Do I drill out the tube passage to 5/8 down to where it intersects the side passage? Do I chamfer the entrance to the hole out to 5/8 so the oil has a smoother entrance? Does it matter? Is there a source for 9/16 pickup tubes? Is it a worthwhile upgrade? Lot of questions, I know. As always any help/input is appreciated.
5/8 tube melling , 20 is5 I believe is the number. Works with any size passages. A chamfer would be good. Not necessary 9/16 is good. 1/2 inch is still better then stock. Just drill the passage to the pickup from pump. If you can, a 6 inch long grinder to round the intersection point .
Really guys? I'm surprised. That stock hole must be no bigger than 7/16". Have you seen the volume of oil that has to flow through that? And then if it wasn't any benefit why did Buick enlarge it on the V6, which you could claim should be using 20% less oil to begin with? Consider if you will that volume of flow depends on the restriction size and the pressure. Also that increases in diameter increase the flow by the square rather than in straight proportion. In other words if you double the diameter you quadruple the area. And finally, that the most pressure the suction side will ever see is 15psi at sea level with a perfect vacuum at the pump. Considerably less on Pike's Peak. Now, do you really expect that system to be able to maintain 3 or more times the pressure on the outflow side without cavitation on the suction side? Considering the outflow journals are the same size? Well, only with very good loss control on the output side is this ever going to work, and then only until you get some bearing wear. No, the better setup is to have 3 or more times the cross sectional area in the pickup as what the outflow journal has, which would allow the inflow at atmospheric to match the outflow at 45psi without any restriction or cavitation. Unfortunately this would require a suction line of 3/4" diameter. However the 5/8" line allows twice the flow so with reasonable loss control provides reasonable expectations of being able to maintain good oil pressure. As a practical matter I generally drill the block to 9/16", yet another compromise, but much better than the stock size and less chance of a breakout. But I'd be much more comfortable with a 3/4" suction line. Jim
Jim, I know we spoke of this before and your theory sounds solid. However in real world testing I've done it does not prove to be needed. Even the stock size suction galley flows more volume than the engine can use. That is unless your bearings are extremely worn out in which case you have bigger problems. The oil volume is really never 1 to 1 input to output. Once the pump hits a certain output it dead heads, makes the pressure gauge go up and recirculates oil within the pump, drawing very little new oil in. If you were running at high RPM, the gauge read 0 and you were not blowing up then you may be passing oil 1 to 1. Also, the larger the suction size is the harder it is for the pump to draw it up. There would be a point in enlarging the suction side that the pump could not pull hard enough to draw oil out of the pan. A 3/4" tube may never even prime. All that said the answer to why the V6 used a larger hole (if they did, I don't know anything about V6) is unknown. It could be as simple as 1/2" or 9/16" drills broke off in the block less often and less blocks were scrapped. Or the drill supplier had a sale on 9/16" drills. As far as I know as a replacement for the 350 a 5/8" tube is all that's available.
Doesn't that pickup tube, whether 1/2" or 5/8", sit about 75% submerged in 5 qt's of oil in the pan sump anyway? The block oil rail hole enlarged from stock, seems would take a bit of extra time to fill up before pressure builds.
Mart, I'm not going to argue with you about it, if you feel like the existing system is fine, go right ahead and use it that way. I'd never consider it. Oil is the lifeblood of the engine and if Buick decided that the suction line was too small I'm going to believe them. It NEVER costs less to drill a bigger hole than it does to drill a smaller one so there had to be a reason. As for priming, you do realize that the pump gears are very near the oil level in the pan, right? (and the filter is below it) So if the pump clearances are correct that should never be an issue. I can't say I've ever had a problem with that. Jim
Jim, mine are all drilled out big. All cover mods done, plus 5/8" from pickup to block, 1/2" rail passage, rounded corner, etc. Under .002 main & rods. What I've noticed is the 1 to 2 seconds more till the gage pops up showing pressure.
We are talking about the 350 engine, not 300. Pump gears are way above oil level as is the filter, not that that has anything to do with it. You will break more 7/16" drill bits than 9/16" when drilling that deep. Ask a machinist. As I also said, if it gives you comfort drilling all these holes then do it. Just as long as you understand there may be drawbacks. It will definitely take longer to get oil to the pump. No way around that. Simple test. Take a coffee stir stick in a glass of water and take a sip. Now replace the stir stick with a section of 1 1/2" PVC drain pipe and take a sip. Little bit harder isn't it. It's no difference for the oil pump.
Nope, never noticed a problem with the oil pressure coming up. Maybe your pump clearances could be tighter. Jim
.0015......they might be closer than yours! Jim, this cover is the same that I used on last block without the big suction holes opened up. It has not been taken apart, just re-installed, so it's apples to apples except for the enlarged block passages.
Well I'm not going to try to say you are wrong but if it bothers you then you might want to think about installing an accusump. The blocks hold up well due to the higher nickel content and modern lead free gasoline so the next wear point would be the bearings. That and the cam lobes. Anything we can do to make them last longer is a plus. Jim
