I finally installed a playback tach to see what is happening going down the track with my 572 CID B1 original heads engine with 1.80 first gear PowerGlide trans.
Engine has B1 cast single carb intake and cam is 282/295 at 0.050"

Staging (footbrake) at 2,500 rpm, converter went to 5,400 rpm at launch.
Is this tight (low stall speed) for this application?

I'm no expert on this stuff but I would think folk might need a bit more info regarding the combo, like weight, rear tyre, rear gear etc.

It will go much faster if you loosen it to within 500rpm of peak power!

YES! The better question is what did if fall to at the shift and where do you shift it? I know nothing about what power you make or where but you are likely 1000 rpm+- short of where it needs to be based on my experience with B1 stuff.

Definitely looser. What are you shifting at? Like Al says I bet your 1000 RPM off. I don't like a lot of RPM fallback with a glide. Right now mine drops 500 at the shift.

I have not run this much...
This run shifted at 7,400 and it fell back to 5,700 rpm.
I don't have dyno data. It does run quicker and more mph shifting at 7,400 instead of 7,000.

I believe the stall is lower than optimal, and just looking to confirm this opinion. I am fine with going slower and 5,400 rpm.
This run was with 32 deg ignition timing. It does sixty foot better with more timing. 1.19-1.20 so far.
About 2750 lbs (I need to rescale the car since removing the iron block/iron head combo at 2845 lbs)
4.56 rear gear, 33" tall tires.

That's what I figured.... Loosen that thing up a ton.

What size converter is it? Bet its a 9 inch. I have the tightest 8 inch anyone can build in my car. 2870lbs 1.18 60 ft. 850 or so HP. Flashes 6300. The next is a loose 9 inch and I don't have enough HP to make that work.

jim, if you are a dedicated bracket racer only, then it may not be important to restall the converter? All you need do is repeat, round after round.

I saw 105 lbs going from an early megablock to the BMP block. Plus you had iron heads before? probably 145 lbs lighter

Put it in high gear, hold the foot brake and mat the gas pedal, see what it stalls to.

Shift fall back is what matters, its also TRUE stall speed. Like I stated earlier you are at least 1000 rpm short if not 1400. I woudl shoot for way closer to 64-6600. Ideally you want that fallback number UNDER 1000rpm

What about using the trans brake to hold the car, pull the 2-step rpm chip and see. Likely somewhere near the 5,400 (+/- 500?).
Even that would make me nervous against the engine's full throttle.

I like the point Al makes about the shift recovery rpm, and I have that data now.

So, the consensus seems to be the converter is a significant reason the car's ET is not as quick as the engine build might think.
And the 4150 carb, too. I can live with 5.50 in the 1/8 mile, knowing the engine has more capability if other things are changed to make use of it.

I was thinking 6000+ stall for that combo. Your leaving alot on the table

That would work. I mentioned that just to see what you have for stall.

Greg, I bet it would be would be much much more consistent with a loose converter. Loose always more consistent for me.

My 3600lb 64 Savoy has a B1 original headed 540. It has been 5.60's back east. 5.70's here in Vegas, it also has a 4150 carb on it, so yeah you are leaving plenty on the table and with a glide if the converter is tight and the drop back is high its gonna be slow. You need to be much closer to 64-6600 if not more with a lite car and a glide.

Yes pulling the chip and wooding it on the brake will tell you as well. Most Super Gas guys leave off the converter, but drop back will tell you the stall speed.

Right! along with what others have mentioned. I'd bet it'll go solidly 5.2's once it's dialed-in but even if you don't chase the ET you'll still have better MPH to compete with.

I assume you have a dyno sheet on the engine. I always went by selecting stall of converter to hit a few hundred rpm below the max torque of the engine and then gear the car to cross the finish line at max HP RPM. I believe what you are seeing on your tach is true flash stall rpm and would use that number instead of any static stall numbers where you just brake torque the engine.

So your flash stall is 5400, I am with Al, you are at least 1000 rpm short. I run a B1 512, with 282 intake duration, since it's a stock block I run it real conservative, flash stall is 6300, fall back is 6100, shift is 6900. Car is about 500lbs lighter than you. HP is 825. I run a 1.80 glide


Joe

Mine pulls down to 6300. Shift anywhere from 6900-7200 doesnt mater. It could probaly be even a touch looser. And thats with a 3 speed. I'll bet it's more critivle with a 2 speed.
Doug