The Stovebolt Site Forums The Shop Area Engine Shop engine miss - how do you chase it?

I have a '54 235 in my 1/2 ton that has developed a terrible miss. Just one of a myriad of problems I've had since the engine was rebuilt in June. Anyway, consider new plug wires, new plugs, with less than 50 miles. Adjusted carburetor and adjusted timing by the book with my local mechanic. New distributor. New and adjusted points (0.016), condenser, etc, adjusted carburetor rebuilt by holly last year....Go figure. The valve and heaed was completely rebuilt too, so no "burnt valves" are causing this. I'm not sure what else to do. It runs like crap - especially on acceleration. What should I check first and how do I know if it's fire or fuel? Would clogged fuel filters cause this? Would water in the gas tank cause it?

The timing will be off if you adjusted the points after timing it. 16 mils seems a little tight on points, 19 might be better. Check the valve adjustment. You can get closer to the optimum timing by ear than by the book on these engines. The book timing is not advanced enough for todays fuel.

thanks...good information. I will re-set the points up to about 18/19, then revisit the timing. should I advance a couple degrees or retard? Also, anyone, what about my questions concerning fuel vs. gas adn the potential water or bad filter issue.

pull the valve cover and make sure you dont have a valve sticking also if the valves are adjusted too tight it will run good cold but the valves wont close all the way once the push rods get hot and expand.

Points are best set with a dwell meter, the gap spec in the book is only a starting reference point. And what baldy says about the timing is correct, it needs to be advanced. I had to go 15 degrees advanced on mine, but I do not have a vacuum advance, so you'll most likely need less than that. Oh, and set the timing with the advance disconnected. Checking the valve lash would also be a good idea as well, might have one a little tight (assuming original 235 w/solid lifters).

gas is fuel i dont understand the question

Get yourself some specially insulated plugwire pliers and pull the wires one at a time until you find the offending cylinder. Then you can isolate the problem and properly diagnose the repair. Don't just throw parts at it, it may be more severe than that. It may also be as simple as a broken spark plug,
Scott

He mentions new wires , double check the wires make sure you have them going to the correct plug . everyone has done this one . Things like this can often be simple .
My grandsons car was running poorly and it was as simple as reseting points and timing and i found a couple of plug wires that were not seated on the dist cap well .

I set points to 021. It cranked immediately. I noticed some condensation on the throat of the carb (rochester B). I sensed water getting in there somewhere. I pulled the carb, looked for water, dumped and cleaned the bowl. Virtually no "trash" and no sign of water. Cleaned adn reasswmbled, put back on and she started right up. I set timing to 4 advanced and drove it a mile still misses terrible on ANY acceleration. will idle fine. What next. VAC advance is 3 yrs old. All wiring is new and correct. I set valves a month ago, but some of you say pull valve cover. I'll do it right now.

I agree with 48bigtrucks. First find out if you can isolate it to a specific cylinder. Then I'd pull the plug and take a look at it. You might even consider switching the wire to another cylinder to see if the miss changes to it. I have seen MANY New plug wires, and plugs that are bad. Inspect the distributor,INSIDE, very carefully for possibly a crack. IF and WHEN you can isolate it to a specific cylinder then the cure is a lot easier. Let us know what you find.

Check the distributor cap for cracks or carbon tracks. A carbon track will look like a barely-visible line similar to a pencil line between wire terminals inside the cap. A little moisture condensation starts the problem, and once a circuit is established, a permanent line is etched into the cap.

If you've replaced the cap and rotor already, ignore all the above.
Jerry

replace the condenser

If it idles fine, you should have no valve problems. 4 degree additional advance is not likely enough to take the accelleration stumble out; try advancing the timing untill the stumble goes away. If it pings on hills, kicks back on the starter, or hunts at cruising speed, you have advanced it too far. Mine runs best at 10 degrees above what the book calls out.

Case Resolved. No 1 and 2 were not firing. Never overlook the easiest and obvious. My mechanic put in new plugs but they were "cold" plugs. No 1 and 2 were fouled. Compression checked to 105~110, approx. Put in delco remy hot plugs, set dwell to 23, adjusted timing w/ light. Also, have an little leak around intake gasket, but basically bad plugs. Question as to why fouled w/ only 20 or so miles. I've been told it doestn' take much. Runs good now, anyway.

what was the knock?

I've seen fouled plugs on several engines before the rings were broken in; just keep your eyes on them for a while.

Brian,

Mr. Goodwrench was trapped in the crankcase...he was banging on the pan..SOS,SOS,SOS!

Stuart

There is no such thing as a little leak around the intake manifold! Any leak around the intake is taboo and if you know there is a leak for sure then that's a quick easy fix to replace the gasket. You’re not going to get the rest of it right till that's fixed.
After a plug reading a compression check would have been the first thing on my list to see what the basic condition of the engine is, so I’m glad to see ya did that. 105 hot, wet, on the compression is a tad low and with two plugs out of six fowling would indicate to me that the rings may be on the wane. Now if the fouling is dry looking and kind of beige in color you may have cracks in the combustion, how’s the water level holding up?
Denny Graham
Sandwich, IL

JD....check the fuel hose at the bottom of the gas tank mine was kinked and take a look inside gas tank as the filter at the end of the fuel line it may have moved up or is clogged. Mine would idle fine then miss like hell on the road due to fuel starvation also check your battery cables mine was rotted at the post and would heat up then fail and would work after it cooled. Change the condenser....warm her up then take her on the road advance the dist. a bit at a time bring a wrench with you. I hope tclederman will chime in as he has a cure for all things truck related...T/C Steve

hey guys...thanks for all the input. as stated, my plugs were fouled, but i' also am going to replace gaskets for the intake/exhaust manifold. of course, there was the timing issue as well. AS for the knock, many of you have asked, the verdict is the wrist pin at no. 1 piston. The news could be worse. mains and rods are good. I"ll probably drive her for a while.

I thought I had this figured out. Today I replaced the intake/exhaust manifold gaskets. Took her out. 1 mile...runs beautiful. Idled great. Turned around, headed back home and BAM.....there goes that X$^(#@ miss again !!! it's terrible on ANY acceleration. I"ve always been able to diagnose a miss on this truck...it's just fuel or fire, right? HELP!!! Just to recap, since my June rebuild, I've got new engine, new valves, perfect set timing (checked, checked, and rechecked), proper set new points, new condenser, new dist cap, new rotor, new distributor, good clean carb, ALL new gaskets everywhere, new exhaust donut.....new plugs last weekend - hot plugs....new wires,.....hmmmm...what else....I did not yet check for a kink in the gas line. My butterfly valve leaks - but this is an exhaust leak, shoudl that make a difference??? Can someone help me find out why this ***** is still missing on acceleration??? My truck is cursed.