Advanced questions at the end of the post.

This in an early model Chev Small Block

- Bought a short block. Block prepped by shop and hot tanked.
- Rebuilt entire engine. Starts fine, but only 10-20 PSI oil
pressure at any RPM.
- Bought new oil pump and pump driveshaft (all aluminum).
- Primed pump
- Installed pump...oil pressure still 10-20 PSI
- Oil pan dipstick reads full!

Used assembly lube on the main and rod bearings; used assembly
lube on the lifters and camshaft. The cam bearings where installed
by the shop, I did the main and rod bearings.

http://members.rogers.com/tdese739/i...ainbearing.jpg
http://members.rogers.com/tdese739/i...ingphasing.jpg
http://members.rogers.com/tdese739/i...ngphasing2.jpg

Clearances:
Bearing clearances = 0.0015" - 0.0025"
http://members.rogers.com/tdese739/i...ugemaincap.jpg


The oil sender bore behind the intake next to the distributor,
the oil pressure gauge is mechanical (I have tried two gauges).

There is oil and air in the tube. Should it be all oil, or is
it fine to have air spaces in the line?

http://members.rogers.com/tdese739/i...lgaugeface.jpg
http://members.rogers.com/tdese739/images/oilline.jpg


Using 10W30 at the moment. Motor has been run for 15-30 seconds
for each test. With old oil pump, twice...with new oil pump once.
15 seconds on, sits for a couple of days. Repeat test once part
has been changed.

#1. What is the oil path from oil pump to pan?

Oil pump, oil filter, crankshaft bearings, rod bearings
pistons, cam bearings, lifters, pushrods, valvetrain, drain
to pan?

#2. Is the oil pressure gauge reading pressure from the pump after
the oil filter...or possibly after the cam bearings?? In other
words, is the gauge reading from a "parallel" port off the pump,
or is it grabbing from the middle point of the oil path.

#3. No oil squirting to rocker arms. How long ins seconds should it
take to get oil to the valve train? What would block the oil from
getting there?

#4. What is causing the low oil pressure? Purge air in block oil passages?

The engine block is dry...lifters not pumped up yet, oil not fully
throughout oil passages?

Not running motor long enough to to get full pressure?

#5. What is proper pressure for such a motor? 10 PSI per 1000 RPM?

Any insight is VERY appreciated.
Thanks,
Tino

 

Try this, seems well written though a bit general: http://members.aol.com/carleyware/library/us1097.htm

20psi at idle is a minimum (with fully warmed oil) and an often quoted rule of thumb is that it shoud increase ~10psi/1,00rpm.

Another thing to consider: "When preparing any new small block Chevy block, make sure that a plug (#33701638) is installed in the oil passage above the rear main cap as shown. If this plug is missing, oil will not be routed to the filter and the engine will not have satisfactory oil pressure. This plug is not installed on new GM small block Chevy bare blocks from the factory." If this plug is not in place, you will not be able to generate good oil presure.

Rich Krause

 

Mr. Krause, you're a life saver!

If only this response would have been captured two days earlier,
I could have installed this plug while swapping oil pumps.


This is a big slap in the face for me...a good eye opener and a
lesson learned.

This would be my third "full" engine rebuild - but this is my first
rebuild receiving a block that did not have core plugs or an oil
restrictors installed.


Hopefully this post will help others avoid a sticky situation.

As for me, once I get over my frustration, I'll jack up that motor
and drop the pan once again. Another 5 hours of work and this
beast will be on the streets.

 

Don't ask me how I know about that little plug . Glad I could help. Let us know how she runs!

Rich Krause

 

THANK YOU SO MUCH AGAIN RICH!

I dropped the pan and the oil pump and - NO RESTRICTOR PLUG!

I've never been so happy NOT to find something!

Anyway, everything is bolted up and fluids are in. I started it
for a few minutes. 20 PSI at idle, and up to 60 PSI at 6000 RPM.

The idle already sounds amazing and it's not tuned or timed.
Comp Cam 292H was the newest upgrade since the blown
motor.

I'll post some pics, video and sound files once I stick the timing
gun and vacuum gauge on there.

 

Hey all, I thought I'd share this sound file with
you. I'm pretty proud of it! After all the crap
I've been through, it's time to get the bragging
rights back

The motor needs air/fuel idle mix setting, a touch
more timing and jetting change but I can't get to
the shop until Tuesday to buy plugs.

I'll post some more stuff when I get back from
the long weekend.

It's compressed audio, but still sounds good.
If you want the AVI video, or wave file e-mail me,
they sound and look much better.

Turn it up LOUD and enjoy!
Have a great weekend everyone.

http://members.rogers.com/tdese739/Compcam292Hb.wma
http://members.rogers.com/tdese739/TinosZ28.wmv