A friend installed a 350 out of a '70 Chevelle into his A......He wasn't sure of the condition before he put it in......He's running an Offy manifold with 6/2v running on the center two carbs.....Here's the problem....It keeps fouling out 3 plugs, the first two on the p*** side and the third on the drivers, which appears to be fuel.....I threw a Unisyn on the carbs and got them set on the money yet it still runs like ****......I have to jack the idle up to around 1400 in order to keep it running otherwise when you drop it in gear it'll stall......Throw another set of plugs in it and he says it feels fine for about 20 miles, then we start all over with the plugs.......Oh, and the engine, even after the new plugs seems like it isn't hitting on all eight even though he says it feels better I'm leaning towards worn cam lobes......What do you guy's think?.....And how would you check that, by setting a dial indicator on top of the rockers and rolling the motor?
It sounds like worn valve guides to me...letting oil past and fouling the plugs...could also be broken, worn or loose rings on the pistions... Don't think it's worn cam lobes...or the gasoline fouling the plugs... As far as it hitting on all eight, that sounds like iginiton to me... R-
I don't understand why you would put a motor in that you haven't checked out thoroughluy first. Do a compression check. Also there is whole set of tests with a vacuum gauge, that can narrow down your problems maybe somebody has the procedures for the va*** gauges. I doubt that flattened Lobes are your problem.
Make sure the intake gaskets are lined up correctly. If they slid a little when the intake was installed it could create a vac*** leak and potentially **** oil into the cylinders. Both of which will make the engine run like ****.
I'm leaning (no pun intended) toward the vacuum leak as well. The fact of it being select cylinders and all...I'd bet the split in the manifold feeds right front to left rear. Loose the seal on that "set" and who knows what. If it's leaking under the manifold it'll draw oil as well but not enough to smoke at all times. Although messy to do sometimes you could spray some carb cleaner or ether into the valley by way of the push rod holes. If it picks up there's your answer.
A small amount of propane will work as well. If the idle raises or smooths out theres a pretty good chance that the intake didnt seal.
Another vote for ignition. I had the same problem with the early-80's 350 that came in my 53 truck. A couple of plugs on the left and a couple on the right fouled. Changed them once I got it running, same deal after 30 miles or so. Changed wires, got better, but still not good. Turned out the cap on the dist (hei), was slightly crooked, causing the rotor to wear into it a bit, ground out the center pickup on the rotor. It just arced wherever it wanted to during the spin cycle. Put a new hei ($89 summit), and it runs like a champ. ***o
Personally I think of two things 1) TIMING and 2) AIR/FUEL MIXTURE. Bring the engine to top dead center and double check your plugwires. Clockwise rotation 1-8-4-3-6-5-7-2 The rotor should point to the #1 cylinder. Set the timing around 10 degrees to start with. Once you get to this point you have eliminated a few of your possibilities!
Well, i'm glad that no one agree's that it's a cam lobe...Seems leaking vacuum or ignition is the popular opinion.....Wouldn't a vacuum leak mean an lean condition?....How would that explain the three plugs fouling? BTW, it's a stock dizzy with a petronix........I told him yesterday to get a set of wires, cap and rotor to at least eliminate that
You've got multiple problems. First, like the others said, be sure your timing and carbs are set right. this explains the stalling problem, and the need fro high idle. But I agree with the valve guides being worn and fouling the plugs. VERY common on SBC's, ;not easily found, either...with compression tests, or leakdown tests. Try replacing the seals first, jiggle the valves when you have it all apart to check for excess clearances. But even this may not show up a guide that is letting oil by, just a really bad one.
Just to give you one more thing to check without spending any money ... timing chain. Put it on TDC and pull the dist cap and roll the engine back till the rotor just starts tp move...make a mark or write down the # and then hand rotate the engine in the other direction till the rotor just starts to move...the other way. If no discernable miss can be heard but won't idle...and there is no va***e leak...this is where I would look next. Gear and chain could be toast.......................
Only running the center carbs all the time/ are the end carbs funtional at all?? Possible vacuum leak there???
A vac leak can cause the carbs to think it's gettin some loud pedal and make some of the circuits deliver fuel at the wrong time, I.E. power circuits. Not knowing the exact carbs it is a possibility. If you find it ya gotta let us know what's up.
Yeah, just the centers and i shot wd-40 down the throats of the others and around the bases with no changes in anything......Just as a side note, he took it home last night.......Now he's not a real gearhead......I get a call today from him thanking me.....He tells me that after he left my house last night it was running so good that he stayed out till 2:00 AM just driving around.....I don't get it......I synced the carbs, added a fuel presssure regulator set at 3lbs.{he didn't have one and he's running 94's}, ****ed with the linkage because the left side carb was opening before the right, pulled the plugs and cleaned, putting the fouled ones in the cylinders that weren't and as far as i was concerned it still was running like ****, but he says different........I knew there was a reason i liked Ford motors He's happy because now he could make the Rumblers Nomads show this saturday
Do the plug look black and shiny when the are fouled or are they black and powdery looking. Black and shiny is oil, powdey black is fuel. If it is fuel, the power valve circuits in the carbs could be leaking fuel. It is common for the power valve to go out. I would look at both carbs to see if one or both are leaking. If the number 3 cylinder is running rich, I would bet the power valve on the drivers side carb is leaking fuel in to the intake. It is possible that both are shot. This would also cause the engine to run rough due to the mixture not being correct. I don't think that you have a vacuum leak. A vacuum leak would cause the engine to idle high, even when the idle jets are screwed in all the way. I believe the increased fuel is flooding the engine causing you to increase the engine idle to compensate for the increased amout of fuel in the manifold. Also a bad power valve will cause a lag under quick acceleration.
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