70 LT-1 oil pump and pick up question

[Steve F.]

What oil pump was stock on a 70 LT-1 and what is the closest and or best pump available?
Also the pick up screen doesn't look like it will work with the 5 quart oil pan. My car is a late build and probably came with the smaller oil pan but I had the larger earlier one so I am going to use it however it looks like I will need to change the pump pick up. What came on the early 70 LT-1 or the mid years with the larger oil pan?

Thanks as always.

Steve

[Timothy B.]

Re: 70 LT-1 oil pump and pick up question

Steve,

The pick-up is available in the aftermarket and the part # will be in the archives if you do a search, I can't remember it.

The oil pump is a standard volume high pressure pump but you better be careful as high pressure GM pumps relieve at 60lbs and the aftermarket versions relieve much higher. The standard volume/standard pressure Melling M-55 has a relief of 55-60lbs so that's what I recommend. If you keep the main/rod bearing clearances in the .002 range you will have no problem achieving that oil pressure.

If you still have the original oil pump take it apart and clean/inspect and check the end clearance, chances are very good it's still in nice condition and good to reuse.

[Terry M.]

Re: 70 LT-1 oil pump and pick up question

What oil pump was stock on a 70 LT-1 and what is the closest and or best pump available?
Also the pick up screen doesn't look like it will work with the 5 quart oil pan. My car is a late build and probably came with the smaller oil pan but I had the larger earlier one so I am going to use it however it looks like I will need to change the pump pick up. What came on the early 70 LT-1 or the mid years with the larger oil pan?

Thanks as always.

Steve

If your engine is original and still has the original engine assembly stamp. CTU = 6 qt oil pan, and CTK = 5 qt oil pan.

[Joe L.]

Re: 70 LT-1 oil pump and pick up question

What oil pump was stock on a 70 LT-1 and what is the closest and or best pump available?
Also the pick up screen doesn't look like it will work with the 5 quart oil pan. My car is a late build and probably came with the smaller oil pan but I had the larger earlier one so I am going to use it however it looks like I will need to change the pump pick up. What came on the early 70 LT-1 or the mid years with the larger oil pan?

Thanks as always.

Steve

Steve-----


Regardless of whether the "5 quart" or "6 quart" oil pan was installed the oil pump pick-up screen was the same. All 1963-82 small block Corvettes used the same oil pump pick-up screen except 1975-79. The screen was GM #3830080. It's discontinued but an exact replacement is available from Melling and Sealed Power.

The original oil pump was GM #3848907. The current GM replacement is GM #12555884. However, I agree with Tim that your current pump might very well be OK for re-use.

[Steve F.]

Re: 70 LT-1 oil pump and pick up question

Thanks, the pump I have is a GM 3821979 which I believe was really for an earlier year although I am not 100%. When I Googled #12555884 it come up as a later LT1 (93-97) does this also fit the 70 LT-1?
I do a search before posting any questions including an advanced search but I didn't see the information listed.

[Timothy B.]

Re: 70 LT-1 oil pump and pick up question

Steve,

That sounds like the casting # on the side of the pump, and that sounds correct. The only difference between the standard pressure and high pressure pump is the relief spring, everything else is the same.

Check the archives for the relief spring length and you can compare with what you have as it may be correct. If so, the pump may be OK to reuse.

[Joe L.]

Re: 70 LT-1 oil pump and pick up question

Thanks, the pump I have is a GM 3821979 which I believe was really for an earlier year although I am not 100%. When I Googled #12555884 it come up as a later LT1 (93-97) does this also fit the 70 LT-1?
I do a search before posting any questions including an advanced search but I didn't see the information listed.

Steve-----


As Tim suggests, the 3821979 is a casting number, not a part number for the pump assembly. The only case in which a part number for the assembly is found on oil pumps is if there is a metal tag affixed to one of the cover screws. Original pumps and older SERVICE pumps rarely have such.

GM #12555884 oil pump was never used for any Gen II (92-97) LT1. GM #12555284 was a SERVICE oil pump for 1992-94 LT1, though. It's the same as the 12555884 except for the installed pressure relief spring.

[Duke W.]

Re: 70 LT-1 oil pump and pick up question

What oil pump was stock on a 70 LT-1 and what is the closest and or best pump available?
Also the pick up screen doesn't look like it will work with the 5 quart oil pan. My car is a late build and probably came with the smaller oil pan but I had the larger earlier one so I am going to use it however it looks like I will need to change the pump pick up. What came on the early 70 LT-1 or the mid years with the larger oil pan?

Thanks as always.

Steve

Why are you replacing the oil pump?

Duke

[Kenneth B.]

Re: 70 LT-1 oil pump and pick up question

Why are you replacing the oil pump?

Duke

I think his question really about the length of the pump body between the 6 & 5 QT pans. Do they take the same oil pump?

[Joe L.]

Re: 70 LT-1 oil pump and pick up question

I think his question really about the length of the pump body between the 6 & 5 QT pans. Do they take the same oil pump?

Ken------


The configuration of the oil pumps used with either the "5 quart" or "6 quart" oil pans is identical. The configuration of the oil pick-up screen is identical, too. The length of the oil pump body is the same for all 1963-96 Corvettes with small block.

[Kenneth B.]

Re: 70 LT-1 oil pump and pick up question

Ken------


The configuration of the oil pumps used with either the "5 quart" or "6 quart" oil pans is identical. The configuration of the oil pick-up screen is identical, too. The length of the oil pump body is the same for all 1963-96 Corvettes with small block.

THANKS JOE That is what I think he was asking. I think he thought he needed a shorter pump or screen for a 5 quart pan.

[Joe L.]

Re: 70 LT-1 oil pump and pick up question

THANKS JOE That is what I think he was asking. I think he thought he needed a shorter pump or screen for a 5 quart pan.

Ken-----


The "6 quart" pan has a longer sump than the 63-74 "5 quart". However, the depth of the sump is the same for both. So, the oil pump and pick-up are the same for both

[Steve F.]

Re: 70 LT-1 oil pump and pick up question

Thanks for all the responses. I am building a new engine for my car so I am not replacing the pump. The number I had listed is of a NOS pump I have on my shelf in the original GM box and I took the number off from the GM box the pump is in. I didn't look to see if there is a number cast in it.

I also wasn't clear as I am using the larger sump 6 quart pan instead of the later pan which is smaller. My questions were both what is the best pump - I bought the Melling and would the standard screen fit as I thought it may not clear but you have all said it does so I went with the standard screen.

As for pump GM #12555884 if you click on the number and do a Google search it comes up on GM Performance as a replacement for a later year LT1/LT4.

http://www.gmperformancemotor.com/parts/12555884.html

Thanks again for the replies.

Steve

[Joe L.]

Re: 70 LT-1 oil pump and pick up question

Thanks for all the responses. I am building a new engine for my car so I am not replacing the pump. The number I had listed is of a NOS pump I have on my shelf in the original GM box and I took the number off from the GM box the pump is in. I didn't look to see if there is a number cast in it.

I also wasn't clear as I am using the larger sump 6 quart pan instead of the later pan which is smaller. My questions were both what is the best pump - I bought the Melling and would the standard screen fit as I thought it may not clear but you have all said it does so I went with the standard screen.

As for pump GM #12555884 if you click on the number and do a Google search it comes up on GM Performance as a replacement for a later year LT1/LT4.

http://www.gmperformancemotor.com/parts/12555884.html

Thanks again for the replies.

Steve

Steve-----


OK, I assumed you were getting the number off the pump so I did not further check it. However, I have now. GM #3821979 was a 1963-released part number for the standard pressure small block oil pump. It was replaced for SERVICE by the GM #3764547 and later by GM #12555284. It would not have been used for 1970-72 LT-1. However, it could easily be converted to the 70-72 LT-1 pump simply by changing the relief spring to GM #3848911. The latter is available from GM for about 4 bucks and will take about 3 minutes to install.

If by "larger sump 6 quart pan" you are referring to the oil pan used for 1963-65 Corvettes with SHP, early 1970 LT-1, and all 1970-72 ZR-1 then you can use the 3821979 pump with the 3848911 relief spring. You should also use a reproduction of the 3830080 pick-up screen. These parts will "fit the bill" perfectly. You could also use the 12555884 pump with the 3830080 pick-up.

The GM #12555884 pump was never originally used for 1992-96 LT1 or 1996 LT4. It could be used as a replacement for those engines but I would strongly advise against it. Those engines do not require and will not benefit from a high pressure oil pump except, possibly, if they were operated under continuous racing conditions.

[Joe C.]

Re: 70 LT-1 oil pump and pick up question

What oil pump was stock on a 70 LT-1 and what is the closest and or best pump available?
Also the pick up screen doesn't look like it will work with the 5 quart oil pan. My car is a late build and probably came with the smaller oil pan but I had the larger earlier one so I am going to use it however it looks like I will need to change the pump pick up. What came on the early 70 LT-1 or the mid years with the larger oil pan?

Thanks as always.

Steve

Steve:

Since you're re-using your old pump, then it would be a good idea to at least partially, blueprint it. Internal shearing and heat are generated when the gear to pump cover clearance is too wide, thereby churning the oil within the pump before passing it. Remove the cover and use a piece of 600 grit wet/dry paper oiled with WD40 on a flat surface, like a thick piece of glass. Lap the cover in a figure-of-eight motion and rotate 1/4 turn in your hand every 15 cycles or so, until all surface irregularities are removed from where the gears seal to the cover. Do the same to the gears, if needed. Then do the same to the pump housing seal flange until you achieve .001" - .002" clearance between the gears and the cover. Grind all casting flash and roughness from all oil passages that you can see, and streamline all turns, bends, and cross sectional area changes.

Because today's lubricants are better than those of the past, you'd be wise to replace the relief spring with a standard pressure. Melling sells assorted springs in plastic bags.