I'm having some issues with my launches and need some advice.

My car is an 87 body that has been backhalved. The rear end is a heavy duty 10-bolt with ladder bars, 4.10 gears and turning 29x11 Hoosiers.

The motor is a 69-70 vintage 350 4-bolt block, with open chamber heads, unknown cam and from what we can tell, flat top pistons. I bought this car from the second owner that I think bought it from the original builder without a motor in it and just put this slightly better than stock motor in it. The carb that came on the car was a Holley 750, vacuum secondary single pumper. The car was stumbling off the line real bad and when I put a 650 Demon on it, the car ran better, idled better and the ET's dropped by over 1/2 a second.

The trans is a TH350 with Summit 3200 stall, and this is currently a foot-brake car.

One of the problems I'm having is that at the line, the converter is starting to lock up at around 1500rpm, and when I've tried to get it up to 2000, it pushed the car through the beams with the front brakes locked. However, if I'm rolling through the pits in 3rd and hit the gas, it will flash up to just over 3000. So why is it locking up so soon?

The other problem is that my 60ft times are terrible. They are running right around 1.9 seconds. What can improve my 60ft times?

 

You're not going to see the converter's full stall on the starting line without a transbrake. My converter stalls at 6200 on the transbrake but I can easily drive around at 1500 rpm through the pits and can load up the engine on the brakes to somewhere in the 4000 rpm range before it starts to push through the brakes.

With an "unknown cam" you're taking a wild guess at what stall speed the converter needs to be.

Hard to say how to improve 60' times. Without knowing a who;e lot more about the engine, that might be all the power you're making to get those 60' time. You might also be getting tire spin or the ladder bars and pinon angle may b=need to be adjusted.

 

Thanks for the reply Alky. I'll be tearing the motor down this winter and rebuild it with parts I know what they are. I imagine that you are right on when you said that is probably all the power the motor is putting out. When I bought the car from the guy (actually traded my Harley Road King with 75,000 miles), he told me that it was a 10 second car. Looking at the chassis it seemed that he was being truthful, but without tearing into the motor it would be hard to verify it. Unfortunately I got a car with a good chassis, but crap motor.

 

building a motor is easy, building a good chassis takes a lot of time and careful measurement.


what kind of MPH/ET are you getting out of it? this may help us let you know if something is seriously wrong

 

Maybe try going off idle and letting it flash... I agree with unknown cam and really unknown motor, its hard to judge what optimal stall should be. If not enough and your low end power is weak, then you wont leave the line hard.

 

Best ET has been 8.617 (1/8th)
Best speed has been 81.002mph

 

that car is making 300rwhp. i would either yank the engine out or get a bottle in there asap.

 

I was thinking about putting in a 125 shot until I could pull the motor apart this winter. That should help and not be too much strain on the motor since I don't know what's in it.

 

i would say you're getting about all that motor has to offer