BlwnTA

iTrader: (18)

First, the bad news

Got a few things worked out but ran into a problem that I'm looking for some help on. We could not pull the car successfully pass 5000 rpms.....right around 4800-5000 rpms it "breaks up" for a second or two. In effort not to hurt the new motor all 9 pulls were done up to that point hoping changes in fuel, timing, etc would clean it up. It got slightly better when I got the "rich" spot out of A/F chart but was still there. I'm lost. So are a few others I talked to today so I'm looking to see if anyone else has had this issue.

Here's the particulars:

It sounds like it misfires and it "bucks" slightly when it gets to that spot.

TR6 Plugs (gapped @ .030)
Thundervolt 10.5 mm wires
OEM LS1 Coils
A/F is between 11.6 and 12.1 from 3200-5000rpms
No Knock Retard recorded by Auto-Tap
Timing is at 17.0 at WOT
Motor only seen 10PSI before he got out of the throttle
Fuel pressure is 70PSI+ under boost
Oil Pressure was steady at 60+PSI

The SC Belt is and SDCE 8-Rib with a gatorback belt....it's set at about 12-13 on the indicator. I wouldn't think it's belt slip but I can't rule that out. With the factory ATI 6-rib it would do something very simliar at lower RPMS....so I need to look into that.

Now the better news

The numbers I did gather were...

500 ft/lbs of torque @ 3100 rpms

560 rwhp/628 rwtq @ 4700 rpms

I'm sure the TQ is near peak but the HP should climb until 6K+ I would think. Plus there's 3-4lbs of boost that have not seen the motor yet either.

Any ideas or comments would be appreciated.

Mark

SDB

iTrader: (7)

if W2W can't figure it out, doubt any "internet wrenches" could fix it!!!

777

iTrader: (21)

RyanJ

I dont think W2W is dynoing the car.

Someone will chime in on the belt tension, but don't most of these guys run 14-15?

I'd personally get rid of the Taylor wires and pick up some truck (6.0) coils.

BlwnTA

iTrader: (18)

Just to clarify...W2W is not Dynoing the car, I'm in Cinti, Ohio. They did a great job on the SB. I'm going to street test it tomorrow (crappy weather today and lots of torque don't mix too well). I will probably adjust the tensioner and street test it again to see if there is a change. The belt was a brand new gatorback 8-rib which kicks ***, but it may have stretched over the 200+ break-in miles, which could have released the tensioner somewhat. Plus with the added torque it made need to be set like you said closer to 14-15.

Hoping Scott (SDCE) and/or ForceFed,Nasty, and Bigbos chime in....they are all traitors but used to have these set-ups!

Of course if I become a traitor I may not have these problems anymore

Phate

iTrader: (2)

Sounds like a problem with valvetrain stability, check the spring tension and the rockers first...if that isn't it then it might be a lifter problem.

smokinHawk

iTrader: (48)

id try replacing with the truck coils
the stock ls1s should be able to pull to that, but maybe they went bad
im sure you checked to see if all your plugwires stayed on.

you got relocation kit for them to, can they be to close together? so problem with that?

BlwnTA

iTrader: (18)

Could be...I have heard of valve float but have never seen it. It did handle 587 rwhp 13PSI without an issue before though. For everyones reference here's the valvetrain specs. Anyone else care to elaborate on this beacuse the old combo had a slightly smaller cam (563/563)

TR 228/230 581/592 114LSA
Comp 918's (TI Retainers) Seat pressure roughly set at 145#
Harland Sharp shaft mounted rollers (1.7's)
OEM Lifters
Chromoly OEM length pushrods

frcefed98

iTrader: (16)

I ran into belt slip with the gatorback at the track, the car still ran great though. I had to retension big time as the gatorbacks stretch fast, intially I set it at 15 for break in. At the track it was near 12 so it stretched pretty good. I retensioned to around 17-18 on the tensioner....after that belt dust was minimal...then I sold it Pretty sure that would have got me my 10 pass if I would've went back to the track one more time..
J

NA$TY-TA

iTrader: (21)

I agree with Jer..... i had good results with the Gates belts..... on my old 6 rib setup they would stretch and id have to go retention the setup..... I think the whole bucking thing might be something else though....... on my old dyno graph when i was seeing belt slip on the dyno.. boost would rise and peak way early and dip a bit then rise again....... Post the dynp graph up.
Kyle

frcefed98

iTrader: (16)

Yep if it got really wavy up top where it happened it'll probably be slip. Valvetrain "looks" sufficient to handle the cam and boost???

Could be an ignition problem, I was experiencing a similar problem before I tore it down. Replaced the plugs...nada, replaced the O2's with the rears...got worse...got new Denso O2's....ordered turbo..and tore car apart. Hopefully its the O2s..if not the plugwires are next, then the coils.
J

99Fbody99

Did you by chance check the lifter peload after your changes? It may be to tight(to much preload) and when the oil pressure gets up its pumpin the lifter near solid and hangin the valves open.

Dave

gen 3 bu

iTrader: (2)

the stock ecu does not use the o2's in wot/open loop. it souds like either secondary ignition cross firing, or valve float. what does the boost do at 5000+ rpm?

MIGHTYMOUSE

iTrader: (59)

try stock wires.. the stock coils are fine. my car would misfire under high load with moroso's.

Pro Stock John

iTrader: (34)

Keep us posted.

You can try swapping wires, but you can load the car and see if that problem occurs at higher rpms.

Race Car Driver

Personally, I would ask W2W or LPE to finish the car and tune it.

CHRISPY

Swap to stock wires and swap the plugs with a narrower gap (just to test if there is a bad one or spark blowout happening)

0.025 or so.

BlwnTA

iTrader: (18)

Thanks for all the good suggestions guys...I'm going to load the car on the street on Sunday and see where and if it does it, then I'll check the belt and go on from there. Guess it could be a number of things...probably going to be one of the them new motor gremlins! I'll keep you posted.

BlwnTA

iTrader: (18)

The tech running the dyno said he thought it was spark blowout based on the feel...and .030" was to wide. I tried to convince him .030 was fine...maybe he could be right...probably try that right after the tightening the belt if I strike out there.

Pro Stock John

iTrader: (34)

I run TR8's @ .030 and 21 psi.

What cam are you running? What valve springs? What spring pressure? Is the car still pulling or falling off?