I built a 408 and have nothing but problems with the heads lifting - I only have 1100 miles on the motor and have pulled the heads 5 times. I have looked in to every reason that this could be happening - a builder at a shop near me seams to think that the CAM is the problem.

The specs on the CAM are as follows...244/ 248 651/ 615 116. The builder from this other shop and the shop re-doing the heads are saying that this CAM is creating too much cylinder pressure. My issue is that the Tuner and my builder say that this CAM should work. To add suspense - two different guys at CompCam can't agree - one says yes, one says no.

So, with that being said - I'm going to have to ask for the help of others. Here are the engine specs...cast iron 6.0, Callies crank, bore 30 over, stroke 4", -30 cc pistons, stage 3 heads 70 cc - compression should be around 8.7:1. ATI twin intercooled 15 psi, ARP pro series studs.

Here is the CAM that the guy doing my heads recommended (I think it is too small) - 222/ 230 566/ 572 114+2. The CAM that I like is...232/ 236 591/ 601 114+2.

I'm looking to make over 700 rwhp, if possible. Need professional input...

 

I have never heard of a cam causing the heads to lift. I know high boost is capable of causing it but I see you are only running 11psi...I think that the 222/230 cam will be much too small for that motor and the 232/236 seems a little on the small side as well for 408ci. Maybe someone with more knowledge on FI and cams can chime in because I've never heard of heads lifting at 11psi...

 

.651/.615 lift? is that right

 

Correct, but I have had a lot of problems with this setup. I need help with which cam to pick. By-the-way, I'm runing 15psi now.


Someone please help...

 

Assuming you are using ARP head bolts and a quality head gasket, are the STG3 heads shaved at all? At the high lift you mentioned a shorter push rod might be in order, especially if the heads are shaved.
The cams being recommended sound way too small for your 408, mainly the duration IMHO. Stick to a .240+ duration and definitely keep the LSA at 114 or larger for your turbo application. The lift at or lower than .600 should be sufficient.

 

I thought he was supercharged?

 

Yes, it is supercharged. And the heads have been shaved .006 (thousamdths) total off the 5 times - a little each time. The combustion chamber is being adjusted to compensate for the milling.

I would like someone to give me the specs of a cam that someone else has had sucssess with on a similar application - I don't want anymore experiments.

 

What kind of gas are you using? Also what gasket? What's ur timing? I've had heads lift when there was detonation. And I've had heads lift with the 6.0 heads. Not sure why but when I swapped to ls1 style heads it was fine. Weird. What kind of head lifting are you getting? Pressure in the coolant or a blown head gasket where coolant is coming out the side of the head?

 

Don't think the cam is the problem man. People have used alot bigger cam than that and not lift.

 

The cam is not the problem. If the heads have been milled each time, them the deck of the block is not flat. That is most likely the problem.

If you are running 15 pounds of boost and are getting the heads reworked, I would defiantely have them o-ringed.

Keith