View Full Version : Oil Leaks

01-06-2009, 12:58 PM
As a winter project, I decided to disassemble a late '62 289 with frozen pistons to see what I had. I've been carting this engine around since 1980. Now that it is apart, I'm cleaning up and inspecting the bare block, I observe that there was significant oil leakage around the core plug at the back end of the cam. Since the vehicle that this engine came from was last licensed in 1970 by the PO, it probably was an "unmolested" engine with some 75000 miles clocked. I wonder how many factory engines exhibited leakage at this point that would be wrongly blamed on the pan gasket, rear main seal or rocker cover gaskets. I'm sure the PO was frustrated by the leakage as the pan displayed all the evidence of extreme tightening. BTW the suspect core plug is in excellent bright metal condition due to being "oil protected".

01-06-2009, 01:21 PM
It's certainly a suspect, although I've not personally seen such an incident. I will say (as I've said many times before) that I think a fair number of rear main seals get replaced as a result of leaky valve cover or lifter valley cover gaskets (distributor base gaskets too!).
Because of the slant that these engines sit with - as well as the blast of the engine fan - leaks from these other culprits tend to run to the rear of the block and down. The results can be oil spots beneath the engine/bellhousing junction. This "evidence", coupled with the lore of leaky rear main seals (admittedly valid to a degree[}:)]) have probably caused more than a few perfectly good rear main seals to be replaced. And it's not a fun job.[V]

1957 Transtar 1/2ton
1963 Cruiser
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe
1957 President two door

01-07-2009, 12:39 PM
I would have to agree Mr. Biggs. The worst case of valley pan leak that I have encountered was on a factory R3. The valley pan was installed with 3 full length cap screws, leaving the centre screw bottomed in the block with a noticeable gap between the copper washer and capscrew head. Given the blowby of the engine there was a good puddle of oil in the valley pan. The engine didn't appear to have been "molested" but I can't say for sure. Another interesting point regarding that engine was that it had a piston with a welded skirt with the circumferential skirt grooves machined through the weld. That would have had to been done by Paxton prior to assembly. After some 50,000 miles the weld had cracked, necessitating replacement. Few things are ever perfect!