I posted weeks ago when I could only rotate the engine by hand 1 rotation. I was able to pull the motor this week and started ripping into it. I found quite a bit of sludge both inside and out. The combustion chambers are coated with carbon. It looks like some of that carbon flaked off and created a ridge around the top of 1 cylinder. Once that mess was gone the crank rotated freely.

Now that the engine is coming apart, what absolutely MUST be replaced? The cylinder bores look fine, a honing will probably be all it needs. If the cam and crank journals look good should all the bearing be replaced? I thought I'd get one of the rebuild kits from summit with new pistons, rings, bearings, oil pump, and gaskets.

What about the cam, lifters, push rods and rockers? The lifters look fine except for some deposits on the lower outside edges. rods and rockers cleaned up nicely.




Cleaned sludge out of lifter valley and brushed carbon build up off piston tops.

 

Yes, I think this would be the way to go. There are many kinds of piston rings material, the harder they are (moly, chrome, etc) the longer they last but also the longer they take to break in. Most of our trucks do not get high mileage over their life and I personally prefer cast piston rings, quick break in, and a little more forgiving in the cylinder as far as when deglazed rather then having been bored.

If it was cheap enough and you have it apart............. for the dollars involved might be a good time to think about a RV cam and lifters or very mild performance grind. Timing chain too. Don’t forget the zinc break in additive for start up if you do the cam.


I rebuilt a engine once with new rings ground the valves but didn’t check the valve guides, because of increased ring seal, vacuum, it sucked oil on deceleration like a politician. Buy a set of rebuilt heads and you done forever. Just a thought.

Would someone please disagree with me, thanks.

 

Having done what you are wanting to do many times and also having done many COMPLETE rebuilds, my advice to you at this point would be to either clean the heads up a little and put it back together as it is or tear it completely apart, haul it all in to the machine shop, and let them check it all out and tell you what it needs. I can tell you right now that they are going to want to bore it, turn the crank, replace the pistons, and rebuild the heads - because that's the right way to rebuild it. A newer EFI motor might get away with a hone and reusing the pistons, but that never happens on an older carbureted engine. No matter how well they're tuned, good old carbs ALWAYS run fat when they're cold and the extra fuel causes wear on the cylinder walls over the years. A rering with fresh bearings might run OK for a short while, but more often than not it will start burning oil and rattling within a year or two. If the cylinders look OK and aren't rusted, it's got a better chance of giving you some more reliable miles if you don't tear the bottom end apart. This, of course, is all subject to opinion, but it's my 2 cents worth from having "been there, done that".

 

If there is much of a ridge around the top of the cylinders then you should have the engine bored to the next nominal oversize. If you know someone with a bore gauge, use it to determine the amount of wear in the cylinders. You at least have to remove the ridge or you will end up with broken pistons shortly after you first run the rebuilt engine. Honing the cylinders will be of little value.

Use a micrometer to check for wear on the crankshaft. If any journal is .002" (or more) undersize then I would have the crank ground to the next nominal undersize.

You didn't say solid or hydraulic lifters. If hydraulic I would replace them as a matter of course. Solids you can resurface the face that contacts the cam and reuse them. This face should be slightly convex and free of any scuff marks. If any one is scuffed or pitted then I would look at the cam for the same scuffing or pitting. If any lobe is found to be scuffed or pitted a new cam is in order. New cam means new cam bearings.

One thing kinds of leads to another. If you have more than 75K miles on that engine then I would replace the timing chain or gears.

Take the pushrods and roll them on a flat surface. Replace any that are bent. look at the ends and replace any that are pitted. Rocker arms, look for pitting or scoring on the wearing surface.

Send the heads to a machine shop to have the valves done.

Lastly the oil pump should be replaced as a matter of course.

 

the cylinders might look fine but how much taper is there.chrome or moly rings will not break into a worn cylinder.i use cast rings.if you want good results bore it.

 

That motor is a precision machine. When it was assembled and run for miles all the parts broke in "together." Over the years all those parts continued to wear evenly and live at the same levels of strength - and degridation.

Now, if you go throwing a new part on here or a few new parts in there, it's going to create stong points in the motor that the rest of the engine will have to tolerate (it's parts that are a little more worn, and it's going to cause those parts to wear at a substantially increased rate.

If the main players in that engine are worn enough to warrant replacement - like bearings, or valves, then chances are very high that all of them are close to needing replacement.

Long story short is that with the exception of a few items - gaskets, timing gear/chain, etc. You either want to clean it and reassemble it as it is, or completely rebuild it. Not half and half.

 

That there is the best advice you can get, bar none! .................

I’m going with the first option on my project (this time) and I might be sitting on the side of the road regretting it!