Converter too tight?

402 sbc with 14-71, 20 od, 37 lbs boost, 34.5 Hoosiers, 4.10 gears in a dragster. 5000 rpm on the trans brake. At the release of brake, our rpm graph shows the rpm goes up to 6500-6700 (converter stall??)then a little dead spot for a tenth or two then then nice rise to the shift point at 8500. Pulls down to 6700 and only gets to 7200 by 660'. 4.24 @166mph. Heads are 18 degree brodix but only have s.s. valves so 10K rpms is out this year.
Goal is to get into the threes. Any suggestions or thoughts?

 

Looks like it flashed to the appox stall and then climbed to the shift rpm. Since it dropped back to appox the same rpm, I'd say the convertor is ok but a little loose. Try leaving a little harder and shift a tad later. Unless you want a 1/4 setup and a 1/8 setup leave it alone until you can run the 1/4 and see what it goes through at, maybe gain another 4 or 5 hundred rpm's. since you run a dragster the et sounds about right, although you can pick up some more by playing with your tuneup.Also in better weather you'll pick up another tenth or so. If you don't already have a spare convertor get one made that is a little tighter, maybe 5500-5800 stall and try that. Remember, order it from a good builder and give him all of you data and he'll get you close.

 

What ratios are in the tranny?

 

jody thats what i was thinking also the 5500 - 5800 i would think would be a lot better back when i ran a blown chevy i ran an ati converter and it was about 5600 but mine was in an altered 125wb

 

don't go too tight or you could start taking out #2 and #4 main bearing.

 

Tell me more blown375. I don't want to hurt my shit and it sounds like you have a little experience with this.

 

Trans gear

1.76 Powerglide

 

I've run both the 1.80 low and the 1.65 low, couldn't tell a whole lot of diff, although I ran the 1.65 in cool spring weather and the 1.80 in June weather. Either way my dragster has 60 ft's of .937 in cool weather to .950 in hot weather. So it seems that a 1.76 should be a good middle ground. Jody

 

60 ft

60 ft is part of our problem, we are only 1.01's. Pulling 10 degrees timing at the hit and putting it back in over 1.5 secs. Then changed it to 5 degrees over same time and saw no change, still 1.01, 4.24 compared to 4.25. Damn bracket car.

 

I leave with 28 to 29 deg. timing, no retards, you need to hit the tires as hard as you can to keep them planted. My junk has gone a 4.006 in the 1/8 with only 26% od in the blower and 950 degree egt's. However a friend of mine Eddie C. has run in the 5.80's with a superman on an AJ motor with a Brunno and Lenco and I think his 60 ft's are around 1.00, so low 60 ft times aren't critical if you make big power, ( I don't hence the need to go quick in the first 60 to have a quick 1/8 and 1/4. ) Put all your timing back in and work with your wheelie bar and tire pressure to get it to leave. What's your car weigh and how much do you run in the nose for ballast? Jody

 

years ago we ran a sbc 6.40 in the 1/4 and the old chevy seemed to love timing..and I might also add deep pockets$$$$$$$$$$$$..if you are going to wannt to go fast and lean on it lean towards a BAE or KB..Dave
www.myspace.com/daveloweswr

 

I would put more screw in the rear end first.