Timing/Carb question

[milit73]

I have searched the forums but could not really figure this out. I have a 383/727 combo in my Superbee. I have replace the carb with an Eldebrock 650 Thunder Series and it run pretty good but will stumble off the line and then go all out. Now I see there is another ajustment for the accelerator pump as this is in the middle hole at this point. Should I move this or leave it as is or is there something else I should do?

Also I bought this engine years ago and was told that the cam was not stock but I have no idea what is installed. I have it set at 10 degrees BTC as my book states but with a different came should I try something else? Again thanks for the help. Jim

 

[HEMI-ITIS]

What's the total timing and when is it "all in"?

 

[RustyRatRod]

I don't know if the pump shot is the problem, but to answer your question, much like a thermoquad, the hole closest to the carburetor delivers the largest pump shot. Much in the same way a 1.6 rocker arm moves the valve more since the pushrod is positioned closer to the rocker shaft on the 1.6.

 

[Meep-Meep]

It's amazing how much a cam will affect how a carb works. If you have a new carb with the factory supplied jetting then it should work pretty well or at least not have huge drivability issues.

What is the manifold vacuum at idle in neutral and in gear? When does it have the hesitation? When you stomp on it from a stand still? Or on tip in like taking off from a light? The accelerator pump should be just fine in the middle hole with a stock type intake. Try bumping the timing to 15 deg initial but make sure the total is not more than 38 deg with the vac advance disconnected. The vac advance should add about 10 deg but only under light load. If your engine has some rumpety-rump cam then you will have some major carb tuning to do.

 

[milit73]

What's the total timing and when is it "all in"?

That I am not sure of at this time.

- - - Updated - - -

It's amazing how much a cam will affect how a carb works. If you have a new carb with the factory supplied jetting then it should work pretty well or at least not have huge drivability issues.

What is the manifold vacuum at idle in neutral and in gear? When does it have the hesitation? When you stomp on it from a stand still? Or on tip in like taking off from a light? The accelerator pump should be just fine in the middle hole with a stock type intake. Try bumping the timing to 15 deg initial but make sure the total is not more than 38 deg with the vac advance disconnected. The vac advance should add about 10 deg but only under light load. If your engine has some rumpety-rump cam then you will have some major carb tuning to do.

It has hesitation off the line stomping on it and sometimes if I hit it wide open going down the road but I think that is when it is not completely warmed up 160 degrees or so.

As far as vacuum off the manifold I will have to get the tools to check that.

 

[67 coronet]

if the cam is not stock,then you need to bump up the timming a bit.why not bump it up about 5 degrees and see how it drives.test and tune is always the best way to figure out a problem.

 

[super-bee_ski]

All good info from above.
Also, Edelbrock has a web site. On this web site they have a instructional video of how to "DIAL" in your carb.
Did you buy the carb brand new?
If so, then you should have a DVD provided by Edelbrock with instructions on changing jets, calibrating your metering rods etc.

 

[RustyRatRod]

Well.....I don't care how good the video is. Metering rods respond to vacuum. If the vacuum is too low, they ain't got a spring that'll make it work. I've been there and done it. I've even tried removing the spring altogether. To me, if you run a big cam with LOW vacuum signal, the Holley or Holley style carburetor is the way to go. I've had more out of the box success with Holley than any other and I've tried a whole bunch.

 

[milit73]

Yes I bought it new and actually forgot about the CD. I will check that out and check the vacuum when I can get that tool.

 

[1948 santa]

Like RustyRatRod said Holley is the way to go #4778-#4779 and total timing at 30 to 38 Deg.

 

[coloradodave]

Disagree. The Edelbrock carburetor will work fine once the timing and tune are adjusted correctly. Throwing a double pumper on a basically stock car with an automatic is not going to solve his problem...

 

[RustyRatRod]

Disagree. The Edelbrock carburetor will work fine once the timing and tune are adjusted correctly. Throwing a double pumper on a basically stock car with an automatic is not going to solve his problem...

I'm not sure I said double pumper. Anyway, I'm a big fan of vacuum carburetors. But overall, you're right, Dave. Normally, you can tune any problems out of an Edelbrock. However, when manifold vacuum drops too low, they are no fun at idle, and there's not a lot you can do to correct it.

 

[Cranky]

I haven't tuned cars by the book in nearly 30 years now. Just the gas alone is way different than it used to be back when these cars were new. Just give it what it likes. It'll let you know when you have too much timing. Back then, you could put in too much timing and it still wouldn't ping but you sure could do some damage after awhile. Generally, I start with 15 initial and go from there but it also depends on the combo you have. Low compression engines usually do better with more too and knowing what your vacuum, cylinder psi etc is all part of knowing what to do.

 

[68suprB]

I agree with advancing the timing. I have a 383 in my super bee, pretty much stock except for the 750 edelbrock carb and comp cam that is too big for the motor. Previous owner had it at about 8 deg BTDC and it was a dog on the low end. I have it at 21 deg initial but because of the cam it only has 5-7" of vacuum at idle, throttle response is better but like yours it stumbles if you stomp on it from a stop or even a low speed...Once it winds up it's ok, but low end just sucks..Not saying the carb isn't all or part of the problem, but the cam may just require higher timing.

 

[coloradodave]

I'm not sure I said double pumper. Anyway, I'm a big fan of vacuum carburetors. But overall, you're right, Dave. Normally, you can tune any problems out of an Edelbrock. However, when manifold vacuum drops too low, they are no fun at idle, and there's not a lot you can do to correct it.

You didn't. 1948Santa recommended 2 Holleys, both of which are double pumpers, mechanical secondaries.