situation with a 1979 international harvester( 345 cid engine)?

just got the truck running last month for the first time on, well since i have known the owner ( 9-10 years). now it has a miss ans what sounds like a rod knock. he replaced the connecting rod bearings and main bearings twice, plasi-guaged them in between to confirm tolerances. we have replaced plug wires to attempt to eliminate a miss that could be related, plugs are clean ( relatively given that the truck does not get warm enough to get out of that warm up phase) we have confirmed good compression in all 8 cylinders, less than 8 % variance from high to low. lowest was 170 psi and the highest was 185 if i remember right. i will be rebuilding a thermo-quad 4bbl carb the next time that i am over there. just what am i missing here?

2010-01-31T23:52:34Z

because he has done so much to the lower end to get rid of that noise, i dont know if it is still a lower end noise or if it is an upper end issue. it does have that beating the block with a sledge hammer effect, that tooth rattling noise that we all seem to love. according to him the valves were just adjusted recently, but that is why i am trying to eliminate the miss to get the engine to run smoothly so that we can adjust the valves. i mentioned to him that the noise could be from a bent push rod beating the inside of the head. he mentioned to me that the problem could have been produced by a new driver (his son ) really abusing the engine at one time. he told me today that the engine was driven for a bit 2 quarts low. i told him that on a 6 quart system, two quarts low is not critical. its not advised to maintain that level for long but this damage should not be the result.

2010-02-02T19:58:56Z

a spun bearing would have a twitch to the oil pressure gauge. bearings have been replaced so mileage is not the issue. cam bearings were replaced the last time the engine was torn down. i do not have the mileage for that but...

larribee2010-02-01T00:22:58Z

Favorite Answer

A mechanic's stethoscope will help find where the knock is. I would listen closely around the cylinder that is misfiring, and around the oil pan. You may need to remove the valve cover and check the clearance. They are not adjustable. If you think it is a stuck lifter, I would add Marvel Mystery oil to the engine oil and run it. Many times it will free them up.
You didn't say how the oil pressure was.

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parton2016-11-14T11:03:35Z

International 345 Engine

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Bill S2010-01-31T23:43:21Z

A rod knock is a pretty distinctive noise. Without being able to listen to it, there's not much of a chance of diagnosing through Yahoo! Answers but a rod knock:

1) gets worse under load
2) pretty much never goes away
3) sounds like someone hitting the engine block with a hammer

The other answer mentions lifters. I agree that's a good thing to check. If a hydraulic lifter is bad, that causes the cylinder it's on to not fire very well also. And sitting for a long period of time is a good way to have a bad (stuck) lifter.

You can try chemicals on hydraulic lifters and it might help. One time, my dad had me remove the hood from our family car -- getting ready to tear the engine down because of a terrible noise and the engine running really bad (my fault for driving it like a maniac). I worked at a gas station and decided to try dumping almost every chemical they had in the engine just to see if it worked. Son of a gun, in about 10 minutes, the lifters (more than one) freed up! The car ran great from then on. I got to put the hood back on and we were done.

After reading the additional information you provided, my guess would still be lifters. A collapsed hydraulic lifter makes a really bad noise and causes that cylinder to run weak, or misfire.

Any bearing issues will eventually get worse. You won't have trouble diagnosing things then :-) If he made any mistakes in reassembling the engine like rod caps swapped, pistons in the wrong cylinder, etc. that could account for the noise. If he's good at rebuilds, my apologies, I'm just listing some possibilities.

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Anonymous2015-08-13T01:55:52Z

This Site Might Help You.

RE:
situation with a 1979 international harvester( 345 cid engine)?
just got the truck running last month for the first time on, well since i have known the owner ( 9-10 years). now it has a miss ans what sounds like a rod knock. he replaced the connecting rod bearings and main bearings twice, plasi-guaged them in between to confirm tolerances. we have replaced...

00

Willy P2010-02-01T00:20:31Z

You could have the timing 180 out?
when you are setting the engine timing, hook up timing light lead to NUMBER 8 CYLINDER the timing should be TDC,
Bad gas ?
index the plugs?
Coil ?
baluster?
If its Hei it could be an ignition module. or the internal connections from the the coil.
Knocking could be timing detonating

Check for message boards about IH maybe someone else has had the same problem.
good luck hope it is something little and stupid.

Use the old poor mans stethoscope an extra long screw driver to the ear trick for listening to your engine. Put the handle up against your ear and the tip on the running engine. Not as good as a stethoscope as mentioned below but it works pretty good.

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