The Stovebolt Site Forums The Shop Area Engine Shop No oil pressure when priming new 235

I just finished assembling a new 235ci for my 53 1/2 ton. When I inserted my drill into the distributer shaft to prime it clockwise, I have no oil running to the rocker arms or even the pressure outlet that runs from the block to the external oil filter. The new oil pump was installed correctly but it seems to be the problem. I have tried several things like reversing the drill slowing counterclockwise and then going clockwise. I can blow air into the block and can feel it at the rocker arms but no oil. I shot oil into the pressure outlet that runs to the oil filter but that didn't work. Is there maybe some trick to priming the oil pump? I'm stumped on this one and don't want to start it up until I know I have sufficient pressure at the heads. Thanks.

You don't say, but you do know you have to have a distributor shaft in place. At least you do in SBC v8s.

yes, I made one out of an old shaft that I inserted into my drill. That allows me to turn the gears.

Is it a 53' engine? Some engines had a full flow filter, and some had a bypass filter. if it's a full flow filter, a block in the oil filter or lines could be causing a prob. but that wouldn't be a problem with the bypass filter. (although it would definately be a prob in the long run)

Did you have your block boiled out when it was rebuilt? Just trying to eliminate a blocked passage as the culprit...

Did you plastigauge your main bearings??? if there is too large of a gap there you won't develop enough pressure for the oil to make it up top.

You might check the clearance between your oil pump screen and the bottom of your oil pan. Too close and it will restrict oil flow

Are you sure that you are watching the correct hole for the oil out? This should be where your oil pressure gauge connects. You should feel resistance on the drill and it can take minutes before it reaches the rockers. The place to look on the rockers is the end of the drain U tube.

No 235 engine (car or truck) had a full-flow oil filter from the factory. A full-pressure 235 would only be possible if someone converted the block. The 1958-1963 261s were the only full-flow oil filters in Chevrolet or GMC engines of that era.

How many RPMs are you turning the drill/pump? I had to turn mine fairly fast to get oil up to the rocker arms.

(Also, I have to ask: did you take the cam gear off the distributor-shaft that you are using to turn the pump? If you have removed the gear, ignore this question - no need to reply.)

Make sure your distributor is properly seated when priming.Make sure your oil level is right.I remember when i did mine,i forgot to hook up the filter hoses,oil pumped all over the floor.

53Chevy -

I feel your pain. I have the same issue, except my pump works intermittantly. It pumps normally for a while, then seems to lose its prime and stop pumping altogether. When the pump is working, it works very well. Plenty of oil to the rockers. Then it suddenly quits, as if the engine were turned off.

I believe the pump has a pressure relief valve on the side of the pump. If the valve is stuck open, the oil pumps straight back to the pan instead of the rockers. I've concluded this is my problem, but I can't think of any way to test this theory short of replacing the pump. Of course I didn't discover this issue until the engine was installed in the truck, so changing the pump is not a simple matter.

you're right, good catch tclederman

Thanks guys, my 235 has the bypass filter and came out of a 1962 truck. I have checked the clearances on the pump and they seem fine. I have tried multiple rpm (both fast and slow) when priming but that hasn't helped. I haven't felt any resistance when priming however. The block was boiled out when the engine was rebuilt so that shouldn't be a factor. Also, there are 2 holes in the block where the oil filter lines connect to. I tried priming without the oil filter connected to the block and still no oil comes out of the block much less the rockers. I guess I may have to pull the pan again to check the pump.

Is it possible you forgot to install the oil pickup tube on the oil pump ?

Just to cover all the bases...
Are you spinning it the right direction?
Guess why I thought to ask this.

regards,
Leon

Does a 1962 235 engine have that special head bolt that allows oil to pass through to the top end ?

What did you figure out ? we are waiting to hear from you.

special head bolt? it should. and my '61 didn't, so someone bypassed it from the block to the head. but on the rebuild, i'm drilling the bolt per pre '68 dave's instructions, bec even though i like vpl, i don't like vol

Here's a little trick you may try if everything else checks out. Take the bottom cover plate of the oil pump housing, then pack the gears with grease. This hhelps the pump pull a vacuum faster, thus pulling the oil up from the pan. I did this on mine, worked like a charm.

lb55 - i'll note that good idea. so, even full of oil, an pump isn't 'self-priming' at that stage of the game. which would be similar to most water pumps. they don't actually pump, but instead, they create a pressure difference whereby the fluid flows to the low pressure/'suction' side of the pump

Bill,

I do not know the answer to this question: is there any chance that the grease in the oil pump might move into an oil line/passage and cause a blockage? I'm thinking of an older/dirtier engine, especially a low pressure 216/235.

Tim

I prefer to pack the pump gears with Vaseline, which works well but dissolves harmlessly in engine oil.

good question tc, and i don't know either. but i did find a note in a '68 manual that makes a point of mentioning loss of pressure due to any air leak at the pickup screen/pipe assembly to pump connections

worst case scenario I would start from the bottom and trace all your oil passages up checking for anything out of the ordinary- if nothing works I would try back flushing the oil passages to see if anything goes through the other way.

Other obvious questions that I might have had happen to me in the past or can think of off the top of my head-

Oil reads proper level or a little high on the dipstick-

Pre filled the filter-

if so equipped check valves are clean and working-

All fittings tight on pump and pump installed correctly-

Check to see with pan off is your special tool correctly contacts oil pump drive?

Just things I have thought of.