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6 bolt oil pump on 7 bolt block?

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stuckwithgsx

15+ Year Contributor
341
2
Sep 5, 2006
Phoenix, Arizona
Ok I searched, and all the threads are inconclusive :confused:

I have a 7 bolt engine sitting in the car. I ordered an oil pump, it came in and I looked at the old one and the new one side by side, they looked the same. (looking at the passage ways and bolt holes to line up)

So I go to put this pump on and it bolts up perfectly, then I start putting the alternater back on and realize the bolt hole for that is about 1/4 to 1/2 inch off.

So I take pump back off, look at them again, and see no noticeable differences other than the "spacer" part for the alternater bolt.

I take both pumps to local welder/fab guy and have him chop off both "spacers" and I was going to use the bigger (correct size) spacer and just have an extra piece fall out every time I take out the alternater. No big deal.

Well the said "spacer" got lost. I found another ceased oil pump from a 7 bolt and plan on hacking that one up and using it.

When I was doing my searching someone said "if you use a 7 bolt oil pump on a 6 bolt block you need to drill holes into the block and pump" There was no further discussion stating where, why, how much, etc.

Also with this pump installed, and engine still put together, I cranked it over a few times to make sure it was priming and doing it's job. Needless to say with the valve cover off my hood got squirted with oil from the 2 oil passages on the drivers side of the head near the cam gears.

So I thought that was enough verification on making sure it's working properly. But i'm not positively certain.

The question. Can you use a 6 bolt oil pump on a 7 bolt block without issues?

The oil pump I have DOES have the holes tapped for the CPS. So I would imagine IF it was a 6 bolt pump it would not have those holes right? The pump description also said it would fit 4g64. Now I don't have any experience with 4g64 and the only difference I knew from 6 to 7 bolt on the pump was CPS.

The welder/fab guy kept the old pump for scrap alum, so I can't pull the new one off for comparison again.

I guess i'm just a little skeptical on this after thoroughly thinking about it now.

So does anyone know for sure on this? I got my head redone and picked it up today, ordered the felpro head gasket set (have mls but block hasn't been decked so it's going to wait) and i'm wanting to get this running this weekend.

Don't want oil starvation anywhere so any help would be awesome! Thanks
 
I have seen a write up on a 7 bolt pump on a 6-bolt block it took some drilling for bolt holes.

If you do this you will need a 6-bolt oil pan and a 6 bolt oil filter housing. You will need an adapter for the crank position sensor I know one of the vendors has them.
 
When I was doing my searching someone said "if you use a 7 bolt oil pump on a 6 bolt block you need to drill holes into the block and pump" There was no further discussion stating where, why, how much, etc.

This is where, why, how much, etc.: 6 Bolt Motor Install Into a 2G Eclipse.

The question. Can you use a 6 bolt oil pump on a 7 bolt block without issues?

Not without modification. Imagine doing the reverse of what is shown in the link above. I'm not certain anyone's done it before as there really isn't anything to gain from something like that.

The oil pump I have DOES have the holes tapped for the CPS. So I would imagine IF it was a 6 bolt pump it would not have those holes right? The pump description also said it would fit 4g64. Now I don't have any experience with 4g64 and the only difference I knew from 6 to 7 bolt on the pump was CPS.

Then it's definitely not a DSM 6-bolt oil pump/front cover.

Here's the DSM 6-bolt oil pump/front cover.
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Compare to the DSM 7-bolt pump/front cover.
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It sounds like you have good oil pressure, but if you are so uncertain, you can get a gauge and find out what the pressure is on cranking/priming so you don't "ruin" anything.
 
Well judging from those 2 pictures I do in fact have the 7 bolt pump. But the far left bolt hole is "switched" per say.

How this is possible i'm not really sure.

Anyone ever seen anything like this happen before?

The black circled area's are visually telling me this is a 7 bolt pump. As well as the oil pan mating surface being curved.

The green circled area is where mine was not lining up. Everything else lined up perfectly.

Anyone seen one like this? Is it for a 4g64 maybe?

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The 4G64 uses the same pump as the 1G 7-bolt and 2G 4G63.

I'm not sure what you've got. Mind posting pictures so we can all see what you are seeing?
 
This is how it sits as of now. The red part is RTV over the castle plug, and is just a reminder for me to never try and use that one again. It was a PITA to get out of the old pump and now it's lock tite'd in there. So next build is just getting a new oil pump and castle plug. And I think you can see where I cut the section out for the alternater. I got a hold of another old 6 bolt oil pump and the "spacer section is the same size as the 7 bolt one that was there. They were both oem pumps. I'm still confused beyond all reason as to why this one came shorter, and 1/4 to 1/2 inch off?


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