AAM Intake Manifold Q
 

Yes I know, there's a ton of info on it and I've read about it. We actually experienced approx 35 hp loss with the manifold so originally took it off and went with the stock intake manifold. HOWEVER, if I'm able to run more boost (20-24lbs) safer, I'd rather go that route and lose the 4% hp. Has anyone actually had issues with their stock manifold cracking or failing?

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Ask Seb what he thinks. Headgasket's start popping at 24psi of boost even if you have a RJM closed deck block and ARP 625's. Not sure how your motor is built but I would be more worried about that. Have you look inside the manifolds runners? You may find some casting flaws that need to be cleaned up. I ran 22 psi sparingly with no issues.

yep! Have Seb Scheduled for 2/13 for a full tuning visit. JMS did a great tune but there's nothing quite like having the "godfather" of all Z's having a look ;)

The JMS Stage 2 Shortblock build included JMS Spec CP Pistons/Carillo Rods, ARP Mains Studs, New Main, and Rod Bearings.

Did have the Cosworth Head Gasket added during the build but again always like to get his input. I'll probably just bring the intake manifold with me and have him take a look at it.

I am in agreement with Spooler. That manifold is only good if it is ported and polished. You would be better off doing a GTR manifold conversion. Just Spooler pointed out the issue is head gasket problems when you get above 18 psi which is long before the upper manifold becomes an issue. The oem manifold will start to fail at about 25 psi. My two cents, don't fix what's not broke!

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Do you have a closed deck block and what head studs were used? I am just asking to help prevent you from doing a blunder like I did. Seb is going to grill you anyways. LMAO.

Sorry to thred hijack what comp ratio are you guys running on your fi builds ?


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I run E85 so I stayed stock compression ratio at 11:1.

This is EXACTLY what I was looking for! Read on a previous thread when I was researching AAM, that OEM manifold started to fail at anything above 20lbs and that's what started my brain going haywire.

Copy that!

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Yep, closed deck option added, ARP L19 Head Stud Kit

As spooler mentioned there seems to be quite a few running different compression ratios. I'm running Wiseco Piston 9:1

I wouldn't do a GTR manifold conversion. The runners are too long and will cause issues in the midrange.

sometimes reading previous threads is a great thing, othertimes it starts a spiderweb of thoughts and worries. lol

Never heard of a stock manifold failure. Im sure it will eventually let go if you keep increasing boost pressure.

Your signature says youre running 800ftlb torque.. that is approaching (if not well-in) the danger-zone for VQ headgaskets. You could be an exception. But if you are looking to stay on the safe side of things, I wouldnt be worried about your intake manifold I would be worried about your headgaskets.

700ft/lb at 4550 RPM and mine were done. It appears the higher the RPM the peak TQ is, the lesser of a problem it is.

There could be some correlation, but I would be surprised if its extremely significant. Perhaps there is some resonant frequency or something occurring somewhere in the upper range that is rocking the cylinders. I would say that torque output is a far less convoluted indication of cylinder pressures than horsepower (torque at higher RPM) or boost levels.

Just because yours failed at 700 doesnt mean it couldnt hold 800-900-1000, or could have failed eventually at 600. Dont forget the fatigue and wear factor. Just like we can run a stock engine at 800 for a while... it will eventually fail, but when it does, you might only be running 600 at that moment.

Actually there was a guy on the forum several years ago Hojin and he had his manifold fail at least twice at 25 and 26 psi. I believe he was at 9:1 compression.

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Compression ratio wouldn’t make a difference. 25-26 is pretty high for a VQ, as they will generally be nearly 1000whp by then if the turbo system is staying efficient. Probably an exceptional case. Seems like 1000hp is right on the tipping point in more ways than one.

Agreed, and that is what he was pushing.

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Yea as Bob (hotrodz) mentioned, if it aint broke, don't fix it. lol. I was trying to fix BEFORE it broke but it sounds like many are having great look with the OEM manifold. Really appreciate the feedback all that the stock manifold can hang

Wouldn't the closed deck and the Cosworth upgraded Head Gasket help with that?

I miss Hojin! Dude became a Dad and then *poof*. lol

I hadn't realized he had his manifold blow, wonder what he did to correct the issue. I'd imagine if it did crack, it's not a devastating repair.

They may help or extend the life of the headgasket seal, but we have discovered they are not an end-all fix for the 1000+ HP VQ. They are still letting go in that power range.

Bob sold him his GTR manifold upgrade a long time ago. LOL
As far as the Cosworth head gasket. There is a better quality one out there. Seb knows which one it is. I gave that info to him and he ordered one to check it out. He liked it from what I gathered.

When my motor was built I was told that Cosworth discontinued the VQ head gaskets so I had to get Cometics. When I had my boost cut issues , I was spiking 27.3psi and after going back to a lower map at 18psi there was no problem. As for the question of compression ratio I'm one of the few tweeners running 10:1. I'll say again I low key wish I had gone with 11:1.
And for sure Seb is gonna grill you to death about the build. I was legit panhandle begging, complete with puppy dog whining to get him to give me 21psi and it did'nt help that the gf was sitting there reading and supervising my response to his email. GF: "You don't argue with Seb, he said that's enough so you're done!!!" Me ( In my Slingblade voice ) : "Aight den."

He never recovered after the last failure. He said he was going get the car up and running again and then he had another baby.:bowrofl:

Hopefully he still has it and didn't sell it.

We talking whp range or base? Really liking being able to keep the Z at that 875whp Mark. It’s so beautiful. Lol

Since its a gray area you could consider it either/or. 875whp is beyond what some cars have lost headgaskets at already.

Just be aware, it can cost you 20k if a headgasket let's go and a long wait. You may get lucky and have no block damage which means it will be cheaper if you want the same result. It's a crap shoot.

Ya its very hard to say. Nobody has pinpoint a root cause of the failures yet. There is a handful of suspects, but none that are really standing out. We will figure out more in time, as more people seem to want to push higher power lately... or at least those who are, are being open about it and sharing information. Who knows, you may be in the clear. There could be some factor or "magic" combination in your engine that does the trick. So I/we arent trying to scare you so much as just warn you that so far, everyone else on record is having issues in that territory. Most people, including me, have only had a single headgasket failure occur in our own hands. So the examples are still few.

I asked Seb about different setups that I would be safe at. His answer was he just didn't know. Nor do I. My next build could still not be safe. I have no idea. I do have someone that is willing to help me through any issues if they arise. That's a rarity in itself. Am I nervous about it. Sure am. Do overs aren't cheap.

Dyno graph my man??????