Car is a 54 chevy with a stock 235. Headers, single Leakchester BC converted to manual choke, Pertronix unit. Outside temp here is about 65-80 F so my lazy ass hasn't hooked up manifold heat - yet. Starts well and runs like a dream till she's good and warm, say 20 mins into driving, then starts to miss on accelleration some times. Seems to get progressively worse till it does it on all but the mildest takeoffs. Its still driveable after about 2 hours, but it doesn't gimme the ooh-ahs like it usually does. I figured its gunna have to be fuel or spark - whats your take on it?
Could be fuel...what carb do you have? Maybe the fuel mixture isn't right? But if thats the case then it wouldn't run well from when it starts..How old is the fuel pump? Does it have the orignal tank in it? I have a 52 and installed a new thank, new pump, new filters, new carb...once you've done all that and it still does it, it could be electrical....
Thanks guys. Its an 82,000 mile survivor I bought out from Cali back in 91. Gen you wine earl scheib paint with more runs than Jessie Owens. Its all orig except for cast iron headers and lowered 4 at the back. I'm running two fuel filters, one ahead of the pump and one ahead of the carb. I initially figured if it was spark or fuel pump it'd do it straight up, but now I'm not so sure. Tom, you might be on to something. Time ta get my lazy ass inna the shed and get the mani heat box ticked Thanks guys, keep those ideas coming
I would expect a lack of manifold heat would cause more issues when cold, not when hot. Is the choke staying open after its been driven awhile? Missing and stumbling after warm up are usually ignition related. Try a different coil, then try going back to points, just to see if it is related to the Pertronix install. I have had a bad plug wire cause an irregular miss, but nothing that would really create a sense of a "loss of power"... Try using different gas. You may have gotten a bad tankfull. It happened to me this summer. Throw in a can of Isopropol to deal with possible water in the gas...
Guys thanks for the info. Whats wierd is that it runs perfectly for say the first 10-20 mins and then starts to deteriorate. Seems like something is slowly warming up and getting alzheimers. Looks like I'll have to round up the usual suspects: mani heat, plugs, coil n points, fuel pump, carby kit and vac advance.
The choke staying closed is a definite possibility. As for lack of heat, it could be similar to carburetor icing....maybe the manifold is just getting too cold from the evaporative effect of the gasoline. Have you tried running it until it starts misbehaving, then touching the intake manifold?
I had a 235 with a mallory electronic dist... no points... mine would act up ever once in a while.. miss while going changing gears, at hi-way speed it would sometime stop running, then resume... all kinds of crazy stuff..........it got worst.........I was told it could be fuel, ignition, etc turns out it was the electronic module,, replaced it and never had any more problems...............so it just might be in your petronix. let us know what you find out...
It is definatley the lack of manifold heat. The intake walls are becoming entirely saturated with Gasoline. I've been there.
When you consider that the factory setup has a butterfly in the exhaust manifold that is controlled by a heat spring, and that as the engine warms up, the butterfly closes, and that the problem Chebby is having is after it warms up, just exactly how can the problem be a lack of manifold heat? Is the car 6 or 12 volts? If 12, are you supposed to run a ballast resistor with the Pertronix? remember, there is no resistor wire on a '54 because it was 6 volts originally...
Okay. From the top. When you spray an aerosol can on your hand, it feels cold, correct? The vapoization of the liquid is what causes it to be cold. Whe the gasoline passes through the carb, then the venturi, what happens? It vaporizes. If given the right application, without heat, it can actually frost up. Thats what happened to mine. It was said that the butterfly valve closes after warm up. Very true. However the intimate mating of the intake manifold with the exhaust manifold is substantial enough to maintain adequate heat to the intake manifold. The factory manifolds were joined by the 4 3/8s bolts, with the gasket in between. Think of it as a pot of water. You crank up the dial to high, to boil water faster. Once it has begun to boil, you can crank it way down, and still maintain a nice rolling boil. Even turn the heat all the way off and it will still remain hot for quite a while, because of the residual heat. The exhaust heat will constanlty remain as long as the engine is running. The actual temperature for the intake needn't be more than 50 degrees. When I was dialing in my various setups, I bored a small diameter hole through the length of the intake manifold, and welded it tight. Then ran the hot side heater hose through it. Problem solved for about 10 bucks.
I'll do the manifold heat thing, but if my manifold was filling up with motion lotion, I'd be getting some backfiring, yes? Manifold is warm to touch. Car is 12 volt with internally resisted coil. Choke is fully open.
If you are using a generator, I would talk w/Pertronix folks about your problem. Do you have a stock distributor to throw in and test out? Just a thought ....
You're over estimating the issue, and the air temps he is dealing with are above where you are likely to have this problem. I'm not saying you shouldn't hook it up, I'm just saying that the description of the problem doesn't fit it being a lack of manifold heat...
I'll be the first to suggest that the float is too high. Your OK when cold because the high float is getting you a rich mixture. After it warms up and it would like to be a little leaner, it's too rich. They don't like that. I got 2 B's on my 235, they used to leak out of the accelerator pump levers/rods. I lowered the float level a lot, way lower than the spec(about 1/4 inch lower). Now they don't leak and performance is great. B's shouldn't leak. Part of the design is the cover gasket at the top of the fuel bowl, it should never get wet up there. BTW, I live where it's cold and humid and don't run heat to the manifold and it's not a problem.
check the the primary elec wire from + side of coil to points chev 6 was notorios for this wire getting brittle and breaking down after engine heated up. when it cooled down normal an easy check and fix tom
A problem of this sort that gets worse as it heats up is generally an electrical problem. Coil and ECM are the main culprits. When you installed the Pertronix, was there any slop in the shaft? can you swap out the dizzy? can you swap out the coil? how old are the plug wires? I would expect a model B with too high of a float level to be dumping fuel out the bottom where the accelerator pump hooks up to the linkage, or seeing alot of raw fuel inside the carb when at an idle. Also make sure that the carb base gasket has a slot in it that lines up with the hole in the bottom of the carb. If that hole is blocked off, the power circuit will be constantly engaged causing running issues as well.
I would be willing to put money on my theory. The intake manifold walls are getting saturated. Probly doesn't idle well either after its been run awhile.
i got a '54 235 in mine, i had similar issues tried new carbs, manifold gaskets, fuel pumps and lines. earlier this year i took the head in and got everything replaced valves hardened seats all the goodies now she runs like new!!! who knows?
Thanks for all the input guys - turns out it was my Pertronix. The magnetic collar that fits over the distributor shaft was a sloppy fit and could rotate back and forth on the shaft some, as well as a little bit of up and down movement My guess is when I hit the go pedal its rattling on the shaft. I put some blu-tack under it and mashed it down good and tight and Voy-lah! I'm not sure blu-tack is my long term solution, but I don't want to stick it down permanently, I just want it firm. Any suggestions? Silicone, Windscreen sealant? I'm going to hook up the mani heat, and prolly buy her a new dizzy cap, plugs/leads, condenser and coil for yule. Cheers
Glad to see you got it up and running again. Sounds like you got a case of an old car being an old car - a little tempermental at time
Yeh mate. A stovebolt will run to wheel barrow tolerances, and the minute you put something electronic near it all bets are off.
LMFAO but its too true. the moment I started working on my 54 I had to do another job that the first one highlighted, and then the 3rd, 4th, and on it went!
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