Oil pump pressure relief springs; pegging the 60-psi gage on SB C1/C2?

[Gary B.]

3814903, used in late C1/C2 small blocks with hydraulic lifter motors with 60 psi gages. The attached PDF is planned as a chapter newsletter technical note in which I compare these springs from an engineering/design perspective that provides some insights into why none of the Melling springs is an exact replacement for the GM spring.

Oil Pump Springs.pdf


Gary

[Scott V.]

Re: Oil pump pressure relief springs; pegging the 60-psi gage on SB C1/C2?

Hi Gary, Excellent article! I am working on building a 340HP for my 63 and was wondering if you have the GM spring number for the SHP solid lifter motors. Thanks!

[Larry E.]

Re: Oil pump pressure relief springs; pegging the 60-psi gage on SB C1/C2?

FWIW> AFAIK GM still sells this spring. A year ago I bought some extra's and replaced the spring in my GM
Oil Pump that was pegging the needle. Results brought is down to below 60#. Car is 66 L75 300HP Base Engine.
Larry

[Duke W.]

Re: Oil pump pressure relief springs; pegging the 60-psi gage on SB C1/C2?

Hi Gary, Excellent article! I am working on building a 340HP for my 63 and was wondering if you have the GM spring number for the SHP solid lifter motors. Thanks!

Late in the '63 model year the two mechanical lifter engines received 55-60 psi relief springs in the same "standard volume" pump as previously used on all '63 engines. This change was accompanied by a switch to an 80 psi gage in the IP, so if your IP pressure gage is 60 use the standard 40-45 psi spring and if it's 80 psi use the 55-60 psi spring. See the latest version of the '63 JG for additional information on the changeover period.

I've always wondered how the plant kept track of which engine and IP pairs to use during the changeover period... or did they?

I'll add that when engines are rebuilt, it is often okay to reuse the oil pump. It's easy to disassemble and inspect for damage or wear. As long as the engine has never ingested any damaging debris it is likely okay with little or no disernable wear because it lives in a bath of OIL. Typical production shops just replace the oil pump apriori because they don't want to be bothered with the simple disassembly, inspection, and assembly process. It's better for them to just replace the pump and charge you the usual price including their parts markup.

Quicker priming can be had by dressing the housing and one gear as necessary to achieve 2-3 thou end clearance.

Good article, Gary.

Duke

[Bill B.]

Re: Oil pump pressure relief springs; pegging the 60-psi gage on SB C1/C2?

Greetings everyone!

In a related, yet unrelated subject, I have a '70 LT-1 that had a Melling M-55A pump installed by the rebuilder. During cold start-up (55 deg F) with 15W-40 wt oil, my instrument panel's 70 PSI gauge would peg against the stop at approximately 1500 engine rpm. It would take approx. 10 mins of driving to get the needle under 70 psi. I felt uncomfortable with that situation.

I emailed Melling and Brian Shimkus wrote back and indicated that the M-55A is shipped with the 78 psi (green) spring - not to be confused with the green 49 psi spring discussed above. He also indicated that the M-55A package also supplies a "standard" pressure yellow spring (58 psi) with a new pin (apparently pins are not reusable). I know that Melling offers a 70 psi pink spring from their website.

I'm thinking next time I have my oil pan down, I'm contemplating reducing the M-55A pump pressure bypass spring from 78 psi to 70 psi. This is a flat tappet equipped engine, so higher operating oil pressures are probably desired compared to hydraulic lifter SBC engines, but I just don't like to see my oil pressure gauge pegged.

Again, not directly related to the original posting, but rather a supplement of some limited data concerning the SHP SBC.

BTW - outstanding white paper on the spring data, Gary!! Obviously, you are an engineer . Keep up the great work!

If anyone has some observed gauge pressure data on stock SHP SBC's, please share. Thanks!

[Bill B.]

Re: Oil pump pressure relief springs; pegging the 60-psi gage on SB C1/C2?

Thanks Duke! Sounds like I may want to use the yellow 58# spring in my application instead of the 70# spring.

(you responded to the thread while I was drafting my post).

B

[Gary B.]

Re: Oil pump pressure relief springs; pegging the 60-psi gage on SB C1/C2?

Hi Gary, Excellent article! I am working on building a 340HP for my 63 and was wondering if you have the GM spring number for the SHP solid lifter motors. Thanks!

[Joe L.]

Re: Oil pump pressure relief springs; pegging the 60-psi gage on SB C1/C2?

Hi Gary, Excellent article! I am working on building a 340HP for my 63 and was wondering if you have the GM spring number for the SHP solid lifter motors. Thanks!

Scott------


The high pressure small block spring was GM #3848911. It remains available from GM.