I moved the mechanical pressure gage to the pickup on the back of block behind the distributor and still no oil presure. I have oil flowing, but no presure. What could be going on? Where could I be missing a restriction?

It almost sounds like the bypass is stuck open in the oil pump. If you have flow and no pressure. When reading it on the side or back of the block that oil galley is directly from the oil pump. If you had the pickup welded on and the pickup is in oil and the pump was torqued onto the main cap you should have pressure. Sometimes you can use an air hose and blow air backwards into one of the oil galleys and hopefully you can move the bypass valve around enough to un lodge it. That sounds like the only thing it can be with out seeing it for myself.

John S.

Where do you blow air? Directly in the oil pan?

in the oil galley where you pulled the sender out.....id try several short blasts

I will give it a try. What air pressure would you recommend?

Does the bypass allow the oil to flow through the cam and main bearings? I am getting oil flow at the filter and both oil ports

I would try 80 psi at first, just be careful of blow back....( oil all over the place)

Ive never tried it but makes alot of sense and havnt known John to be wrong

Is the bypass in the oil pump. I know there is a bypass in the pad were the oil filter is. Is there also one in the oil pump. This was my first (pair) of Big Block Chevys and I don't reminder the oil pump that well

Yes, the bypass I am talking about is in the oil pump top cap. Remove the sending unit from the top hole in the back of the engine and put the air in there. You should use a rubber tipped air nozzle, push it in the hole and blast air a few times to make sure you get all the oil out of the oil galley. You should hear a hudge bubble in the oil in the pan. After that let the air flow a few times to hopefully unlodge the bypass. You kinda want the oil in the galley when you hit it hard with air because the hope is to use the oil flow backwards to help loosen the bypass valve.

Good luck, let us know how it goes. After you blow air, put the sending unit back in or the plug or the gauge and start the engine up. Keep an eye on the gauge.

John S.

i have a sneaking suspicion that someone failed to put the oil galley plugs back in after the block was cleaned and it is just pumping the oil straight back into the front cover...

also... wern't there two types of distributors ... one that sealed the oil gallery internally and one that didn't ?

I will try it tomorrow. I have been priming the engine to check for oil pressure. The st engine shows oil pressure this way, but the port doesn't. Why do you say to start the engine. Is it a valid way to check with a corded drill priming the pump and a mechanical gage.