I‘m in the slow process of rebuilding my 261 Chevy 6. The crank needs to be ground and I think I found why the engine was lacking oil pressure. The pump looks good , it has no wear marks , but cleaning and inspecting it, I found the relief valve spring had a few broken coils… I‘d like to reuse the pump if I was able to come up with a new spring for it. Any ideas where I should go shopping?
If your having the crank reground talk with the shop doing the work. Melling used to offer kits that would have a new spring plunger and gasket. I never really bothered because the pumps weren’t much more money especially if I factored in labor.
I know. But I´m kind of a cheapskate sometimes, and a 100$ plus stovebolt oilpump is an easy 200€ unit ´til it´s shipped here, that´s why I thought I´d try and see if I can find out what specs a replacement spring has and see if I can find one locally. If that´s not the case I see a new pump in my future Thanks, that´s a great idea. I will ask them and also look if I can find something out about the Melling rebuild kits.
You could find a stiffer spring and up the pressure a bit. If the pump isn't worn, why replace it? You will need to find a way to run the pump with a gauge to set it. GMCs run a higher pressure, I think about 60 psi, and the pump is higher volume. I don't know how good the new replacements are.
Tonight I took some measurements and guestimates off my broken spring. Outer diameter is 8mm, wire dia is 1 mm and the overall length used to be 56-58mm , whatever that is in inches. I found a spring that is 8x1x60mm that ´ll go and pick up at my hardware place next week. Then I can test and see at how many psi the relief valve opens and go from there.
Can't get a positive that the 235 oil pump is the same in my search's. If it is, Melling's K29 is the repair kit. Several vendors sell it but the cost isn't cheap since it's just the spring your after. Keep in mind, you can guess all you want about the springs size. But what about it's rating? Very important.
rockauto does not show a pump for a 261, but I think it´s just the same asfor the 235. Mine has M45 cast in it which make me think it´s a Melling M45. As far as the spring rating, my approach would be to run the pump and see at what pressure the relief valve opens. Then preload the spring until it opens in the 45-50 psi range, I think I read somewhere they were in the 30 -40 psi range from the factory...
Found Mellings info and it's the same. https://www.melling.com/parts-lookup/ Doing the testing, nothing further to say.
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