Ok so I had a GM hot cam in the my 94 Z28 and ran 11.98 @115 swapped that cam to a bigger custom cam and made 45rwhp extra. The trans went out after so I rebuilt it and went up on the stall. The car now runs 12.23 @110 with the same 60ft.. I thought bigger was better? WTF is going on?

 

lol sorry to hear that man what kinda gears do you have? also did you get a tune?

 

Bigger isn't always better. It's odd that you gained power, but lost ET/MPH. What are the specs of the new cam and what else is done to the motor (cubic inch, heads, bolt-ons, etc).

 

It's a stock bottom end LT1 with 23X/23X cam, AFR 180cc heads, longtubes, and 373 gears.

 

What converter?

 

^ Ditto. And are you sure it was restalled properly? Can you feel that it flashes to 4k?

 

Its a RevMax stage 3 converter, when I got it back from the shop with the 4000 installed it felt real loose at wot, it felt kinda inefficient. I thought this was normal with a big converter but the timeslips dont lie. With the 3500 it pulled much better up top. I got 1.65-1.68 60ft with both converters. I believe my peak torque is at 3800-3900rpm if that helps any..

 

Can you do any data logging... Where is it flashing to? What are the shift drops?

Chris

 

With a 23x/23x cam your max torque should be more in the 5000+ range.
If your max torque were in the 3800 range range then a 4000 converter would be too high- by the time it flashes your torque is already dropping off. You want a stall speed "in the meat" of your torque curve, not after it.

But the big QUESTION - did you get the PCM retuned, because a cam change requires a major tune change.

 

Restalling (I've heard) can cost efficiency as the price
of moving the stall speed up, if you only change one
piece of it rather than putting together a targeted
design.

Is your LT1 really at peak HP with the "4000" stall
stretched out to whatever RPM, or has the higher
stall allowed you to run on the other side of the
fading HP curve? Or are you simply the victim of
lost efficienty? If you had a dyno curve and a scan
you might be able to see what's up, in that vein.

 

Yes I retuned the car and it picked up 45rwhp. Then the trans went out. I then took the mid tube headers off and installed longtubes and the 4000 restalled converter along with the new tranny.. Do stall change and longtubes require a new tune? My torque curve was flat from 4750 to 5750 then it started to drop. Hp peaks and flatten at 6100 and TQ peaks and flatten at 4750 I shift at 6400. Dyno runs were made with 3500 stall and mid tube headers. I just found the dyno sheet..

 

It seems to flash a tad higher than 4000. Maybe 4300ish

 

id get a retune man it couldnt hurt honestly and it MIGHT just fix the problem

 

probably the stall its self.

 

That ^^

 

So you guys think I should go with a spanking new 4000? Or get a spanking new 3600? I'm lost right now..

 

id say get a new 4000 and one that has been proven.

 

Are you the problem isn't with the rebuilt trans?

 

Another good point ! I forgot the trans was rebuilt also.

 

It would be hard for a trans to suck up that much power without almost immediately overheating and blowing ATF out the vent tube.
A higher stall should not require a retune.
Long tube headers might change the VE tables by 1%, not enough to worry about even if running SD. And definitely shouldn't matter if running MAF and/or Closed-loop.

Several sponsors here are running Xmas sales on their converters; that might be the best way to go. I personally prefer lower stalls for street driveability, but since strip performance is important to you, you have a 3.73 rear and a hot cam, a quality 4000 stall should give you the best performance.