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Discussion Starter · #1 ·
Tried searched, but couldn't find this exact subject. Does anyone know the difference between an early '84-'91 and late '92-'99 Evo oil pump. Reason I ask is I have an early pump and a late engine (S&S 111, That I'm assembling. I'm assuming this would be a "later" style). Is it just a difference in the cover plate or oil passages in the pump itself.......or? Rather not buy another pump, if i can swap cover plates. The pump I have is a high volume TP unit. An S&S is some serious $$$. Good stuff, but rather put the money into the rest of the build.
 

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the L92 up are breather heads where the older models vent to the atmosphere. Not sure if that makes a difference on the pump. I can't remember if the vent on 92 down models is from the pump or case without looking.
 

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the body of the pump and pump cover are different. The bottom two bolt hole are slightly further apart on the later pump. This puts more gasket surface around the gears. The pump body and cover are not
interchangeble but the gears, shaft, keys, and seal is the same.
 

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I was just standing next to an early evo ( 1986) and my 93 and the difference I saw was where the fittings are on the cover. The early pump had two on the top and mine has the vent and feed on the face of it.
 

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Discussion Starter · #5 ·
the body of the pump and pump cover are different. The bottom two bolt hole are slightly further apart on the later pump. This puts more gasket surface around the gears. The pump body and cover are not
interchangeble but the gears, shaft, keys, and seal is the same.
Thanks, nice that they made it idiot proof, I need all the help I can get. And that tells me that the S&S engine is using the Later Pump. I have a new (S&S HVHP ) pump body with the cover and both idler gears but no shaft or driven gears, that I got with this engine. It was a mock up with no guts, no flywheels, pistons etc. If I knew where to get the missing parts, I'd be in business. The gears are much wider and more of a spur type gear as opposed to the stocker.
 

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The only place that you are going to find the HVHP gears are from S&S. The shaft is the same as is the seal, keys and clips. There should be a two or three letter code stamped into the side of the case above the oil pump. There is a chart in the catalog that you can match that code to to determine which bolt/passage pattern you need for your pump and gasket. Whatever you do, do not use stock HD gaskets with that HVHP pump. It actually uses a gap in the gasket to move some of the oil. A stock gasklet will block the flow. The cover should allow you to run the feed and return lines however will work best for your application. As far as breathing goes, You can set that motor up to be either a top breather, bottom breather or both. It is going to depend on whether your cam cover has the passage into the bottom breathing chamber or not. If you choose to use the bottom, use both of the passages. Which heads do you have? If you have the correct heads for the 4 1/8" bore motors, I would use the breathers built into the heads. It is a much better system.

I almost forgot. With that motor you need to run the HVHP pump. There are piston oilers like a twincam that need the extra oil volume of the HVHP pump. That's actually why the pump was introduced.
 

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Discussion Starter · #8 ·
The only place that you are going to find the HVHP gears are from S&S. The shaft is the same as is the seal, keys and clips. There should be a two or three letter code stamped into the side of the case above the oil pump. There is a chart in the catalog that you can match that code to to determine which bolt/passage pattern you need for your pump and gasket. Whatever you do, do not use stock HD gaskets with that HVHP pump. It actually uses a gap in the gasket to move some of the oil. A stock gasklet will block the flow. The cover should allow you to run the feed and return lines however will work best for your application. As far as breathing goes, You can set that motor up to be either a top breather, bottom breather or both. It is going to depend on whether your cam cover has the passage into the bottom breathing chamber or not. If you choose to use the bottom, use both of the passages. Which heads do you have? If you have the correct heads for the 4 1/8" bore motors, I would use the breathers built into the heads. It is a much better system.

I almost forgot. With that motor you need to run the HVHP pump. There are piston oilers like a twincam that need the extra oil volume of the HVHP pump. That's actually why the pump was introduced.
Damn, thanks for all the info. I have the S&S heads, that came with it, and built them up with new valves, springs etc. Going to run a .600 lift Axtell cam. I also have the Super Stock cam cover. Checked all the piston skirt to oil jet clearances,etc. Really appreciate the info, sounds like you've been down this road a few times. What do you think about running the reed type breather in a Stroked( 4-5/8th"s)Shovelhead?
 
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