Been a bottle fed truck for numerious years but going a new direction. My motor is a hair over 11:1 compression. i know for FI you want considerably lower. how low do i need to be? The motor is already forged and i really dont feel like sending back to cali to be redone. Im running LS3 heads on it right now with 65cc chambers. I was thinking my only option is 317 heads. I just hate to give op the flow of the better heads. Will the long run gain be better and worth it?
Slowest in Oklahoma...
Ideally need about 8:1 - 8.5:1 compression. But there are some guys running higher with rear mounts or smaller front mount turbos. Might wanna pm some members who run turbos. Im lookin to run twins on my truck, soon as I get my $ right to start piecing it together
11:1 is pushing it. Lowering it to 317 heads would be a great move. Don't worry about the flow with FI you are forcing the air through. You could sell your other heads and do just fine.
2006 Superior Blue Trailblazer SS AWD, Stock as a rock
Sold: 2002 GMC Sportside Denali front end with a 2002 LS1, FLT level 5, Yank 2600, Trick Turbo, T76, Nelson intercooler, 60LB injectors, Warbro fuel pump, Eaton locker, Magnaflow, 3.42, Nelson Performance Tuning (speed density).
Sold: 1981 GMC LB RC 1500 2002 4.8L 4L60E 12 bolt 3.73 Richmond Lock Right AC PS Nelson Performance tuning
just because youre pressurizing the intake doesnt mean that head flow isnt important... it might not be quite as critical but it definitely makes a difference!!!!! you will be able to make some power with stock 317s but a good port job would still be highly recommended!!
01 Silverado
speed sometime on ls1tech ive looked this up many times , and looking towards to having a fairly high compression boosted setup probably at end of next year, if i can ever get what i have now off jack stands lol
high compression less boost higher octane.. response is at a drop of a foot !!
Simple: 408 on steroids!
single digits coming soon!
ideally you want, the highest compression you can run without knock so it will spool almost instantly. That all depends on octane, boost and chamber design really. idk if i would go as low as 8.0:1 but i would keep it 9.5 or below. Maybe find a set of 317's for cheap and send them off to get a mild port job and get some bigger valves in there, then sell your ls3 heads and intake to recoup some $
04 RCSB 5.3, Homemade 80mm FM, TU1, TH400
That's actually what iv been talking to a guy about. Leaving compression and running e85. Mines on jackstands to. It's been up there alot lately lolOriginally Posted by skeet
speed sometime on ls1tech ive looked this up many times , and looking towards to having a fairly high compression boosted setup probably at end of next year, if i can ever get what i have now off jack stands lol
high compression less boost higher octane.. response is at a drop of a foot !!
Boost the 11:1 it will do great. I have done both, if your already forged, you will be fine. Just my .02
Boost is an offset for compression. Final compression is where the power is at. An 8-1 engine will need a lot more boost then an 11-1 engine to make the same power. The lower the compression the lazier the engine will be while not in boost. To offset that you can up your timing while cruising but only so much.
The higher the compression the better your fuel, timing, and parts need to be. And you have to keep your air charge cool to cold.
If you are good with tuning you can run higher compressions with great results. If you miss it; it will eats itself up with knock.
Keep an eye on air fuel, air temp, fuel quality, (meth adding), and timing, and you should be fine.
Myself I am at 9-1. But our plans are probably different then yours. Not much street driving for me.
very good info, thanks for sharing!!
thats pretty much where i'll sit! already forged
dunno but the thought has been in the back of my mind ever since the dang mishaps i been having screwing with this NA crap lol!!
been doing alot of reading, dont plan on daily this truck much anymore !
Simple: 408 on steroids!
single digits coming soon!
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