Help please!!!

[framerjoe6]

I have a 1983 miller custom jet. 460bbf. when you stomp on the gas it thinks about it for a second. Even if your at half throttle and then get on it, it sits there then will do its job. Then when you let off the gas it dies? Just had the top end redone including carb re-build. (holley 650). Runs great other than this problem, and this was happening before and after rebuild. Any ideas why its doing that? Was told when fixed carb was to small for motor?

[boatermike]

in my opinion, the 460 bbf needs 850 cfm and i would pick something easier to tune than a holley

[Jacob]

'when you stomp on the gas it thinks about it for a second. Even if your at half throttle and then get on it, it sits there then will do its job.'

If this carb is equipped with an accelarator pump, that is probably where your problem is. Many people modify an engine and forget to match the accelarator pump to the engines needs. They sell kits with different cc pump set-ups. A 650cfm carb should be sufficient for a mild 460. I had a 800cfm on a tuned -up 460 and after learning how to calculated carb size to engine efficiency, I found that I could have went smaller. Good Luck

A 460 turning 5000RPM requires a 665 cfm carbhttp://www.holley.com/TechService/FA...ory=Carburetor

Check out this link


http://www.holley.com/types/Accelera...ce%20Parts.asp

[Auggie2612]

'when you stomp on the gas it thinks about it for a second. Even if your at half throttle and then get on it, it sits there then will do its job.'

If this carb is equipped with an accelarator pump, that is probably where your problem is. Many people modify an engine and forget to match the accelarator pump to the engines needs. They sell kits with different cc pump set-ups. A 650cfm carb should be sufficient for a mild 460. I had a 800cfm on a tuned -up 460 and after learning how to calculated carb size to engine efficiency, I found that I could have went smaller. Good Luck

A 460 turning 5000RPM requires a 665 cfm carbhttp://www.holley.com/TechService/FA...ory=Carburetor

Check out this link


http://www.holley.com/types/Accelera...ce%20Parts.asp

Holley's are known for blowing Accelorator pumps out, especially if it has backfired through the carb at some point on you..

[Darkside's Calling]

Actually, Holleys blow the power valve, not the accellerator pump. It's possible that IF the power valve is blown it could be over fueling already and the accellerator pump shot is flooding it then clearing, and on decell the higher vacumn would draw overrich also.

It could also be the wrong spring in the secondary (assuming vacumn secondary since it's a 650), may be opening to quickly. try going to a slightly stiffer secondary spring and see if that helps.

Also, check your timing, not enought initial timing could cause a lag adn also contribute to the stalling on decel. should have about 10-12 degree's at idle, with max 36-38 depending on compression, cam, and fuel.

[Auggie2612]

Actually, Holleys blow the power valve, not the accellerator pump. It's possible that IF the power valve is blown it could be over fueling already and the accellerator pump shot is flooding it then clearing, and on decell the higher vacumn would draw overrich also.

It could also be the wrong spring in the secondary (assuming vacumn secondary since it's a 650), may be opening to quickly. try going to a slightly stiffer secondary spring and see if that helps.

Also, check your timing, not enought initial timing could cause a lag adn also contribute to the stalling on decel. should have about 10-12 degree's at idle, with max 36-38 depending on compression, cam, and fuel.

Thought about what I said earlier and I see you corrected me, Power valve is what I wanted to say.. Thanks

[boatermike]

i bet 3/4 throttle on a bigger carb, having the throttle in the sweet spot, might be better than a smaller carb wide open.

increased turbulence in venturi resulting in better initial atomization and a better mix is a better pop

[framerjoe6]

thank you all

[JP Love]

Better torque with a smaller..... For accelarator pump...

[gatahiti]

things to check

accelerator pump, check to make sure its actually putting out, and make sure there is no slop in the linkage. If it has a 50cc (big pump) it usually uses the black cam on the throttle shaft. If you have a big pump and its too much, you can go to a smaller cam and not swap the housing. The small pump usually does the trick in 95% of cases. This is a pretty decent article:

http://www.stockcarracing.com/techar...ent/index.html

Also if the pump isnt working and you decide to pull the squirter, pull the carb, there is a ball and a weight on top of it under the squirter. Both of which can magically disappear places your dont want it too. Sometimes the weight can be left off the ball and will cause a strange high speed enrichening that will make you postively go crazy because you can pull a bit of fuel through the acclerator pump circuit.

Like noted above, if this is a vacuum secondary carb you can have the wrong spring, binding in the inhibit linkage on the "driver" side (as in a car), a misplaced diaphragm (VERY easy to do!) in the actuator, or a missing O ring between the secondary chamber and the body. If possible and safe get someone to ride back there and look at the linkages as you get on the throttle and see if the transition onto the secondaries is smooth or if if kind of hangs and then the plates yank open. It should be a sort of gradual thing (thats why vacuum secondaries rarely ever "bog" when you floor them, the secondaries operate based on the engine's needs) and be smooth. Also, be certain the secondaries arent opening at idle, a misadjusted inhibitor link will allow this. And make sure it doesnt have a sheetmetal screw in there....

I am assuming all of your choke related bits are functioning properly and that isnt the issue.

Now if this is a 650 double pumper (has accelerator pump on both bowls) you get the headache of tuning two accelerator pumps.

We have a couple of Holleys we could never make run exactly right. Even after ultrasonic cleaning , new specific to that carb kits, metering block swaps, even one base plate swap it just would never run right. I suspect the carb bodies themselves had a casting flaw that manifested itself later in the carb's life.

When all else fails search out and make friends with your local hot rod crowd someone might even loan you a different carb to test with in exchange for a ride.

+1 on the timing and make sure the advance is working while youre at it

did you do a cam swap on the top end job?