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ok badvibe's runs like crap and only for a couple of seconds. new everything from coil to sparkplucs including dizy. tried a different carb, same thing. compression check put 1, 3 & 4 real close to 128 each. #2 was zero. adj valves, tappet 3 & 4 needed it. compression no at 15 for #2.
what do you guys think?
Was this a recently fully functioning motor, and then upon start up, developed this issue?
If the motor has not been run in quite some time, I would say sticking valve from fuel varnish.
it was a running engine. symptom of running crappy intermittently made him rebuild his carb and drop in a new dizy. after timing it it ran great across town, 'bout 10 miles then died and would not restart. towed home. that's when he replaced the coil, wires and plugs. even swapped the rodchester for a zenith of a running series.
is it possible that after timing the truck the distributor wasn't tightened down enough and wiggled back out of timing?
it's been timed and retimed. w/ diz loose for adjusting it'll start to fire but never gets running.
With the 1st compression test reading zero in #2, and then doing a valve adjustment and repeating the compression test and now getting 15lbs in #2, is it safe to assume that this is a valve problem and not rings?
More history, the motor has less than 10K miles on it. Was a good running motor. When it was redone a few years ago I bought a short block from BP and had the head rebuilt locally. Have always run unleaded gas, was told the head has hardened seats.
It started running rough several weeks back. I'd re-time the motor and it would run good for a few days or a week and then need re-timing. I've had dizzy issues in the past so I bought a new dizzy. Plopped that in, checked the gap, timed it by ear and drove it about 15 miles across town, freeway and city streets, ran good. Jumped in it to head to a friend's house and it died on the way. Have not been able to get it to run other than momentarily/badly since.
Over the last few weeks I've replaced the coil, high tension wires, spark plugs, distributor. I've rebuilt the Rochester carb, second time in the last 2 years. I've tried running the truck with a Zenith off scott's ambulance which runs with that carb. I'm hoping now that it's a valve issue and not rings.
Sounds like you have arrived at the valve vs rings stage.
1. Pull #2 plug.
2. Inject about a tblspoon of oil.
3. Perform compression check again.
If compression comes up, its rings (you just sealed them, temporarily). I highly doubt its rings.
If compression does not change, its valves. Pull valve cover, put #2 at TDC, pull rocker arm, then check valve stem height. If not equal, you have your hanging valve. Tap with a hammer, or apply downward pressure to emulate the rocker arm. Does the valve SNAP back into place, or hang?
Then again, it could be the head gasket failed. Either way, off comes the head.
The most under-rated and under-used diagnostic tool for carburetted engines is the vacuum gauge. Everyone should have one. It'll answer all your questions about bad rings or bad valves.
Here's a pretty cool site that tell how to use them and graphically depicts the meanings of the different readings you may encounter in troubleshooting:
http://www.secondchancegarage.com/public/186.cfm
pretty good stuff. now if we could just get it running we could use it. your link is one i will be savingQuote:
Originally Posted by SafeAirOne