The Stovebolt Site Forums The Shop Area Engine Shop tried everything - still a terrible miss

Guys/Gals...I've tried just about everything under the sun to get my truck running smooth. Seems the harder I go the farther I get set back. As stated in my earlier posts, she (235) runs great at idle, but misses like hell on ANY acceleration. EVERYTHING on the firing side is brand new, so I'm inclined to believe the problem lies with the gas. Plugs foul easy. Float is adjusted per the manual. manual Choke isn't stuck. No line is kinked. accelerator pump is squirting. new properly set points, cond, rotor, plug wires, plugs, cap, distributor - yes ALL NEW, meaning less than 20 miles. Set timing w/ light last weekend...seems perfect. NEW rebuilt engine and head, incl...new valves. New manifold gaskets w/ no obvious leaks......3 yrs/2000 miles on vacuum advance, about the same age on the coil. 12 volt system.....finely set valves. Any ideas from the PROs on this thing???

dublenaught,

The question would be what have you overlooked...the answer would be nothing. This means one of the systems you have deemed A-1 isn't! These trucks are almost stone age simple!

If plugs are fouling, and by that I mean they no longer fire...permanently until changed, they are 'shorting out' from some material being deposited on them, or the ignition is SO marginal that it can't overcome a moderate amount of cylinder pressure and fuel.

When the engines misses like hell on acceleration, and you let your foot off the gas, does it return to a smooth idle?

A fouled plug stays fouled until replaced or cleaned and reinstalled. Are your plugs fouling.

A miss on acceleration can be caused by many things. Usually ignition, but sometimes excess fuel that drowns out a plug or plugs. When you back out of it, the problems clears.

Do you change plugs each time to get the truck running properly again.

You mention gas..isn't this fresh new gas or is there more to this tale. Don't give up, it's something right before your nose.

There are no obvious things missing like the wiper vacuum line and the firing order is proper...153624, clockwise, from the front!!
Stuart

Please check the fuel pick up line on the sending unit in the fuel tank...the sock may have climbed up and is cutting the fuel off and get fresh gas.... what does you vacuum gauge read it can tell you a lot...these are all the things that made my truck run like yours now she is sweet as can be... for now....I hope tclederman chimes in nothing gets past him...hang on help will be on the way T/C Steve

My truck is very much original, except for 12 volt, thus I still use the old vacuum system for the wipers. I noticed a small hole today. Should that matter to my problem???

Yes, and you will have to go through all your tune-up procedures including idle mixture and timing after you fix it.

OK, today I've blown several hours again on finding out what the heck is going on. I am desperate. I put on a new coil......just in cases - and put in new plugs. The "old" plugs (they had about 3 miles on them) were fouled with black carbon...so, too much gas, right? I rebuilt the carb yesterday eveing. ....gas flooding out the top, so I adjusted the float level so that gas would not be allowed this high as to overflow. Still no result. The engine runs worse by the minute. As for the vacuum hose, I just pulled it off. No different result. If anything, we're going backwards here. I actually getting some pop back from the carb now. I went though all the electrical 2 weeks ago, so now I don't know which way to turn. Help.

Crack in the dist. cap? Theyre very hard to see,look for a carbon line between two terminals.

i once was given the wrong size spark plug , they were too short, and it caused a miss that i could not get rid of, put longer reach plugs in and presto i was in tall cotton.

jeff mays

I was given plug's that had been too long one engine ran fine the . . .well let's just say it closed the gap. . .

would start it use a rubber handled plier's and remove and reinstall each wire one at a time with it running if any wire or wire's that don't cause the miss to get worse are bad . . . I've new wire's that came faulty. . . anotherthing to try is start it and run it on the complete dark so you can see any arch's. . .


Mike. . .

yeah u will need to make sure it want hit the pistons, the plugs the auto store gave me would not even thread down in the hole long enough for the probe to be out of the socket.
jeff

Could it be possible that you are one tooth off on your timing gears? Just a thought.

A little off topic but nice ICE CREAM ! truck. . .

Mike

Just pulling the vaccuum hose loose without plugging it will definitely make it run worse.

i have it on the road now i will post new pictures of it soon as i take em, it has really come a long way.. thanks for comment.
jeff

I'd buy an ice creme from ya even if i had to drive old stove bolt down to see your's. . .

I would take the old 62 before i would trust the ford or dodge that far. . .

I think Jim Meier hit on something here. I was one tooth off and it ran like crap before. The guy set the timing with a light, but man he sure had to advance it considerabley, I noticed on the dist mount....I'm thinking about 8 to 10 degrees is the reading as she sits. So if this is the cause, which way should I rotate to dist...one tooth "forward" clockwise, or backwards?

Hy dublenaught and guys, when you converted to 12 volt did you install a ballast resister, or a coil with a built in resister? If you didn't your coil can get too hot and break down, giving you poor or no spark, hope that helps.

The 12 volt conversion was years ago. there's nothing wrong w/ the ballast resistor. I installed a coil 3 days ago, right after the post you see above. It isn't the coil. I'm putting a new carb on this thing tonight. We'll see if it's the carb.

Thanks for all the posts. Unfotunately, nothing is better. I have put on a new carburetor from NAPA - well, remanufactured anyway. It runs exactly the way it did before I put it on....terrible !

Plugs are getting black soot - covered in black soot for just a few minutes of running. My butterfly valve is free moving and just flopping around. I fear that somehow, it's almost as if exhaust is getting into the intake manifold and is "fouling" the plugs, and making the engine run poorly. Can I block of the exhaust atop the butterfly. I live in a fairly warm climate and have a manual choke.. Do i really need this butterfly thing, anyway? Could this alleged "mixing of exhaust and intake fuel be causing the missing problem?

Yes JD, the heat riser is nessasary for a smooth running engine, inspite of what some are going to tell you. Other wise General Motors would not have wasted money putting one on every engine that they made.
Has anyone messed with the heat riser bias spring by any chance?
Looking at the heat riser weight from the front, when cold the spring should be holding the weight all the way in the full clockwise position. As it warms up it will allow the weight to rotate to the open or counter-clockwise position.
Denny Graham
Sandwich, IL

J.D.: I had a similar problem on my 261, and obviously from the good feedback it could be a lot of things that cause that problem. For your information, in my case, I installed new points and set them as per spec. It ran fine at idle but would hardly run beyond that. I found that the points were not opening & closing properly at speed because the mechanism that was supposed open & close them was not aligned properly. Even after buying another new set it don't work. It seemed like they weren't the correct points. I tried the original points & it worked fine. I eventually went to a HEI from Langdon & it works great. Just another thing to check. I find that when something unexpectedly doesn't work, in my case it is the last mechanical adjust/alignment oriented thing I did that is the most likely cause.

I'm going out of town for a long weekend, so I'll have to take a look next week. Anyway, I still don't know what is blackening all the plugs immediately. I'm talking while sitting in the driveway....just a few minutes. What ever is responsbible for that, is probably the same reason the engine doesn't run worth a darn. It even shakes and shimmers at idle. I'd have to get it in front of me to resp to Denny's open/closed question. Can't remember. Donsz, I'll take another look at teh points...I've looked at all this stuff a thousand times.....Obviously, I've overlooked something. I've never been this frustrated with this truck.

My brain says "Vacuum" problem.

If you removed the vacuum hose and it doesn't run any different...doesn't that say that you have little or no vacuum to begin with. Do yo see any evidence that the Dist advances on exceleration?
Vacuum leaks? Leaky intake manifold?

Just my $.02. Best of luck resolving this.

Keith

w/ regards to the last two posts, the compression was checked last weekend....about 98 to 105 across the board. This is a new rebuilt engine with 160 miles. The valves are new. The head was serviced w/ new seats, etc, so it's not a burnt valve. Same for the rings. Brand new. The "vacuum" hose I removed - is the only vacuum hose on the engine - the one that runs the wipers. There is quite a suction, and the idle goes down considerabley. The "quality of the idle" is no better though, just lowered RPMs. the dist advance moves and is fine. I would tend to think a vacuum problem. I pulled the manifold last night, and I did not see any holes/breaks etc though between the exhaust and intake portions. I'll clean it up and take a second look when I return next week.

I would check valve clearance first.

Then check for vacuum leaks, propane from an unlit torch around the manifold/head connections or squirt them with oil.

Black plugs could be caused by a low vacuum condition causing the carb power circuit to open.

Put a vacuum gage on it and check the level and pulsing if any.

Let us know.

With no disrespect intended, perhaps you need to amend your testing methods.

It is extremely simple to test the entire ignition system. Find a garage that has a diagnostic oscilloscope, and hook up the engine. A healthy ignition system has a set pattern on the 'scope. You can also measure the firing voltages at the plugs. If the pattern is wrong, there are books showing each possible pattern. We detected a bent cam in a distributor on a Chevy 6 in just this fashion, after a bunch of good mechanics gave up.

If the ignition system is normal, check the fuel system by temporarily adding an electric pump piped to a different source.

How much vacuum to you have at idle?

Jon.

Just for whomever is interested, I've finally been able to bring closure to this thing. ....the culprit???? I re-replaced the condenser and points...figured what the heck, only cost me $11. Guess what? Runs like a dream. I suppose I either got a bad set, or ruined them trying to start the engine. Read over the posts here and look at all the stuff I went over......sometimes, indeed, it's the simplest thing, and just because you buy a new part, does NOT always mean it works.

I recently went bonkers with the same sorta deal,,a brand new dist. cap that was cracked!!
After going around in circles for a couple evenings,a friend with better eyesight than mine saw the carbon lines between two contacts. I'd used every cuss word i knew and was even tryin to think up new ones.
All for a 10.00 dist. cap...................

This has been a very informative thread. Glad you found the solution!

99% of the time, it is usually the simplest thing that causes the most problems. For some strange reason, we let our brains get into overdrive and overlook the obvious stuff. Glad you got it worked out and are back on track. Just take a few extra Prozac, and don't sweat the petty stuff, or pet the sweaty stuff.
DJ