Dauntless Assessment

Oh wise CJ5 gurus, I seek your knowledge and advice on my journey to a restored 1970 v6.

Preface: This jeep spent the last 20 years as a yard mule at my uncle's house for plowing snow and hauling firewood (the bags of rock salt I found in the back worked wonders on the floor pan ). I got this thing started after sitting for several months in a lot. It would bog down at idle here and there, but ran smooth on the 25 mile ride to my house.

I have the motor torn down to the block, with rotating assembly still intact. I am trying to determine how far I need to go from here.

I measured all of the bores, top middle and bottom, horizontal and vertical, and they're almost all coming up 3.750", with one or two measurements at 3.751".

I took a .002" feeler gauge around all of the top rings, didn't make it through any of them.

There is some marking in the bores, but all pass the fingernail test aside from a slight ridge in cylinder 3 which I can barely feel.

The inside of the block is surprisingly clean, I don't see any sludge buildup on the internals, and there was very little inside the oil pan.

Camshaft bearings look like they're in good shape, no visible wear on the camshaft either.

I'm debating if there is a need to tear it down further at this point, or just clean the cylinders as much as I can and rebuild later on down the road. This jeep will be an around town and plowing my driveway vehicle once all said and done. Thoughts?

These pics are how it looked when I got in there, have only taken measurements so far.

 

If it has been running.......You should have done a Compression & Leak down test on it before you pulled the heads...........not saying you still can't clamp the heads back on and do the check , but new gaskets may be needed. If I had it to that point I would at least pull a rod and main Bearing and take a look.......If the front and rear seals are not leaking what do you have to loose by running it? Do the Compression & Leak Down test..........that will tell you what you need to know.

 

I agree with Tarry99. And one of the cylinders shows a lot of scoring at the top and at least one piston top shows signs of severe detonation or foreign material bouncing on the top. Hard to see very well on my phone.
Pull the main and rod caps and see what the bearings look like since you are pretty much there anyway.

 

Guess I got a little too excited to tear into it, hindsight is 20/20

The heads definitely need some work, they have a fair amount of buildup on them. Maybe I'll get them 100% then reassemble for a test.

 

I've seen a few cylinder heads, and those do not look bad to me. They are covered in carbon, but that's from rich mixture and operating conditions (cold and short running) typically.

Sorry to pile on, but I agree with the assessment above. You learn the most about engine condition from a running engine, not one that is torn apart. Aside from the compression check and/or leak down, you'd typically look at the oil pressure and the spark plug appearance. This will give you an indication of the bearing condition, and whether you are passing a lot of oil through the rings or guides.

If you want to save money and do only what's needed to keep the engine running reliably, you pretty much have to put it back together and run it, then do the recommended tests. If you are going to do the full rebuild regardless, just take the parts to your machine shop and have them measure and evaluate. They will recommend what needs to be done. IMO this is pretty much all you can do with the heads, other than run them as--is.

IMO - if I had already decided on a full rebuild, I would consider a short block exchange with reconditioned heads, or a long block. I don't think you'll save a lot of money doing the assembly yourself, if you go the whole 9 yards with new pistons, cam, crank kit, etc. To me, assembling an engine is fun, and I trust my work more than some factory worker, but that decision depends on time, facilities and experience.

If your bore measurements are accurate, you have no taper. A seasoned engine will have some bore taper. The amount of taper is proportional to how long the engine has been in service. New pistons are the most expensive part in a rebuild, and with mnimal taper you can reuse your pistons with new rings if you hone the bores and install iron rings. That's overlooking the bore damage seen above, that looks eroded like detonation? I don't know how damning that is - maybe Nick can comment further if he can get a look on a monitor.

 

Appreciate the feedback as always. I'm definitely leaning towards the money saving route.

 

here are a bunch of us talking about my junk engine.
I need some engine advice | EarlyCJ5.com

You can lap the valves. you should take off the rocker arms and inspect them. make sure your oil system is not clogged and clean it out. Your cylinders look to have pitting and scoring. If you want this thing to run perfect you need a rebuild with a bore, probably new pistons and rings etc. CHECK YOUR CAM. I bet you have some significantwear Check your lifters for dished ends with that cam.

All that being said, it won't matter if you do any of it if you're not doing the full rebuild route except for the cam and lifters. That will make a huge difference if you're missing lobes.

Personally, I would lap the valves, check cam and lifters and replace if required, put in new bearings and oil pump and drive it. If you read the above posting you can see how I feel about this stuff. Rebuilding the engine yourself is not to terribly difficult, but installing new pistons on the connecting rods without the correct tools sucks super bad.

 

If you are down to where you are now, I would consider at least pulling the pistons and crank put to further see the bearing conditions. From what I see in your pictures, there is still crosshatching showing on the cylinder walls-very little wear. If the bearings look perfect, reuse them in the EXACT positions they are in.
Clean everything up, have a shop do a very light hone to deglaze the cylinders and have a quick valve grind. Install new rings, maybe bearings, seals, timing chain, and you have a fresh engine. If you reuse your cam, you must keep each lifter in the exact cam lobe position.
This way, you know what you have.
-Donny

 

x2 on looking at the cam. On these engines, oil pressure at hot idle is often almost at zero. The first place most of these show wear is the cam and lifters from lack of oiling. Far too many of these Jeeps get torn down with the best intentions only to never get put back together.

 

it almost looked like some pitting on cylinder 4 wall. unless it is the picture

 

thats what i see too

 

I'm gonna pull #4 tonight and see how it looks.

Hoping to get away with cleaning up heads, lapping valves, bearings if needed, hone and re-ring. I'm comfortable doing all of that myself and limiting machine shop work to the flywheel resurface.

 

looking at your rods and caps they were stamped with numbers which might suggest the engine was rebuilt?

 

what i did to my heads was gasket match and a good port and polish of the intake and exhaust chambers. cost me a die grinder bit and some other bits for the polishing and time. these aren't like ford heads that have huge restrictions in there but it does help if you do this just don't go too crazy cuz you can get some crazy flow (tumbling) if not done right.

 

Since it's already tore down this far I think you ought to go all the way and finnish tearing it down.
A full gasket and seal set will definitely be required.

You can likely get by with a cheap rebuild if you follow Donny's advice.
But the heads may need a full rebuild.

Maybe all you'll need is a hone job for the bores .
It's quite possible that all crankshaft journals may be in good shape as is.
Or it maybe just needs the crankshaft polished and all new rod and main bearings.

I have a set of STD. OEM NOS piston rings available in case a simple hone job does the trick on the bores.

 

That was me

 

What was the reason for the teardown to begin with ?
I'm in the "do it now while it's torn apart" group.
Do it once, do it right.

 

I'm swapping everything to another frame, had it out and knowing the history, looking at the amount of crud on the outside, the amount of 'nature' hanging out in the bellhousing, and valve cover gaskets crumbling in my hands, I figured it was worth a look.

Initial plan was just new gaskets and seals, but since it's going to be out of the jeep for a while and was sitting there whispering "take me apart", I couldn't resist!

 

Looks like I might be SOL on the easy way out...

#4:


Found a nice gouge on #5 too:


Bearings look like they've seen better days too, main bearings have similar pitting:


Not sure on this front cam bearing:
r

Queue the music?

 

# 5 might be repairable. i would take the block and heads down to a machine shop and have them checked out. your this far into it and the money spent will last a long time with getting this rebuilt and you know what you have.