BB Oil Pressure

[Joel T.]

Hi All;

I've just got my 1965 BB back from the machine shop after a rebuild... The motor has about 150 miles on it since break-in on their bench. As I am driving it I am naturally keeping an eye on everything including oil pressure.. The car has the correct 80# gauge in it.. Driving around I will see about 40# + or - which I suspect is fine. My concern is at idle... where I am seeing only about 20# via the gauge. Is this normal?

I will zip through the shop manuals to see if they say anything about this but was wondering if you guys had any thoughts....

Thanks!

Joel

Duke, I know you will probably read this... How long should I keep the break-in oil in the car before I replace it with CJ-4??

[Joel F.]

Re: BB Oil Pressure

Joel,

20# is fine at idle. The old rule of thumb I learned is 10# per 1,000 RPM for safe operations. I suspect the actual pressure requirements however is actually less, but 10# is a good safe rule of thumb.

Joel

[Joel F.]

Re: BB Oil Pressure

P.S. -- I'd change that break in oil ASAP. A lot of dyno operators will drain the oil, and disassemble the filter after a break in to look for any particles or signs of trouble. Also, if the shop used GM's EOS break in the oil should be changed as EOS can clog a filter.

[Jason A.]

Re: BB Oil Pressure

Hi All;

I've just got my 1965 BB back from the machine shop after a rebuild... The motor has about 150 miles on it since break-in on their bench. As I am driving it I am naturally keeping an eye on everything including oil pressure.. The car has the correct 80# gauge in it.. Driving around I will see about 40# + or - which I suspect is fine. My concern is at idle... where I am seeing only about 20# via the gauge. Is this normal?

[Donald T.]

Re: BB Oil Pressure

Jason,

Based on your avatar, aren't you a little young to be driving? How do you reach the pedals?

[Michael H.]

Re: BB Oil Pressure

Same for my 66 L72. May be as low as around 18 at a slow idle on a hot day.

[Jason A.]

Re: BB Oil Pressure

Jason,

Based on your avatar, aren't you a little young to be driving? How do you reach the pedals?

I have custom painted flame-job booster seat and wood blocks on the pedals.

Yeah, you should see the looks I get when I drive around smoking a cigar.

[Donald T.]

Re: BB Oil Pressure

I have custom painted flame-job booster seat and wood blocks on the pedals.

Yeah, you should see the looks I get when I drive around smoking a cigar.

Now that's funny!

[Duke W.]

Re: BB Oil Pressure

Duke, I know you will probably read this... How long should I keep the break-in oil in the car before I replace it with CJ-4??

You didn't use CJ-4!!!???

What did you use?

Duke

[Joel T.]

Re: BB Oil Pressure

Hi Duke;

I didn't do the rebuild myself... The guys in the machine shop filled it, including a break in additive, when the built the motor.... I honestly do not know what they used but the rebuild engines for a living so I need to assume they know what they are doing...

I was going to run it about 500 miles before the first drain... the reference to CJ-4 was for that event. Based upon what I am hearing, I should probably drain it sooner... like now...

Joel

[Duke W.]

Re: BB Oil Pressure

Based on my experience most "professional engine builders" don't really know what they're doing and need very close supervision, but anyway...

Here's what I recommend for fresh engine maintenance assuming an "assembly lub" was used on the cam/lifters and valve train.

1. 15W-40 CJ-4 or CI-4 with a bottle of GM EOS for initial fill.
2. Change the oil filter only after cam breakin or one hour of operation.
3. Change the filter only again at about 500 miles. (top off the oil with CJ-4 or CI-4 after these two filter changes.)
4. Complete oil/filter change at 1000-1500 miles with CJ-4 or CI-4, no EOS.

The reason for the first filter change is to remove the solids from the assembly lube, which are trapped by the filter along with early wear particles and any debris/dust left in the engine from machining and having the internals open during the rebuild.

The second filter change is to remove additional wear particles. At this point the engine should be 90-99 percent broken in.

The original ZDDP-rich fill of C-category oil and EOS should remain in the engine to the 1000-1500 mile point when there's about a 99 percent change that the engine is 99 percent broken-in, and all wear particles, dust, debris, and assembly lube solids have been trapped by the filters. Use CJ-4 or CI-4, but no EOS.

Also, don't baby the engine. During the first few hundred miles limit throttle opening to about 3/4 and revs to about 4000 during acceleration, but you need brief periods of relatively high load. Also vary engine speed/load as much as possible.

It's possible the break-in an engine "too easy". A twistly mountain road drive in a moderately sporting manner is a good way.

If you have to do a lot of freeway driving, starting from about 55-60 MPH slowly accelerate to 65-75, then lift all the way off and start the process again at 55-60 MPH. Two hours of this will have most of the break-in done.

New engines can generate a lot of wear particles, plus the assembly lube and microscopic debris that is always present in a fresh engine. This is the reason I recommend all the filter changes, but the ZDDP rick initial oil/additive fill should remain until well after initial breakin is done - just to be sure.

Duke