Some background on the engine, 8BA new rebuild with 200 miles on the rebuild. The motor after the rebuild didnt have the best oil pressure when warm but was worse at a warm idle. I have a full flow oiling system on it and the oil pressure sender is downstream from the oil filter and figured the oil filter may be some of my trouble with the pressure. I installed a stainless steel cleanable oil filter and that helped some but still not right. I put the 200 miles on it to see if there was going to be any engine problems before taking the pan off. I have read some of the problems with the mellings oil pumps posted by Bruce Lancaster and some others so I figured that was my problem (new Mellings pump installed on the build). I read the posts after installing the motor and firing it up. I figured the pump housing was machined undersize at the drive gear end of the pump as had been found on some of them. I had an old worn spiral geared pump and a great straight geared pump. I found the wear from the spiral geared pump was from worn bushings. I will show pictures as I go. The two old oil pumps I thought I would take the gears from the worn bushing pump and install them into the other pump with the good bushing. I found the gears were a little bigger diameter than the straight cut ones so this wasnt going to work. I dropped the oil pan and removed the Mellings oil pump to verify it had the bad housing. I measured it with micrometer and it was within a .0005 of the OEM pumps. Doubled checked all the dimensions again and still the same. Now I am thinking I have an internal engine problem (not a good feeling). I decided to take the pump apart to check the internals and I found the byp*** seat was offset in the byp*** bore and larger than the OEM pumps. The seat would not let the byp*** valve seat to hold pressure. To verify this I forced a piece of tygon tubing into the byp*** hole as shown below and could blow air through it by mouth. I then tried the same test on the other pump and no air or suction would byp***. Byp*** valve taken apart. Byp*** seat but it doesnt show very well. Now I was stuck with having to use the housing with worn bushings and I got to checking some of my cans with the stuff I saved but would probably never use and found a couple of bushings that was perfect for it. Below are a few pictures showing making a puller and changing the bushings. A note on the small threaded adapter shown, it has to be thin enough to drop into the opening shown and then thread the all thread into it. Notice the different lengths of the bolts that hold the pickup tube to the pump. Use the short bolt in the hole closest to the cover plate. The picture shows the short hole and if the longer bolt is used it could distort the gear bore causing the pump to seize or not tighten the flange and it could **** air instead of oil. Rebuilt pump and now waiting for pan gaskets (to be here this Wed.) then I will see if this was all for naught and end my posts with shame. Hope this helps someone. Vergil
Excellent - hope it works out for you - sounds like the byp*** valve was the culprit. Maybe this is more common than thought before & it's a QC issue with Melling - minor clearance issues on housing + small errors in the byp*** seat = poor oil pressure! Keep us posted!!
Just for reference, side clearance specs for pump gears are in the '49-53 manual, end clearance is not...I decided to use the number from a Dave Vizard SBC pump rebuild, I think .007... Stock pumps (were in my junk box til I read Ol'ron's findings on new ones) checked in spec at sides, needed some minor work at end clearance. Ron found major and very variable slop where pump goes into block, not an issue with original pumps. This area was a major pressure loss for the new Melling that started Ron's investigation...cain't trust anybody no more...back to genuine Ford stuff. Repro people are at full capacity making hubcaps and chrome strips that don't fit, now are expanding into the new field of mechanical parts that don't work... It's not well known, but it's obvious on close inspection that Henry stole his oiuling design from the successful 265 Chevy design...works well when you can get useable hardware. Recent posts indicate Melling is now producing shaky pumps for the SBC market too...
I owe it to you and Ol'ron's posts, looked on the ford barn and here. Thanks for the posts pointing us in the right direction.
Great post. But anyone who knows my history with flatheads and oil pressure wouldn't be suprised at my post traumatic stress type reaction while reading. Be sure to let us know results.
So--Henry could crank out a million good pumps per year, now by applying advanced industrial technology, computerized quality control, and laser guided computer fed machine tools we...can't make...any??? Social pessimism, anyone??
Excellent work, Vergil, I'm going to be pulling my pump, and will be checking the byp*** valve very closely now! Bruce -- my thoughts exactly -- this is progress?!
just my .02 here origional pumps arent hard to rebuild and o/h kits are available, ive done a bunch of them
Where do you get kits from? Might get one to do another pump. I agree they are easy to rebuild, the information is what I had found on my oil pump and how I repaired it.
i get rebuild kits from early ford v8 sales in ny....i better start start cleanin the crud off the mountain of old used pumps out back before the rush for them starts...
What do you mean by full flowing oil filter? I see no modification done to your pump like the systems I've seen before. If you have the byp*** filter can up on the head your pressure problem may be that the lines you are using are not stock style from the block, The original style lines have a small orifice that is necessary to maintain oil pressure at acceptable levels. If this orifice is oversized or not there the pressure will be quite low as you have stated.
I bet everyone has discontinued the rebuild kits since these nice new pumps became available... Bushings are readily available from industrial suppliers. KD and Snapon make a nice bushing driver set with drivers similar to that in graduated sizes endlessly useful on old Fords; this is one case where the Chinese replicas, available for dirt, are OK too, since they are low stressed tools... A new Melling pump would make a nice parts kit for a good Ford casting, IF gear fit is within spec--as posted above, side clearance figures are out there. If you do strip a Melling for any useable parts, be sure to beat the casting flat with a sledge hammer so it doesn't end up destroying another rebuild in the future...
We must have got the one good Mellings pump. Our 8BA got it's total reconditioning last year and went together with an "out of the box" Mellings pump. Now at about 6000 miles it idles at 20 psi (hot) and goes down the road at 50 psi @ 60 mph......and that is with Mobil 1 synthetic in it. I've always had good luck with Mellings but in light of the findings we see here, I guess it will bear watching in the future. Great posts on this subject!!!! Bruce is "da man".
Thanks Virgle I had a bach of bad ones a few years ago which promped me to make a test fixture. It was there I found the discrepency in the size of the housing. I thought of the by-p*** valve but on the two that I checked the valve seemed to be OK. However your test is more convincing. Thanks again. Ol' Ron
A fascinating train wreck of modern technology...expensive new pump, hopeless...60 year old pump from garbage can plus two new bushings... Is there anything of modern manufacture for a flathead you can just buy and confidently screw into place?? Seems like a lot of horror stories... And this stuff is GOOD detective work--who would have thought the byp*** area would have been machined on a couple of different axes?? Seems like any modern method would have cut bore and seat on same basic tooling without moving anything.
You can make a "full flow" filter system by doing some modifications at the back of the block. They don't require any modifications of the oil pump. Maybe Bruce can put up the "how to."
Excellent tech. Does anyone know if the big Melling M-15 (Zepher) pump is plagued By the same issues? Doc.
This post was rather interesting but rather than bad mouthing parts there is a rather large gray area that has not been addressed. What was the original oil pressure reading? This is like screaming my engines running hot, well how hot? Or asking how full is full? While there has been a lot of work done to the oil pump , nowhere does it state what the original oil pressure readings were. Was it 15lbs at idle or 50lbs.? These are not high oil pressure engines, its not like a SB Chevy so if you are looking for high oil pressure numbers for piece of mind you better look somewhere else. High pressure is not a necessity but an adequate volume of fluid to lubricate all the parts is. Since these are essentially a low rpm engine they do not require a high pressure oiling system and pressures from 15 lbs to 50lbs are more than adequate. This was an interesting read and before Bruce continues flipping out on inferior parts, there is a little more information necessary. This might be an exercise for no gain. Old time mechanic told me if it wasn't knocking not to worry and I somewhat believe him, heck most people just rely on the oil pressure warning lite anyway, if its not on must be ok!.
My Mellings pump puts out 60psi at idle (cold) and between 45 and 50psi (hot). I built a full flow oil filter set up (not the rear gallery type, but modified the pump itself) and it's been good. That being said, I'm running new bearings all around which helps the pressure a lot. Flatman
Sorry I forgot to mention the pressure, 5-6 lbs at warm idle, 900 rpm, on the road about 35 psi at 2100 rpm. For the work and money spent on the motor I figured it should have better oil pressure than it had. New bearing, new cam, .010 - .010 crank and clearances checked. More work done on it but nothing to do with oil pressure.
I think the problem was ID'd as relief valve seat eccentric to position of its plunger and hence unable to seat way up above. That's a consideration that leaves the engine completely out of the equation, as much of the oil can't even get to the engine...this is a fatal flaw, not reasonably fixable when there are alternatives. It is also a very strange failing, since I think most modern machining procedures would cut everything in one hole and on a single axis in one operating position on one machine... I'm adding this into my databank of horrors including the new Chevy pump castings shown on here a few weeks ago and Ron's discoveries of new mellings cut too small to seal at the block juncture. Is Mellings now just an office ordering pumps from Sri Lanka or something?
Came back today to check on progress, Thanks for the up date. I'm not so sure how you have this plumbed in but I'm leaning to think that you are not taking an accurate reading. If you just have the factory canister plumbed into the back of the block this really isn't a full flow system. At this time I would suggest that you disconnect the oil cannister input line, plug the port and retake the oil pressure reading at the oil pressure port at the back of the block. This should establish an accurate engine oil pressure reading. What did you get for oil pressure after modifying the pump?
The oil pressures given are after the rebuild. I traded for the block and rebuilt it so I don't know what the pressure was before. Here are a couple of pictures of the oiling setup.
Ok, I'm not the go to guy for pressurized oil systems but as neat as this looks it appears as suspected. You are getting a low idle reading due to the plumbing, that 1/2" line is causing a drop in pressure due to its size and by pulling a reading after the large tubing it is showing a lower than expected oil pressure reading at low RPM. Just change out the lines to a 1/4" line and you will probably notice that the pressure comes right up. This is probably still best considered as a partial full flow filter rather than a full pressure system.
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