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Strange stumbling after the stall/shift, we're stumped

2K views 14 replies 8 participants last post by  wanger 714 
#1 ·
Big block Chevy about 675hp, 1.80 powerglide, 4.10s, 3260lbs, footbrake car, 10.20's 134mph.

Car had been running great, won the first points race of the year, next race (weather was a little worse) it started stumbling climbing off the stall.

Launch around 2500, stall around 5500, when it starts to climb it starts stumbling/struggling, it wakes up right before the shift at 6700, drops to 6000 on the shift, bogs for a split second to 5800 then clean rest of the track but obviously slow. (10.23 first TT, 10.39 next pass, put in new plugs, went 10.34). The day before it was 10.19-10.22 in 7 runs.)

Plugs look perfect, timing was good, fuel pressure was good on the runs, went through the fuel system and tore apart carb, found nothing. We're pretty stumped. What do you guys think?
 
#6 ·
Next door neighbor has a round track car that sits outside on many evenings still on the trailer. We had some hard rains and water got in his tank. They had a hell of a time figuring out what the heck was going on. Finally saw some water in the bottom of the float bowl when they were pulling the carb back apart.
I would have the op try someone else's carb if at all possible
 
#7 ·
I had a slipping sprag a few years ago, at the shift I would either drop about 1200rpm (Glide) or about 2500rpm. Was easy to tell when the damn thing slipped on me! Car would fall on it's face, I had to hold a tenth just to keep racing until I was able to pull it apart.
 
#12 ·
We are racing Saturday, so only have Friday night to test a few things. We think it could be in the cam lift/squirters. We are running a brown and blue cam with 40 squirters and think when the weather is getting really bad it is not using up all the fuel.

In great spring air 300ft, we went 9.95 @137 with 1.499 60ft, in the bad summer air, 2000ft+ we're mid 10.20's @ 133 with 1.56x 60 fts. It's not stumbling at the hit but just crazy slow in 60ft.

We also think the new converter may be 200 tighter than that we were running before, which would only become tighter in the summer, but wouldn't make it stumble but just be slow.
 
#15 · (Edited)
Here's a couple time tickets from last weeks Sportnationals. Notice our 60 foots verses yours. My weight is different from run to run here, but I have 30 less horsepower than you and the same weight car as you. I'm going to put you to work on those 60 foots when you get this problem solved... LOL . Just trying to point you in the right direction so you know where you "should" end up .. Good Luck
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