small block oil system MYSTERY............
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Joined: Oct 2003
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From: I'm bleeding, making me the victor!
small block oil system MYSTERY............
I'll keep this as short as possible. My last engine had a problem. VERY little oil to the top(heads). It cost me two new camshafts before I caught on. First cam with a standard pump, then a switch to a high volume/ high pressure pump with the new cam. Oil pressure indicated by the gauge was acceptable for both pumps. I have removed this engine and examined it closely. All oil passages ABSOLUTELY clear, no unusually loose tolerances on the crank, all oil holes in bearings, etc. line up properly. I built this engine exactly like I have built at least a dozen other small chevys I have assembled in the past and they all ran great. I used all new parts except the crankshaft, block, and head castings. It has given me 'fits' beyond compare! Nobody I have spoken with has any idea so far. Maybe someone here has any ideas??? :confused: :confused: :confused:
Le Mans Master
Joined: Mar 1999
Posts: 6,744
Likes: 1
From: delmont pa
Cruise-In I Veteran
Cruise-In II Veteran
Re: small block oil system MYSTERY............ (PRESSURERAT)
too much clearance on the cam bearing will do this because you have a large internal oil leak. also the cam bearing should be installed with the oil holes at a 5:00 o clock position when viewed from the front of the engine with the block right side up. "O" ringing the distributor housing where it goes thru the lifter gallery is another thing to try to cut down on internal oil leaks. :chevy
[Modified by clem zahrobsky, 10:37 AM 10/26/2003]
[Modified by clem zahrobsky, 10:37 AM 10/26/2003]
Melting Slicks
Joined: Oct 2001
Posts: 2,065
Likes: 1,395
From: Halifax, Nova Scotia, Canada
Re: small block oil system MYSTERY............ (PRESSURERAT)
A couple things come to mind.
- Are there any internal casting cracks that could be bleeding off the oil.
You didn't mention how long the engine lasted before it caused problems.?
Is this a mild street driven engine or a modified engine with some 1/4 mile trips.?
This is out in left field.
I had a oil problem several years ago.
When I was running some 1/4 mile trips, open headers, and getting good traction, I happened to notice that at the top end of first gear I would loose oil pressure.
Not something you would notice, however it caught my eye one run.
Only happened in first gear, max power, and very seldom on the street.
The problem ended up being a Chevy design problem.
My engine had the long oil pan with the pickup near the front.
Under strong "G" forces, the oil would climb up the back of the pan and expose the pickup.
I changed to the short pan and appropriate pickup and never had the problem again.
Barry
- Are there any internal casting cracks that could be bleeding off the oil.
You didn't mention how long the engine lasted before it caused problems.?
Is this a mild street driven engine or a modified engine with some 1/4 mile trips.?
This is out in left field.
I had a oil problem several years ago.
When I was running some 1/4 mile trips, open headers, and getting good traction, I happened to notice that at the top end of first gear I would loose oil pressure.
Not something you would notice, however it caught my eye one run.
Only happened in first gear, max power, and very seldom on the street.
The problem ended up being a Chevy design problem.
My engine had the long oil pan with the pickup near the front.
Under strong "G" forces, the oil would climb up the back of the pan and expose the pickup.
I changed to the short pan and appropriate pickup and never had the problem again.
Barry
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Joined: Oct 2003
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From: I'm bleeding, making me the victor!
Re: small block oil system MYSTERY............ (Barry's70LT1)
If there are any cracks, they can't be seen by the naked eye(if at all). The engine was a mild street driven 350 and the problems occurred from the very first day. I used the long pan at first, then put the stock short one back on during my pump change. I bought another block to use, but I am still wildly curious about this one. :smash:
Drifting
Joined: May 2003
Posts: 1,634
Likes: 2
From: Melbourne, Victoria, Australia, the World
Re: small block oil system MYSTERY............ (PRESSURERAT)
I had a block with a porosity between the water and oil. Took over a year to figure it out. ended up stripping the block and filling the water galleries with kero to check for leaks. Symptoms were oil in the water and occaisionally water in the oil. I know a lot more now.
:banghead: :banghead: :banghead:
Yours may be a porosity between oil and air.
:banghead: :banghead: :banghead:
Yours may be a porosity between oil and air.
Race Director
Joined: Sep 1999
Posts: 11,361
Likes: 383
From: Plano TX
Re: small block oil system MYSTERY............ (PRESSURERAT)
How did the cams fail? Cam journals or lobes? The journals are lubed by oil passages, the lobes by splash oil from the crank and some return oil from the heads.
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Joined: Oct 2003
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From: I'm bleeding, making me the victor!
Re: small block oil system MYSTERY............ (zwede)
Lobes both times. The journals on the cam and the crankshaft both looked great. I just had not much oil coming through the pushrods. All the parts up top had wear or signs of excess heat('blue' color). Also, I should note there was no water in oil or oil in water. I am checking the cams today to see if they were same lobes.
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From: Albany N.Y.
Re: small block oil system MYSTERY............ (PRESSURERAT)
# 5 cam bearing is were the oil is fed to the lifters. Have someone look or take that bearing out to see if there is any obstruction or if someone put restricters in to control the oil to the lifters. Also check the distributor fit it the block, it closes the oil gally to make pressure. If it is a after market distributor check it against a stock one. Lifter fit in the bores also needs to be looked at closely.