Edelbrock carb issue

[MacGyver72]

Hey everyone. I need some help. I recently installed a new edelbrock 4bbl performer carb on my 350 and it was great for the first week. Now it idles extremely fast. The choke is working, the idle screw is not seated on the throttle linkage cam and there is plenty of slack in the cable for it to do so. I haven't checked the throat for a foreign object holding the throttle open but that's my next move. Anyone have any thoughts?

[hugger6933]

Is your return spring strong enough? I remember some OE Carter carbs in the 70's that if the spring got weak or broke the carb would open anywhere from a cracked throttle to wot!

[Boog]

Vacumn leak below the carb. ?

[MARKDTN]

Originally Posted by Boog

Vacumn leak below the carb. ?

A good place to start-look for blown out gasket or other leaks.

[RUSHNBOBO]

Be sure your choke is full open when warm (if not make proper choke adjustments) then observe the fast idle cam screw (make sure it is not touching the cam, when full open)..... it may need to be adjusted down.

[GASoline71]

Did you bolt the carb onto a stock spreadbore manifold? Did you use an adapter?

You have a bad air leak somewhere.

Gary

[RUSHNBOBO]

vacuum leaks suck

[s102000]

Originally Posted by GASoline71

Did you bolt the carb onto a stock spreadbore manifold? Did you use an adapter?

You have a bad air leak somewhere.

Gary

I agree, if you have the stock manifold you have to use the correct adapter...

[domeier]

I had all four of the primary throttle plate screws loosen up on my 4106. The plates were sliding around and would hang open, which raised the idle. Thank Jeebus I caught it before any of the screws fell into the manifold. They're installed now with fuelproof Loktite. Should have come like that from Edelbrock.

[MacGyver72]

I used the proper adapter but I'll check for an air leak. thanks a lot guys. What puzzles me more than this has never happened to me before is that the throttle cam isn't touching the idle screw as if the throttle was being held open by something.

[RUSHNBOBO]

check fast idle adjustment ....should be on the opposite side, this is for cold start and keeps the plates open slightly when the choke is closed or partially closed....could be stuck or your choke appears to be fully open but isn't. This will keep the fast idle cam on the set screw....and plates slightly open.

Also as noted in above posts, look down the carb throat while operating the accelerator and see what else if anything could be keeping the plates open. domeier, makes a good point, quality control ain't what it used to be....don't assume that those plates might not be loose, it just takes one screw on the primary or secondary, to keep the plates open. If you can't see anything obvious, take it off the truck...and inspect every moving part closely, you'll probably find it right away.

[MacGyver72]

I'll check the throttle plates tonight. That sounds like the culprit. I'll get some loctite for the screws too. Thanks a lot guys for all the help. I'll let you know what I find.

[GASoline71]

I've seen cats accidentally install those adapters upside down. Also the adapters can just lead to leaks anyways. I stopped using them back in the 80's. Just went ahead and got an aluminum square bore intake manifolds.

Gary

[MacGyver72]

I found that the throttle plates were not closing all the way. I loosened these and after retightening them corrected the issue with the mains but the secondarys are still showing ever so little daylight through. I adjusted the choke and it IS better but I still can't get it to idle below 1100. I have the adaptor on correctly and there seems to be no drag there but I now have a performer intake to install and will do so as soon as i receive it from the polisher. Thanks for the help guys.

[hugger6933]

Spray some carb cleaner around the baseplate [with the engine runnig of course] and listen for any RPM change I think it is there

[hugger6933]

Also check the big fitting on the back of the carb to make sure the leak is not there

[RUSHNBOBO]

Originally Posted by MacGyver72

I found that the throttle plates were not closing all the way. I loosened these and after retightening them corrected the issue with the mains but the secondarys are still showing ever so little daylight through. I adjusted the choke and it IS better but I still can't get it to idle below 1100. I have the adaptor on correctly and there seems to be no drag there but I now have a performer intake to install and will do so as soon as i receive it from the polisher. Thanks for the help guys.

Hugger6933 is right about that hole directly on the back of the carb, it is direct manifold vac and is left open when new, make sure its plugged, or has some hose to brakes or other source attached. This is a very common mistake.....make sure your absolutely not chasing vacuum leaks before moving on. There is often a distinct whistle from a manifold vacuum leak, but it can also be more subtle.

You can even disconnect all the vacuum lines and plug them temporarily to eliminate things such as a punctured brake diaphram etc. Also a small propane torch (not lit ) on LOW works good to find leaks.

When you say you see daylight through the secondaries when closed, this is a bit troubling. At idle 700-800 rpm, the plates should appear to the naked eye to be closed...they only need a few thousandths gap to hold this rpm. How much gap do you have ? can you run a feeler gauge through and measure it ?
Are your primaries now touching the adjuster screw when turned in a few turns ?

While you tightened the plates did you firmly hold the throttle arm closed? ...if not there is a little play and you may have tightened them slightly off center...it just takes a tiny bit to open those plates and the rpms will go up.

Ok that's a lot of questions for now ....process of elimination....one thing at a time and you'll get it.

Rush.......

[MacGyver72]

These are all good suggestions, I'll check them out tonight. Answers to your questions Rush. Most of what you have asked I have checked and found no issue. The secondary plates are a couple thousands open. I did hold the throttle closed when tightening the plates but could not get them closed any more. I really think that is my issue but I will certainly check the base gaskets and the coupling to the brake booster first.

[domeier]

I had a 600 Holley on my truck when I bought it, but I gave it to a buddy when I bought the shiny new Edelbrock. Bad move. I've spent a whole lot of time getting the throttle plates adjusted correctly, not to mention those loose screws mentioned above. Also, there's a lot of slop in the throttle plate shaft. No excuse for that besides lousy machine work at the factory. It doesn't suck air at the throttle shaft (not yet, anyway,) but that's one more thing you should check. You can spray a little carb cleaner at the outer shaft bushings and see if the rpm changes.

Something's still not right if you can't get it to idle below 1100 rpm.

If all else fails, see if any of your buddies are dumb enough to trade you a Holley for it!

[MacGyver72]

OK. there are no vacuum leaks and the base gaskets are good too. Issue is definitely mechanical to the carb. I'll take it off again today or tomorrow and figure it out.

[MacGyver72]

OK everyone. I finally got this thing right. The throttle plates of the secondaries were not closing all the way. Just loosening them didn't fix it. I had to remove them and replace them on the shaft to get them to close completely. It seems that they needed twisted sllightly in the bore to properly match the machining on the edges which had no obvious anomalies so no filing had to be done.

Thanks for all the help and advice.

[RUSHNBOBO]

Originally Posted by MacGyver72

OK everyone. I finally got this thing right. The throttle plates of the secondaries were not closing all the way. Just loosening them didn't fix it. I had to remove them and replace them on the shaft to get them to close completely. It seems that they needed twisted sllightly in the bore to properly match the machining on the edges which had no obvious anomalies so no filing had to be done.

Thanks for all the help and advice.

Glad you finally got it, I knew we were on the right track when you said the plates did not appear to be closing all the way; that had to be it. Stop back any time.......the bill is in the mail