C1 Oil Pump question

[Donald H.]

This is for my 1960 engine rebuild. The fellowing helping with my engine rebuild hasn't done a 283 in a number of years, but he thinks there was a different oil pump for the solid lifter 270hp engine versus the base engine.

Anyone know if this is correct? I want to put in the correct stock type pump and not a high volume one.

Check Zip, Corvette Central, and Paragon and they only have two listed, one standard and one high volume.

Thanks,

Don

[John H.]

Re: C1 Oil Pump question

This is for my 1960 engine rebuild. The fellowing helping with my engine rebuild hasn't done a 283 in a number of years, but he thinks there was a different oil pump for the solid lifter 270hp engine versus the base engine.
Don

Don -

The '73 issue of the P&A 30B shows the same oil pump for all '59-up C1 applications.

[Donald H.]

Re: C1 Oil Pump question

Don -

The '73 issue of the P&A 30B shows the same oil pump for all '59-up C1 applications.

Thanks,

The GM part numbers I have are 3821979 for the pump and 3764113. Is that what you show?

Also, if I look at the picture on Paragon's and Corvette Central's websites they appear to be the same pump. I can see M55 casting.

Zip's looks like it may be different.

I not sure which to buy or if it makes any difference?

Don

[Joe L.]

Re: C1 Oil Pump question

Thanks,

The GM part numbers I have are 3821979 for the pump and 3764113. Is that what you show?

Also, if I look at the picture on Paragon's and Corvette Central's websites they appear to be the same pump. I can see M55 casting.

Zip's looks like it may be different.

I not sure which to buy or if it makes any difference?

Don

Don------


The original oil pump for your application was GM #3764547. This part number was superceded several times over the years. The current replacement part number is GM #12555284. The GM #3821979 was a 1963 replacement for the 3764547. Later, the 3764547 "came back" and replaced the 3821979.

I believe that most, if not all, current GM oil pumps for Gen I and II small blocks are manufactured by Melling. I think your best bet for a replacement will be the Melling 10553. This may be the same as the GM #12555284 or the 12555284 may be the same as the Melling M-55 which is inferior to the 10553.

I think what you engine builder is thinking of is one of 2 things. First, he may be thinking that some 283's used a different oil pump. And, he's right. 1957 283's (as well as 55-56 265's) did use a different oil pump. This oil pump, which is long-ago GM-discontinued, can still be obtained under Melling M-46. I wonder how many of these they sell anymore?

Another thing he might be thinking of is the fact that most 63-65 327's with solid lifters did use a different oil pump than engines of the same period with hydraulic lifters. Actually, the only difference was the installed pressure relief spring. However, different oil pumps were not used for 283's with solid lifters versus mechanical lifters; for any given year they used the same oil pump.

By the way, the GM oil pick-up screen for your application was GM #3764113. However, it's GM-discontinued. No problem, though. Sealed Power #224-1346 is identical.

[Timothy B.]

Re: C1 Oil Pump question

Donald,

If you keep the rod and main clearances approx .002 be careful with the Melling pump. The Melling will provide trouble free operation but the relief pressure will be approx 60PSI.

This may not seem like a problem to some but my 327/300 with Melling pump has this issue and I don't like it. When I get some time I am going to make a cap to install on the output side of the oil pump with a gauge so the relief pressure can be set by shortening or changing the relief spring.

Any ideas on this are welcome, probably the best approach is to buy the GM 45 PSI spring and install in the Melling pump, check the pressure relief and go from there.

[Dan D.]

Re: C1 Oil Pump question

I have just been fighting this issue on my 327. The Melling M55 pump is the one with the whimpy casting that is prone to breakage. Do not use it. The Melling 10553 is the best pump for this application. It has the full size casting, similar to the original GM pump. However, it is standard volume, high pressure. Standard volume is fine - just what you want. But the high pressure is not what you want. It comes with a 70 PSI pink spring installed (Melling # 55070). They include with the pump a 58 PSI yellow spring you can use (Melling # 55058). This is okay for 63 and up solid lifter engines with a 80 PSI gauge. For older and hydraulic cam engines you should use their green 49 PSI spring, # 55049. I talked with the Melling technical people this week. They are sending me a green spring at N/C. Do not try to adjust the length or tension of an existing spring. This is a crap shoot at best. Melling technical line is (517)787-8172 and they are helpful and knowledgeable. I do not know about Sealed Power, except they may just be Melling's.
Gook Luck. -Dan-

[Timothy B.]

Re: C1 Oil Pump question

Dan, I too received the green 49lb. spring from Melling and have not installed it yet.

My M55 pump is a 1980's pump that is the thick casting. I believe the original relief spring is black maybe natural in color and the green spring Melling sent looks stiffer then the black spring. I am not convinced that this spring will yield less pressure on my M55 but I don't know about the 10553 pump there may be some different spacing where the spring rests.

Don't get me wrong, it's a very nice pump with pin oiling and assembled better than the GM pump the way the shaft goes completely through the drive gear then a drilled hole and roll pin to keep the gear locked to the shaft. I just don't like the additional oil pressure.

[Dan D.]

Re: C1 Oil Pump question

Well Tim, don't know now. The man says it is a 49 # spring - I have to take him for his word on that.

I am still at least 2 or 3 weeks away from starting my engine. That will tell the story. Wonder if there is a difference between an older M55 and a new 10553. When I get my spring I will measure it and post the length, wire dia., and # of turns. You might call Melling and voice your concerns - see what they have to say. -Dan-

[Timothy B.]

Re: C1 Oil Pump question

Dan,

Melling is not interested in hearing from me but I would appreciate it if you can report back the pressure with the green spring after your run in of the engine.

There could very well be a slight difference between the older M-55 pump and the 10553 you have.

[Dan D.]

Re: C1 Oil Pump question

Sure Tim,

I was going to do that anyhow - for all to see. Might have the spring today, but more likely tomorrow. -Dan-

[Dan D.]

Re: C1 Oil Pump question

Received my 'green' spring from Melling today. Below is a spring configuration I just did on all 3 springs:

Pressure color P/N length dia. wire dia. # turns*

49 green 55049 2.3 .314 .037 23

58 yellow 55058 2.17 .318 .042 21

70 pink 55070 2.27 .315 .041 21

* Number of turns includes the doubled up turns on both ends.

I can't seem to picture the pressure differences from these numbers, so I have to take Melling's word for it. Wish I had a pressure gauge.

The 10553 pump is standard volume, high pressure. It comes with the 70* spring installed, and a 58* spring included in the box. If you want 49*, you will have to order it. It is the full size casting, like the OEM.
The M-55 pump has the wimpy size casting. I believe the spring configuration is the same as the 10553, but I can't be sure.

Gary Ramadel, I would think hard about using your M-55 pump, especially with the high pressure spring. I don't know how hard it is to break this casting, but if you do it is most likely the end of the engine. I took my M-55 back to my machine shop and got a 10553. They gave me full credit for the M-55. -Dan-

[Timothy B.]

Re: C1 Oil Pump question

Dan,

Thanks for the #'s on the springs you have for the Melling oil pump. The green spring is exactly the same as I have and the yellow spring measurments are the same as the natural spring that came with my old M-55.

In the archives there are specs for the GM 45psi relief spring and it may be interesting to compare.

[Domenic C.]

Re: C1 Oil Pump question

hi joe i have oil pan gm # 359937 with trap door on a 283 270hp engine dual quad on 1957 corvette and wondering what melling oil pump to use and what spring pressure ? thanks for your help domenic

[Joe L.]

Re: C1 Oil Pump question

hi joe i have oil pan gm # 359937 with trap door on a 283 270hp engine dual quad on 1957 corvette and wondering what melling oil pump to use and what spring pressure ? thanks for your help domenic

Domenic-----


Assuming that the engine block is a 1957 block, original or otherwise a 1957, you will need to use a Melling M-46 pump. This is a standard pressure, standard volume pump, as-original. In conjunction with this pump you will need to use a Melling 55-S oil screen/pick-up assembly. These pieces are compatible with an original 1957 block + your GM #39937 replacement oil pan.

[Joe M.]

Re: C1 Oil Pump question

My engine on my 1960 was rebuilt 9 years ago and ever since that time, at cruising speed, the oil pressure gauge stays at 60 psi. At idle, it drops. My mechanic informed me that he did not install a high volume pump (I did not ask what type of pump he installed). I suppose the gauge could be incorrect. I have wondered about the high reading for 9 years, but the engine is working just fine; so I guess there is no reason to be alarmed.