Oil Pressure Relief Valve Spring

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I have a 1933 836 with hydraulic valves. The oil pressure relief valve spring appears to have been broken, their is only the one piece. Can anybody advise what length the spring should be, and what tension.

The valves clatter at idle, due to low oil pressure. Please advise what oil pressure the engine should idle at when hot.

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Hello Bruce, and welcome.

The pressure relief spring often has an unfinished end. I usually put this end into the hollow in the cap screw/bolt that encloses the spring.

Oil pressure is not what keeps Pierce Hydraulic lifters pumped up. The check valves inside the lifter assembly catch and trap the engine oil, and if these are leaking, then the valves will clatter.

Your oil pressure should be around 10#-15# at a hot idle, using 15w-40 Rotella T oil. Lower oil pressure at idle is not a product of the relief valve or spring. The relief system only controls maximum oil pressure. Most 8cylinder engines will run at 30# to 40# at 30-40mph in high gear if the engine is in good shape..

If the oil pump is worn, and the engine bearings are worn, then you will not have your relief valve open at all, the excess clearances will let too much oil through to build up pressure.

An engine can run for a very long time as long as it has some oil pressure, and the engine is not called on to produce a lot of rpm and power.

Greg Long

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Bruce, I measured the oil pressure regulator spring on my ’35 845 Eight as follows:

wire dia – .063

OD .405

ID .275

length – 2.12 uncompressed

20 turns total

10 turns/inch

solid ht approx.26

Calculated spring paramters

k = 31 lbs/in

Mine had a corrosion pit that I worried would fatigue and cause the spring to collapse, so I found a close substitute from Lee Spring. They had a 10 minimum quantity to order and I currently have 8 on hand if you want one (no charge).

That spring is not a perfect dimensional replacement, is slightly longer and I added a .125 thick shim washer to get the the same cracking pressure.

I think a broken oil spring could possibly give you valve clatter since it would bypass a large amount of oil flow from the oil galleries that feed all the bearings and the lifters. The lifters are sensitive to the amount of flow reaching them as they have a tight clearance that is constantly leaking. I chased a tapping lifter that had .001 more clearance than the other 15.

Jim

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