Oil leak 312

[oldgasser]

Could use some input please.
I have had a professionally built 312 done which I have run on my engine stand a number of times to check for any defaults/ bugs before installing with everything as it should be & running 70 to 75 Ibs oil pressure I used a Best Gasket neopream rear main seal & installed it to their specs. I install the motor in the car & once the rest of the car being a 57 Ford Convertible was ready for its maiden run I proceeded to take it out on short runs to get other bugs out of the car but each time I brought it back into the garage there was always a sign of a oil leak more so on the right hand side I have checked & re-checked all the areas that would possibly develop a leak. The last time I tried to find the leak I had a friend sit in the car on the hoist & we ran the motor for approx. 10 minutes + at 1800 RPMS with no sign of a leak but when we shut the motor off it squirted out about 2 table spoons of oil out of the rear of the engine I could not see up in behind the flywheel properly to identify where it would be coming from?? the rear frost plug is new & same as the journal plugs. I have checked & pulled the distributor changed o ring & paper gasket. checked valve cover gaskets ect ect. Any input would be appreciated.
Thank you in advance.
Ron.

[KULTULZ]

There is a kit whereas you put a chemical (dye) into the crankcase oil and can detect any leakage with a black light.

There also seems to be a problem with BEST GASKET instructions as far as the 312 rear seal install.

[thomasso]

I have had those neoprene rear seals  fail in two 312s.  The on in the retractable tore,replaced with crummy new non asbestos type, still leaks.  Put a neoprene set in my conv. after the late rope type one put in by my in rebuilder failed.  Will be putting a true old asbestos rope type in when I get the energy.  Does any one have a 312 that doesn't leak?

[KULTULZ]

TECH INFO - http://www.eatonbalancing.com/2008/09/10/neoprene-rear-seal-installation-for-the-y-and-others/

This article is from 2008 and there have been seal re-designs and update articles.

Maybe this will help somewhat.

ALSO-

And last but not least, use some sealer on the outer edge of the cam plug when installing it. Although there’s no oil pressure between the plug and the rear of the camshaft, there is still oil residing in that area and seepage from a rear cam plug is very often mistaken for a rear main seal leak.

SOURCE - http://www.eatonbalancing.com/2011/10/21/rear-camshaft-plug-installation/