Jay's timing cover

[Urgefor]

I'll be reassembling my 390 before long and figured it would be a good idea to be proactive in relation to "new additions".  One of those being Jay's timing cover.  (really need a party emote..  anyway)  On Jay's site it has the following regarding the crank seal:

The cover accepts the standard FE front seal, installed from the rear. It also accepts a 351C front seal, that installs from the front. This allows easier seal changes, and the possibility of using a double lip 351C front seal for dry sump or vacuum pump applications. When using the 351C front seal, some machining of the stock FE crank spacer is required.

I want to have the crankcase sealed off (sans breather of any type) and let the PCV valve pull a vacuum on it.  With my current setup this will mean 10 to 11 inches at idle.  I recall seeing talk from Jay at some point about using both the FE seal and the 351C seal together but the concern was about the 351C wearing out from lack of oil exposure.

What is currently the best option for crank seal(s) configuration(s) using Jay's cover knowing the crankcase will need to be able to hold a small amount of vacuum?

[jayb]

You won't get 10 inches of vacuum in the crankcase if you have that vacuum in the intake.  The pressure pulses inside the engine will see to that.  In fact if you put a gauge on the crankcase I'd be surprised if you see even 2 inches of vacuum, and it certainly won't be steady.  The only real good way to get vacuum in the crankcase is an external vacuum pump or dry sump system.  For your application, the stock FE seal will be just fine.  If you want to overkill it, Peterson Fluid Systems makes a 351C seal designed to work with their dry sump systems.

[Urgefor]

Thanks for the info Jay.  I've run the engine as noted in my initial post, but never checked the crankcase with a vacuum gauge while it was running.  My observations were the PCV valve would go silent a few seconds after startup and the oil fill cap was definitely being affected by atmospheric pressure if you tried to remove it. Took a good amount of effort to get it off and the classic "whoosh" of air rushing past the cap into the valve cover.  After your input, the question has become at what amount of crankcase vacuum would one need to switch from the FE seal to the 351C seal? 

I found this on Peterson's website, but am not sure which seal you were referring to.  I'm not against machining the crank spacer and using the 351C seal to avoid having to R&R the timing cover if an external vacuum pump were added at a later date.

[jayb]

Pretty sure it was the SM85338 front crank seal that has been used before, not 100% on that though.  You would have to call them to confirm - Jay