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Discussion Starter · #1 ·
Hey guys. I have a turbo LS combo that’s making puzzling power. Maybe I'm
Asking for too much. It just seems way off to me.

6.0L -gen4 rod.
9.25 CR (wiseco piston 4.010”)
317 heads.
BTR stage 2 turbo cam.
Holley sniper intake.
holley cast single turbo manifolds.
holley HP efi.

billet wheel VS S480 turbo. T6 1.32 96mm
4” down pipe.
27”X4” A/A Intercooler.
th400 PTC 9.5” 15-0 stator
9” with a 3.50 gear.

we struggled On the dyno. At least I think I did.
on pump 91 making 7-7.5psi on wastegate spring it made 410whp to start and after putting 20degrees in it, it settled in at 465whp peaking at 6100.

iat’s from 80-95 degrees. Highest was 110 after a few back to back pulls.

on 100LL fuel and the boost controller on it made 20-21psi and we had 18-19 degrees in it.
it started at 680whp and after adding all the timing we made 750whp at 66-6700.

we tried AFR from 11.2-11.8 on both pump gas and 100LL. Didn’t make a huge difference.

the motor is fresh.
i checked leak down and stone cold it’s 6-8% on all holes.
compression is 155-165 on all holes with first pump being 90 minimum. Cold engine

checked and verified static timing twice it’s perfect. Dropped trans pan, fluid is like new and inside of pan was like new. No material in it, no dragging band etc.

I feel like it’s down 100whp on both fuels ??
I just feel like the tune, mainly timing and AFR if kinda crispy for the power we achieved. On pump gas we added two more degrees so 22 total and it picked up 3-4hp. So I feel 20 degrees was there limit on pump gas.

i feel this way based on other combos I’ve done also recently:

6.0L 317 heads fast lsxR stage 1 Morris blower cam in a 98 vette with a 4l60
Procharger d1sc air to air.
pump 91 and water meth (washer fluid)
13 psi and 16 degrees

6.0L 10.0 CR 243 heads.
whipple 3.0 tremec t56
7.0 psi 17-ish degrees

I thought the turbo combo would crush the blower combos. I guess I could put more spring in it on pump gas, dial back the timing and make more boost to get it closer to 550??

1,393 Posts
Discussion Starter · #4 ·
Cam timing is correct. I degreed it and matched to the card.

yes I agree. Disappointed.
next day on the dyno a 2006 vette 6.0 ls2 Stock intake , with camshaft and headers made 420whp.

1,393 Posts
Discussion Starter · #8 ·
Lifter preload is good. I’ll verify my notes tomorrow. Should be around .080”.
gm ls7 lifter.

msd plug wires. Excellent condition. Have about 1000 miles on them when the engine was NA last season.

Spark plugs were Br7’s up to about 680hp and changed to a -8 for the 750 pulls.
Gapped at .020”

coils are ls2/3 GM coils. They are used. Customer supplied them and were on the engine last season when it was NA and carbed also.

plugs looks good and decently even. Took one degree out of #7 and a 1/2 degree out of #3&4.

on spring pressure and pump 91 peak power was 6000-6100.
100LL and 20psi was 6700.

it has stock gm steel wheels on it for dyno and 26-27” cooper cobra. No issues with tire spin on the dyno. We have drag radials on order for the track of course.
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