The Stovebolt Site Forums The Shop Area Engine Shop 1953 235 dipper

A friend of mine has a '53 235 low pressure babbitt pounder with no oil to the rocker arms.
He sent me a picture of the oil distributor on the left side of the block and low and behold, there is not a short copper pipe coming out beside the oil distributor.
There is no threaded hole in the boss where the earlier models had the short pipe coming out.
I am guessing that in '53 they stopped routing the oil pipe through water jacket.
The coupler which joins the rocker shafts and provides for oil supply to them, does not have a copper pipe coming up through the block and head like earlier low pressure engines had.
I am assuming that the oil supply is coming from drilled holes in the block like the full pressure engines do.
He is going the pull the side lifter cover and send me some pictures.
I shall return with questions once he does that. Can't tell what's in the pickle barrel til you git the lid offen it.

53 saw several transitions, including the first few full pressure 235s- - - -mostly in Corvettes. Is he sure it's a spray-oiler? The oil distributor on the driver's side makes me think so, but without a complete teardown, it's hard to tell. Does the side cover go all the way to the valve cover, or is it one of the ones with a short pushrod cover?
Jerry

That sure sounds like a 235 MUCH later than '53. I had a '58 235 that routes the oil supply from the oil gallery inside the pushrod area to the center of the block and up into the rocker oiler. Some of them needed a center drilled head bolt. The engine I had did have a drilled head bolt but didn't use it. I don't have it anymore so I can't take pictures. Like Jerry said, the height of the pushrod cover will add some more info.
Can you post a picture that he sent you of the oil distributor.

[on edit]
Here's a cross section diagram out of a 55.2 shop manual showing the lubrication system. The tubing connects at the rear camshaft bearing boss inside the pushrod cover. This would be a full pressure 235, not a spray oiler.

He sent me a picture of the oil distributor on the left side of the engine. It is kidney shaped and held on by 3 stovebolts. He said that he will send me pics once he pulls the side cover.

The stamped number beside the distributor is LAA661236.
It has a short side cover.
The brass oil connector between the rocker arm shafts is fed with oil by a pipe which is press fit into the head just like a full pressure 235.
The oil line under the side cover goes from the lower left to the upper right and has threaded fittings on both ends just like a full pressure 235.
There is a 1/8" pipe plug in the head right above the distributor just like a high pressure 235.
There is a kidney shaped stamped metal cover for the oil distributor held on by 3 stovebolts on the left side of the block just like a low pressure engine, but oddly does not have the 3 inch long copper pipe coming out of it which normally goes into the side of the block. The boss beside the cover is not drilled or tapped.
I am curious to know if there is even an oil distributor under that cover.

What is the block casting number? The website below lists lots of serial number prefixes and casting numbers, but there's no "LAA" listed for either 216 or 235 engines.

https://www.gregwapling.com/hotrod/corvette/cast.html

Jerry

Carl - Your friends "LAA661236" is the serial number for a 1953 Passenger Car (models 15-21-2400) "Regular 235" according to the info in the 1953 Truck Data PDF from the GM Heritage Center. The 1st pic below provides that data.

The 2nd picture below, taken from the 1953 Passenger Car Data PDF, provides the full "Engine Lubrication System" description. The only engine oil splash lubrication described involves the cylinder bores and piston pins.

Quoting from the above manual page- - - - -"Connecting rod bearings- - - -pressure streams directed against connecting rod scoops"- - - - - -yes, it's a Babbit bearing spray-oiler. The valve train lube seems to have been updated to a similar system to the pressure-oiled 54-up 235. The idea of ANY 216 being a "splash-oiler" is a myth.
Jerry
'-

The oil distributor on that engine is likely just to feed the nozzles that spray oil at the rod scoops. There might be a spring loaded valve like the oil distributor on the 216s have. But the rocker oiling comes from the rear cam bearing like the 1958 235 I had with the tubing behind the rocker cover.

Good find Dan!
This engine definitely came from a car.
It may or may not be in a car currently.
I haven't seen it in person...

He removed the pipe under the pushrod cover and put a gauge on the port and turned the engine over with the starter and it read 30 PSI.
The pipe is clear and he blew air through the other hole at the middle of the head which leads to the top of the head and air made it all the way to the brass connector on the rocker shafts.
He is going to put the pipe back on and start the engine to see if he gets oil to the rocker arms. If not, he's going to remove and thoroughly clean the rocker arm assembly inside and out.

I just referenced the 48-51 Chevrolet Truck Shop Manual and it indicates that all 235 engines made after '49 no longer had the oil line going from the oil distributor through the water jacket, going directly to the rocker shaft connector.
Instead, oil to the rocker arms was provided from the rear camshaft bearing.
The purpose of the oil distributor has always been for providing more oil pressure to the spray nozzles aimed at the connecting rod dippers as oil pressure rose from higher RPM.

It's supposed to take 15 PSI oil pressure in the main oil gallery to open the valve in the oil distributor to supply oil to the rocker arms. Anytime pressure dropped below that point (not uncommon on a spray oiler) oil flow was stopped to the rocker arms to save the lower end. Pretty smart engineering, actually! Rockers can survive much longer with minimal lubrication than the connecting rods can.
Jerry

Jerry,
With the advent of the changes made to the low pressure 235 engines from '49-'53, where they changed the supply of oil to the valve train to the rear camshaft bearing rather than from the oil distributor and through the water jacket, does that indicate that oil distributor no longer played a part in managing when oil was allowed to make it to the valve train?
In The Manual there is a reference to an orifice between the rear camshaft bearing and the copper line under the side cover to meter the oil supply to the valve train. The orifice likely prevents the valve train from hogging too much oil from the crankshaft and the camshaft.
I would also suspect that sludge blockage of this narrowing orifice could be the culprit for many no-oil-to-rocker-arms scenarios.

I'd have to trace an oil circuit to be sure, but I'm going to make a SWAG that the oil distributor became non-functional once the oil supply moved to the rear cam bearing oil gallery. A simple 1/16" orfice would have been all that was necessary to restrict oil flow to the rocker arms in that case, while still supplying sufficient oil to lube the rockers and valve stems, similar to the flow control used for a bypass oil filter. I have seen many stovebolt rocker arm systems that have obviously been running virtually dry for thousands of miles, usually with the bottoms of the rocker shafts seriously worn, and the rocker arm tips deeply pitted from rubbing on the valve stems with no lubrication. For some reason, there has been little or no wear to the rocker arm bores in those situations.
Jerry

Well, my buddy now has oil to rocker arms. He likely inadvertently cleared the oil passage in the block coming from the rear camshaft by removing the oil line under the side cover and turned the engine over by the starter. There is an orifice in that passage which would be a good place for a booger to hang up.

He developed a problem with backfire through the carburetor, so I walked him through setting the octane selector at zero and set the timing with the needle on the ball.
He says he's ready to race me now.

The ole boy got the engine running but now has a strange bucking/surging situation in second and third gear once the RPM rises.
The 216 idles great and runs strong under load, so I don't believe that it is engine related.
I rode with him to see what he was talking about as far as bucking is concerned. It moves you back and forth in the seat as though you were speed shifting. Not too violent, but clearly annoying. It does it the whole time once you increase RPM to cruising speed and only stops when you let off the gas.
I had him depress the clutch pedal ever so slightly to see if the bucking would stop before the clutch completely disengaged with the flywheel. Low and behold, it stopped bucking and the current speed was maintained as long as some slight pressure was kept on the clutch pedal.
What's going on here?

Carl - I think that question needs to get asked in a new thread in the Driveline forum. It kinda sounds like clutch or further back issue and as you said, not engine related.

I'm going to disagree with Dan on the issue being the clutch. The clutch pedal being slightly depressed give it the opportunity to slip and damp out the bucking.

I would have him look at the carburetor float level. I had a new car that surged at highway speed years ago. I took it in to have the dealer fix it and the service writer swore that it was because "the spark plugs had to seat" and had to "get a glaze on them." I kid you not! Knowing enough about engines I challenged him and took my case to the service manager. It turned out to be a simple float level adjustment. Never had an issue after they corrected that.

You might also want to run a volume test on the fuel pump. At idle, a good pump should put at least a pint of gas into a catch can in 30 seconds, with the engine running on the fuel in the float bowl.
Jerry

He has swapped in another carburetor which made no difference whatsoever.
The bucking which is going on does not seem to significantly alter the RPM of the engine to my ear, nor the power of the engine judging from the seat of my pants.
This 216 has 30,000 original miles on it and is very strong. It likely has been sitting for some time though. He bought it used from a little old lady recently and hasn't driven it much at all.
For now, I am going to recommend that he drive it to see if it gets worse before it gets better.
I'll let him know to do the fuel pump volume test just in case my ear and the seat of my pants is out of calibration.