whats wrong ???

[cmegga]

oK I have a new problem arising. I have an 81 rebuilt this spring, boared 20over eldebrock rpm heads, 600 cfm performer carb w/ eletric choke and a 3500 rpm cam.

The issues I have been having is at take off, when I hit it good of the off a stand still it cuts out on me. It only happens when I gun it, the car seem to cut out and I hear a pop out of the carb. Then a second later it comes back on. It almost feel like if you were to hit a rev limiter on a car that has one, except this is from a dead start.

It has been running fine other wise. I check the check and that is coiming off like it should.

Any ideas what could be the issue here??

 

[DDLS3]

cmegga,

Your problem could be a super rich condition with the carb or maybe a timing/advance issue. One thing you could try if you chose, is to lean up the accelerator pump setting on your carb. The lever is connected by a linkage near the front of the carb. You will see 3 holes in the linkage, most likely you are currently using the outer most hole. Move the linkage to the inner most hole and give it a try. If it eliminates your problem yeah!!!! If it doesn't then I would look for someone in your area who is clever at tuning carbs and setting up engines. A little experienced help is hard to beat sometimes.

 

[69MyWay]

I think you are too lean. You need to richen up the accelertor punch circuit, and make sure the rear secondaries are opening at the right time.

This is a common problem with that carb.

You might call the tech line for better advice.

 

[cmegga]

Im not sure if its related or not, bit I also run the Edelbrock foam air filter, that little triangelular one. Due to hood clearance. And I have been melting the foam . Always one hole in the dead center after about 2 weeks of driving . Is this normal ??


Anyone have any simple advise for a novice on playing with the mixture as to make it run richer / leaner . Their are two adjustment scews in the front of the carb will these let me do some fine tuning ??

 

[page62]

Use a "drop top" filter instead of that cheap foam thing!

Have you had any backfires? That would burn a hole right quick. Other than that, you've got me scratching my head.

 

[cmegga]

Any idea where I would find a drop top filter ?? I have been looking for a better filter solution, but had no luck. The stock set up wont fit even wit the top off or atleast be able to close the hood. I have a 2 inch riase after I change my manifold. Any places I find a good low clearend filter would be apreachiated.

 

[RalleyRed]

cmegga,

I'll let someone with some experiance help you with the tuning issues.

I just want to tell you that you really want to fix this backfiring situation fast, I lost an original 780 holley due to melting the venturi's(sp?). Original or not you don't want to destory a carb, they're not cheap to replace!

Rick

 

[AKRAY4PLAY]

cmegga,
it sounds that the overlap of the cam you have is dropping the vacuum at idle too far for the carb set up you have. the result is the fuel/air mixture is not atomizing very good because most carbs have a hard time metering fuel with little cfm and small vacuum. edelbrock sells a good tuning kit with a very informative booklet. you will need to change metering rods and springs to get that carb to work worlds better. the book is written in plain english that everyone can easily grasp the concepts and wealth of information contained in it. as for the air filter, k&n makes a good drop base set up that should clear your hood. i think the air cleaner and tuning kit are around $80 a piece. best of luck, brian

 

[cntrhub]

That puppy sounds way too lean at the bottom end. There is more air than fuel entering the engine...especially WOT at a dead stop. Start off with a launch at say 15mph, and then stomp on the throttle. What happens? If it falls on it's face again, you might want to fatten (go rich) the secondary jets.
Forget about adjusting the idle screws. The primaries are used to handle the idle fuel supply. You could move the accelerator pump plunger arm closer to the diaphram to increase the initial squirt for added fuel. If this doesn't help, recheck float level.
But, first things first. Make sure the iginiton system is advancing properly, and you compensated for your engine mods. Start with the ignition first...then chase a fuel problem.

 

[cmegga]

I have the msd 6a ignition, so im thinking that would be adiquate for the ignition.

Also I did the metering rods and springs as well about a month ago. I called edelbrock and they gave me some part #'s for a spring kit. they had me use the pink springs an a shorter metering rod. My mechanic did the instal and it seem to perform better afterwords. I dont notice the porblem till this week and it has been pretty consistant. That kinda what making me think it might be an adjustment .