kwiksilverz

Ok, I have an 05 GTO with a 9.4:1 bottom end and an APS TT kit. I am running ~17-18 psi with 19 degrees of timing (alky kit too) and if I drive it hard, it will push coolant. I am using stock GM MLS head gaskets with ARP bolts and stock heads. I am curious if anyone has any ideas here. My thoughts are-
1) I am only running a 2.5" cat back- too much back pressure?
2) just the typical LS1/2 sealing issues at these levels and I should try a different gasket
3) I had a couple "oopsies" when getting the tune dialed in, wonder if it could have burned a gasket? Though it does not appear to have symptoms of a blown gasket, if I drive at lower psi levels, it is fine.
4) stock heads just flexing too much no matter what I try?
5) any/all of the above combined.

The car runs great, does not over heat, etc. I can drive it 3000 miles without even thinking of checking the coolant, but if I drive it hard, it will push out of the over flow. It will also hold quite a bit of pressure over night- if I pull the cap off the day after running it hard, there is quite a bit of pressure there, further proving that it is certainly leaking compression into the cooling system.

What gasket recommendations do you guys have for a setup like this? O-ring isn't really an option since I am not pulling the block. Anyone have any experience with the Cometic Phuzion gaskets? From what I read of Phuzions claims, they seem like they should fit the bill nicely, but would like to hear from others before spending ~$500 on a set- ouch!!

Noyzee

iTrader: (37)

get felpro mls gaskets, get copper spray and spray them, be sure to get the surface (head and block) CLEAN!
you may want to look into arp l19 head studs you can tq them way down.
stock heads also have the small deck and dont seal as good.

hope this helpsabit

JMBLOWNWS6

iTrader: (17)

Yup 30 to 40% more clamping force. The studs are on backorder lately. Thank god I got mine when I did. There not cheap. Your looking at $500 for the set. But its like have 1/2 head studs

MIGHTYMOUSE

iTrader: (59)

just put new gaskets on and no more oopsies.. they are always the reason for me. and as a personal rule of thumb anythign over 17psi i mix in race gas.

kwiksilverz

Thanks guys. Mightymouse- I was wondering if maybe one of the few "hiccups" was what caused it, but it seems fine at low boost (under 10 psi) and then does it at higher levels, so I was leaning towards it being the heads lifting. Doesn't hurt to pull the heads and check things out though, the GTO is easy to work on. As for race gas, I have not been getting any knock with the alky, though I do run it in the 11.2 range on the street for an extra margin of safety. The funny thing is even on the runs where the tune wasn't right, it still never knocked, just went pretty lean. Do you run stock gaskets? What heads? I know the stock heads don't seal as well either, as mentioned above also, so I am wondering if this is just going to be the nature of this thing unless I do different heads?

Has anyone ever run the Phuzions here? I'm curious if they really do help in situations where the heads are lifting?

kwiksilverz

Hmm, what do you torque those studs to? I was told not to go too tight or you'll start to distort things? I just used the bolts and torqued them to the ARP specs (think it was ~70-75 or so?). I wonder if i should try a re-torque, but I can't see an MLS gasket needing it.
Joe

MIGHTYMOUSE

iTrader: (59)

doesnt really matter. once you lift them once they will lift easier / earlier the next time.. but thank goodness they always seem to seal back up out of boost (MLS)

kwiksilverz

OK, so then you are saying that the stock heads and gaskets *should* seal at my levels (17-18 psi, possibly up to 20 psi, 800/whp/800tq) though if all is good in the tune and such? If so, I'll just get another set of stock gaskets for it. I don't have a problem with it pushing if that's just the nature of things, but if there is a solution, I'd rather go that route. Thanks bud!
Joe
PS- should I keep the ARP bolts, or do the studs have more clamping force?

z-ya

iTrader: (1)

Use studs,ditch the headbolts,use a high quality gasket on a pristine sealing surface and hope.

kwiksilverz

As for pristine sealing surface- I can't get the block decked or anything since it is in the car, but it is as clean as it can be with no scratches, gouges, etc. Maybe I'll get the heads resurfaced just to be safe.

So the standard ARP studs have better clamping than the bolts?

As for "high quality" gaskets- I have been trying to get a recommendation. I would like to know what the recommended gasket would be in this application and what kind of experience people have been having with them- stock, the SCE Titans, Cometic, Cometic Phuzion, etc. Now, as for the "hope" part- does that mean that there may be issues at this level anyway? I have been playing with turbo cars for years, but the LSx turbo stuff is new to me. Thanks!
Joe

machinistone

Clamp load.

You need studs and new gaskets. Get the heads surfaced at at shop where they know how to get the Ra correct for MLS gaskets. Slap a set of Cometic's and ARP studs and you will be fine.

You also may have some tune problems that are causing the cylinder pressures to spike too high and push pressure through the gasket.

kwiksilverz

I never really had any tune issues timing wise, so I don't know what could push the pressures up- but I did have a few lean mishaps. I am running a stock cam and only a 2.5" cat back, so I was worried that may not be helping things much as for pressure.

As for finding a shop around here that knows anything other than setting the heads up and milling a couple thou off, it isn't going to happen . Any advice on what to tell them so they get it right? Which cometics are you recommending- the standard ones or the Phuzion? I cringe at the thought of ~$500 for a set of head gaskets, but if they work that well and I won't have to worry about problems, it is worth it for me. Thanks for the advice!
Joe
PS- any advice on where to get the Cometics?

Noyzee

iTrader: (37)

with the basic arp studs i go to i think it was 70 or what ever arp says, but with the l19 studs its like 85, and with my new lsx block im going to go 90

NA$TY-TA

iTrader: (21)

Dont waste your $$ on those $500 gaskets...
The GM MLS gaskets have went pretty far....
My last set started to weep a little under boost and finally blew last time at the track.....20+ psi...
Ill be doing what you dont want to do.......
O-ring the block and heads w/ copper gaskets...

kwiksilverz

NA$TY- it's not that I "don't want to" o-ring the block and heads, it's that it's all together and in the car, so I can't realistically o-ring it. I'm not really in the mood to tear the whole thing apart right now . What head studs are you running at those levels? What is your typical boost setting? I am aiming for ~20 psi, but the thing is my car is driven almost every day, so I need something that will hold up to daily punishment . I guess i can always turn the boost down for day-to-day stuff and crank it up when it's time to play, but I kind of like it "as-is, where-is" and ready to go all the time.
Joe

stevewix

I've had no issues whatsoever since using fel-pro's new gasket. It's important to have both surfaces totally perfect as well.

kwiksilverz

do you have the PN for the fel-pros you use? As for "totally perfect", well, it is the oem deck surface but cleaned spotless before assembly. Heads, I'll get resurfaced for insurance while it is apart. Just really torn on gaskets. I agree about not wasting money on $500 head gaskets, but if they do what I need them to do (stock heads, 17+ psi, daily driven) with no issues, it would be worth it in the long run. I'm wondering if a majority of my problem is the ARP bolts instead of studs though. I'll get it torn down shortly and inspect things. I just don't want this to become a routine thing lol.

I heard the standard cometics are very picky about deck surface, is the oe surface safe for them, or no?
Joe

427

iTrader: (3)

The studs will be helpful if you keep changing gaskets! As for the OE surface, it is very nice but some of the newer machines can improve on it a bit. You will probably have a local guy that can cut them right, you just need to be sure he uses MLS gaskets. I like the newer Fel Pro MLS, they have held well up to 20 PSI in some engine dyno testing. I did blow the Cometic Phusion gaskets, but we tested above 25psi, they might hold 20.


Kurt

Pro Stock John

iTrader: (34)

If it were me I'd try the MLS head gaskets and keep an eye on the IAT's. Like Kurt Urban once said, keep the IAT's below 150F. I think your timing sounds a bit high (19 degrees) for 17-18 psi with alky and a 9.4:1 compression. Seems like you might be over the line of safe.

I'm running 8:1 348ci; A1 head studs, AllPro heads; 24-26 psi; C16 gas, 19 degrees of timing; 867rwhp unlocked T400; mls head gaskets.

If I ran 18 psi with meth, I'd personally start out at like 15 degrees of timing and would monitor what it's doing.

Jimmy P

iTrader: (177)

So does anyone have any more info on these? We are about to install a F1C on my 402, and I wouldn't like to be pushing water.