carb gurus-cmon in

[85stangt]

WOW I WAS JUST READING THROUGH THE POSTS AND SORRY TO USE THE WORD "GURU" -LIKE 10 OTHER POSTS HAVE GURU IN EM ...LOL-------------to start off, i have an 85' gt auto, with the mods below excluding an hei dizzy. heres the deal i have a holley 600 vacuum secondaries and its set up fairly well(i bought it new) but off the line it just doesnt seem to be as mean as it could be--like it wont break the tires loose(i ran a 15.0 3 times in a row at 92-93-93 mph with a 2.27-2.25-2.24 60 foot with the tires not breaking loose at all...but i dont expect them to at the track)anyways so i thought i would put in a lighter spring to allow the vacuum secs to open sooner. (stock is 2735 rpm) so i installed a spring to open them at 1650-- with that set up i was able to spin a lot...except then i got a bog shortly after shifting into 2nd..so i put in a spring to open them at 1935..now i have maybe a chirp off the line and a small bog after 2nd...so whats going on here?
how can i get a strong powerband from idle on up---im putting in a spring in a little bit to open them at 2200--but should i stop wasting my time with this and trade my carb in for a 650 dp? times were ran with 2735 spring and with out my hei dizzy --sry about length-- what do ya guys think?

 

[85stangt]

i guess the question is too specific, wheres thumper when u need him?

 

[79'293stang]

a good stall would probably do good since its an auto, its not anything about carbs but i think it would help you out the most comin off the line.

 

[battyice]

Normallly if poor off-line response is actually carburetor related, it is due to the accelerator pump. There are many different size nozzles available for your holley; some for a strong quick shot of fuel, others provide a smaller shot of fuel over more time.

The other thing than can cause an off-idle hesitation is if you are running the wrong powervalve. If your engine is totally stock, it may very well pull enough vaccum to cause the powervalve to open later than it should.


If you are still running stock gears in your car, you willl definitely experience a bog if you move to a lighter spring for the vaccum secondaries. With a stock converter the problem will be even more pronounced. As mentioned above, getting a higher stall converter would really improve your off-the-line performance; and you will be able to move to a lighter spring to get those secondaries opening quicker...and thereby destroy your tires

Destroying your tires won't really improve your 60' times, but you get the idea...

 

[rd]

This is most likely not a specific carb problem as much as a gears and converter issue.

You are launching, and the pump shot is getting you off the line, then the tires hook, and the converter is nearly hooked, so it holds the engine rpm down. You don't have enough rpm or airflow to open the secondaries until you get to 3000 or more rpm. The time between the two events (launch and the engine getting to 3000 rpm) is the bog, or at least a slow acceleration period.

You may cover up some of this with pump shot and timing. However, the best solution is enough converter to get the engine in its power range immediately upon launch. Then you will have enough airflow to open the secondaries, etc, and the engine will be in its powerband the entire run.

Your sixty foots are exactly like mine were for five years with my 79, with its stock c4 and converter, and even with a 2200 rpm stall converter. It was fairly consistent though and a good bracket car.

Put the same motor in my 82 with a 3000 rpm 10 in TCI converter, and it took 5 tenths off the sixty foot, and the et, etc. At launch, the engine goes to 3000 rpm, the secondaries open, it is on the cam and it stays that way through all 3 gears. Awsome change. I put the lighter springs in the carb, plugged the vacuum advance, and it runs strong and consistent.