317 vs 862
317 vs 862 Hey all, I'm a LS newb coming from SBF. I've got a stock bottom end 5.3 and I was wondering in a boosted application if the 317 heads or the 862 heads would be best? I have both an they're off the motor so It makes no difference which ones I run.
Thanks
Thanks
My opinion is to run the 317's.
It will take less boost to make the same hp with a better flowing head(317's are a much better head). This is beneficial because the less boost yiu run, the less the compressor heats the intake air. This will make the engine less detonation sensitive at the same power level.
I personally would flat mill the 317's to try keep as close to stock 9.5:1 compresssion as possible
It will take less boost to make the same hp with a better flowing head(317's are a much better head). This is beneficial because the less boost yiu run, the less the compressor heats the intake air. This will make the engine less detonation sensitive at the same power level.
I personally would flat mill the 317's to try keep as close to stock 9.5:1 compresssion as possible
IMO if your on a pump gas setup 317's are the way to go. My 8.6:1 (317's with dished pistons) 5.3 made boost too quickly to be streetable. My current 10:1 5.3 doesn't feel noticeably different out of boost.
Last edited by Forcefed86; Mar 20, 2014 at 11:27 AM.
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Man I hate this statement. It's total BS. Your talking about 4% loss in NA HP. Thats like 13 flywheel HP on a 5.3. Missing 13hp sure doesnt make an engine "a dog out of boost". I'd bet you couldn't even feel a difference. And for the small hit you take NA you'll be able to run much more boost.
IMO if your on a pump gas setup 317's are the way to go. My 8.6:1 (317's with dished pistons) 5.3 made boost too quickly to be streetable. My current 10:1 5.3 doesn't feel noticeably different out of boost.
IMO if your on a pump gas setup 317's are the way to go. My 8.6:1 (317's with dished pistons) 5.3 made boost too quickly to be streetable. My current 10:1 5.3 doesn't feel noticeably different out of boost.
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Verdad Gallardo If you've had personal experience with both, I don’t know how you could feel that statement is true. A point of compression is not a game changer power wise on any engine IMO.
Man I hate this statement. It's total BS. Your talking about 4% loss in NA HP. Thats like 13 flywheel HP on a 5.3. Missing 13hp sure doesnt make an engine "a dog out of boost". I'd bet you couldn't even feel a difference. And for the small hit you take NA you'll be able to run much more boost.
IMO if your on a pump gas setup 317's are the way to go. My 8.6:1 (317's with dished pistons) 5.3 made boost too quickly to be streetable. My current 10:1 5.3 doesn't feel noticeably different out of boost.
IMO if your on a pump gas setup 317's are the way to go. My 8.6:1 (317's with dished pistons) 5.3 made boost too quickly to be streetable. My current 10:1 5.3 doesn't feel noticeably different out of boost.
Man I hate this statement. It's total BS. Your talking about 4% loss in NA HP. Thats like 13 flywheel HP on a 5.3. Missing 13hp sure doesnt make an engine "a dog out of boost". I'd bet you couldn't even feel a difference. And for the small hit you take NA you'll be able to run much more boost.
IMO if your on a pump gas setup 317's are the way to go. My 8.6:1 (317's with dished pistons) 5.3 made boost too quickly to be streetable. My current 10:1 5.3 doesn't feel noticeably different out of boost.
IMO if your on a pump gas setup 317's are the way to go. My 8.6:1 (317's with dished pistons) 5.3 made boost too quickly to be streetable. My current 10:1 5.3 doesn't feel noticeably different out of boost.
TECH Apprentice
Joined: Sep 2013
Posts: 355
Likes: 19
I would like to hear from others that have run both. I talked to a guy that switched from 317's and went to 862's and said it ran better. He also said it was a dog with the 317's on low end. Myself, I have no experience, so I can't say either way. Some say to put 2 in valves in the 862's and clean the ports and valve pockets up and they work great on boost. Anyone out there with dyno results from both?
Yes, but I am regurgitating it from a book written on the subject with data to back it up. As well as direct personal experience. This is not the same as mimicking what you read on a forum where anyone can throw out these so-called "facts" with no personal experience or knowledge on the subject. Yes depending on the cam and initial compression and many other things results will vary. I did say "about 4%" and that is a very commonly accepted "rule of thumb" for 1 pt of compression. Especially when dealing with OE engines with typical compression ratios, small cams, reasonable RPM etc...
Last edited by Forcefed86; Mar 19, 2014 at 09:36 PM.
Yes, but I am regurgitating it from a book written on the subject with data to back it up. As well as direct personal experience. This is not the same as mimicking what you read on a forum where anyone can throw out these so-called "facts" with no personal experience or knowledge on the subject. Yes depending on the cam and initial compression and many other things results will vary. I did say "about 4%" and that is a very commonly accepted "rule of thumb" for 1 pt of compression. Especially when dealing with OE engines with typical compression ratios, small cams, reasonable RPM etc...
I guess my personal experience might hold up here if you want to hear it and believe it:
4.8L with 317 heads = dog on the street
4.8L with 862 heads = snappier response and better spooling
This was with THE SAME TUNE, only adjustment was to the VE table to smooth it out.
T56 trans, PTE7675 turbo.
317 heads will make the motor a pooch, hands down.
I have done it and regret doing it.
All it did for me was waste time, head gaskets, money and a few months of trying to get the car to be more responsive
At the time, I wanted that "low compression high boost" set-up that "all the cool guys had"
Well, 9-9.5:1 compression + boost is awesome!
If the is right and you keep your timing within reason, no need to have an 8:1 motor or anything less then 9:1 for that matter.
4.8L with 317 heads = dog on the street
4.8L with 862 heads = snappier response and better spooling
This was with THE SAME TUNE, only adjustment was to the VE table to smooth it out.
T56 trans, PTE7675 turbo.
317 heads will make the motor a pooch, hands down.
I have done it and regret doing it.
All it did for me was waste time, head gaskets, money and a few months of trying to get the car to be more responsive
At the time, I wanted that "low compression high boost" set-up that "all the cool guys had"
Well, 9-9.5:1 compression + boost is awesome!
If the is right and you keep your timing within reason, no need to have an 8:1 motor or anything less then 9:1 for that matter.
Staging Lane
Joined: Dec 2011
Posts: 63
Likes: 7
Man I hate this statement. It's total BS. Your talking about 4% loss in NA HP. Thats like 13 flywheel HP on a 5.3. Missing 13hp sure doesnt make an engine "a dog out of boost". I'd bet you couldn't even feel a difference. And for the small hit you take NA you'll be able to run much more boost.
IMO if your on a pump gas setup 317's are the way to go. My 8.6:1 (317's with dished pistons) 5.3 made boost too quickly to be streetable. My current 10:1 5.3 doesn't feel noticeably different out of boost.
IMO if your on a pump gas setup 317's are the way to go. My 8.6:1 (317's with dished pistons) 5.3 made boost too quickly to be streetable. My current 10:1 5.3 doesn't feel noticeably different out of boost.
Saying that, I wouldn't hesitate to run one with stock 862's if I didn't already have the 317's ready to go.
Man I hate this statement. It's total BS. Your talking about 4% loss in NA HP. Thats like 13 flywheel HP on a 5.3. Missing 13hp sure doesnt make an engine "a dog out of boost". I'd bet you couldn't even feel a difference. And for the small hit you take NA you'll be able to run much more boost.
IMO if your on a pump gas setup 317's are the way to go. My 8.6:1 (317's with dished pistons) 5.3 made boost too quickly to be streetable. My current 10:1 5.3 doesn't feel noticeably different out of boost.
IMO if your on a pump gas setup 317's are the way to go. My 8.6:1 (317's with dished pistons) 5.3 made boost too quickly to be streetable. My current 10:1 5.3 doesn't feel noticeably different out of boost.
A 317 head flows more than an 862, period. 1pt (or less if it's a flat top 5.3) of compression is not enough to tip the scales in the 862's favor.
No way there is 40ftlb difference in two 5.3’s stock for stock with a 317 head swap alone. Also most aren't pulling tree stumps with their turbo LS setups and could care less about the power curve under their stall RPM. As far as an "RPM low enough to be out of boost". What auto setup has any kind of RPM band out of boost at WOT over the stall speed? Are we talking about a 200-500rpm window? Is that window what makes the engine a "dog"? I'd see positive pressure WOT as soon as the converter "flashed".
Last edited by Forcefed86; Mar 20, 2014 at 10:15 AM.
