317 Heads on 99FRC?
Thread Starter
Burning Brakes
Joined: Sep 2008
Posts: 1,151
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From: Mechanicsburg PA
317 Heads on 99FRC?
I recently purchased a 99FRC with a modified motor. The previous owner gave a list of the modifications but one thing he left off is the heads. He told me in conversation that the heads came off a truck. "Why" I asked and the response was "they flow better". At any rate, when I look at the passenger side head, near the throttle body it is stamped with "317". Can anyone fill me in on what exactly these are and any pros or cons to them?
Thanks, Brad
Thanks, Brad
Race Director
Joined: Oct 2002
Posts: 16,477
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From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
They are 6.0l truck heads.
They are the large-chamber (71cc) version of the LS6 heads (which are 64cc).
Supercharger/Turbo guys commonly use the 317 heads to lower compression ratio, allowing for more boost w/o detonation.
If your car isn't boosted, while they will outflow LS1 heads, you have lost compression, and it's probably not a great upgrade for a n/a car.
They are the large-chamber (71cc) version of the LS6 heads (which are 64cc).
Supercharger/Turbo guys commonly use the 317 heads to lower compression ratio, allowing for more boost w/o detonation.
If your car isn't boosted, while they will outflow LS1 heads, you have lost compression, and it's probably not a great upgrade for a n/a car.
Race Director
Joined: Oct 2002
Posts: 16,477
Likes: 26
From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
There is one other possibility too, if you know anything more about those heads (like who did the work on them).
Patriot Performance used to use 6.0l heads, and weld up the chambers to a much lesser cc, and commonly sold them as "LS6 Style" heads. The reason being is the 6.0 castings are/were cheaper to buy than "real" LS6 heads.
If that is the case, then it's fully possible you would have more compression than stock.
Patriot Performance used to use 6.0l heads, and weld up the chambers to a much lesser cc, and commonly sold them as "LS6 Style" heads. The reason being is the 6.0 castings are/were cheaper to buy than "real" LS6 heads.
If that is the case, then it's fully possible you would have more compression than stock.
