Just got done with my tbi, carb swap, must say extremely impressed by the results, anywayz, at low engine speeds if i smash it it hestisitates, like bogs for a second, i and most of the people Ive talked to think its running to rich, one person (who actually help me rebuild the carb) says its runnin too lean. Anywayz, Have the idle at like 800rpm, timeing like 5 degrees advance (toned it down some since it backfired out the exaust when ever I turned it off) kinda fixed the problem but I think it was that my idle was way 2 high, was at like 2grand or something. Anywayz what do you guys suggest I do to fix this.

 

Here are the basics: The main metering system of a carb draws fuel from the bowl using the lower pressure caused by air being drawn through the booster venturi. At an idle, there is no fuel being drawn through the main metering system because there is not enough pressure drop through the booster venturi by the low air flow of idle.

When you open the throttle, air starts flowing more and creates the lower pressure in the venturi. But, there is a lag between the air flow increase and the fuel being drawn through the main metering system. This is compensated by the accelerator pumps, which squirt in a little extra fuel into the air flow while the fuel is being drawn through the booster venturi.

Most likely, you need more of an accelerator pump shot, especially in the secondaries.

 

IF it falls on it's nose for a second and then hauls butt it's lean 99.99% of the time. Like five7kid said, you need to have at the accelerator pump to fix the problem in all likelyhood. If it's a holley carb, new and all stock you will probably have a #25 primary accelerator squirter. Replace with a #31 and your problem will likely be solved.

Yes, keep idle speed down to about 800 where you have it. You can probably bump the timing up another 4-6 degrees (depending on what distributor you have in there and how much cetrifugal advance it's got built into it).

Shutting down from a 2000 RPM idle will almost always result in dieseling/run-on with a fully warmed up motor. Unlike fule injection, a carb keeps right on metering fuel into the intake even after the key is turned off as the motor spins down, so if there's something "glowing" hot inside the combustion chamber it'll keep right on running.

 

Thanks guys imma mess with the accelerator pumps 2day and let you guys konw what happens, apriciate it :hail:

 

a little off topic but do you plan on running your combo at the track soon. its almost exactly what im going to be putting together this month. any times/impressions would be nice.

 

Yea glad you mentioned it i am going to the track this wednesday hopefully if I can stop this oil leak lol.

 

Went to the track guys , this is with an out of sink carb (still havent gotten it tuned right still bogs at low engine speed.

Anyway the first 2 i wont even mention cuz theyre were just imbarrasing (stupid carb, thing almost died on me when I launched.)

My best time was a 14.16 @ 96.92 with a 2.28 60ft, and a very impressive reaction time of .984 (doesnt change the 1/4 time). 91 degrees outside.

Since the last run I had a 2.28 60ft i figured if I could bring it down to a 2.1 id be 13.9s easy, so I tried to launch it a little higher spun the tires all the way through first and second, figured what the hell might as well trap a 13, I MISSED 3rd so that time came in at a 14.55 @ 96.31 with a 2.31 60ft, and an 1/8th of 9.41seconds hence missing 3rd.

With a little bit better driving, and a tuned carb I would have been a high 13 second car I believe, better luck for me next time. This is with the exact set up I have down below. A little cooler air would have helped as well it was hot, however I should still have hit a 13. Hope this helps you out, 164k on my stock bottom end guess im pretty happy that I know i could have hit a 13, mad that I didnt.

 

This was on 255x60x15 street tires, here are the time slips.

 

judging from your mph your definately right around very low 14/ high 13 second times. sounds like with some carb tuning you should be a solid high 13 second car. your still on a 305 bottom end right? id me more than happy w/ 13's from a mild n/a 305.

does your rpm air gap manifold fit under the stock hood?

 

Man, drop a tenth off that 60 foot time and you're there! A non-bogging carb will help that out. Much easier to modulate the throttle for traction when it's not bogging. Times look good for the mods you've done.

BTW- when you're bracket racing you want to cut as close to a .500 reaction time as you can. You're giving away 4 tenths on the launch. Try leaving on the last yellow- you'll pick up those 4 tenths and beat the other guy to the finish.

Remember, it's your ET PLUS your reaction time (both you and your car have to be as close to perfect as possible to win) that determines who gets to the finish first. First one to the finish line wins, who doesn't redlight or run under their dial-in time. Even if you're running a tenth slower than your dial-in time that's nothing compared with 4 tenths by "snoozing" at the tree and cranking out a .900 light.

BTW- this STILL applies to some extent even when you're runnign "heads up" with no dial-in or handicap. Even if you're car is significantly slower a good reaction time (vs. the other guy) gives you that much of a head start. So if you run a 14.0 and have a perfect .500 RT you'll beat a guy in a 13.8 car that has a slower .800 RT.

14.0 + .500 = 14.5 seconds to the finish line.
13.8 + .800 = 14.6 seconds to the finish line.

You'll be at the finish a tenth sooner than he will (even though he'll be passing you through the traps). His numbers will all be faster than yours but you'll get the win light. And at the end of the day, that's all anybody cares about.

 

Yup stock bottom end with a lil over 164k on the miler lol. And the rpm air gap did fit with an adapter plate and my tbi, now it wont fit because My carbs spread bore, manifolds square, that was like an inch and then my nitrous plate is another half inch, so i have a big circle in my hood lol ill take pictures, hopefully ill get the video up soon enough. And no i did not use nitrous Its just set up 4 it.