quote:Originally posted by Bosswrench:
Quoting Mike Cook, ex-Pantera racer and Bonneville specialist, 'At 6000-up rpms, the valve covers of a 351-C are full. This leaves approximately 1 qt in a stock (5-quart) pan'. So I'd say each rocker holds about 2 quarts. Mike made a temporary-use plexiglas rocker cover ala Smokey Yunick for his drag race testing.
All this is because a stock pump delivers so much upstairs oil in the stock configuration, and the drainback ports in stock heads are small with two of the 4 being convoluted and often plugged with debris. Note that only some (or none) of this may apply to aftermarket heads and blocks with modified oiling systems.
I can't speak for other heads but my A3 heads retain oil differently than the iron heads do?
The hollow part of the iron head casting near the bottom valve cover rail is filled with aluminum on the A3 head some. I suppose this reduces the volume of oil the valve covers trap in the heads?
The amount of oil in the covers is also part of the issue with running these engines hard AND attempting to use a closed pcv valve system. You just don't hook the thing up like a street car and go racing.
The entire pcv needs to be re-engineered and frankly, it ain't easy to do. There are issues that remain.
If I try to explain why, it's sort of like trying to explain the difficulty in working on weightlessness while still in the Earths gravitational field. You can only simulate the situation for a short period of time.
I thought Mike was speaking figuratively when he said "full". I thought it was more like within about an inch of the top of the covers, which explains the siphoning tendency and the need for 4" tall breather tubes?
@ JFB. Here's a scan of the page from the Boss 302 section of the Ford Off Highway Parts manual.
They suggested drain back tubes from the valve covers to the oil pan. Some strongly disagree and say they do not work. I can't agree or disagree.
There were several sources for this information back in the day. You had Ford Engineering, KarKraft which was responsible for a tremendous amount of these modifications then you had people like Bud Moore who contributed engineering as well.
I will say that I have never actually seen a car with this modification done to it but I don't need to extrapolate much at all to envision where the need for it came from?
It may be that to run a pcv valve successfully in MY car the pcv valve may need to be installed through the intake manifold.
The 427 Fords had a similar set up in 63 and 64 but with just an open breather, not a pcv valve.
I hate to start drilling into the manifold but there would not be the issue of siphoning oil out of that location?
