Edelbrock advice needed

Normspeed · March 27, 2007, 05:25:38 PM

I have a buddy with an Edelbrock 600cfm on a 350 Chevy. Always ran good but lately it developed an intermittent backfire through the carb at highway speeds. It will pop anywhere from once to three times then run ok then pop again. If he pushes the throttle down til you hear the secondaries open it runs fine. It's just right around the top end on the primaries. I'm thinking lean mixture. Someone suggested it might be a low float level. Anyone had a similar problem? What cured it?

model a vette · March 27, 2007, 06:04:12 PM

Check the condition of the hose going to the vacuum advance.

EMSjunkie · March 27, 2007, 08:28:27 PM

Quote from: "model a vette"Check the condition of the hose going to the vacuum advance.

I agree, sounds more like a timing issue rather than a fuel issue.

but what do I know :?

Vance

Grandadeo · March 27, 2007, 09:53:56 PM

I hear ya Norm. Check the hose, vacuum advance - may be an epidemic, and the timing.

Lee

C9 · March 28, 2007, 08:30:44 AM

Low fuel pressure?

Vacuum leak? (Strikes me as a likely culprit.)

Metering rod stuck closed? (I've had em stick open, seems the opposite could be true.)

Points ignition? (The rubbing block could be worn down and the points almost closed. This acts like a carb problem, but usually at low speed.)

Stick a vacuum gauge on the engine and see what you get.

You may want to peruse the Edelbrock carb manual.
Lots of good information in it.
I've followed their tuning recommendations and was especially pleased at how the engine ran after moving from 350' altitude to 3300' altitude which required a touch of leaning the carb down.

Go here: http://www.edelbrock.com/automotive/eps_intro.html

Normspeed · March 28, 2007, 12:15:29 PM

It has the HEI distributor. I'll look for the Edelbrock manual and see what it says, and take a look at the initial timing and vacuum advance.

enjenjo · March 28, 2007, 01:40:27 PM

Check the timing chain for wear. Also a cam going away can cause this in the early stages.

Rrumbler · March 30, 2007, 08:22:56 PM

Yeah! Any and all of that stuff, plus, take a look at the plug wires.

My story: '68 396, Holley 750, points ign. Started acting like that, so I tried all of the usual; went through the carb with a fine toothed comb, same with the distributor, scoped the timing out, nothing worked, and it would ease up a bit, then set in again. Finally, one day, one cylinder went dead, and by the time I got home (some 40 miles) it was running on only six, and popping and smelling real bad. #7 and 8 cam lobes were gone - almost, litterally. I hope that's not the case for your friend.

The plug wire business is sort of the same kind of story. Fresh rebuilt I6, but in the interest of frugality, my friend had me use the old wires, and everything seemed fine, until it got really foggy in the morning, then dried out in the afternoon. I went throught the same drill: checked all of the usual suspects, no joy. Then, a guy that I was fussing about it to asked me if I'd looked a the plug wires; seems he had had that experience. DOH!!! The resistance on some of them was so high, that it's a wonder they would fire at all - and probably weren't. Replaced - okee dokee; no more problem.