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I believe that is the proper fitting. Also don't believe any restriction to the tappets will be an issue because there is no flow to speak of. The pressure will still be there but the minimal volume amount to keep lifters filled or lubed shouldn't be much.

I do have the small hole in the post in the middle of the oil canister, nothing else on the other side going to the tappets but the oil line itself.

That sounds correct. A small hole or narrow slot in the central tube of the oil filter housing. I agree with HH56 about the fitting having a restricted flow to both filter and tappets. Like he says not a lot of flow needed, and pressure is there to keep the lifters pumped up. I am going to check the fitting and oil filter on my 356 and see what they looks like. I believe your question has helped us all. Thanks.

(o{I}o)

The oil filter-hydraulic lifter-oil pressure sending unit fitting on my '47 Custom (356 engine) is just like yours. My oil filter (Fram) also has a small hole in the center tubing in the filter housing. As I recall, it is the same diameter as the restricted ones in the fitting. While there, I also checked the pressure at this fitting and measured 40-45 lbs. A bit on the low side as the manual says it should be 50 lbs.

(o{I}o)

JW

Is that pressure reading hot or cold? I'm going through a 1941 160 that i bought recently with a mysterious past. The pressure is above 40 lbs cold, but falls significantly below that after abut 1/2 hour of driving. I'm starting the investigation....

Regards


John Harley

I would really think, for these motors, that 40 cold and around 20 idling, hot, would be a good reading. Someone said somewhere, that it only takes a few PSI to float a bearing. My 288 ran smooth and was perfect, albeit dirty and grimy, and had about those same readings.

Quote:

John, connecting into the oil pressure gauge/hydraulic lifter/oil filter fitting with a mechanical gauge I had a reading of 40 lbs with a warmed-up engine at idle speed. Move the speed to fast idle and it went to 45 lbs. My other oil pressure gauge (Stewart Warner mechanical) that is connected to the last tap on the main oil gallery reads a bit lower. It shows no more than 40 lbs at running speed and temp and down to 20 lbs at idle. There seems to be a difference between what pressure is available for the hydraulic lifters and for the main bearings. I would appreciate it if you would share your findings with us. Thanks.

(o{I}o)

JW, sounds like you have a nice, tight engine; a pressure of 40 psi at hot idle is certainly fine. With hot, idling pressure that good the reason you don't hit 50 at road speed is probably a bit of fatigue of the spring in the oil pump relief valve. If you wish to bother for peace of mind or whatever, you can almost certainly achieve the spec. 50 psi at road speed by adding the thinnest of shims to the spring in the oil pump relief valve.

The higher pressure spec for the 356 engine is no doubt because you have 4 more main bearings with their associated clearances which allow additional pressure loss.

As to the filter restrictor, it really shouldn't make any difference to the engine operating oil pressure if it's in the tee before the filter supply line, in the fitting at the filter inlet, or in the filter outlet (internal post) though placing it on the supply side would seem more logical as it would maintain the pressure differential across the filer media, with a restrictor on the outlet wouldn't do.

O_D --- The 21st Series shop manual calls for 50 lbs for the 356 engine, and 40 lbs for the 282s, measured at the fitting. Thinking about it, the difference in pressure between the circuit that supplies the hydraulic lifters and the one supplying the rest of the engine, as measured by separate gauges, must be due to them being on separate circuits. The original electric dash oil pressure gauge is connected to the lifter-filter circuit. I was thinking about installing a thin shim under the pressure relief valve spring to boost the pressure a bit. What thickness would you recommend, .050-.060"? Thanks.

(o{I}o)

I only had occasion to shim 1 356 pump relief valve and it was too long ago to remember the particulars, but I'd think something considerably less than you're thinking. It's a short, stiff spring, maybe something in the order of 0.015" to 0.020" for a start? It's so easy to get at that a little trial and error wouldn't be much work.

Something else to think about - if the pump cover plate has ever been removed and the gasket replaced, the thicker the gasket the greater the pressure loss across the end of the gears - the original gasket was VERY thin - when I did the last one I used a piece of supermarket shopping bag craft paper, shellaced. If you do take the cover plate off, check for gear wear patterns on the cover; these also act as a path for lost pressure and if so, the plate can be surfaced back to smooth.