seen talk on forums about this engine trans combo but never actually seen anyone do it before. Have you? From what I read the AX15 is quite a bit stronger then an s10 or Camaro 5 speed. When doing some research I found that the starter is on the wrong side just like the other FWD to RWD swaps so the AX15 bellhousing needs to be notched. I think a Fiero clutch kit has the correct spline clutch disc to fit the AX15 input shaft but I'm not 100% sure on that. The end of the AX15 input shaft where it goes into the pilot bearing is 0.75 OD. Do you happen to know what size hole is in the crank for the pilot bearing on the LZ9? Looking through rock auto of various 60 degree v6s applications I'm finding varying OD pilot bearing sizes 0.83 and 1.09, etc.

[@modeverything1]

You probably could raise the plenum, but it depends on how much hood clearance you have. The pilot bearing size I would imagine that it would be the same as an older 60degreev6, but I have not done any RWD manual swaps yet. That dose sound like a great swap!

[@pingpong9656]

I need to take of the LZ9 intake manifold from a Chevy Uplander - having a hard time getting the bolt off the back (top bolts on ignition coil bracket) on the alternator side - wiring harness and steering pump lines seem to be in the way. Do you have any tips on how to remove those back bolts? Mainly the one on the side of the alternator?

[@modeverything1]

Unfortunately, it's been a long time since I worked on one in a van. I think I usually get them with an extension and a flex head ratchet.

[@kastellolo5212]

You need 15 mm wrench for the alternator bolt, 13 mm for the two ignition coil brackets and all the manifold bolts and finally 10 mm for the throttle body bolts if you are just removing the intake. Cheers.

[@doubledcrawls]

Do you know if you can use the newer style lz9 intake from 09-10 on a 2007 older style lz9?

[@modeverything1]

I believe they are the same as the LZ4 plenums, but I have not had my hands on one to confirm.

[@norelation5344]

Any modifications that are junkyard or new performance parts a lz9 3.9l

[@modeverything1]

I have not heard of anything myself for vehicles originally equipped with this engine... other than someone was using a larger throttle body from a stock LS engine, but I have not tried it myself.

[@hardcorehockey3692]

Would the lz9 intake bolt onto my LZ4?

[@modeverything1]

It will bolt up but you won't have any way of controlling the variable runner in the plenum without swapping the pcm and wiring harness

[@arthurjones2454]

Is it possible to bolt this on and run it with no retune or will it run like absolute shit?

[@modeverything1]

I have not tried it, but I would imagine it running poorly in some areas of the rpm range. It would be interesting to see what it would do!

[@arthurjones2454]

@@modeverything1 gotcha. Was thinking about installing this on my 3.5 aura for a little more kick

[@xx_dragonprince_xx8993]

Will a supercharger fit on the lz9?

[@modeverything1]

Nothing from the factory will bolt on and I don't know of any aftermarket that bolt on. But a custom supercharger setup would work!

[@6loccswitextentions177]

Yep got a malibu ss lz9

[@Jason-um3tz]

How's the motor holding up

[@modeverything1]

Unfortunately, since I changed jobs a few years ago I haven't had a chance to work on it. But I am working on getting back to it in the new year!

[@ragalyisp]

I'm working on an lz4. I have the block at the machine shop, seems to me the flow on the intake side is sufficient. The exhaust ports and exhaust manifold are definitely the choking point. Im considering having them gasket match the exhaust ports and opening up the manifolds a bit while I have em sitting on the bench here.

[@modeverything1]

Nice! Headers should be a big improvement on these engines! I did some work on my heads but did not want to go too crazy without doing some flow bench testing.

[@gtaashwagandhaman7551]

Is it possible to swap the LX9's 3.5L intake manifold to the LZ9 3.9L👀😱 with out a problem?!

[@modeverything1]

It will not bolt up, they changed the bolt hole location on the LZ engines. The lx9 plenum will only swap out with 3100/3400

[@gtaashwagandhaman7551]

@@modeverything1 DAMN!!!

[@vicsvlogsandmods698]

Ok so hope hopefully you'll see this soon.. got a 07 LT and has an LZ4 intake i want to say.. i got an Lz9 motor out of an 06 police... im swapping the whole drivetrain and was wondering would i need to swap the plenums as well due to the wiring harness or direct fit? 😭

[@modeverything1]

Use what ever plenum that matches the wiring harness that you are using. If you are swapping a LZ4 plenum on to a LZ9 you may have a engine light on for the runner control. If you get the pcm tuned you should be able to have the code removed for the runner control.

[@vicsvlogsandmods698]

@@modeverything1 ok so the guy doing it did say they were going to swap the intake to the one that came with my car bc the wiring harness is slightly different on throttle and such.. but other than that everything else should be pretty straightforward.. thank you i appreciate you! Idk if i mentioned this but both are 3.9 and i do have the pcm out of the cop car as well so i was going to use that bc the cop car doesnt have DOD like the civilian car does

[@S944Porsche]

If you still have the LZ4 intake handy, would you mind measuring the height from the gasket flange to wherever the high point on the plenum is at both TB end and non-TB end?

[@modeverything1]

Highest point is the boss for the brake booster hose at approximately 3.5". The TB sits much lower!

[@S944Porsche]

@@modeverything1 Thank you. Could you also measure at the very front face between cylinders 1/2?

[@pighater951]

Same ass my 3.9 ltz impala

[@modeverything1]

Nice! The later years the 3.9 just got the lz4 style plenum.

[@MattyLight30]

So my 3.9l 08 impala has

[@meltedfusitediy6625]

Look at LGD 3.9l Chevrolet engine on 2010 impala. its the flex fuel version of LZ9 my 2010 impala has it and it does have vvt, but not the variable intake manifold length. looks like the 3.4 intake

[@modeverything1]

Yes I believe around 2009 GM got rid of the variable runner plenum and used the lz4 style.

[@jeremyb4493]

I got an upsized MAF sensor and throttle body along with an autocal setup for my 3.9 work van last year....if work slows down and if Overkill ever responds to my emails maybe I'll get it all setup lol

[@modeverything1]

Nice! Let me know how it works when you get it done! I'm going to have to get a different MAF for mine as well.

[@jeremyb4493]

@@modeverything1 I've been trying to contact the owner but no replies the last few months. I sent my existing engine and tranny tunes along with the datalogs, just waiting on a response. He's pretty much the premier 3.9vvt tuner, located in Canada. The 3.9 LZ9 is a great, smooth, punchy engine, I love it!

[@overbuiltautomotive1299]

dad just bought 2 of these i am now thinking of just junking them impalas n doing rwd cars both have 3.5l run great i wish i never seem them really auction fervor i guess lol

[@modeverything1]

Nice! I may try a 3.5l in another project down the road! My 3.9 will probably end up in my truck after it does its time in the Alero! Lol

[@sosamontana8ten822]

I’ve Got A 3.9L but My 3.9 Has The LZ4 Intake 🤔

[@modeverything1]

GM stopped using the variable runner plenum in the last few years of production on the lZ9. Can't remember but i believe around 2009 in the cars they did this?

[@tiles3458]

@@modeverything1 why did they stop? Can I swap the intakes if I wanted to? From lz4 to lz9?

[@modeverything1]

No idea, guess they figured that it made enough power with out the variable runner plenum... you could but you you would not have any way to control the runners without swapping the harness and pcm.

[@AJKMonkey]

I have a 2007 3.9 with the Lz4 intake