Inliners International Forums General Discussion Engines Awfully Rough Idle

I don't know what else to do, I've replaced points, cap, condenser, and rotor button on the distributor. I've also rebuilt my Rochester MV monojet carb and put on a new manifold gasket on my Chevy 250 but it still idles like crap. It shakes the entire car when it idles. I've adjusted the dwell to exactly 33 degrees and no matter what I do to the timing, it still runs awfully. I left the old wires and spark plugs because the wires look pretty new and the I took out the #6 plug and it was just slightly covered in brown as it should be. Do you guys have any ideas what is making it idle so awfully?

Thanks

IS it hitting on all 6?
(If it's not an HEI) pull 1 wire at a time out of the coil, make sure it drops RPM to assure that cylinder was working.

Look for vac leaks with a feeler gage or wd40 spray (when not too hot as noted already).

Try your spare carb.
On anything this old, you GOTTA have a spare, known good running carb, as I noted before I like the good old Roch BV carb. Borrow one if needed.

I've been working on cars for a few years (over 40) and like to think I'm pretty good, but still, when I have trouble it is often related to whatever I played with most recently.

Was it idling crappy before you took the carb/intake apart?

it was ok before the rebuild but I got it back to how it was before the rebuild (which still wasn't great) because I fixed a stupid mistake. There was a PCV valve on top of the valve cover that goes into the manifold and I just plugged it back in and that lowered the idle and smoothed it out a bit. It's still pretty jumpy. I don't have any other ideas. And I don't have a backup carb :-(. It runs well above idle besides the 2600rpm-3000rpm where it has a spasm and like wants to die. Any other ideas?

Do you have a 'tune up chart' for you engine or a service manual? If the answer no to both, then I'm sure that you can either find one online or someone here can help you.

I've been watching the posts and noticed no discussion of how much vacuum at idle or above idle and no mention of timing (base, mechanical, vacuum advance or total).

You are still running the stock cam and head, correct?

JimW asked some good questions - it is a stock 250?
Also, ya gotta have a vacuum gage, right?
What does it read at various rpm's, and is it steady or fluttering?

What happens if instead of plugging that PCV back in, you just PLUG it or hold your finger over it?

I'd definitely find a spare carb though - take a chance at the next swap meet, find a clean looking/cheap Roch B/BC/BV carb. Any of them will work on there at least good enough to run for a while during these kinds of problems.

yes it's a stock 250. Also, the little clip that holds down the distributor broke into 2 pieces. Where would I get another one?

Thanks

also, I just cleaned off the spark plugs with a wire brush and gapped them and it runs way better. I might just need to get a set of new spark plugs.

I just REALLY need to find another distributor clamp. I also need another manifold clamp.

Not sure but wouldn't a V8 Distributer hold down work? Especially one with the elongated hole. The flange is about thesame size. Just a suggestion test your plug wires with a meter for resistance. A miss drove me nust once and it was a wire. Clean them off with brake clean first....Good Luck

what should the resistance be?

alright just checked all the wires and the short wires were no more than 3kΩ and the longer wires were no more than 6kΩ. So they're fine. I'm not sure why but it still occasionally doesn't fire. It runs pretty smooth now but when it doesn't fire, it makes it jump a bit still which is still really annoying. I can just stand in the back and listen to the exhaust pipe and it will miss every 6-9 firings. what's up with that? Do I need to close the spark plug gaps? Or decrease the dwell? What's up? Thanks

haha alright guys. Changed the gap from .035 to .028. Runs PERFECT now. Thanks for your help guys