Technical Blown flathead.

Hi. I built myself a flathead with a 371 blower on it. Running 25% under, has comp thumper cam, and a 500cfm 2 barrel motorcraft carb. I have a t400 behind it. It idles fine until I put it in gear then it just falls on its face, it won’t even rev up with my foot to the floor. Once the truck gets moving it seems to come out of it and seems to have adequate power. Looking for some ideas on what I should be looking for/ change.

 

Wrong torque converter stall speed?

Read this: https://revmaxconverters.com/part-understanding-torque-converter-stall-speeds/

 

I 2nd the torque converter opinion.

 

Not enough air flow at low rpm due to the 25% underdrive?

 

It’s a stock converter, I was considering changing it to a stall. As for the blower speed, I had originally set it up with a pulley that was running it about 30% over and it was still doing the same thing. What do you suggest running for a converter. I was thinking of using a 3-4000 stall

 

That converter could have a broken oneway clutch in it. You shouldn’t need a real high stall converter. That cam is not that radical.


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I wouldn't go that high with the stall, maybe 1500 to 2000. What's the red line on the motor?

 

The red line is probably 4500-5000. I’m assuming that if a converter would stall at 3500-4000 behind a small block that it would probably put the flathead in that 2500 area.

 

Try an adjustable high idle stop. The stock convertor should be ok with that cam.

 

Sound's like it need's more initial timing.

 

I had a guy in the truck with it in gear and foot on the brake. Rolled the timing from one extreme to the other and could make it worse but only slightly better, not good enough to use.

 

Is it making any boost when you open the throttle?

 

At 3800-4000 I have 2lbs. From what I have read I didn’t want to be over 7. Thought this would be a good start.

 

So I found my problem. The torque converter I used had a bad stator. It had come loose off of the clutch hub and was jamming its self between the turbines. Threw a new converter in a away we go. Thanks for the input