Hello, first off, sorry if this is the wrong forum for this question. I'm helping one of my clients, not automotive related, with a new project vehicle they bought and let's just say the list of issues is growing faster than the budget. The vehicle is a 1946 GMC Cab-Over flatbed gin pole truck that was plucked out of a field in Nebraska. The current dilemma is the old 236 I6. We pulled the valve cover gasket and oh my goodness was there some horrific crud in there. A little picking at the brownish crud revealed decent looking metal underneath but it's hard to imagine that all oil passages are clear so starting the engine seems risky at best. My question is what would be the best way to clean the engine? I assume a complete teardown and rebuild would be ideal but I'm just curious if there is a reasonable/viable alternative. Not trying to be cheap but everybody has a limited budget, or they at least try to have one.
My vote is that there is no free ride or miracle product. Some will swear by various additives and methods but others have done studies that appear to shoot down all the popular tricks as "snake oil". Unless you can get it clean of any chunks and run the oil passages in situ, I'd pull it. I think that's often a faster and easier solution than trying to do it in place. Plus such thick junk on the top end is a sign of an engine not well maintained. Just an opinion.
Had a 352, bought the truck running and just cruised it. 6 months later, bent valve. Removed the valve covers and it was a mess. Stopped up with crud. Pushrods couldn’t oil the top end. If I would have pulled the covers when I bought it, I would have probably removed the engine and cleaned it up and at least resealed it. Had to be pulled later anyway eventually. I’d consider removing the pan and side covers and wash it out as best as possible. Check compression and go from there
the easiest thing to do is remove the distributor and get a 1/4” rod about 12” long. Flatten one end with a hammer on your vice to the thickness of the distributor tang. Use a 1/2” drill turning it clock wise and watch for oil out of the rocker arm assembly center over flow. It’s in the center of the shaft draining into the push rod hole. It’s fed from that 1/8” line on the front of the block going up to the right front of the head. If you have oil there it’s probably going every where. Taking the pan off is pretty easy in the bigger trucks and gaskets are available from Best.
Thanks for the replies. We may try the tip from "jimmy six" but removing the engine is probably the best way to go, and at this point just about everything else has to be pulled for one reason or another so why chintz out on the engine. As far as cleaning agents go, is there a preferred product or DIY blend for tackling really heavy gunk?
Your the first one to mention a 236” GMC. Are those the first three numbers on the distributor bolt down flat? Most every one has heard of 228, 248, 270, and 302 GMC 6’s but there were 236 and 256” also.
Sounds like what we used to call a “ Quaker State” engine. Add a quart of Quaker State when it got low, no need to change it, it got fresh oil all the time. About all you can do is tear it apart and hot tank it. Doubt you’d ever get all that junk out any other way.
My first car was a 65 Mustang that was 11 years old at the time, 92K miles. There was a lifter tick and I decided to dive in and replace it. Pulled the valve cover and the sludge was like a jello mold, valve cover-shaped and had the Ford script pressed into it. I cleaned what I could out of it and buttoned it up without going after the lifter. Probably was hoping that would get better with more oil moving around. Eventually, crud (likely that I loosened up, but missed removing) got into the pan and jammed the oil pump. I think if removing the engine and just rebuilding it is a legit option you can afford, I wouldn't rinky-dink with it. Do it right, or it will just cost the same later. You'll lose time and money if you just mess with it. Some old-school folklore is to run ATF to help loosen some oil sludge up. Tranny fluid is like 10W oil but the routine is to run a quart for 25-50 miles before a change. Means a running motor and some heat cycles.
I bought a Dodge pu that was 9 years old but had about 50k on it years ago that had an oil leak at the back of the intake. When I pulled the intake there was a layer of junk from head to head of mostly baked and dry oil. After poking around we found that only the bottom 2" or so were open. I spent a couple of days and pulled the pan cleaned everything up and put it back together. The thing still had to come out because the rings were stuck to the point of pushing the dipstick out along with the oil on my 10 mile drive home. I tried the ATF also .
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