I just put a big block in my car and it has a decient amount of cam

248 duration .595 lift.

What I notice at idle:

To get the car to idle at 750 in gear I need to set the idle in park to 1150-1200.

When in gear it wants to creep forward.

Is this an indicaiton that I need a higher stall converter?


Thanks
Tom

 

first what stall is in the trans now. second with that cam i would run 3500rpm stall and 4.11 gears this would make the car MOVE out from a dead stop. if you can git it to hook

 

Not sure what stall is in it now. I just was not sure if a lower stall converter could cause the symptoms that I am seeing or should I be looking elsewhere.

 

Yes. A low stall speed converter with a higher HP/Torque engine equals rpm drops in gear. Stock 700r4 torque converters are not good with a big block assuming you are using the old one. I have a carbed 350 in mine and it dynoed a 375hp at the crank. With the stock torque converter in now I have to set the nuetral idle at about 1400-1500 rpm. In gear it drops down to 800-900 rpm. With a higher stall speed converter you wont fully engage the converter until you get closer to your stall speed. Stall speed does not mean that you will have free reving until you reach the advertised stall speed either. Only torque converters that are not considered street converters begin to give these kinds of problems.

With most after market torque converters you will have a higher speed the more torque you put into the converter. So if i run the same torque converter that is advertised as having a 2800-3200 rating I will see closer to 2800 with only a mildly built engine where I will see closer to 3200 the more power I put in. Your best bet is to match your engines torque range with the torque converter.

I had a chart on matching hp to torque converters but I cant find it. I'll see if I cant find it again and post it later.

 

this is the chart I was talking about.

TRUE STALL

400 HP 3000 3500 4000 4500 5000
450 HP 3100 3700 4300 4800 5300
500 HP 3300 3900 4500 5100 5600
550 HP 3500 4100 4700 5400 5900
600 HP 3600 4300 4900 5600 6200
650 HP 3800 4500 5100 5800 6500
700 HP 3900 4600 5300 6100 6700
750 HP 4100 4800 5500 6300 6900
800 HP 4200 5000 5700 6500 7100

This is a guidline from a guy who custom builds converters. As you can see his converters advertised stall speeds are based at 400HP. So if you have an engine pushing 550HP and you buy his 3000rpm stall speed converter your actually going to see 3500rpm stall speed.

 

[B]

This combo would be great with a carbed set up, but a bit much for a TPI IMO.

 

If you read his first post it says he just dropped in a big block. I would imagine it's carbed anyway but that wouldn't matter with a BB anyway.

Sounds like a good seup IMO.

 

I must have missed the first sentence in the post. I did see the TPI in the profile, and drew a dumb conclusion. Sorry.

 

actually guys this is in my nova (see in sig), I did't specifically state it because sometimes threads get locked not third gen related etc.

I tried to keep it generic so if in the future others had a similar situation if they searched it would be beneficial also.

I guess my final question would be that at 55-60 I am turning 25-2800 rpms.

If I were to go with say a 3200 rpm converter and am crusing at 2600 rpm, wouldn't the converter not be totally enguaged and be partly slipping at this rpm and lowering gas milage and creating excess heat?

I do have an additional trany cooler to handle the heat so that is not my major concern. And with a 461 I know that I am not going to get good gas milage, however, I think you get my point.

I just don't want to go with too high of a stall.

Thanks
Tom

 

I guess I explained it kina of screwy. It's not that the converter doesn't fully engage. The engaging of the converter has to do with the amount of torque you are outing into the converter. Hence why it's a torque converter. Street strip converters (generally converters with 3200 stall or less) still fully engage while cruising. It's when you apply instant torque from a dead stop. What it does is give you that time for the engine to get up to the RPM at which you produce the most power. It allows the torque to build up for launching the car from a dead stop. You need to make sure your buying a street strip converter, not a full competition one.

If you have an engine like mine that's built with a cam/intake combo that gives a peak power range of 3000 to 6500 rpm, then a torque converter with with a 2800-3000 rpm stall is perfect for getting the whole shot. That way I start with plenty of hp at take off. You really need to know the power range for your engine when purchasing a new torque converter. 2800-3000 is a good start for over 350HP at the flexplate.

I am using a 3000 rpm converter and produce 375HP at the fly and also run a 100 shot when I'm at the strip. I have (had until I blew the tranny) no problems getting around town cruising. I would say if your pushing 450-500HP with that big block of yours I would go with a 3000 and you'll wind up actually having a stall of 3200-3300rpm.

 

Thanks for the clarification and explination.

I think a new torque converter is in my future.