High Volume Oil Pump advice

Curt in AZ

Curt in AZ

Senior Member
I am assembling my freshly machined 8CM engine. The main bearing clearance is .0025 (plastigauge) and the thrust bearing measures .003. So the mains are at the upper limit and the thrust is larger than spec. I didn't check the camshaft clearance.

No doubt this engine will have low oil pressure with these clearances so would it be wise to replace the stock oil pump with a Melling M15? Thanks for advice.

Curt
 
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I had an extremely bad experience with a high volume oil pump. It was in a freshly rebuilt engine in my Corvette, but I believe that the problems are universal. It pegged the oil pressure gauge and blew so much oil into the engine that it compromised the valve guide seals. I learned the hard way that "Hi-Volume" oil pumps are NOT a solution for second rate rebuilds. Take it back apart and do it right. I think some others on here will also tell you that they take more power to turn and add extra heat into the engine. Again, do it right from the start.
 
I doubt that you will experience low oil pressure with those clearances on the bottom end, especially if the cam is tight. A high volume oil pump is of no value to any flathead short of one built specifically with loose tolerances for racing. A high volume pump that is restricted to low volume flow just takes horsepower to add heat to the oil.
 
Those clearances will not be a problem with a good M-19 pump. It is more important for the cam to have proper clearance.
 
Okay, having a thrust at .003" is fake news so lets review micrometer readings...

Point tens, hundreds, thousands, ten thousands etc...

Lonnie
 
drolston said:
A high volume oil pump is of no value to any flathead short of one built specifically with loose tolerances for racing. A high volume pump that is restricted to low volume flow just takes horsepower to add heat to the oil.
Click to expand...

Exactly the sentiments i have read from Ol Ron.

I should pile on here, with a tale from the past. I refreshed an OT van motor with a valve job, tow package cam, and a high volume oil pump. It ran great, the guy I sold it to was very pleased. That is until one day. while hauling his daily load down the highway, it spit out the rear main seal.:eek:
 
I strive for these clearances. The bearings run cooler. And what do you consider low oil pressure, I like 10 at hot idle and 40 at cruise. I know the relief valve is closed preventing over heating the oil.. and Max flow is cooling the bearings. Only ised the M15 oncein the stock car and it ruined the crank and bearings.
PS I don't like their M19 either. I use a stock ford pump.
 
You guys are amazing! Ron thanks for sharing that you strive for .003. I'll measure the cam clearances and continue the build if they are correct.
 
Binx said:
Okay, having a thrust at .003" is fake news so lets review micrometer readings...

Point tens, hundreds, thousands, ten thousands etc...

Lonnie
Click to expand...

Lonny, what do you mean by fake news? I've double checked with dial indicator and the clearance reads .004, probably more accurate than the .003 I got with feeler gauge. Guys on the HAMB say .004 - .007" so the crank thrust is fine by these specs. The 1953 manual gives a tighter spec. Nothing in the ten thousands range.
 
I strive for .0025 on crank and rods. .004/.008 on the crank backlash. stock street cam be alittle tighter.
 
The build in my signature is coming up on 7 years now, still runs "like-a-top" according to my good friend Ron, the owner.

Here are the clearances measured very accurately with "a micrometer & a bore gauge", actually "dead accurate" so to speak!

The mains have .0025", the rods .002", end play is .004", and cam journal-to-cam brgs has .002". Every dimension was "built-in" during the build.

The cam brgs were "Teflon" coated to help get that number where we wanted.

Eagle crank was new along with the Scat rods, Clevite brgs all around including the cam brgs!

Not a single oil pressure issue, idles in around 15/20, runs with 45/50. This is all with a "bone-stock" Melling M-19 pump! Unit probably has about 30,000 miles or more on it now.

Thanks, Gary in N.Y.

P.S. Happy Father's Day to all here!
 
When building the race flatheads we bore gauged the rods and mains and had the crank ground to avheave the desired clearances. Because we used floating bearings I had the side clearance of the bearings opened up to .015/.o2o and the rods .010/.012 or as close as possable with the equipement we had. Got these numbers from Bill Barth and have used them since the mid 60's I also used Pensoil #40 racing oil. The last engine I build using this method was in Ron Horrells 296 engine. Ron replaced this engine last year with a 294 blower motor. but said the 296 was running great after over 10 years. I'll have to find out how many miles are on it. I cut the flanges from the early rod berings.
 
Ron, why did you cut the flanges off,are not the later 2.00 floaters the same width.?
Lawrie
Was it to use the later rods?
 
Ol' Ron, With your race engines, what piston to cyl wall clearance would you run?
I dropped my current build off at the machinists with a set of Ross pistons, asked him to bore only, in order I can ascertain the block will indeed clean up with no issues. Explained that I had other operations to perform before final honing with torque plates.
He has bored and honed to finish size! Why cannot I find anyone who can follow customers instructions? Anyway, thinking , depending on how much the block distorts with torque plates, might be able to hone it a bit more to ensure round bores, but with the corresponding increased cyl wall /piston clearance. Hence my question- how much did you run?
 
I like to run .003/.oo4 in a street engine. If you have a blower orplan on racing it .004/.005. I use 180 ststs in all my engines I like to get alot of heat into the pistons, keeps them nice and tight. Now, I don't like the Ross piston on the street I use Egge @.002. Much quieter.
 
My following comments are for high-performance builds --> toward the race end of the spectrum.

I'm pretty close to Ron on the bearing clearances as well as the piston to cylinder wall clearances. If I'm running full-floater rod bearings, the most important thing is to really size/fit them to the rods and journals - takes a bit of time and I like to have 6 to 8 sets of bearings to work from (to find the 'best' 4 sets). Having enough side clearance is key when running larger rod bearing clearances - you need to get the oil through the bearing to cool it.

On the mains, sometimes I'll run a bit more on the rear (especially if it is a race engine) - .00275 to .003 is about right. I do this as the rear main can get quite a bit of heat into it from the clutch - so having a bit more clearance isn't a bad thing.

I like to have .0045 to .0055 on forged pistons in a race engine (the larger number for blown applications) . . . maybe closer to .004 on the street. I also have switched over to running 1.5mm, 1.5mm 3.0mm rings if I have a bore where I can use them. I really like the mm ring packages -- we use them at Bonneville, on our road-race cars and also I put some 1.5, 1.5, 3.0 Total-Seals in my recent 284 cube street engine.
 
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