Won't stay running after intake gasket replacement

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jcarr210

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So I swapped out intake gaskets recently and since then it just won't stay running. Essentially I'll fire it up and it will idle way high at like 2500rpm for 2 seconds then die. This will happen over and over. If I rev the hell out of it pumping gas it will hover around 3 grand but will eventually die.

I'm assuming there's a vacuum leak but not sure where. One thing I can think of is I reused the carb gasket that looked perfect when I took it off. Also when I placed the intake down it was off center a bit so I had to lift it and put it down again. I don't know if that moved the gaskets or screwed up my rtv beads in the front or back. Nothing is disconnected and there are no unplugged ports on the carb. With the cam I don't even know how much vacuum it should have normally vs with a vacuum leak. Also, I can't keep the damn thing running long enough to spray around and try to find it that way.

Oh it's a 340, edelbrock heads, edelbrock air gap manifold, big cam, and used edelbrock intake gaskets. I'd really appreciate some advice to point me in the right direction. Thanks.
 
If the intake is new...it might need a milling, if it sits too high...it will leak air at the ports. Does it smoke as well?
 
No the intake is new though I never would have thought of that. Car isn't smoking thankfully.
 
aluminum intake? did you change the intake or same intake, new gaskets?
 
jcarr210 said:
reused the old carb gasket
Oh it's a 340, edelbrock heads, edelbrock air gap manifold, big cam, and used edelbrock intake gaskets. I'd really appreciate some advice to point me in the right direction. Thanks.
Click to expand...

That might be an issue, but I couple that with the new intake being of poor fitment.
 
Sorry I messed up. The intake is not new. I just replaced the gaskets with edelbrock gaskets that came with the car. I'm having a buddy come over in a bit to spray around while it idles for 2 seconds to see if we can find it. Does vacuum leak sound like a reasonable explanation or could it be something else? I literally just pulled the carb which is a Holley street avenger, the edelbrock intake, cleaned it all up, and put it back together. It ran great prior to replacing the intake gaskets.
 
Take the intake off and start over. It didn't seal
The only other thing it could be is you missed something hooking up the carb
 
Yeah no progress since then...been too busy to really mess with it but I'm off for a while now and getting back at it. That pcv hose is connected as is everything else. If I can't narrow it down here in a bit I'm going to try the carb gasket first and if not I'll do it all over again. Thankfully it shouldn't be on there like concrete this time.
 
did you mess with your carb settings at all?
idle speed screw and the idle mix screws???
 
Didn't touch a thing on the carb. Yeah I knew it ran perfect before and figured I screwed something up and didn't wanna try fiddling with the carb.
 
This is kind of old but turns out I was an idiot. I finally got around to messing with the car and with carb cleaner I was able to find the vacuum leak at the carb to manifold gasket. When I lifted the carb off I saw that I somehow put a thin washer on one of the manifold studs between the intake manifold and carb so it never layed flat and leaked like crazy. Pulled it off, threw on a new gasket, and runs great.
 
jcarr210 said:
This is kind of old but turns out I was an idiot. I finally got around to messing with the car and with carb cleaner I was able to find the vacuum leak at the carb to manifold gasket. When I lifted the carb off I saw that I somehow put a thin washer on one of the manifold studs between the intake manifold and carb so it never layed flat and leaked like crazy. Pulled it off, threw on a new gasket, and runs great.
Click to expand...

AAAHHH, ha ha ha ha ha ha ha.

Oh, I mean that sucked. :D

Happens to the best of us sometimes, but at least you didn't just sell it because of that.
That would be unforgivable.
I bought a 66 Ranchero for 200 bucks once and when I checked into it the check ball in the accelerator pump circuit was gone but they had replaced everything electrical under the hood with new.
I went in the house and got a BB from my son's air gun and dropped it in there (the ball seat looked about that size)
Drove that thing for years, and then sold it for WAY more than I paid for it.
 
I pulled a few boners myself. We all have. Once while putting brake pads in a 65 Corvette, I put them in backwards on one wheel. Gee, what was that grinding noise. Another time on the same car, I put the throwout bearing in backwards. Gee, what is that grinding noise. I have more, but you get the idea. Chin up, mate.
 
Your fortunate. Most of the time when an old piece of gasket is left on the carb or the intake and then you install a good gasket over, you stand a good chance of snapping an ear off of the base plate when you tight it down. I've made that dumb mistake in my lifetime.
 
I have a friend back in to 90's that got a nice 72 Chevelle for WAY cheap because the PO thought the engine was blown. Resealed the intake and he burned rubber in it for years! He might even still have it. ;-)
 
I was replacing the trans on a 4x4 truck once and was in a hurry to get it done.
Well, I got everything all back in and on the truck and went to lower down to put fluid in it and tripped over the converter laying on the floor.
 
Haha well I don't feel so bad it seems everyone has ha d a brain fart moment. I'm especially glad I didn't break the baseplate. The torque converter and throw out bearing stories must have really sucked...much bigger job than lifting off a carb.
 
TrailBeast said:
I was replacing the trans on a 4x4 truck once and was in a hurry to get it done.
Well, I got everything all back in and on the truck and went to lower down to put fluid in it and tripped over the converter laying on the floor.
Click to expand...
Did the same thing many years ago, Built a 3514bl Cleveland for my 72 Ranchero. In walks my brother in law (RIP), that don't know a torque convertor from a fraction convertor, and says pointing to the convertor "Don't that belong in there" as it was sitting on the garage floor. I was almost ready to crank it up!
 
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