Alright, heres the long story of my problem.

Basically I have a stock cube LS1 with good rod bolts, fresh bearings and rings. Less then 1k on it. Fast 92mm intake, PRC stage 2.5 heads with valves recessed for MS3. Yank 4400 convertor, 4l65e and a 9" with 3.70s. So built the motor 6 months ago and had an MS3 in it. Had a vig 3200 which was way to small. Had it restalled to a 4k and still was way to tight and not right at all. Stepped up to Yank PT4400.

Car still seemed like a dog down low, no power under 3k. Go to track and cant 60ft at all. 2.0s all night long. 12.40s at 114 all night.
So.....
Have Pat G spec me out a cam. 230/234 .600 .602 111+3 Swap out cams, retune and now the car feels great. Lots better down low.

Take it back out to the track tonite. Same times, almost identical. But the kicker, I lost mph. Only trapping like 110 now. We cannot figure out what the problem is. Car seems to be hooking just fine. Its not blowing the tires off. Running bigs and littles, 26x10.50 Et streets. Car has stock springs up front with strange coil overs. Stock springs and shocks out back with about 1 1/2 coils cut in the rear.

Ive tried launching it from idle all the way to where is pretty much pushing through the front brakes and nothing changes. The other kicker is on the street the thing is a monster. From a roll its just stupid. Car pulls strong as hell all the way to 7k.

Im just about to my wits end, and cant just keep throwing parts at it.

 

who's tuning it? any track videos? even w/ that shitty of a 60', the car should still trap alot higher.

 

I'll ask the way obvious just in case...

Traction control on?

 

Any possibility the exhaust is hitting anywhere? Reason I ask is I just helped a guy out a couple weeks ago that had this happening, and it was kicking the knock sensors on and making the car pull all the timing as soon as he floored it...

Car ended up hagin a bad tranny mount, and the motor mounts were a little sloppy, poly motor mounts and a poly tranny mount fixed everything.

Sometimes it's a screwy problem that will cause a car to do that.

What did the car dyno, what's it weigh, and how old is the tranny? Other possibility is the transmission is slipping like a **** and you don't know it... what's the car going thru the traps at rpm wise, have you calculated the driveline slippage?

 

I'm his buddy/tuner. The car is tuned in open loop SD and is spot on, 12.8-13.0AFR on my dynojet wideband and 27-28* advance with no spark retard present anywhere in the logs. Car has not been on a chassis dyno. I tuned a t56 car last month with this exact combo except it had a ls6 intake instead of the 92mm and it goes 11.60s at 118 with a mediocre driver. All the cars I tune run the numbers they should except for this one and there's a bunch of us scratching our heads over it.

There's got to be a mechanical issue somewhere, it just seems to be down on power everywhere. The car dead hooks off the line, but it just won't 60ft at all and it's down 4-5mph up top from where it should be for our DA. The trans is a freshly built 4l65e by a reputable builder, stall is a brand new yank pt4400.
We're looking for places to start troubleshooting.....maybe the timing set is off? He didn't degree the cam. I suggested to leak it down thinking maybe the rings (standard plasma moly) possibly didn't seat after the rebuild or maybe one of the valves is leaking? Any other thoughts/questions/suggestions are welcome!

 

I will never understand why someone wouldn't degre the camshaft when you have the engine out getting rebuilt.. that makes absolutely no sense.

I'd start looking at that, valve float issues, and get the car on a dyno and see what it's doing.

Also, just becuase the tranny was jsut built doesn't mean it's right, drain teh fluid and see what it looks like, it'a like 15 bucks to change the tranny fluid, at this point I'd start looking at stuff like that, but definitely get the car on a dyno, it should be well over 400 rwhp, if it's not, then the car's certainly down on power.

 

Start with the simple stuff, as stated, and get it on a dyno ASAP. Don't throw more parts at it until you can see that info.

 

2.0 60' is the problem. I doubt the cam being a tooth off is going to cause that especially with 114mph. Is the car starting in first gear?

 

put the car on a dyno and get a REAL number, not a seat of the pants feeling
also what kind of tires are you launching on?

 

Running a 26x10.50 Et street. I am uploading vids from last nite right now.

 

First run is just off idle to the floor. Second is loading the covertor till Im about to push through the brakes. Notice how it sound like somethings lugging the motor really hard when I launch?

http://www.youtube.com/watch?v=lYee5y0S_tQ
http://www.youtube.com/watch?v=27LANuccJSY

 

Im no expert but that sounds like tranny issues, But then again, if it was slipping the Rs would jump up right, not lug down like yours is?? Humm.. Need more gear maybe ?? Idk..Im just posting to see a good outcome and hopefully its a simple fix!

 

Get the car on a dyno.. something is very wrong there. The car sounds like it's down a cyl or something to me, it's lugging really bad.. I'd guess it's a tune related thing, or there's actually something wrong.


That bounce off the limiter usually is eiher a really off shift point, or the typical 4ljunkie failing.

 

Car takes off like you have a stock stall. Something weird there..Here is my Yank SS4000 with 335 rwhp..It hits a lot harder, 1.60 on this launch..I think it's a Trans/Converter issue myself.
http://www.youtube.com/watch#!v=-7L7XSd1LXs

 

I have a data log in spreadsheet in someone wants to take a look I can email it.

 

It looks like you have tranny issues. That 2-3 shift sounds horrible. My buddies car was doing the same thing yours was doing and it was his trans.

He also had weak valve springs too and it was making him lose mph thru the quarter too. He was losing 6-7 mph from both issues.

 

We have been fighting the 2-3 shift issue a ton in the tune. We have it to where it wont ever do it on the street, but as soon as I go to the track it bangs the limiter 2 or 3 times and the then makes the shift. Im really thinking its in my trans.

 

I'm 99% that it's tune/trans at this point. The way it leaves, well looks like it's making 200 hp.... that plus the limiter bang, believe me there's issues there.

 

Sprag rolled over?

 

I had the trans at my builder when I got the pt4400 in the fall. I bought a 4l65 that was tore up, and had him put all the good hard parts from it in mine.

But.....My valve body has stayed the same and never been apart for like 4 years. And even back when I was cam only with 17s and DRs the car would never 60ft. Ive always wondered if I have some kinda pressure issue or something goin on.