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Old 08-21-2005, 12:29 PM
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235 w/new head runs rough

I rebuilt this engine 20 years ago but I doubt it has 10,000 miles on it. Being yound and foolish at the time, I rebuilt the block however did nothing to the head. The engine burned oil(blue smoke) for 20 years. I suspected the valve guides and I bought a rebuilt head(new valves,guides etc) on Ebay and the smoke is gone..yea baby! So I guessed right for once.

The engine runs rough however. I know there are many possibilities for this that I should research first but I'm sure someone here will render an opinion.
I did the "pull one plug wire off at a time thing" and three plugs made a big difference and 3 plugs made no difference. Also one plug wire shocked me thru a pair a gloves while the rest didn't. The tappets have been re-adjusted while hot and double checked while running. Plugs are relatively new. Only started a handfull of times on thes plugs.

I should:

A) do a compression test

B) Get new plug wires

C) do a complete tuneup

D) all of the above

E) other

F) Get a real life

Anyone want to make their best guess?




Last edited by Slickriffs; 08-21-2005 at 12:37 PM.
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Old 08-21-2005, 03:35 PM
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Check and make sure it doesn`t have a intake leak, take a propane torch unlit, start the engine and turn the propane on, go around the intake ports and carb pad with it, if the engine idles up you found a leak. Next I`d do a spark test, you can pick up a spark tester or make your own with a old spark plug, see if the offending cylinders are getting any spark. if all seems okay then do a compression test. It`s possible the valves on those cylinders could have the valves held open. remove the valve cover and cycle the engine by hand, watch all the rockers and make sure all of them make a full motion.
If the engine has solid lifters it should be in adjustment if the specs are correct, if it has hydraulic lifters, back off on the lock nut on the offending cylinders and see if it clears up.
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Old 08-21-2005, 04:57 PM
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Doc here..

Couple of things not said..

Has this Car sat 20 years since rebuild? (Maybe off / on over that time?)

And Was the EBAY head rebuilt (complete new valve job?)

The Head if not totally rebuilt could have Lead deposits (from the old days) beginning to wear away , (precision..) Causes bad running...you might want to check that out..if you can contact the old owner..

If it sat even on and off all that time, try dumping the fuel from the tank, and replace with new, check/replace the fuel filters, test the fuel pump for volume / pressure.

Do a Total tune up..Plugs , points, rotor, cap, wires, PCV, Adjust the Carb Check all your vacuum hoses for Weather checks , cracks, falling off, and / or mis-connected..(shouldn't be that many on that engine.)

Do a compression wet/Dry while your changing plugs..write down the stats per hole..should be good..but ya never know..

Next Get a Vacuum gauge, start and run at Idle, monitor it...17 to 20 In. Hg.? With a Steady , not fluctuating needle?

Check the advance plate on the dizzy, be sure it's not rusty, and hanging up on something..

One of those should cure the problem...All of them will make it run better/efficiently..

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Old 08-21-2005, 07:58 PM
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Thanks double and doc..


The propane thing is new to me..seeing that I just hooked up the intake manifold after installing the head..I can't rule out an intake leak..It was a b_tch getting the manifold on on..


The head came with the bill of sale from the rebuilder in Orlando. I'll have to re-read it..Not sure if the seats were changed...But I know the valves and guides were new..Not only did the bill of sale mention it..but the valves looked like bathroom fictures..never fired.

I used the truck on weekends for about 10 years then it sat for about 10..with just an occasional start. New Gas. I did notice that I seem to have to adjust the carb what I would call unusually rich to get it to run the best.

I'll have to do some leg work..which I knew I would..But I really find other peoples point of view very interesting. Need to get back to the basics.

Thanks guys,


Last edited by Slickriffs; 08-21-2005 at 08:07 PM.
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Old 08-28-2005, 02:24 PM
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Update and thanks

Got this straightened out:


Did compression test..all good..still need to do vacuum test.


Bingo! Propane elevated rpms. Barrowed a torque wrench and the only bolt I could get the wrench on due to space limitations was way under torque. I adjusted the bolt with the engine running and could physically hear the rpm's raise as I tightened it. Unfortunatly..Can't get a socket on the other bolts..but a did tighten them further with an opened end wrentch. They did feel "soft". I'll possibly shorten a socket to be able to get in there with a torque wrench.

Overall huge improvement. Thanks so much.

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