Heads and cam how much will it reduce boost
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Tire Smoking Tranny Blowing Director
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From: Barto PA
Heads and cam how much will it reduce boost 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
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
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.......
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.......
TECH Apprentice
Joined: Feb 2014
Posts: 328
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From: Baton Rouge La
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
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
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.
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.
