LS3 Head gasket lift (Boost)

[CGT]

I am having trouble pressurizing the coolant system on my supercharged Camaro under boost. It is 11.5:1 with tvs1900(27,000 rpm blower speed) at 15-16lbs of boost. Stock gm head bolts, .036 Cometic mls gaskets, E85 fuel.

I'm wondering what peoples thoughts are on what will fix this. There are no signs of blown head gasket, and causes no issues under regular conditions. I've purchased studs for it, and am contemplating swapping the studs in, one by one without pulling heads. Any opinions on that? Will the studs fix the problem?

Or would a thicker MLS gasket with more layers be the fix? This is a world I don't have a ton of experience in. Any opinions welcome please. And no, a tunnel ram is not in the budget

[Frankshaft]

I would suggest biting the bullet and buying the custom aged 625 studs. They tq and clamp harder

[CGT]

I would suggest biting the bullet and buying the custom aged 625 studs. They tq and clamp harder

Custom aged? Like beef? I can only imagine the price. I feel violated for what I paid for these ARP's already. 350.00 for 20 studs is ridiculous to me. But I just want this thing fixed.

[user-17438]

Check your tune..

[CGT]

Check your tune..

Tune is nails, got a ton of time in it, but I thought about maybe taking some timing out of it just to see if it would fix the problem. No detonation at all. E85 is great!
I'm just getting tired of it making a mess and overheating every time I wanna have some fun. Thanks for the input

[user-23911]

It happens all the time with E85 and boost.
It's too much timing that does it. Too much compression too. You don't want 11.5 to 1.
Seen lots of engines come off the dyno with bent rods when tuners don't know how to tune.


Fancy bolts won't fix it because it's not a bolt problem.
It's too much peak cylinder pressure which distorts the heads and lifts them BETWEEN the bolts, not AT the bolts.

[CGT]

It happens all the time with E85 and boost.
It's too much timing that does it. Too much compression too. You don't want 11.5 to 1.
Seen lots of engines come off the dyno with bent rods when tuners don't know how to tune.


Fancy bolts won't fix it because it's not a bolt problem.
It's too much peak cylinder pressure which distorts the heads and lifts them BETWEEN the bolts, not AT the bolts.

Yeah, it was a NA engine that I was chasing power on prior to supercharging it, thus the compression and stock bolts etc. Interesting on the timing comment, that has crossed my mind. Thanks for the input. Do you have and idea or range of what you'd want to see in it for timing? Thanks again. It definitely doesn't detonate with the timing that's in it now. But that doesn't mean it don't have a bunch of peak pressure like you said.

[user-23911]

Maybe start with 10 deg total at 1 bar boost.
Then bring it up slowly.
9 to 1 CR would be better but with more boost.

[CGT]

Maybe start with 10 deg total at 1 bar boost.
Then bring it up slowly.
9 to 1 CR would be better but with more boost.

Ok thanks. It got 18 to 20 in it now depending on how much ethanol content the sensor is seeing. This problem arose when gping from 12 up to the 15lbs.

[ptuomov]

So is the case that the problems come from high peak cylinder pressure combined with a large bore area? If so, long stroke, small bore, lower compression, later ignition timing, and higher boost are the way to get a high power without putting too much peak force on the head.

[In-Tech]

Joe's right, it's not detonation, it's preignition. Ignition timing will probably not help. Lower IAT will. Alcohol content does help a detonation issue as octane is raised, however, as forgiving as it is, preignition is a non forgiving factor. If this is a non hydraulic app, decrease the lash and it will help cool the piston during overlap, increasing boost(engine restriction) will sometimes help too as it increases overlap cooling.

[ptuomov]

Joe's right, it's not detonation, it's preignition. Ignition timing will probably not help. Lower IAT will. Alcohol content does help a detonation issue as octane is raised, however, as forgiving as it is, preignition is a non forgiving factor. If this is a non hydraulic app, decrease the lash and it will help cool the piston during overlap, increasing boost(engine restriction) will sometimes help too as it increases overlap cooling.

I thought Joe was saying that it’s just the inherently too ridiculously high peak cylinder pressure with normal combustion and without pre-ignition and/or detonation.

Hard to imagine that preignition would not lead to detonation with the original poster’s engine. I’d guess you’d also hear/measure detonation if it would be suffering from preignition. You’d also be seeing some other more terminal engine problems than pressurized coolant...

[KnightEngines]

Seen this a lot with Subaru's, on E85 you can put enough timing into them that even without det/preignition they'll lift the heads, seal up again straight away after a pull.
It's not a tune issue, tune can be perfectly safe from a combustion viewpoint, just the pressure rise with the extra timing that E85 allows is too much for basic head clamping.
Fast pressure rise = HP/TQ, not a bad thing, just gotta hold them heads down!

With the new billet subi cases & using ARP2000 14mm head studs the tune can be pushed even further coz the heads don't lift, there has been no adverse affects (other than faster boost reponse & a buttload more midrange TQ) & teardown says everything is happy, it was never a tune issue, just a materials strength issue.

The next limitation in the line seems to be the head castings, they do lift/distort between the studs, but once the block integrity & clamping was sorted the threshold where the head castings are the limit became much higher. For drag racing it is now possible to push 40psi/1000+hp through them, but for endurance racing the reliable limit seems to be around 34psi & 850hp without going to exotic gas rings or other fancy sealing solutions.

You probably won't get away with just swapping in the studs, once the gaskets have crabon tracked they'll keep leaking under boost.
But thin head gaskets are a plus, not a minus - the less head gasket surface area exposed to combustion the better.

[CGT]

Thanks for all the suggestions. Yeah, i would think the knock sensors would pick the pre ignition up. But like I said this is a relatively new world to me. Whats the fix? Are head studs worth a try?

[KnightEngines]

Yeah, ARP2000 studs & fresh gaskets, give the heads a light skim too.

Ramp the boost in a little slower till you're sure it's good, or reduce timing till after peak TQ - either will work, which one better suits the combo & use is up to you.