Discussion in 'Small Block Tech' started by Mark Demko, Nov 16, 2021.
Dallas Brown does a vid on V6 and V8 timing covers.
That's good as far as it goes but there's a lot more to it than that. One basic fundamental fact is the difference in the pressure between the suction side and the pressure side. The suction side will never see more than 15-16psi of pressure moving the oil through the pickup and the suction journal because that is all the air pressure we have at sea level. Create a perfect vacuum at the pump and it's still all you get. Whereas the pressure side can be 2 to 4 times greater. This was not taken into account in the video and explains why the pressure side passages do not have to be as large as the suction side.
I took a bone stock OEM 300 with low miles, opened the suction galley to 9/16", installed a V6 pickup, ported the pump, installed the stabilizer plate, and reduced the pump gear end clearance to the minimum possible and with no other changes achieved 65psi at idle with 5w30 oil. That's with the engine warm and heat soaked during a long trip. So there is no need to rework the pressure side, and I'd just leave that alone. The two most important things are pump end clearance and bearing clearance. If those are right, even with the stock suction sizes oil pressure will be acceptable.
BUT making the pump suck through a straw is not the best practice, as Buick decided. The formula for the cross sectional area of a tube is cobbler. As in: pies are square. So divide the diameter by 2 to get are, multiply it by itself to make it square, and then multiply it by 3.14 to get cobbler and you're in business. So the area of a 7/16" hole is 0.150 square inches. The area of a 9/16" hole is 0.248 square inches. So the 9/16" suction journal under 15 psi of air pressure can deliver nearly twice as much oil to the pump as the 7/16" hole and that is enough for any but the most extreme racing engine. You can go to 5/8" in the block but it's risky, and you may end up installing a brass tube to seal up a breakout. This is why a piloted bit is needed.
I do think that porting the pump and especially the stabilizer plate is helpful. But I wouldn't go as far as reducing the gasket sealing surfaces to do it or making the transfer holes in the pump body much larger, just smooth and round the corners to reduce vortexes and improve the smoothness of the flow.