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lg1969 10-24-2008 11:56 AM

Low oil pressure on SBC
 
A long time ago I had a problem with my 307 sbc with low oil pressure. I rebuilt the 307 with new crank bearings, and replace with a high pressure oil pump. Once I had the 307 together and had it running, the oil pressure was very low at 40psi cold, and 5-10psi hot. It should read 80 psi cold, and 40psi hot. I discovered the distributor was cause of the problem. The oil travel around the groove of the distributor housing then through the lifter gallery was leaking. I replaced the distributor with another one and to my supprise the oil pressure jumped up 80psi cold and 40psi hot. If any of you guys have low oil pressure on your sbc, before you take the block apart, check the distributor.

Jmark 10-24-2008 01:51 PM

That's a good tip! If the dist. housing was wobbling around a little, over time it could loose it's size and leak a lot of oil right back into the pan.

19791980camaro!! 08-07-2010 01:12 PM

??
 
what do you mean by the housing was leaking?? i have a 350 and has very low oil pressure. change the oil from 10.30 to 20.50 and pressure comes up everywhere. just wanted to check about the distrib housing. problem thanks

19791980camaro!! 08-07-2010 01:14 PM

??
 
also on that note how old was your distributor that was the problem one

cobalt327 08-07-2010 01:45 PM

Quote:

Originally Posted by 19791980camaro!!
what do you mean by the housing was leaking?? i have a 350 and has very low oil pressure. change the oil from 10.30 to 20.50 and pressure comes up everywhere. just wanted to check about the distrib housing. problem thanks

The distributor body forms part of the oil passage- that's the "groove" seen down near the gear in the photo below. If the dist. body was machined undersized or was damaged/excessively worn, this would create an internal oil leak from the groove that would dump oil back into the pan- and might also lower the oil pressure.

http://chevythunder.com/lg_HEI_2.jpg

TylerS10 05-28-2013 11:23 AM

Damn I know this is a old post but I think this my be my problem also. New motor doing the same thing.

oldbogie 05-28-2013 12:27 PM

Quote:

Originally Posted by TylerS10 (Post 1679555)
Damn I know this is a old post but I think this my be my problem also. New motor doing the same thing.

If you look at the picture above your post you will see the distributor has a grrove in the bosses above and below the oil groove passage. This is not necessary but probably isn't large enough to result in the problem.

You need to be sure the distributor is fully seated. If it catches the pump intermediate drive shaft just wrong, it will turn the pump but will be positioned to either obstruct the lifter galley and/or expose a leak back to the pan.

Bogie

lg1969 05-28-2013 12:35 PM

Well, this problem happen to me again and it happen the second time on my 406 sbc.
Who says lighting does not hit you twice.

TylerS10 05-28-2013 01:26 PM

Now that I think about it my MSD 85551 had o rings and was told to take them out. Did not have this problem til I did that.

lg1969 05-28-2013 03:56 PM

Bad mistake.

cobalt327 05-28-2013 03:57 PM

Quote:

Originally Posted by TylerS10 (Post 1679589)
Now that I think about it my MSD 85551 had o rings and was told to take them out. Did not have this problem til I did that.

That might be an indication that your block was machined for use w/the O-rings; a factory production block isn't meant to use them unless modified for them.

BTW, the tops of the castings should be chamfered to allow the O-rings to slide into position w/o damaging them.

TylerS10 05-28-2013 05:01 PM

Quote:

Originally Posted by cobalt327 (Post 1679641)
That might be an indication that your block was machined for use w/the O-rings; a factory production block isn't meant to use them unless modified for them.

BTW, the tops of the castings should be chamfered to allow the O-rings to slide into position w/o damaging them.

Yea that block came from a friend and was sitting for 10 years who knows what was done to it. 70's something block just said 350 on the casting. I had the machine work done a long time before I purchased the rotating assemble.

Richiehd 05-28-2013 06:03 PM

Quote:

Originally Posted by TylerS10 (Post 1679589)
Now that I think about it my MSD 85551 had o rings and was told to take them out. Did not have this problem til I did that.

If I remember right, your motor was eating up distributer gears, that's why the o rings were removed. Maybe that housing is undersize, compared to a non oring housing?

TylerS10 05-28-2013 06:58 PM

Quote:

Originally Posted by Richiehd (Post 1679688)
If I remember right, your motor was eating up distributer gears, that's why the o rings were removed. Maybe that housing is undersize, compared to a non oring housing?

Yea it was the end play on the gear that caused the timing to jump. The gear was walking up and down on the cam. I did that first and the o rings second when the new gear came in. The timing is rock solid now just the oil pressure problem now. Its always something so far. :confused:

Richiehd 05-28-2013 07:44 PM

10 psi for every 1000 rpms for SBC. I cut a small groove in mine and still have 30 psi hot oil pressure idling.


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