hey guys. this is what the hamb is for. I just rebuilt a SBC 400 for my truck, runs killer. problem is, I have less than 5lbs of oil pressure. I have measured from above the filter, and up at the manifold. when I first start er up I get maybe 7lbs, then it drops between 0 and 5. crap. I hear that 7lbs is acceptable, but I am lower than that, and I'd hate to scatter it by not doing a simple pump change. I will be pulling it this weekend, so my question is - should I go for a high volume, or a high pressure job? Any reccomendations? Thanks!
check the expansion plug under the main cap also somtimes gets forgot about.Also if you didnt take the oil pump relief spring out when you welded the pickup on you might have cooked it and are bypassing alot of oil.
The under-rear-maincap is the champion left out part for the SBC...and should be LOTS of fun to fix. The other great one is right near the oil pressure sender halfway under tha manifold, but it isn't that one because you'd likely have noticed by now that the entire inside og your garage was soaked in oil... Don't waste time on a high volume pump--you have a big hole somewhere and need to find it!
DON't GO HIGH VOLUME. Unfortunately there are tons of spots that could be the culprit. ranging from a pump problem, to excessive bearing clearance, to a missing plug... How does the oil pressure come up as you break out of idle. Does the pump begin to make pressure or is it low througout the range? A dumb dumb check would be replacing with a new std volume oil pump to see what happens. If that doesn't work you may have to drop the crank to fix the before mentioned plug and/or check main bearing clearances... fun fun..
Have you *ever* had an oil pump be defective, causing real low oil pressure in a new engine? I've never heard of it happening....
I'm sure we all know that ANY new part can be bad and even if it isn't the case here it's less of a problem to change the pump first.
well. when I say rebuilt, i mean torn down and cleaned, then re-assembled. with some upgrades along the way. HOWEVER, i did not touch the oil pump, which i am now realizing was a mistake considering how cheap they are, and how big of a pain-in-the-ass it is to pull the motor. as for the pressure, it is a slow buildup to a little over 5 when warm, and that is with pretty big revving, over 2500 at least...
how far torn down? did any of the oil passage plugs get removed and not replaced? Could be the pump, but not real likely, unless maybe the pressure regulator valve in it is stuck open.....or the pump is not mounted properly, or something like that.
i got one of these in the shop right now, guy bought it as rebuilt...were finding out it was just cleaned up and some new bearings thrown in it..fuckers what do you mean by torn down and cleaned up, did you measure the bearing clearances when you reassembled it? did you put new bearings in it...it does sound like the plug under the main cap is missing, which not only results in low pressure but that plug directs the oil into and out of the filter...so if it is missing you are not filtering either stop revving it to 2500 if you have only 5lbs of pressure.....you should have plenty even with a stock pump...i run melling hv 55 or the new 10 percent pump depending on where i set oil clearances......but a stock pump will be plenty if oil pressure ...you need to tear don and find the problem if its not a gauge issue also is the pickup on the pump correctly? Fred
How bout the pickup tube falling off bumped up too high off pan bottom when installing pan ,or if you welded it its probably the spring as said earlier.
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