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Tractor Talk Discussion Forum

OT-Stumped with my engine problem

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Josh H

08-08-2005 04:08:31




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I have an old Ford truck with a 300 motor. It was running rough and my mechanic did a compression test and told me the head needed rebuilt. I took the head off myself, and he rebuilt it. Now I have reinstalled it, and the truck will only run on the front 2 cylinders. I torqued it properly, used a new head gasket, the plug wires are not crossed, and it has good compression. I have never worked on something with hydraulic valves, but the pushrods are in correctly, and the rocker arms all move when the engine is running. The PCV valve that sticks into the valve cover makes a constant tapping noise. What could be going on? My saturday project aimed at saving me a few bucks has turned into a big headache! Thanks for any advice.

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Greg Co

08-08-2005 15:52:48




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 Re: OT-Stumped with my engine problem in reply to Josh H, 08-08-2005 04:08:31  
Josh, I agree with some of the others here. It sounds like you have the valves set too tight and they are hanging open.
I would back the nuts off some on the rocker arms. Start the engine, continue to back off the nut on each rocker arm until the rocker arm rattles. When it begins to rattle run the nut back down just until it stops rattling, then slowly give it an additional ½ to ¾ turn. Repeat this on each rocker arm and then the valves will be set. If this doesn’t fix the problem at least you know the valves are set right and you can move on to the next item. Those 300’s were real good engines and I cant help but to think it is something very simple.

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Bryan in Iowa

08-08-2005 15:25:23




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 Re: OT-Stumped with my engine problem in reply to Josh H, 08-08-2005 04:08:31  
Have you ran compression test since you installed head? sound to me like valves are too tight . whoever did the machine work may not have taken enough material off the valve stem. find which cylinders are low on compression and try backing off the adjusting nuts if if that brings compression up ,, you may need to double nut them , rather than tearign head off and setting stem length



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TomTX

08-08-2005 13:29:27




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 Re: OT-Stumped with my engine problem in reply to Josh H, 08-08-2005 04:08:31  
Josh, you answered your own question, when you said you never worked on anything with hydraulic lifters. They have to be set. You are probably running them so tight that the valves are not closing at all. Call your mechanic friend and ask him about the adjustment procedure.



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RustyFarmall

08-08-2005 07:27:55




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 Re: OT-Stumped with my engine problem in reply to Josh H, 08-08-2005 04:08:31  
Josh, that PCV valve just might be the culprit. Remove it from the hose, and hold your thumb over the end of the hose. See if it gets better, might want to plug the hole in the valve cover at the same time. Check out ALL of the rubber vacuum hoses, they have a tendency to dry out and crack over time, and even though they look good they can still create some serious vacuum leaks.



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T_Bone

08-08-2005 07:26:45




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 Re: OT-Stumped with my engine problem in reply to Josh H, 08-08-2005 04:08:31  
Hi Josh,

Sounds like to me you have the cam out of time and if that's true then bent push rods.

If the timing gears are aligned then check for bent push rods or hyd lifters colasped.

T_Bone



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Josh H

08-08-2005 09:25:07




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 Re: OT-Stumped with my engine problem in reply to T_Bone, 08-08-2005 07:26:45  
Thats what several other people have said, but I never changed the timing, or even took the front cover off. Thanks for the advice though,
Josh



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Ludwig

08-08-2005 07:19:13




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 Re: OT-Stumped with my engine problem in reply to Josh H, 08-08-2005 04:08:31  
Have you done a compression test?
Did you have the head planed? Maybe it was a bit warped?



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shannon from ohio

08-08-2005 07:03:06




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 Re: OT-Stumped with my engine problem in reply to Josh H, 08-08-2005 04:08:31  
Maybe the valve lash is too tight on the remaining cylinders holding the valves open a little bit??



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Allan in NE

08-08-2005 04:25:23




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 Re: OT-Stumped with my engine problem in reply to Josh H, 08-08-2005 04:08:31  
Josh,

Haven't a clue as to your troubles, but I can tell you that some models with that engine were famous for warped manifolds. And, the trouble usually shows up when you break 'em down for repair.

Did you have the manifold planed while the head was being worked on? Could be that it is sucking air and that you have a gigantic vacumn leak at that intake.

Tryin' to help,

Allan



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Josh H

08-08-2005 04:39:38




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 Re: OT-Stumped with my engine problem in reply to Allan in NE, 08-08-2005 04:25:23  
Before I decided I needed professional help I thought I would be able to fix it on my own. My diagnosis was leaking intake, and I set about to replace the intake gasket. In the process I cracked the manifold. After getting it all back together (with new manifold and gasket) the truck ran the exact same. So, we are both thinking on the same track, but we're both wrong. O well. Thanks for the advice!
Josh

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RustyFarmall

08-08-2005 06:40:28




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 Re: OT-Stumped with my engine problem in reply to Josh H, 08-08-2005 04:39:38  
Josh, Allan is correct about the manifold, and you pretty much figured it out also, but I want to add that these engines were also famous for devouring the gasket between the carburetor and manifold. Somehow, those mounting bolts just won't stay tight.



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