Walt Dupont lectures on V8 Oiling

[31chevy]

Nice explanation Walt. I agree with you oldford2 I would be very interested in fitting floating rod bearings as this is one of the reasons I did not rebuild my own engine (among others).
Gary.

[Walt Dupont--Me.]

Originally Posted by jimTN

Great talk Walt, you sure don't sound like someone from around here. I would add one thing I always check. On the 38-48 blocks there are oil passages that go to the water pump bearings. I have always cleaned them out.

Jim TN, yes it's good to clean those oil holes to the water pumps BUT, there is no oil pressure in those holes, they just go to a cavity in there and the cam gear throughs oil into that cavity and it just runs down into the water pump hole to feed the early pumps with the bushing. The 8BA pumps have sealed bearings and don't need that oil hole. Walt

[Walt Dupont--Me.]

Originally Posted by peewee2you

Walt, excellent video and understanding of the oil distribution throughout the Flathead.
My question is in the first video you showed the oil pump and where the screen picks up the oil via the pump takes it in and carries through that slot in the oil pump into the chamber where the oil pressure sender unit would be on the top side of the block. My question is when you put the screw driver through the rear main hole of the block where the crank shaft journal would be lubricated, you stated that the oil would travel from that oil sender chamber? I was trying to keep track of the slot that the oil comes out of the pump and into that chamber when you stuck the oil pump in the block and ligned it up with the bolt hole so the pump would stay in place, and it appears that the slot in the oil pump that delivers oil is facing opposite of the hole in the block for the crank journal galley hole. I was expecting to hear that the slot when pump in place would have faced the opposite direction toward the galley hole in the block for the crank rear main lubrication, so now I guess what happens is that so much oil is picked up and shoved through that slot and that the oil pressure chamber fills up enough to where the oil travels through the block hole to lubricate the crank journal. I hope that made sensen, I do get a bit wordy.

It just seems like it would have made more sense for that slot to have faced in the opposite direction than it is when bolted into place and shoving oil directly at that hole in the block for the crank, facing the way it does it seems like it comes through that slot and just splashes off the block wall in that chamber and fills up with oil and then streams into that tiny hole. Thanks again for my on going education....

peewee, with the volume of oil comeing out of the pump there is only so much going up that 1/4in. hole to the rear main, there is plenty of oil going around that pump body to go up that big hole to the sender unit and to the main oil line. Walt

[Ol' Ron]

Walt
One thing you forgot to mention. The oiling system of the flathead is so good that Chevy copied it to the extent that the rear main doesn't get filtered oil when you make the 25 cent oil fikter modification. Great Job,like to get up ther again, but my travling days are over. Take care. Ol' Ron

[fourtydlx]

Walt: Thanks a lot,

[Ronnie]

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No offense to anyone.

No intention to hijack this thread.

Just the facts.It's been mentioned many times!!!! and is not correct.

I don't know where the urban legend began that a small block chevy doesn't filter the rear main but it is not true.All the oil that is pumped out of the oil pump has no where to go except to the filter.Take a look at a stripped block and push a small rod through all the oil passages and you will discover the true passages for oil none to the engine before the filter,all after the filter.

[Ol' Ron]

I'll have to go check that. I saw a fellow many years ago show me this and I took him at his word. sshame on me. Unfortunately I haven't seen the inside if a SBC in almost 50 years since we ran a 283 at the drags in a 39 chevy coupe. Best times were low 14's and mid 90's not bad. I'm still going to check.

[TomT/Williamsburg]

Originally Posted by Wily Kyote

The elongated slot in the oil pump... I just removed an oil pump that had a round hole, instead. Were some of them round, or might this one be originally from a French motor? The head of the hold down bolt is metric measurement. As are the heads of the oil pan bolts.

The elongated hole is on the higher pressure 8BA pumps - the earlier style 59 pumps just had a hole I believe.

[Wily Kyote]

Thanks TomT.

[1937pickup]

Hope this works-here is a schematic of the small block chevy oiling-very similar to flathead.

[Ronnie]

Originally Posted by 1937pickup

Hope this works-here is a schematic of the small block chevy oiling-very similar to flathead.

Note the flow all oil flow enters the filter and then goes to the bearings.Rear main is not by itself.

[Bruce Lancaster]

[Ed Pitts]

Walt, thanks for opening the door on a really interesting subject that we just take for granted. Good job as always! Ed

[Ronnie]

Originally Posted by Bruce Lancaster

That pic is correct no flow to rear main.

[Bruce Lancaster]

Look at a detail of the rear oiling routing above:

Oil comes up from the pump through the rear main cap to the vertical passage.
First routing is the diagonal low in block...right and down to the rear main, left to feed the filter.
Oil is stopped from going higher by the little cup plug that is indicated here by an arrow, forcing it into filter and to the bearing also.
From the filter it feeds out the middle and back over to the vertical passage above that plug and goes on up to meet the main gallery and the side galleries for valve system.
Rear main gets its oil right before the filter. This is well documented in the soup your Chevy books and can of course be checked out visually on a bare block.
In Smokey Yunick's book, I think the "Power Secrets" one, he discusses this at length...he describes a couple of ways to get full filtering, then concludes that there is no prob with the stock setup anfd trying to modify it is a waste of time.

Picture shown is an '86 up type block, but oiling routes weren't changed.
Picture stolen from: http://www.chevytalk.org/fusionbb/sh...hp?tid/192284/

[1937pickup]

The interesting thing is the 10psi by pass-does this mean that over 10psi oil goes around the filter or under 10psi by passes the filter. In either case it means not all oil is being filtered all the time-very similar to a flathead filter.

[Ronnie]

Bruce your statement is partially true.

Look at the enclosed pictures.The hole everyone seems to believe delivers oil to the rear main is there as it was the only way to easily drill the connecting passage at an angle from the saddle to the intersecting passage to the filter as drills only drill straight and not around corners.The two holes join at an angle as per drawing.One hole drilled each way.What is not shown in that drawing is the oil hole for flow to the rear main.What is also knot shown is the rear main saddle with two holes.The drawing is also only the block with no bearing installed.The large hole you speak of is covered up when you install the rear main bearing preventing oil to the bearing from that hole.The large one is below the bearing tang slot.Gets covered with bearing shell.The smaller hole over and down is the true real main oil gallery hole.It lines up with the only hole in the rear main bearing shell.Oil here has been filtered.
Can't tell you about Old Smokey's documentation but that theory is incorrect.So is any other book that would explain it that way.He probably didn't say that but somehow it was misunderstood.
Any one who has put a crank in a small block can attest to the large hole covered by the bearing.I have built many small and big blocks the oiling is same in both.

[Bruce Lancaster]

The 10 refers to pressure from oil going into filter and building pressure there because it can't get through fast enough. On a chevy with passenger car post-1968 spin on filter this happens a lot, according to the builders, when oil is cold and at high RPM. Lots of oil bypasses. According to one book I have, the earlier cannister filter had both finer filtering and more flow from its large element, which explains Chevy keeping it as police, truck, and taxi filter for several years after '69.
The various HP books recommend early filter or long truck filter or aftermarket setup with two filters in parallel. Full flow is a misnomer apparently with the standard setup. Racers with one of the greater capacity setups can block the bypass valve because their engine get frequent oil changes and don't have to worry about accumulated dirt.

[Ronnie]

Originally Posted by 1937pickup

The interesting thing is the 10psi by pass-does this mean that over 10psi oil goes around the filter or under 10psi by passes the filter. In either case it means not all oil is being filtered all the time-very similar to a flathead filter.

Yes that is correct.The bypass valve is in the filter adapter that is part of the engine.Common for gm engines.However all systems have a bypass valve and in other engines that valve is incorporated into the filter itself and the pressures differ a few pounds from engine to engine.The bypass pressure relates to how much pressure differential there can be until the valve opens up and bypasses the filter.In a cold climate there is no full flow until the oil warms up and the differential pressure drops below the valve setting.Good observation on your behalf.

[OldDad]

This video needs to be preserved, along with the New England dialect (and its many sub-dialects), the Salt Lake City dialect, the Tennessee dialect, the Louisiana dialect, the Georgia dialect, the Wyoming dialect, the Northwestern dialect, the Philadelphia dialect, Missouri dialect, the Bronx dialect, the West Los Angeles dialect . . . missed more than a few!

I could listen to Walt talk on any subject for hours on end. It's music to our ears out here on the other side of the country. Too far removed from it by the generations. My family from Rhode Island, Bucks County PA, Detroit area (before La Salle), Illinois, Missouri, and so forth back when. All mixed into something kind of bland out here, but guess that depends on who's listening to it!

And I couldn't care less how the rear main on a sbc gets oiled, as long as the rear main on my go-get-it '72 GMC is still getting some from somewhere!