Just swapped from a TPI setup, engine is a mild 350 with a melling torquer cam, the idle is supposed to be "good", it sounded stock with my TPI, no lope at all.

I put on a GM ZZ4 manifold and an Edelbrock 600 Performer carb with electric choke, Holley fuel preasure regulator at 6.5 lbs, using the original in tank electric pump with fuel return properly hooked up and working.


When I start my car up it sounds like I have a huge lumpy cam in the car, almost like a dragster only at about 700 RPM. The idle actually sounds *really* fricking wicked, but I know that my setup shouldn't sound anything like that, so I assume something is wrong. It has no problem idling, never bogs out or dies, and accelerates just fine.

Now, the manifold has spots drilled for an EGR, which is currently blocked off. I can tell that the block off is leaking, so I think that might be my problem.


Also, on the highway when I'm cruzing, I can feel the car "surge" just a little bit, but I don't see any changes or bouncing in the RPMs. TCC is not locked. I'm told this can possibly be "vapor lock" or something?


Any ideas? I can't seem to get the EGR spot to block off good, so I'm probably going to pick up a manifold that has no provisions for an EGR what-so-ever.


Thanks! I'm new to carbs

 

I got the EGR plate to seal better, I used some high temperature RTV, it's sealing alot better now, but the gasket is already blown out, I'll get another gasket as soon as I can. The better seal has corrected both the idle problem and I think the highway cruising surge problem as well :-D

I have one question, there is a female vacume hole on the carburetor below the electronic choke, there wasn't a vacume cap included with the set to plug it up. Someone else told me that he was wondering about the same thing on his Edlebrock 600 EC, does anyone know anything about this vacume hole? Should it be left unplugged?

Thanks!

 

No vacuum hole should be left open. The only thing you can leave open is the bowl vent, but those are near the top of most carbs and it is only on emission controlled carbs. I say that cause alot of people mistake that for being some kind of vacuum line, but all it really is is a breather for the fuel bowl and a emission line goes from it to the charcoal canister. Other than that, I aint sure what your vacuum hole could really be for, except maybe an accesory type deal. Maybe for a thermostatic air cleaner? Anyway, try blocking it off and see how the idle of the car reacts. I would imagine it shouldn't be left open if you have no use for it.

 

On edelbrock carbs........

Looking at the front, left to right, you will have 3 vacuum ports. left is ported, middle is PVC, and right is manifold. Don't leav ANY of them uncovered.

Here's a nice link for tuning it, and just ask if you have problems.

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


Tom

 

The only vacuum line that is left unplugged is the one on the electric choke. It's very very small in diameter, I'd say it's about the diameter of the ink tube inside a standard BIC writing pen. I put my finger over it, one of the levers on the choke moved up a tad bit, but I didn't notice any change in how the engine sounded. I guess I could just cram a piece of rubber inside there, it's like a small screw hole with no threads, it's not a male end.

The 3 male vacuum ports on the front are covered. The middle goes to the driver side valve cover, the driver side vacuum is capped and the passenger side vacuum port goes to the distributor. The rear vacuum port goes to the break booster I believe.


Well, I got the EGR plate to seal 100%, no sound or air coming out (that I can tell, even following my hand around the entire seal, no air). Now the funny part is, the "huge cam dragster idle" is back. Earlier today I got the EGR plate to almost (but not quite) seal 100%, and the car idled like a purring kitten, smooth and steady. Now later today after the EGR is sealed 100% the dragster idle is back.

I had to crack my cutout open for a few seconds just to hear what it sounded like with open headers... I kid you not it sounded like a dragster or prostreet car at a 1/4 mile track. I'm worried that something else is going on here, I touched nothing but the EGR plate 3 times, and the idle went from dragster to purr to dragster, each time I shut off the car and started it up again, no change in the idle.

Anyone have any theories as to what might be wrong? Thanks for that link, I'm going to read up on it.

 

What are the stats on the Cam?

Have you checked to see what your timing is at? And just for S's &G's, check to see if your intake hasn't come loose. Also remember that the ECM was making adjustments for you based on a few different sensors. The only thing the carb has is teh booster signal and what YOU put it at.

 

whats S's and G's? I don't know what the timing is at, it's a little bit advanced I think. Just did it by ear.

The cam is a Melling MTC-1 cam, it's very mild, it's supposed to produce good torque and good gas milage.

http://www.melling.com/production1.htm first cam on the list

 

Sh*t's and Giggles.

Not really sure. Thought that overlap might be coming into play...but then again maybe not. I'm just as stumped as you...

I'll leave this one for more of the experienced guys. Sorry.

 

I think I might have found the problem, when I pull the #1 plug wire the idle doesn't change.... that would mean either the #1 plug, or the #1 wire is bad, right?

Well, that sounds like a possibility... how do spark plugs/wires go out, do they kind of fizzle in and out before they go? or do they just go? Because for part of the day yesterday the idle was just fine, but before and after then the idle was crazy again.

I'll pick up another spark plug tomorrow and see if that works.

 

You maight have nicked it or kinked it. I've had a few plug wires go out before, not not just at idle...I'd be safe and change both....Good Luck.

Keep us posted.

 

new plugs and wires, the idle sounds a little bit better, i think.

Here is a recording of it, granted it's not warmed up during this recording, it doesn't sound much different once it's warmer, only a tad bit slower. I'll try to get a better recording tomorrow, it was way to close to the car when we recorded it, I tried to clean it up as best I could.


www.danielbuck.net/wip/idle.mp3


Does that sound like a miss, or does it sound like cam? Anyone here have a Melling MTC-1 cam, does yours sound like this at idle? I have 1.6 rockers.

 

Hard to hear it...I'll wait for the other recording...

 

you said it feels like it surges whn you are on the highway and up to speed right. i had a nissan 300zx and it did that. the plugs and wires mostly the wires were bad and i replaced all of them and it cured the symptomes. that cam will not lope like that. i have a 327 350hp cam 222/222 447/447 at.050 and it doesnt lope like that. cap and rotor too. especially if it feels like its surging. thats a sure sign of bad wires.
flores

 

the surge isn't there anymore, it's just the idle now. I think the surge was from the EGR plate leaking. when I fixed that the surge went away.

Speaking of plugs, I put in ACDelco's and gapped them to .45, is that a good gap specification? The wires are Accel 8mm wires.

 

45 is good. you can verify this by getting a repair manual at a parts store ( or just pick the appropriate book up and quickly find the specs acting as if you are only glancing at the book out of intrest in buying it.) This assuming your sticker on the underside of your hood is no more.