quote:Originally posted by PanteraDoug:
This is the first that I've heard about a cavitation issue.
I never heard of the C oil pump having cavitation, or sucking air, at any rpm. These engines have been raced hard since the beginning of their introduction and the significant oiling modification for sustain high rpm is to restrict oil through the lifter galleries.
The designs of the Cleveland oil pumps is no different than any other engine. for racing purposes it is recommended to braze the oil pickup tube to the oil pump body but that's just to keep the tube from vibrating loose.
I was referring to some things mentioned in Sticky 3:
Quote from sticky 3:
The diagnosis of this problem which I find most compelling is based on hydraulic system engineering; Roy Johnson suggests the problem is cavitation which occurs first at the oil pump. Jon Kaase has commented “what the 351C needs is not a high volume oil pump but a standard oil pump with dual inlets”.
Johnson has further suggested cavitation manifests again in the main lubrication passages resulting in a sag in oil pressure in the middle of each passage as engine speed increases.
The large ports connecting each tappet bore to one of the two oil passages expose the motion of the tappets to the oil passages.
Jim Kuntz has commented on the detrimental effect of the "lifters chopping up and down in the main oil supply". Thus cavitation resulting from the rapid motion of the tappets spreads to the oil passages through these ports.
As the clearance between the tappets and the tappet bores increases so does the severity of cavitation. So as a motor gets older the lubrication system cavitates worse.
Has anyone seen a pump with dual inlets for the 351c ?
I do some work with hydraulics myself and i often thought that the 351c may have some cavitation issues effecting lubrication quality.
Industral hydraulic pumps with smaller volume than the 351c pump would have larger inlets, maybe 1" or 1 1/4"NPT and they spin more slowly than a 351c pump, maybe only 1440rpm, so if the 351c pump doesn't cavitate at all that pump would be pretty outstanding.
I've had 351c and 302c engines in cars that have been well maintained, oil changes done on time or even early with top quality oils and filters used, never left with low oil level and have not been driven hard and on teardown had all the bearings worn down to the base metal.
I do feel there is more to the subject than just straight common sense may suggest....??