Corvette C3 Forum 1968 through 1982

Rough Idle

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  #11  
Old 05-24-2009, 12:33 PM
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Originally Posted by SCHOON
Pulled plugs today, 2 were wet with gas.
Put news one in and car has a lot more power then before, idle still on rough side.
Now the question is what made the plugs wet?

Schoon
A fouled plug will get wet from not firing properly. You can get a bad plug from the parts store on a regular basis, seems not to be much quality control f/ any of them. If you got alot more power after installing new ones, that'd probably be your answer. Now that the engine is running pretty good, check the color of the plugs after driving it afew days to see if they are all the same, meaning all the cylinders are firing equally. If one is different from the others, you can run the checks on that cylinder. If you trace wet or dry plugs to one manifold runner, then one side of the carb isn't working correctly; maybe a stopped up port, etc.
As mentioned in another reply, a rough idle can be the cam you have. A vacuum gauge will tell you alot of things. If you have one, use it and read the booklet that comes w/ it.
If you don't have all the crap smog devices that came on the early/mid 70s to early '80s cars, you're better off, as having a strictly mechanical and smog device free engine makes it easier to figure out when something goes wrong. It's straight simple mechanical logic.
If you have more problems with the car not running right, I'd look at the carb. Read the plugs first.
 
  #12  
Old 05-24-2009, 01:28 PM
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Jim,
My carb is shot!
Havn't re-checked the new plugs yet.
Tried to reset the foats and one of them fell apart.
My idle was set at 6oorpms and every time I stopped it would be at a different rpm.
Ordered a new 700cfm Holley dp from Sumitt.

Schoon
 
  #13  
Old 05-25-2009, 05:59 AM
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Originally Posted by SCHOON
Jim,
My carb is shot!
Havn't re-checked the new plugs yet.
Tried to reset the foats and one of them fell apart.
My idle was set at 6oorpms and every time I stopped it would be at a different rpm.
Ordered a new 700cfm Holley dp from Sumitt.

Schoon
Forget the plugs. W/ a bad carb, it won't matter. When you get the new carb, you can adjust it, install some new plugs and then keep a close eye on the them, they'll tell you everything.
Glad you found your problem.
 
  #14  
Old 05-29-2009, 04:51 PM
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Bad day today for me.
Put the new Holley 700cfm, dp on the vet.
Started her up and there was a very loud noise coming from engine sounded like a supercharger.
Checked all the vac connections and snugged the nuts holding the carb down.
Still same noise plus the car would only run for a few seconds and die out.
Now I am at a total loss so I call Holley tech and speak with them.
They thought I was nuts so I let them hear the noise over the phone.
They said never heard anything like that and I should call Sumitt and get a new carb.
Makes me think they have had this problem before.
So now I call a mechanic friend of mine who said put the old carb back on and see if you hear the noise, why didn't I think of that.
So I put the old one back on and when I was tightening one of the nuts I cracked one of the bosses on the manifold containing the threads. Maybe this was the problem, a slight crack causing a nasty vac leak.
Now I need to find some type of epoxy like JB W eld and see If I can fix the new problem.

Not my day!
Schoon
 
  #15  
Old 05-30-2009, 11:12 AM
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Oh ****!! Total drag. Yes, the noise could be a vac leak caused by the carb not seating, but did you actually have that cracked thread situation the first go-round? And w/ a leak like that, the idle should have gone WAY up. Did it?-I mean during the first go-round, the first time you did the changing of the carb-old to new. Even w/ three sides snugged though, w/ a good gasket, there shouldn't have been THAT big of a leak. If indeed I'm understanding what the noise really sounded like.

There is some kind of apoxy that'll fix that thing. I have used JB weld on a manifold years ago, my 223ci 6 cyl. Ford pick up engine, where there was a vacuum fitting (a capped-off source f/ something that my truck didn't come w/) that I can't remember how I did it (19 years ago), but I cracked the manifold and filled the whole thing in, threaded hole, crack and all, w/ JB Weld. Today, it's still the same way and runs like a champ. I fixed that manifold as I had bought, three years prior, the only other manifold like it, and there were no others, locally, to be had.
Please post and let me know what's happening w/ your situation.
 
  #16  
Old 05-31-2009, 07:33 AM
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Jim,
You are right the first time I started it up after installing the new carb the idle went up to approx 2000rpm's.

I used Loctite weld to fix the manifold now waiting for the replacment carb from Holley.
Stay tuned.

Schoon
 
  #17  
Old 05-31-2009, 08:25 AM
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Schoon,
Did the carb base have some kind of warp to it? WOW, what are the chances. Yes please, keep us posted...
 
  #18  
Old 06-06-2009, 05:44 PM
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Smile

OK, finally got her all back together.
Had a tough time keeping the accelerator bracket from moving back and forth on one of the studs holding the carb in place.
Had to weld a piece to keep it in place.
Anyway first couple of times I took her for a ride and nailed it i wasn't really impressed.
The new carb made a lot of nosie but the Vet just didn't fly.
Went home made some adjustments and took her back out.
This timethe Vet scared the crap out of me, holy **** rubber in 3 gears.
No that's what Im talking about.
Don't know what happened but I sure am pleased with the results.


Schoon
 
  #19  
Old 06-07-2009, 07:39 AM
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You gotta love it! Love the smell of burning rubber in the morning.
How was the service when you swapped the carb out?
Any fix that took that long will require a lot of seat time to prove it out.
 
  #20  
Old 06-07-2009, 04:09 PM
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Burning rubber smells like victory.
 


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