i have a car that runs mid to high 5.70's. small block with a BLP 750 alcohol carb. i have a #1 stop under carb stop, air on air off.

my other car has same stop using a 900 quick fuel gas carb. i pull it back to 4300 on stop and shift while on the stop. it is really good and the graph looks perfect.

question is. i have never really had much luck getting an alcohol carb to repeat well on the stop. i basically have tried to run the alcohol the same way as gas as far as rpm and stop timers. for those who t-stop alcohol where should i start.

on gas i go out .20 shift .70 on for around 2.5 to 3.0 seconds. i could buy a gas carb to put on when i throttle stop this car but would like to make the alcohol work. it is really good bracket racing but to be honest i have not tried to throttle stop it yet. would like a good starting point.

ep-thanks

I've only ever run a stop with alcohol, and I run the stop RPM very similar to you. I use an electric stop, and my car is slow so all of the throttle stop events happen in Low gear and I shift downtrack on RPM. Also because the car is slow, I go out 0.500 before the stop comes on, and it's usually on the stop for 1.8-2.2 seconds.

I don't notice the car to be less consistent on the stop than when I'm bracket racing wide open. It's always been great.

Thanks Tony

The biggest thing I found throttle stopping alcohol was the float level. Most builders ship them with the floats as high as possible for volume. I feel like the carb was getting upset and sloshing when dropping out of the wheelie. I lowered might three flats and things got much better.

quote:

Originally posted by SP 124X:
The biggest thing I found throttle stopping alcohol was the float level. Most builders ship them with the floats as high as possible for volume. I feel like the carb was getting upset and sloshing when dropping out of the wheelie. I lowered might three flats and things got much better.

Bogacki had a recent video about troubleshooting via datalogger. The car was going fat after landing from the wheelie, and lowering the floats a bit solved it. Was pretty interesting.

quote:

The car was going fat after landing from the wheelie, and lowering the floats a bit solved it.

The above is an issue. Also many guys that T-stopped alky carbs over the years have cut a slot in the stop butterflies because of the volume of alky flowing through the carb and wanting to puddle on the stop butterflies when it's shut down. This fixes that. Hope this helps.

SL...

What does the car weigh and how much power?

Weighs in at 2350 race ready. 4:86 gear and probably 550 or so hp. Runs mid to high 570s 1/8 mile @ 118

ep

You may need to raise the stop RPM. How big is the engine?

not big. 406 sbc. i was thinking of pulling the rpm up from 4300 to 4500-4600. i was thinking of .50 out shift 1.00 @ around 4500.

ep-

update for those who care.

tried shifting on time but really am not fast enough to make this work. although the stop rpm came down to 4350 and did not move across the stop timer. i went out .30 shift at .70 for 1.5 sec. it was nasty and consistent just slow. needed to go 6.40.

changed to .30 on for 1.20 shift at 6500. went 6.30. next pass was .30 shift 6500 for 1.60 went 6.47. third pass after seeing a ratio and went 6.40. stop creeps about 150 rpm.

went to IHRA race at galot. 1st pass 6.37. 2nd pass 6.40. 3rd pass 6.410. all creeped about 150 rpm.

i didnt really swing my numbers very much and it moved .005 in 60' and about that at the half track. air was very stable over the first couple of days. morning of day three barometer is up .20, water grains are double and humidty is double and vapor pressure is up. i guessed that to be .03 slower so i sped it up .03. i lost .025 in 60' for some reason and can only go 6.415. i am puzzled as to why the 60 slowed down or if maybe the water in the air had the stop rpm low. i did not record that run so i dont really know. i was pleased with the alcohol but just need to no what to look at to predict what is going to happen.

any thoughts are appreciated

ep

EP if my reading is right the stop was opening back up at 1.50/1.60? not sure what your 60ft is but your timer setting may be such that you are contaminating 60ft numbers with stop timer just a thought if so get it out past 60'before opening stop back up that way you know if 60 is moving any imo .... also save the alcohol for dranking lol

60'was 1.452 to 1.457 at two different tracks until the weather change and went to 1.477. all of my other split times were the same. i only have about 10 runs or so the way i have it now. i am wanting to run some ihra super rod at 6.40 next year so just trying to figure things out. i am definitely through the 60.

ep

Generally, a higher barometer will make for a better leave/60 but if the stop RPM was lower due to moisture, that would be a bigger factor.

I was wrong lenny. The barometer was down .20 not up. I felt like on alcohol that was worth .02 and the added water in the air was worth .01. But i was strictly guessing as i am unsure what will move it on the stop

ep