Thread: Blown collector gasket causing rough idle when cold?

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Here goes another thread, I apologize but I'm running through a laundry list of little issues with this truck as I just got it a little while back. It should be kosher soon!

So I've been told by one person that this exhaust leak could be causing a very rough idle when the engine is cold. Once it's up to around 180 degrees and you go up the road about a mile it completely goes away. ( could make sense as the pipe expands and seats as it warms up)

I've heard from an expert that it is the issue, then I heard some rumors that it shouldn't cause this issue. The gasket was almost non existent when I pulled the pipe apart. I ordered some rather nice collector gaskets off summit to replace it.

What's your take? An issue or no. Oh and this is also a manual choke edelbrock 600 brand new, timed at 36 degrees. The choke open or closed makes no difference.

A collector leak is not going to affect your idle quality. If that were the case you would expect a rough cold idle with your headers open, right? I'd say that you have a minor carburetor problem, or perhaps your plugs may be a bit weak - hot enough when everything is warmed up, but a slightly weak spark when cold. Have you looked at your plugs for electrode color? Changed plugs since you got it? What plugs are in the engine?

Yea they are new plugs gapped down to .35 I think it was. I had a shop time it and tune the carb. That's when he told me about a header leak which I fixed with some nice earl gaskets. They actually did the plugs when they timed it, I haven't pulled one since though. He cited the header leak as the issue actually, that's fixed though.

Could a bad voltage regulator in the alternator cause it for some reason? Maybe improper voltage to the distributor? I know it needs done as its not putting out what it should

Have you tried different choke settings, other then full open or closed. You control that cause it is manual, happens to be my preference also. Are you saying at a fixed RPM it is running ruff as if missing or you are blipping the throttle to keep the motor from stalling?

Has this truck been sitting not driven before you got it? The plugs changed were they black as if running rich, what do they look like now ? How many miles have you put on it since you bought it, few or a couple of hundred? Maybe it just needs to be driven. Could run some Marvel Mystery oil down the throat of the carb to clean up the heads, valve guides and seats. These are just some things to consider.

When it is up to temp and all is well it could indicate the need to be driven, take it on the hi way run it 60 or so for 10-20 miles. Cars as well as any machine needs to be run, exercised to keep them running well.

I am wondering what you are trying to say here and what makes you think this ; "Maybe improper voltage to the distributor? I know it needs done as its not putting out what it should"

What kind of system, point, hei, msd type?

Originally Posted by pepi

Have you tried different choke settings, other then full open or closed. You control that cause it is manual, happens to be my preference also. Are you saying at a fixed RPM it is running ruff as if missing or you are blipping the throttle to keep the motor from stalling?

Has this truck been sitting not driven before you got it? The plugs changed were they black as if running rich, what do they look like now ? How many miles have you put on it since you bought it, few or a couple of hundred? Maybe it just needs to be driven. Could run some Marvel Mystery oil down the throat of the carb to clean up the heads, valve guides and seats. These are just some things to consider.

When it is up to temp and all is well it could indicate the need to be driven, take it on the hi way run it 60 or so for 10-20 miles. Cars as well as any machine needs to be run, exercised to keep them running well.

I am wondering what you are trying to say here and what makes you think this ; "Maybe improper voltage to the distributor? I know it needs done as its not putting out what it should"

What kind of system, point, hei, msd type?

Good info, yea the truck sat for awhile before I purchased it. It doesn't have many miles on it I think less than 5000. I'm not sure how long it sat before I got it, not a terribly long time from the condition.

As far as the ignition it's a Mallory electronic ignition which I just did the cap, rotor, plugs and wires on before the shop timed it and tuned the carb.

I probably have driven the truck a few hundred miles since I got it. Maybe 200, I was daily driving it over the summer so that all the little issues would come out, they did the truck actually shut down on me while driving it.

After this alot of little things came out. I so far I replaced
-The cap, rotor, wires, plugs
- put a new 600 edelbrock carb on it ( an oversized 750 Holley was on it)
-all new vacuum and fuel lines
- earl header gaskets and Percy's collector gaskets

This was all before it went into the shop to be fine tuned. They said it ran good with 36 degrees of timing, and it does. In fact I drove it today for awhile and it runs perfectly. The shop said take care of the exhaust gaskets and then if it's still off to bring it back in.

Now the truck had only been parked 3 days and it was almost dead. So that alternator needs attention soon. This is why I think it may be the issue. I also haven't played with the choke to much yet.