top end rebuild?

Hello everyone, got a couple questions. I was trail riding this weekend and ive always had a little ticking in the top end of the motor but i noticed that while getting on the gas on hill climbs this weekend i heard a light knocking sound in my motor. It sounded like it was coming more from the lower end. I was planning on doing the top end soon but not sure now. The motor otherwise doesnt smoke and is preety solid. Really dont have the money for a total rebuild . Anyone got any ideas on what i should do? Thanks in advance...

 

Possibility knocking under power maybe coming from a drivetrain component that is seemingly coming from engine... trans, xfercase, driveshaft, diff. Check those first.
Check total valve assembly and adjust/retorque as required for ticking.
I've asked same question about my ticking, answer, "run it till it drops".

 

Drop the oil pan

I'm newer to engines than most people on this site (read my posts if you don't believe me), but in any problem, the more information you have to base your decision on, the better. I would pull the oil pan, and look for metal fragments in the pan. I would look and see if there are any visible signs of bearing problems. Then I would have a helper turn the engine slowly with a big wrench while you watch (and listen). Fixing a small knock now, is much cheaper than replacing the whole bottom end over something stupid.

I had a mechanic buddy who was asked to check out a car with a GM v6 in it, and he saw no problems, so he advised the guy to buy it. Two weeks later, the guy is taking it on a trip, and it starts knocking, and then it starts really knocking, and then it started the metal on metal sound that you just know sounds expensive. The guy drives the thing like 600 miles, and somehow got it home, but one of the crankshaft bearings had broken, which caused the crank to turn untrue, which bent the connecting rods, and caused the pistons to not go up and down true, which wore the pistons and the cylinder walls horribly. (Im done scaring you). By that point, the only option was to pull an engine from the junk yard. Had he stopped and spent the money for a tow, and fixed the bearing, that engine would be strong today.

Good luck, hopefully it is something small (like my headgasket job that turned into pulling pretty much the whole front end off)

Doug

 

I agree cide1. I just went through the process of replacing timing cover, timing chain, oil pump, and main bearings on my 304 (they say I am A.R., it had to be clean and done right). When I was done, I figured just a little more work and I could have rebuilt the whole engine.

The best "trick" in the world is to learn how to isolate your problem.

 

About isolating your problem. I've found a mechanic's stethoscope or a piece of tubing works real well in isolating where an engine noise is coming from. It will help you track it down as to what cylinder it's coming from or what valve, etc. Definitely get in there and at least isolate it. Then you can come up with a gameplan as to what you want done.

 

Sounds like what happened to me when I had my CJ7 with the 258. On my way to work one morning the engine was noisy so I stopped in a service station. The guy said, "Sounds like it's in the bottom end, better get it home right away". I did like he said, home was only 2 miles away. I tore down the engine and only 300 dollars later I had new crank bearings and a newly turned crank, otherwise I would have been engine shopping, and at the time CJ7 parts were at a premium and hard to find. What Brian said about checking the oil isn't stupid, what got me into this mess in the first place was a leaky main rear seal and a crappy factory oil pressure guage.

Paul

 

Brian, I hope you werent serious about the oil level thing? My 12 yearold son knows that. Ive totally rebuilt this jeep in the last three years, except for tearing down the motor completly. I will say i have never rebuilt a motor before but i have been an aicraft mech. for over 20 years. The jeep doesnt leak or burn any oil. i just replaced it before the trail ride up at grayrock...

 

Broken motor mount? Worn fuel pump or fuel pump eccentric? Driveshaft u-joint?

If it's main bearings, usually you'l have a deep thunk-thunk-thunk rather than a knock. A rod bearing, wrist pin or piston slap sound similar. Piston slap will usually be worst when the engine is cold, before the pistons expand and fill the bores. Trying to recall... the main difference in a wrist pin and rod bearing knock is sensitivity to oil pressure. A rod bearing knock will get worse as the engine warms up and the oil thins, and a worn wrist pin doesn't change.

If I couldn't isolate the problem, I'd pull the pan and inspect and/or plastigage the rod bearings. With a cast crank (like the V6), if you can hear a rod knock, you can pretty much guarantee needing to replace the crank and bearings. Steel cranks are another story...

 

Thanks for the info. Tim. Ill be pulling the oil pan this weekend and i have a buddy coming by to take a listen.. I didnt want to have to tear into this motor right now but it dont look to good.

 

How was the oil pressure?

 

The oil pressure is good. Like i said the motor runs good and doesnt smoke. I didnt pull the pan off yet, to many other home projects this last weekend.

 

two things to check that I have seen.. check the timing chain tensioner to make sure the timing chain is not flapping around.. it makes a weird ticking sound and check the rocker shafts.. mine were wore out ad the rockers were wahcking around in there....


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