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Hi fellow bolters. My 49 3/4 ton has a 1957 235 in it. It has brand new plugs, points, condensor, rebuilt dist., and new copper wire/plug wires. It also has a new coil. The plugs get carboned up just after a very short time of running, and I have turned the mixture screw on the carb all the way in, and back out about 1 1/2 turn. It also seems to have a very slight miss at higher idle. It's not real bad, but noticable. The gap on the points and plugs are set at the recommended setting per the shop manual. The only thing I haven't replaced is the carb. Before I do that, I wanted to get some of you bolters thoughts. I'm scratching my head here!!!

Thanks!
KT

KTHOMAS
How many plugs are burning rich? If it is just one or two they maybe missfiring under commpresion at a higher speed this is fairly common with brand new plugs that have been flooded.

kthomas,

Other than the slight miss, does the truck run OK. If you didn't pull a plug and see it had carbon on it, would there be another reason that you thought something was wrong with the truck?


Stuart

I had the same problem and symptoms with my 235. I went to an HEI conversion and set the timing. It now runs smooth with no missing and a noticeable increase in power. I was having a problem with the gap setting changing (per the dwell angle I was measuring with the engine running) when I initially tried to tune up the engine with the old points system. I have since learned that this can be caused by a worn distributor shaft. I don't know if this was the problem in my case or in yours, but the HEI system and new coil have certainly been a vast improvement over the old ignition system. By the way, I started out trying to adjust the carb as well, figuring that it was a fuel problem.

If you are getting black carbon on the plugs it is a rich carb condition. Make shure there is a passigway in the carb base gasket to the vacuum hole in the bottom of the carb. Pull the top off the carb & check the float level. Make shure there is no gas in the float. check the power valve piston. It should pull up & spring back & knock the ball off it,s seat.

I had the same problem with carbon on all six plugs. Replaced the coil, plug wires, cap, rotor, points, 4 different sets of plugs and still had carbon/black smoke in five munutes or less.
I then tried using Champion J-12-Y plugs. Carbon went away and engine had more power. Problem solved.

Also, like Wrenchbender said, make sure the insulator/ base gasket has the hole and is lined up correctly.

When adjusting the mixture screw, with the engine running, try turning the adjusting screw in almost all the way, the engine should stall. If it doesn't then you have other problems.

What is the compression on each cyl.? Where do you have your timing set? Is it realy an engine misfire or is it surging like wrong timing advance? Are you valves adjusted correctly? I need more info.

Lumbergh may be onto something, as a worn distributor shaft could certainly cause those headaches.
-Lurch

Hey folks! Thanks for all the replies! I took the Carb apart and checked the float drop, and it was off, so I set it properly, 1-3/4". There wasn't any gas in the float. I then worked with the timing a bit, and so far it seems to run a bit better. But, it still seems to have a miss when I rev up the engine from an idle, and hold it. It seems to cut out some. The dist. is new/rebuilt. I just got it a while back from Orielly. The compression is good. The engine only has about 500 miles on the overhaul. The insulator under the carb is ok. It does have the hole, and I'm not sure how it can get missaligned since it slides over the 2 carb mounting studs. Heck I don't know what's going on. I may convert it to 12V and try the HEI dist and coil. I still may try a new carb.
Thanks again to you all!!
KT

That's what I originally thought in my case, but it seemed that no amount of carb cleaning/adjustment helped. As it turned out, it was the ignition system. The misses were causing a "rich" fuel/air mix resulting in plugs that were quickly coated in carbon. Since adding the HEI and new coil, no problems. I'm not saying it couldn't be a carb problem, it just seems that's where he has already been focusing with no good results.

Also, how have you been checking the dwell on the distributor, electronically or by setting the gap with a feeler gauge and placing the cap back on the distributor. In my case, I would set the gap, tighten the set screw, and put the cap back on, then watch the dwell angle rapidly change on my dwell meter. Have you checked the dwell angle (point gap) using a dwell meter or just with a feeler gauge?

Hey Lumbergh! Yeah, as much as I mention the Carb, something keeps telling me ignition. However, it stumps me with everything in the ignition system being new. I went out tonight to start the ol'e truck up, but all it did was crank and crank. I don't know if I flooded it or what. It was too hot to stay out and check it! But other than going to the HEI, I don't know what to do. As far as the points, yeah I use the old fashion feeler gauge. I honestly have never used a dwell meter. I quess I could get with a mechanic and have them check it with a meter.
KT

I know this is going deep but have you checked or adjusted the valves, checked the valve springs?

kthomas
loosen all your plug wires off so you can pull each one away from the spark plug individually. with the engine running at the speed that it misses (this may help islote the missfire.)