hotrod32: 4/4/2000 - 8:36:31 PM
Melling oil pump
How many of you gearheads are running the M-15 oil pump? Is it worth the extra money?

JWL: 4/4/2000 - 9:23:58 PM
RE: Melling oil pump
No, the hi-volume pump is not necessary.

rodnut: 4/4/2000 - 10:55:36 PM
RE: Melling oil pump
The Melling hi-volume M15 pump was developed mainly for use in flathead racing engines. These engines use increased bearing and con-rod side clearances, causing an increased loss of oil that the stock pump could not keep up with. Hence, the 'hi-volume' pump. It should not be used in an engine built with factory clearances.

51al: 4/5/2000 - 7:23:50 AM
RE: Melling oil pump
rodnut why shouldnt the m15 be used on a stock motor does the oil pressure change i didnt run one only because it did not fit my pan did i dogde a bullet.

JWL: 4/5/2000 - 10:45:37 AM
RE: Melling oil pump
No, the pressure does not necessarily change. It does not ''hurt'' anything to run the M 15, it simply is not needed.

rodnut: 4/5/2000 - 12:15:29 PM
RE: Melling oil pump
Once again, I have to disagree. I had a long discussion several years ago with Smokey Unik about oiling systems, and one of the things that we both agreed upon was the over use of hi-volume oil pumps in stock clearanced motors (it's the first thing the Chevy guys purchase to put in their new motor, whether they need it or not)! The problem lies in the fact that the pump puts out way to much volume for the stock clearances to expell. The extra volume of oil has to go somewhere, so it lifts the relief and, on most pumps (ours included), is dumped back to the inlet side of the pump. This continual recyling (the relief will basically never close in this situation) builds unnecessary heat in the oil, as well as creating cavitation which aerates the oil - both things are bad news. Again, do NOT use more oil pump than your engine is designed to use! The Ford engineers knew what they were doing when it came to sizing the pump to the application! Stick with the stock (M19) pump on all but heavily clearanced motors!

MTflat: 4/5/2000 - 4:48:25 PM
RE: Melling oil pump
Oh, swell! I put an M15 in my 8RT that I'm about ready to fire up. Even hammered out the oilpan to fit and now this is giving me something to think about ... I just followed my grandpappy's school of thot that 'if a little's good, a lot oughta be better'. It'd sure be easier to swap back to the 19 now rather than wish I had... any thots?

Ron Holleran 4/21/2003
M-15 and other BS I sent a thread to Dale on the use of the M-15, but it may have been lost in the shuffle. It went like this. The Hi-volume M-15 comes in handy when running racing clearances in an engine, The recommended loose bearing set-up is .0025" Rods and mains. Some builders may vary this but this works well with Clevite 77's in the 8BA rods. The floaters run a little tighter about .002" all the way around. Now comes the critical dimension that very few people check, and that is Rod and Main end clearance. I'll take Mains first, for street .006-010" for comp .010-.015" on the rear thrust surface. This is consistent with standard shift . More clearance can be given to top speed engines. The stock rods are pretty tight at .006"-.010". I like to see .010-.015". For competition engines this should be opened up to .020-.025". A good place for the M-15. Now you ask why?? Oil not only lubricates, but it cools. In order to cool the bearing it must get in and out. That's why you see those big oil coolers on those modifides. Large end clearance is bad for a street engine because the rings can't handle the excesss oil thrown up on the cylinder walls. Under Full throttle the rings are "Tight" in their bores. In Light cruise conditions we run a hi vaccum in the cylinder and Oil control becomes a problem. Good reason to use a 4 ring piston. I feel that 40-50 lbs is more than adequate in all Flathead engines. Just some secret stuff that keep these engines together. Keep em runnin while I'm gone. Ron

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