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Old 05-17-2007, 04:07 PM
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350 won't idle under 1000 RPM

I'm having some troubles with my 350 sbc. I had another post made but it was getting long and stretched on. So here's a new one thats more "all in one"

When driving down the street the car randomly started stalling when the RPM's go under 1000. I pulled up to a stop sign and my car stalled. It does this all the time now and I'm not sure whats wrong. It seems to be missing but I'm not sure. The #8 cylinder was missing so I changed the spark plug and it still misses. My wires were stripped a bit and electrical taped so I replaced those aswell with brand new ones. The intake was just redone but there doesn't seem to be any leaks. I have sprayed carb cleaner around the edges of the intake while it was idling but the idle didn't change(I cranked it to idle at 1500RPM). The car runs over 1000 RPM but sounds like it's still missing a bit.

What should I look at? Burnt valve? Seized valve in the valve guide? Should I do a compression test?

Vehicles a 1974 Nova SS with a 350 and turbo 350 transmission. Same engine problem whether its 1,2,3, neutral,reverse, park all that. Its got a 2200-2500 stall with a stage 3 shift kit and full manual valve body. So there's almost no vaccum lines to worry about other then the distributor advance, power brakes and my vaccuum guage.

I think thats everything. This is my daily driver. Can anyone help?

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Old 05-17-2007, 04:39 PM
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First thought is a massive vacuum leak. Since #8 is giving you problems, first do a compression test on that cylinder.

If that proves ok, i'd block one breather with duct tape or some kind of plug, then pull the PCV valve and get it running and put your finger over the PCV hole and see if it starts sucking on your finger. If it does, you may have an intake gasket leak on the inside of the engine. Possibly the wrong gasket was used and it's finally slipped out or sucked in or ?????? Simple test for an area you can't see.

Mark
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Old 05-17-2007, 05:42 PM
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I have to agree with vacuum leak. Did it run OK after the intake change for a period of time and then start this issue? You may have more than one problem. Try to isolate the source of the skip(compression, bad cam lobe, ignition problem ect...)and then look for the vacuum leak. If not obvious, pull the intake anyway, just to make sure.
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Old 05-17-2007, 05:52 PM
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I had a shop do the intake. So they told me that they would redo it for free if that was the problem. I paid $200 for them to put the intake on so I sure hope they will do it for free. If it wasn't at his shop at the time I would have done it myself.

The car's only getting about 18psi of vaccuum at 1500 RPM. I'm thinking I'll do a compression test on a few cylinders and see what I can come up with. Right now I'm not running a PVC system I just have two breather caps. So there shouldn't be any vaccuum pressure under the valve covers?

When the engines warming up I can see blowby smoke coming out of the breathers. I'm guessing I don't have an internal vaccuum leak because of this. The car was running fine for a while after the intake was put on. About a week of daily driving.
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Old 05-17-2007, 10:24 PM
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Hmm, blowby from both covers is not a real good sign. While any engine will have blowby, the vacuum leak (if that's what it is ) is only affecting one cylinder. It doesn't take much to lean out one cylinder and the evidence of blowby is not a solid indication that there is not vacuum leak.

Start with a simple compression ck and then try what I suggested, although the excess blowby may override a small leak.

Mark
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Old 05-18-2007, 12:14 AM
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The blowby was just coming out of the passenger side valve cover. I'll do a compression check tomorrow if I can get a chance. Long weekend! Got the whole day to work on the nova tomorrow.
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