Mark IV Big Block Oil Pumps

[Joe L.]

Re: Mark IV Big Block Oil Pumps

Mark Nagy, one of this group's contributors, told me the original oil pump in his 66 427-425 had the casting number 3860370 and 1.30" gears. I think Joe had it nailed from the beginning. This was a production pump for 66 SHP big blocks. Maybe Mark will chime in. Melling apparenty tested his pump recently and was quite impressed with it.

Patrick-----


Yes, in fact Mark's pump is what got me started on this quest to verify the specifications on the 65-66 Mark IV oil pumps. I was surprised to learn that his pump had the 1.30" gears as I thought that all Mark IV except ZL-1 used the 1.15" gears. George Wright had this pump with the same body and cover casting numbers as Mark's original pump. He sent it to me and I confirmed the internal specs.

I have every reason to believe that Mark's pump is original to his engine.

Is it possible that GM used the same 3860370 body casting for pumps with different length gears? Yes, I suppose it's possible but I highly doubt it. I know of no other case in which the casting used for a Chevrolet oil pump was not specific to a particular internal configuration, including length of gears.

[Joe L.]

Re: Mark IV Big Block Oil Pumps

what about the Z-11 ???

clem------


The Z-11 used oil pump GM #3848907. This is the standard volume, high pressure oil pump also used on most 63-72 SHP solid lifter small blocks.

[Joe L.]

Re: Mark IV Big Block Oil Pumps

Joe,

Thanks for posting your findings about the gear height for 65-66 big block. It's also interesting how the idler pin is lubed by the groove in the cap. I know there are others that will be interested in this information.

That original looks like it's in nice condition.

Timothy-----


Yes, the pump is in absolutely superb condition. While I, personally, don't usually re-use oil pumps, there is absolutely no reason in the world why this pump could not be re-used. Of course, we don't know the history of this pump so we don't know how much actual service it has experienced.

However, Chevrolet oil pumps usually show very little wear even after very high mileage. That's because they are, by definition, well lubricated. With regular oil changes the pumps can be virtually "immortal".

[Clem Z.]

Re: Mark IV Big Block Oil Pumps

here is a picture of the pan that pump goes with. http://www.chevelles.com/classifieds...=48344&cat=all

[Clem Z.]

Re: Mark IV Big Block Oil Pumps

oil pump with screen.
1.652 3879643 PASS. (396, 427) PUMP ASSY., Oil w/screen .................

[Clem Z.]

Re: Mark IV Big Block Oil Pumps

better pan picture. http://www.chevelles.com/classifieds...e=oilpan12.jpg

[Michael H.]

Re: Mark IV Big Block Oil Pumps

oil pump with screen.
1.652 3879643 PASS. (396, 427) PUMP ASSY., Oil w/screen .................

Yup, that's the 3879643 part number I posted earlier. The unique oil pan is 3879633.

[Joe L.]

Re: Mark IV Big Block Oil Pumps

Joe:
The oil pump that I think came out of my 69 ZL-1 looks a whole lot like the 66 pump in your thread but the body casting number is different. It body casting is 3863688 or 698 (the numbers are very hard to read); the lid casting is 3860376 same as yours. The gears are 1.30" and a Corvette pickup screen was tack welded on. The old Chevy power books list the ZL-1 pump as 3969870 with 1.30" (not 1.38") gears and a welded on screen.

Patrick-----

Are you sure that the body casting is 3863688 and not 3963688? Also, some photos of this pump would be helpful.

[Patrick B.]

Re: Mark IV Big Block Oil Pumps

Patrick-----

Are you sure that the body casting is 3863688 and not 3963688? Also, some photos of this pump would be helpful.

I'm going to my garage today and I will take some pictures. Fortunately the oil pan is not on yet. It is certainly possible the 8 is really a 9; I was puzzled why a 1969 part would start with 38, but the lid casting number is certainly the same as the 1966 part in your photo.

[Clem Z.]

Re: Mark IV Big Block Oil Pumps

Joe,

Thanks for posting your findings about the gear height for 65-66 big block. It's also interesting how the idler pin is lubed by the groove in the cap. I know there are others that will be interested in this information.

That original looks like it's in nice condition.

a better way to lube the idler gear is to drill a .062 hole in the root of one of the gear teeth half way up.

[Joe L.]

Re: Mark IV Big Block Oil Pumps

I'm going to my garage today and I will take some pictures. Fortunately the oil pan is not on yet. It is certainly possible the 8 is really a 9; I was puzzled why a 1969 part would start with 38, but the lid casting number is certainly the same as the 1966 part in your photo.

Patrick-----


Yes, I'm also surprised that your pump uses the 65-66 cover. However, it might be that the patterns for it were still in existence and the designers wanted the oil groove which is present on the 65-66 cover but not on the 67+ cover.

[Patrick B.]

Re: Mark IV Big Block Oil Pumps

Patrick-----


Yes, I'm also surprised that your pump uses the 65-66 cover. However, it might be that the patterns for it were still in existence and the designers wanted the oil groove which is present on the 65-66 cover but not on the 67+ cover.

Here are some pictures of the pump. The casting numbers on it are not as easy to read as on the pumps you photographed. The 8's and 9's are indistinquishable to me.

[Patrick B.]

Re: Mark IV Big Block Oil Pumps

Here are some pictures of the pump. The casting numbers on it are not as easy to read as on the pumps you photographed. The 8's and 9's are indistinquishable to me.

Here's another shot of the pump casting number. Here's a couple of shots at the pad also. This is original grain (despite a touch of sandpaper cleaning at the left edge) and it is very smooth. There is certainly a range of roughness in factory deck finishing, but some big blocks especially were finished very smoothly.

[Clem Z.]

Re: Mark IV Big Block Oil Pumps

better pan picture. http://www.chevelles.com/classifieds...e=oilpan12.jpg

if anyone has the david kimble 2011 calendar put out by chevy called "the beauty of the beast" you look at the cover sketch of the chevy 427 NASCAR mystery engine you can see the horizontal weld seam on the oil pan. this pan has been around since 1963.

[Michael H.]

Re: Mark IV Big Block Oil Pumps

if anyone has the david kimble 2011 calendar put out by chevy called "the beauty of the beast" you look at the cover sketch of the chevy 427 NASCAR mystery engine you can see the horizontal weld seam on the oil pan. this pan has been around since 1963.

Clem,

The oil pan for the 1963 427 Mystery Motor was very similar to the one Chev released for service in late 1965 for big blocks. Different part number though.

There were two different oil pan designs for the Mystery Motor.