Cool28

iTrader: (2)

Well I purchased a f1a and then decided since I have 317 heads might as well put them on as well. Since I'm putting heads on might as well do a cam and then replace oil pump lifter timing chain etc lol.

Originally this kit was set to make 8 psi on a stock motor. So I'm wondering how much lower will my boost be with heads and can? I want to do once and done so would like to know if I could run 12 psi on h/c with 93 oct or just stay with the pulley I got on the s/c

Compression ratio should be around 9.7to 1 with these heads

SwampWS6

iTrader: (7)

Not an expert in FI, but from what I learned so far with my FI build you prolly would be safe up to 15psi or more. 9:5 - 9:7 is optimal CR for those motors so cram the boost in their!

Im running 10:5 CR and Im limiting myself to about 10psi until I get better at tuning. So your 12psi should be more than fine.

Someone please chime in if they think Im wrong.......

Kip Fabre

Kind of a question that could go a few way’s. A cam/head change could drop the boost depending how much more overlap you have. It will cause the boost to go right out the exhaust .More intake flow or larger runner volume can drop the presser. Cam timing can drop the presser. Even if the boost will drop you still may have enough boost to maximize your combination. Meaning if you have a compression of 9.7 with a 6 pounds of boost with the better heads and cam change for a given rpm you may only need 6 pounds of boost. Look at it like this you could have 2 cams one will make 8 pounds of boost and make 600hp the other makes 6 pounds of boost but will make 630 hp. So the highest boost does not make the best power on all combinations.

Sales@Tick

iTrader: (3)

Sometimes dropping boost pressure with a larger cam and better flowing heads to make more peak power is not the best way to do it.

Dropping pressure with a larger cam or cylinder head and keeping airflow rates the same or greater will normally drop compressor efficiency. This heats up the incoming intake charge more, and power cannot sustain as far into the RPM range if the compressor is less efficient.

I would rather a customer need to run more pressure(boost psi) to achieve a given power number. Note that this is not always true.

9/10 times with this scenario(mainly with larger displacement V8 engines) running more boost for a given power number the compressor wheel will be more efficient. Meaning a smaller cam can be used to make more torque and bring boost on sooner. The compressor wheel being more efficient will then carry that higher torque figure further into the RPM range as the wheel stays efficient longer. This can make more peak power and more average power.

Larger cam and larger heads(or higher flowing) is not always best for a turbo combination.

The turbo being used and keeping it efficient as long as possible is the most important part of designing an induction/valve train package for a turbo engine.