The Stovebolt Site Forums The Shop Area Engine Shop 235 engine detectives wanted

Just to prevent confusion, 235's do not have metal/oil shields.
Just a spring retainer.

Dave is right about the oil shields, but Jerry makes a good point about not using both, o-rings and positive oil seals (attached to the top of the valve guide). Now I have to remember if I made that very mistake on mine. CRAP!
Carl

OOPS! Gotta watch out for us old round track racers- - - -I've built so many small block V8's I tend to remember things wrong! Thanks for the heads-up!
Jerry

With all the emphasis on oiling, here's where I am now. It occurred to me that if I had partially blocked oil vent holes on the #4-6 valves that the crud came from somewhere. So I pulled apart the rear half of the rocker assembly and ran the used rocker arm shaft through the parts washer. I cleaned out some old oil sludge. I put it all back together and it's still oiling the rockers unevenly. #4 exhaust isn't dry but it doesn't weep oil from the vent hole. #6 intake spouts like a geyser. I changed the oil and filter so now I'm running 10W30 detergent instead of 30W non-detergent. None of the valves are bone dry and they all have some sort of inner seal/shield under the metal cap inside the spring (umbrella?) that only reveals about 1/4" of valve stem above the valve guide to splash oiling off the spring. I squirted all the valve stems with a shot of 20W50 oil from an oil can for good measure. All the springs are installed correct side up. So with all this tinkering, oil changing, and sludge cleaning, what else could I do but go for a test ride? It ran great cold, but at the appointed time and distance, same old @#%*! Seizing valves. Intake and exhaust both from the sound of it. I limped home and pulled the valve cover and used a length of garden hose as a stethoscope to try to isolate the noise. #4 exhaust (the one with no oil from the rocker weep hole) sounded noisier than the rest.

Does this starving/geyser scenario on the rear #4-6 rocker assembly sound bogus to you guys too? It's all clean now and I can't figure what's up. I could reverse the new front and used rear rocker arm shafts and see if the problem migrates to the front #1-3 assembly. I could start up two other trucks with 235's in them and see if they oil the same way. Or I could quit screwing around and HOPING that the problem goes away the easy way.

If you have not read my Blog post about rocker oiling I would suggest starting there, LINK.
You may have the wrong combination of rocker parts.

The paperwork that came with this engine called it a "58-59". It came with these rockers and has the pinched off center tube. But this geysering #6 rocker vent has the inner oil groove lined up with the pressurized supply hole rather than offset. Kind of sounds like 58 rockers on a 59 engine to me. All four different rockers have numbers 85, 86, 87, or 88 cast into them. Regardless of who screwed up on this originally, it's my problem to solve now. I think that I need to get these rocker ducks in a row before I start messing with disassembling valves. Thanks Dave.

You're almost there, brother!

25, 26, 27, 28 are supposedly the numbers on 1958 truck rockers arms.

I think the 1959 Truck Shop Manual Supplement does not list codes for rocker arms.

Maybe Pre'68 Dave knows the 1958 and 1959 codes on car 235s?

I started making a list of rocker casting codes a while back but gave up. There are overlapping numbers, so I only go by 1950-58(exc 216), and 1959-62, when sorting them in groups, although there are subtle differences within those years.

We really should have a "beating a dead horse" icon on the smiley list.

Jerry

October 1962 Catalog

Rocker arms 1959-62

inlet left 85,
inlet right 86,
exhaust left 87,
exhaust right 88

Also (or)used for 1950-58

http://www.gmpartswiki.com/getpage?pageid=65381

The horse isn't dead, Jerry, just tired and in need of rest and rehabilitation. Thanks for the parts info, Oilrag. Very helpful. At first, I thought my theory of the mixed rockers was kaput so I went and pulled each one for a visual inspection. The suspect rocker, #6 intake that spouts oil, is dual numbered 85 and also 5 and is the only rocker with the inner oil groove lined up with the vent hole. The other 11 are offset. So, I have one 50-58 rocker (cast3837025) messing up my oiling system. Regardless of what the future may reveal about this engine, I need to clean this up. If any of you could sell me a 59-62 LH intake rocker, it would fix this issue. If I need to buy a complete set of all 12 rockers and shafts from a lower mileage 235, I'd be open to that too. (303) 697-3351

When I went for my test ride last Saturday, I swore to myself that if all my HOPEFUL tinkering didn't work, that was it. I suspended my insurance coverage for the 48 Suburban today so no more test drives until this engine is fixed right. I intend to pull the head and check valve to guide clearance (.001 to .0027?) and also look for burnt or bent valves. I intend to get rid of the "umbrella" seals and go with the valve-stem-out-in-the-open small O-ring type seals that I have on my other 235's. I think that more oil splashing on the stems would work better. The amount of residual metal-shaving debris on the top of my oil filter when I changed my oil for the second time since start-up has me wanting to inspect my lifters to see if some of them are sticking all the way open. These are all ideas that I got from all of you, 235 engine detectives, and I thank you for your help. I've learned a lot and expect to learn more as I progress. My premier indoor work space is monopolized now with a partially assembled 52 GMC so I don't anticipate working on this 48 again until next summer. But I will print out all of this thread and keep my in my shop manual as my trouble-shooting checklist. Thanks again! Dave

Old post but did you ever get it fixed??

OP has not posted since Oct of last year. Doubt if he is paying attention anymore.