Crank Scraper

[jmarsey]

Hey Keith,

I have a crank scraper on my KC yates / 331 that you built for me a few years back. Do you think the scraper is limiting oil to my solid rollers above 3500 rpm? You used Crowers. The motor runs great.

Thanks, John

[Richard Hudgins]

Keith,

I would interested in this as well.

Please take the time to give John your thoughts.

I know he is a old customer and well outside of your normal product attention span.

But I think that he has a proper technical question that needs sorting out.

And there are probably other folks here who need to understand mid-engine oiling as well.

[jmarsey]

Originally posted by Richard Hudgins


Keith,

I would interested in this as well.

Please take the time to give John your thoughts.

I know he is a old customer and well outside of your normal product attention span.

But I think that he has a proper technical question that needs sorting out.

And there are probably other folks here who need to understand mid-engine oiling as well.

Hi Richard,

Good to hear from you. Keith got right back to me but via private message. I should have posted it but didn't think anyone was interested. I was not asking about the windage tray so much as the scraper. But I think he answered the gist of my question. My valve covers have spray-bars to cool the valve springs which adds additional oil to the top end for drain back. So there should be plenty of oil from above. Also Crower makes an excellent solid roller with superior oiling design. I know the scraper adds hp but always wondered about splash reduction. Here is Keith's reply:

"John the oil that the lifter get (is) from the drain back oil plus the oil that goes through the lifter galleys and falls on the lifters should be more than enough. The main thing the windage trey does is to keep the crank from wipping the oil and keeping it of the crankshaft. I feel that there is still plenty of oil flying around in there for the lifters. Thanks, Keith"

[Kevin_Johnson]

Hi John,

I saw your question while running a search. The mains and rods are constantly ejecting oil tangentially/radially even in engines with a windage tray that effectively seals off any chance of the rotating assembly contacting the sump reservoir. The two quadrants you are concerned about are 90 degrees BTDC and 90 degrees ATDC. "Classic" style scrapers at the oil pan rail or beneath do not hinder this oiling whatsoever.

In fact, scrapers should actually increase the amount of oiling these components receive. Why? At higher rpms the rotating assembly creates a pressure differential that draws this ejected oil into a cloud wrapped around the spinning bottom end rather than letting it follow its previous direct path where it would land on the components, in this case the roller lifters. The scraper acts to disrupt this pressure differential and allow the oil to be released.

This is also why dry sumps are not generally known for causing this sort of lubrication problem even though they remove oil from the crankcase as quickly as possible -- far more than a scraper in a wet sump system. [Though many dry sumps use scrapers or louvers/directional-screening -- a type of scraper to increase their efficiency.] The reduced atmosphere induced by the scavenge pumps lessens the windage effects and allows the direct ejected oiling to proceed as before.

Ford has been using scraper type devices in various of its V8 engines for over 45 years, as have many other oems.

[jmarsey]

Hey Kevin,

Great information and makes total sense. Oil windage and the finer points of the oil pan have always been of interest to me. But not many of the pros have been able or chose not to elaborate beyond the basics. I know the oil cloud vortex you mentioned can sometimes suck a fair amount of HP but always wondered what the oil was doing above the tray and scraper vs. no scraper.

Thank you for your insightful reply, John