lost et and mph

[BAD67]

went to the track last weekend and made my usual 3 passes then was put on the trailer bracket racing,car use to run 11.80's now i lost almost .3 tenths and 3 mph .was runnin 115 mph now its going 12.0s @ 112.only change i made was carb had a 750 holley dp on it switched to a 650 mighty demon could this be the prob, or should i look elsewhere?

[lun40119]

I know a bit more bout your engine, and I think you should put the 750 back on it, you said you didn't loose 60ft, just on the big end, how did it compare at the 1/8. Were the track condition, and weather the same???????

[BAD67]

in comparison to the 11.80 passes the weather was diff 60° then 80° last time out. 60' times were the same. 1/8mile with the 11's was 7.57 and with 12.0s 1/8 miles were 7.71.motor is 355 sbc 10:1 solid cam lunati 40134 .517 .543 lift 239 249 duration @.050 heads are dart 200 cc alum, all msd ignition.3500 stall converter

[lun40119]

If your car weighs 3100lbs with you in it, you lost almost 8% power. I think that if you put the bigger carb on it, you will see the mph come back.

Don and Bill are prolly better with the et numbers, but that 1/8th et on the 12 sec run seems bout .10 slower. I would be curious to see the difference on a dyno those 2 carbs you have back to back. I didn't try a 650 on mine. I am running the ultra 750 on the turd and lovin it :D

Jake

[want-a-be]

When I was Racing I once ran an 830 with anular booster on a 350 with 200 cc heads and really liked it.

Don

[Awesome Bill]

If that is all you changed, that is the problem. The size of that carb should of picked your engine up, not fell off. With the hotter wheather, you could of been racing in a low front, which causes everyone to be slow, Were they? If your the only soldier out of step, then its what you done. I have had some success with Barrys stuff but more not than do. It seems your most likely lean because the lack of mph. But you will most likely have to do some homework. Check the plug color, is it black or very dark? Is it clean and white, you know what to do if any of these comply. The float level could do this, wide open throttle check? Before you shoot the horse, just bolt the 750 back on and run it next weekend and see what happens, that is your best bet. If it does come back, call Barry and ask him why his race carb runs that much slower. I hope he does not tell you you have to purchase another one but a 750 this time. Check out what I said and go over your install. You will find it. You should of had better 60 with the smaller carb along with a better 1/8. Smaller carbs always pull faster from bottom to top especially with a tight converter.

[Trmnatr]

went to the track last weekend and made my usual 3 passes then was put on the trailer bracket racing,car use to run 11.80's now i lost almost .3 tenths and 3 mph .was runnin 115 mph now its going 12.0s @ 112.only change i made was carb had a 750 holley dp on it switched to a 650 mighty demon could this be the prob, or should i look elsewhere?

You posted this also on www.chevelles.com , You had many people suggest using the 750

I would start out with 78/78 jets with no power valves if a race car

[BAD67]

That wasnt my post on the chevelle site you must have me mixed with somebody else