Carb Problems?

[John Walker]

Clem; or anybody else who might know. Below in a thread I asked about vacuum cans going bad, Duke responded with some good info and suggested Clem could help with the carb problem. I think what is happening is I am getting a transient lean condition which is causing the motor to "pop" back through the carb and the shock wave is breaking the vacuum can diaphram. The car does not bog when standing on the throttle but, before everything is real good and warm every now and then it will pop back. Question, do I need to change the cam on the accelerator pump to increase the fuel shot? or maybe something else?

Thanks in advance John

[Clem Z.]

Re: Carb Problems?

you can try the pump shot by moving the cam or even install a large diameter squirter. moving the cam will give you more pump volume by making the shot last longer and a larger squirter will give you more volume the instant you hit the gas. what is the part # on the carb? make sure there is no play in the pump linkage,the pump arm should more with just a light movement of the carb throttle arm and the pump shot should start quickly.

[John Walker]

Re: Carb Problems?

Clem; the carb is a 750 street demon. (holly design and holly parts interchange) The motor is a 454HO GM crate engine with HEI w/mechanical tach drive and when the car runs it runs very well. I am running 12degrees intial with 36 total all in by about 25/2700 rpm. No bog, no detonation, just every now and then when not fully warm or on starting I get a pop back and this has been destroying vacuum can diaphrams. When I get the pop the motor stumbles and then runs or stumbles and dies. This is my wifes driver so I am in the dog house when she can't just get in and drive. Thanks John

[Clem Z.]

Re: Carb Problems?

does this carb have a choke,if it does i would make sure that the choke pull off is set correct and you could try tightening up the choke coil a notch or two so the choke stays on longer. this will help in the first 1 to 2 minutes after start up if this is where the problem happens.

[John Walker]

Re: Carb Problems?

Clem; yes it has an eletric choke which has been headache since I put the carb on. At first it worked perfectly then within a month began sticking on, I ajusted the installation then it worked intermittantly and now does not want to come on at all. I will have another go at it this week. Thanks again, John.

[Clem Z.]

Re: Carb Problems?

make sure the butterfly is not binding on the choke housing somewhere as you may have to loosen the screws and move it around or take it out to file down the spot that hits