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Discussion Starter · #1 ·
Hey guys. I have a turbo LS combo that’s the power seems way off to me and lazy. I’m stumped. Been through the whole car.

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. And upwards of 120 on some first pumps.
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 discouraged 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
715whp

6.0L 10.0 CR 243 heads.
whipple 3.0 tremec t56
7.0 psi 17-ish degrees
550whp

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??
 

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You verified TDC with a piston stop?? Cam was degreed in correctly and at what ICL vs the cam card?? Leakdown is pretty high for a fresh iron block. Was it torque plate honed?? What did engine initial break-in consist of??
 

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Your other combos didn't have a TH400 and a 9" in them. If everything seems correct and you just don't like the dyno numbers... should probably run it down the track. Some cars are just not dyno queens but turn perfectly acceptable times. This motor isn't exactly an apples to apples comparison either, with the low compression and short runner deal.
 

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Discussion Starter · #4 ·
I agree the heads aren’t great. It’s the “average 6.0 LS” that everyone builds.

yes camshaft was degreed correctly by me.
ICL was correct and matched the card.
I can only assume it was Tq plate honed. Engine was originally machined and built at another shop when it was the same long block with a carb and NA.
it came to me for a “tick” and I found 1 trunion was torqued on the round side, not the flat. And it beat up the valve tip a little.
i fixed it , we the through the entire engine to verify everything, bearing clearances, degree camshaft, touch up valve seats, installed heights etc etc.
and customer had me do the turbo kit, efi etc etc.


break in, it was fired and up to operating temp, and checked for leaks.
Had driven break in oil, BR40 based on clearances.

Driven twice for about 4-5 miles each time to get a couple Heat cycles on the new rear gears.

after that trailed to the chassis dyno and made some pulls to break it in. Decent load, allowing for decel etc.

doesn’t smoke,catch can breathers are clean and the cans are empty.

I feel the motor is sealed up real well. Runs excellent

I really want to send the converter back for inspection. It’s just a pain and ties up a shop stall.

I will drive it and see how it feels on the street. And take to the track maybe first before I tear the converter out.
I’ve just never had any combo I’ve built disappoint me.
 

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Dyno should be able to tell you converter slip on the gear ratio vs mph setting.....at least a ball park. Does it feel way loose?
 

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I agree with TurboII on verifying TDC with a piston stop. A timing mark that leaves you even 5 degrees retarded will knock off a lot of power.

I always wonder about leakdown and compression numbers when I hear what others have and the comments on them. I have 2 identical SBF engines (9.5 compression ratio) that I have down numerous leakdown and compression checks on over the last 10+ years. I do my leakdown and compression tests with the engine at ambient temperature so the numbers are "off" compared to the numbers if done with the engine at least warm.

Results for me are normally 85-90% on the leakdown and 115-120 on the compression test. Based on what I hear from others my engine should be puffing smoke, burning oil and not making good power. Yet I take the car to the track and my 3500lb car runs 8.80 at 158mph with 18lbs boost like a clock. Turn it up to 30lbs and it runs 7.9x at 175mph.

This is not a challenge to anyone else's numbers or what the numbers mean, just observation of my data that has been consistent over the last 10 years. I just wonder if leakdown and compression numbers are like dyno numbers - they only numbers relevant to your combo that should be "consistent" between each cylinders are good to keep track of for comparison to future tests to identify problems.
 
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85 percent? Is this checking from 100 lbs pressure and it shows 85?I cant imagine anything having 85 percent leakage and runs at all?
 

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Discussion Starter · #8 ·
On the dyno the converter seems super tight to me. I’ll street drive it tomorrow afternoon or Monday when the rain quits here.
Cam was degreed, and I did verify TDC this week on it. Twice. Both times same result. Then checked/ set static timing in the ecu accordingly.
 

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On the dyno the converter seems super tight to me. I’ll street drive it tomorrow afternoon or Monday when the rain quits here.
Cam was degreed, and I did verify TDC this week on it. Twice. Both times same result. Then checked/ set static timing in the ecu accordingly.
Take the up-pipes off and run the engine n/a? If you're starting with a weak base power number boost can only get you so far....just an idea.
 
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85 percent? Is this checking from 100 lbs pressure and it shows 85?I cant imagine anything having 85 percent leakage and runs at all?
Using my setup, the supply gauge reads 100, the "leak" gage reads 85 so the leakage would be 15%. Either way makes sense depending on how you look at the numbers. In my case 100 on the leak gage would be a perfect 0% so my typical numbers are usually 10-15% leakdown.

Unless there is "something wrong" going on I usually don't think twice unless the number drops below 80%. Usually I'm doing this test to look for or confirm a head gasket leak or some other problem. Once I found a cylinder at 50%. It had a leaky intake valve but ran fine up to 14lbs boost. Any boost above that it would pop going down the track. I spent a few hours trying to fix an ignition problem until I finally found it with a leakdown test. Now I have EGTs on each cylinder and watching those numbers. They will point to problems quicker than anything else.
 

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That sounds like a roughly 400 crank HP n/a combo. With 7.5 reason says it would be roughly 600 hp. How does the timing look on the strap? Someone mentioned testing it n/a. Might be a good idea. Maybe the trans and converter are working against you.
 

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Interested in this, as almost identical to my new build, except stage one cam. Guessing you are reading the plugs. What size crossover pipe. Sometimes I wonder about dyno numbers, as opposed to actual results. They say the Holley manifolds are good to 1000 HP, I think Steve Morris has pushed them past that.
 

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I know when I installed a PTC converter in my ride the car slowed down pretty big time...just too tight. And that was MY fault for overestimating how much power I was making when consulting PTC. Ended up putting the old sloppy cheap converter back in and car felt great lol.

If it feels too tight now, it probably is
 

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Discussion Starter · #14 ·
Yes. I have been reading the strap. On the pump gas tune and 7-7.5psi I was at 20 degrees. To make 465whp.
22 degrees only made 3-4 more hp. So I put it back down to 20. Just seems like a lot of timing to me.


I know 400’s will soak up some power for sure
The cross over is the stock Holley 2.25” one.

I’ll bet the converter is too tight. It’s. 15-0.
I’ve been using PTC for 8 years and have never had one be wrong out of the box. But I guess I also over estimated what this combo could do based on “what everyone else on the internet” was making with similar combos.

I’ll try and test drive it today.
 
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