korvette4u

89 , fresh bottom end ..
prelube with drill shows lots of pressure. 55-60 psi.. install distributor , fire it up and as soon it hints operating temp 180 . the pressure falls to near zero/
two gauges install one at the oil filter and the other is dash both read the same . oil is 10 - 30w mobil..
oil to lifters and front engine is visialbe.

Does anyone have comments as to may be why this happeing?

Pete K

Yeah, something is screwed up.
Galley plug popped out, or the one under the main cap is missing. Any bearing may have excessive clearance, or has spun. Bad oil pump is a possibility, as well as the pickup falling of or cracked.
Check the pump and pick up. If they are ok, pull the motor back out.

BLOCKMAN

Pete if the plug is missing under the rear cap all that happens once the oil filter is full it just bypasses a the oil filter and goes the path of least resistance.

This has been cover many times on this forum and I actually dynoed a circle track engine last year and changed the pan and this was a one peice seal block we draopped the rear cap and push out the ball bearing which in place instead of the cup plug, Finished the oil pan test and no change in pressure if anything it may have been higher maybe because the oil did not have to go through.

Here isa link to look over and do a search on this site no one has ever given a reason for low oil pressure only that its written in a book some where.
http://speedtalk.com/forum/viewtopic...er=asc&start=0

Pete K

Yep, but the origional poster is still screwed.

WW7

Yes he is..I just hope its something easy like the oil pickup...WW

BLOCKMAN

No doubt something was over looked and probably was just bolting parts together out a box or 2

korvette4u

i took picture of the assembly .reviewing them i found that:
1) front and rear oil cam plugs are installed.. so thats eliminated...
2) new bearing including cam were installed by machine shop..( if they are correct and sized ??? well i checking that too) , but gotta check everything before i rip out..
3) going to check if plug is installed between oil filter and oil pump .(under rear main cap) the verticail oil bore is 9 3/4" from top intake seal surface to underneath rear main cap.. the plug sits 1.450" below main cap.. so if measuring from top of engine the plug should be approx 8.300 to 8.350" below top intake plane.. if the rod drop through then. the logical explanation is no plug.. i thinking to check this this afternnon..

check and found YES <<< a plug located at 8.470" which is ok .. the depth needs only to approx..

gonna start one more time: listen for bearing noise either crank or con ..disconected knock sensor

any body else got ideas?
started ok... pressure at idle 25-30 lbs then goes down to 10-12 then to nothing. pressure at 2000rpm is 45-50lbs..
what the hell is going on?

mtwoolford

yes I have an idea...and no I don't want to talk about where I got it from.

was the lifter valley, crankcase or pan possibly painted ? I've seen engines, including diesel engines that you can stand up inside the cylinders, routinely painted with absolutely no problem.

I've also seen the wrong paint used and the paint chips accumulate around the pump pickup to the point that the pump couldn't produce any pressure; at first start up the chips are in the bottom of the pan and pressure is ok, but the longer the engine runs the more get sucked up and trapped in the oil pump pickup screen. and the pressure continues to drop.

A rag inadvertently left in the engine will cause the same symptoms.

drain your oil, inspect it; pull the oil filter, cut the can apart, and inspect the filter media.

hopefully your problem is something just that simple.

Pete K

Maybe the oil pump pick up is too low, or way too high?

korvette4u

thanks but, i measured 5/16" without gasket.. so that puts it right in .. no paint

any other suggestion please?

Harsh20

was everything cleaned completely before assembly. we have had race engines where we ran them once and the oil filter and oberg would be totally restricted with shavings. we changed engine builders of course after it happened twice.
just something to consider

Pete K

I have seen that many times on the dyno, but only with a Fram filter. If you have a Fram on there, take it off.

korvette4u

yes// good idea

WW7

This is a good idea, the filter media could have collapsed and is blocking the return of oil.I have had this happen with a Fram filter, but mine happened after it was on for awhile...WW

patricksmithahhh

whats the pressure supposed to be at when warmed up at idle???

Pete K

That is dependent on the type of oil pump, bearing clearances, oil viscosity, and oil temperature.

JAKE

Several years ago, a routine oil and filter change (FRAM) resulted in ZERO OIL PRESSURE on fire up. Putting the OLD filter back on and pressure returned to normal.

I returned the FRAM for another brand and, after installing the new filter, the problem was solved - GO FIGURE!

Try a different brand filter. That could eliminate the filter as a possible cause. Inexpensive and easy.

Jake

ks5shooter

patricksmithahhh

stock oil pump oil at say 180 deg 10w30 k&n filter at idle pressure it at roughly 20lbs

c-4 lhozwalte

is there any chance you mis-matched the rod caps.they are made to go only on the rod they were sized with.did the crank spin freely after the main bearings were installed?either way better have that motor out of there soon or you could be replacing alot of parts.