Boost plus stock GT-40 = ?

[5liter]

Who is doing it? My car has the top end off of a 93 Cobra, and I wanted to know about head gasket issues. How much boost? I popped mine for the second time making 12 psi. The car is not lean, but several people have told me the stock heads don't have enough ass to hold it under heavy loads.

Whos doing what? Issues?

 

[sled]

get the heads checked, then buy ARP head bolts. what were you running your base and overall timing at?

 

[5liter]

I am running ARP head bolts. Base timing is 10 degrees. I also run a Crane TRC2 and two bar MAP. I have it set to pull 2 degrees of timing per pound of boost.

 

[Big Ben]

Curious on this, as a Helion is in my future.

 

[boosted306]

Get in contact with Bernard with www.Quicktimeturbosystems.com. He did a kit for a good friend of mine and he makes 444 on an 8lb spring. If I understand correctly the stock motors or GT 40 motors can hold an 11lb spring and a safe tune for right at or over 500 horses. I am going to let Bernard build me a kit soon and run 11lbs on a 351w d9ae casting. He knows his stuff and makes great kits. He has been super on informing me of all that I needed to know about boost and what everything can handle.

 

[LEE93COBRA]

Who is doing it? My car has the top end off of a 93 Cobra, and I wanted to know about head gasket issues. How much boost? I popped mine for the second time making 12 psi. The car is not lean, but several people have told me the stock heads don't have enough ass to hold it under heavy loads.

Whos doing what? Issues?

first, if base timing is set at 10 degrees and you are pulling 2 degrees for every # of boost, you are pulling way to much timing. Based off that you are pulling 24 degrees of timing out at WOT. IMO that is more than likely your problem because you only have 2-3 degrees of total timing in the car at WOT. Which will cause the car to run like shit. Adjust your timing retard box to only pull your timing down to 15 degrees or so of total timing at WOT. In other words change it to where you pull out 1 degree of timing for each psi of boost

 

[sled]

thats what i would do, but i would probably run a little more timing though. like maybe 18-20 degrees total. depending on how hot your AIT's are and your A/Rs.

 

[sled]

sorry, it posted twice for some reason.

 

[19COBRA93]

Some people have great success with GT40's and some don't.

I made 622 rwh with stock GT40 cast irons running 21 lbs of boost. I used ARP bolts torqued 100 lbs upper, and 90 lbs lower (this is way overtorqued), and Felpro 8548pt2 head gaskets. No O-ring'd block or heads.

The key is to not let it detonate. With the thin decks of these heads, they just can't hold the cylinder pressure that occurs with detonation. I used alcohol injection to resolve those issues.

 

[Kevins89notch]

first, if base timing is set at 10 degrees and you are pulling 2 degrees for every # of boost, you are pulling way to much timing. Based off that you are pulling 24 degrees of timing out at WOT. IMO that is more than likely your problem because you only have 2-3 degrees of total timing in the car at WOT. Which will cause the car to run like shit. Adjust your timing retard box to only pull your timing down to 15 degrees or so of total timing at WOT. In other words change it to where you pull out 1 degree of timing for each psi of boost

Thats the first thing I thought. I ran a 8psi vortech on my 89's stock engine. I set the initial timing to 12, and took about a little over 1 degree per psi. That put me right at or under 20 degrees total. I'm no tuning expert, but that wsa good enough for an 11.9, a cross country drive, and over a year of being my daily driver, and being beat on nonstop.

Curious on this, as a Helion is in my future.

:bowdown: I so want to do a turbo kit as well.

 

[carguy19]

Im running a bone stock cobra motor with the right injectors and a pms, 12 #s w and s trim.

414 rwhp 404 tq

 

[5liter]

Some people have great success with GT40's and some don't.

I made 622 rwh with stock GT40 cast irons running 21 lbs of boost. I used ARP bolts torqued 100 lbs upper, and 90 lbs lower (this is way overtorqued), and Felpro 8548pt2 head gaskets. No O-ring'd block or heads.

The key is to not let it detonate. With the thin decks of these heads, they just can't hold the cylinder pressure that occurs with detonation. I used alcohol injection to resolve those issues.

Thats what I was needing to know. I never heard any detonation, but it blew pretty good.

 

[19COBRA93]

Those gaskets are pure crap when boost is involved. However, you had some sort of tuning issue there, you may not have heard detonation, it's not always audible. Looking at that gasket, you definitely had some.

Now that I look at it more, it appears you lifted your head some too. You can see at the top of the cylinder on the gasket where the compression was pushing into the coolant jacket.

 

[5liter]

This is what it did last time.

 

[19COBRA93]

That's typical head lifting and real common with these cast iron heads. That's why I strongly suggest overtorquing the head bolts, and offset torquing the upper ones more than the lower ones by 10 lbs each. Which, I should note, helps but doesn't cure the problem.

 

[5liter]

That's typical head lifting and real common with these cast iron heads. That's why I strongly suggest overtorquing the head bolts, and offset torquing the upper ones more than the lower ones by 10 lbs each. Which, I should note, helps but doesn't cure the problem.

Can you recommended a better gasket? It am not going to o ring or anything, but is there one you have had good luck with?

 

[LEE93COBRA]

Felpro 9333's and please put some timing back into that motor. I am serious you have your timing so far retarded that it is contributing to your issue

 

[boosted306]

Get some cometic gaskets

 

[19COBRA93]

The only difference between the 8548's and the 9333's is the fire ring, which won't help your situation. Cometics/MLS gaskets are a good option, but again, you're getting head lift, which will happen with cometics as well.

I think you just need more clamping force. Make sure you use good lube on the head bolts, and over torque them a bit with the upper ones more than the lower ones.

 

[5liter]

I am de-boosting the car. With my wife about to graduate and all I just don't have the time or money. The blower is For Sale in the classifieds section.