Engine oiling modifications for improved reliability

[BEpine]

Has any Sunbeam owners with a 1725 engine done this modification, and is it necessary just for a daily driver, not racing.

1. Groove the center main journal on the crank the width of the groove in the bearing shell and approximately .060 inch deep.

2. Drill the oil passage from the main oil galley to the center main all the way with a 21/64 inch drill bit.

3. File the oil pump housing to provide no more than .001 inch of end play for the pump gears.

4. Obtain a new oil pressure relief valve or shim the old one to provide 60 psi of oil pressure. These valves are also prone to sticking if the pistons are too tight.

5. Be sure and remove all the oil galley plugs and thoroughly clean the block. Don't have the block cleaned at the machine shop without also cleaning it thoroughly yourself before assembly.

I'm restoring a Series 3 Alpine. Have a 1725 engine that I rebuilt for my series II back in 1982 and never installed it. I tore it down to clean it up and am now putting it back together. Not sure if I should at least drill out the oil passage before reassembly.

 

[sunalp]

When rebuilding 1725's I alway open up the main oil passages. More oil can't be a bad thing!
Cheers!
Steve

 

[puff4]

Yep, did all those things (and a LOT more) to my engine when I rebuilt it several years ago.

 

[RootesRooter]

Did Alpine racers in the day shim their PRV's to 60 lbs? Some of them must have considered it, but I haven't read of any. I'll stay with the reliable 45 psi with the steel bodied, Arrow Range PRV that doesn't have the sticking problem.

Beyond that, for a daily driver I would balance the works and leave it at that. Maybe add an aluminum oil pan.

 

[alpine_64]

I know people above are not suggesting bodges... Quite the contrary...but so new members domt get the wrong idea...

The adjustable prv mods are a good thing to do... BUT... They do not fix Low Oil Pressure.

If the car has low oil pressure you can do thw OPRV mods and increase the pressure ...but the motor still has clearance issues be it oil pump or rod, cam bearings... Those need to be addressed before there is a benifit of increasing the pressure control... Otherwise you mask a problem for a bigger failure.

On the race prepped motors you can run higher oil psi but depending what you are running you might have to dowel pin the bearings so you dont float them with higher psi.

 

[sunalp]

steel bodied, Arrow Range PRV that doesn't have the sticking problem.

Where do you find those? I'd be very interested to find them.
Steve

 

[Alpine 1789]

The earlier PRV's pop up from time to time and I would think some of our guys here might have one. As I recall, the same valve was used on the late cars when Rootes discovered the potential problems with the brass ones. You just need the valve and the corresponding oil filter base. I put a modified/adjustable one on SV a few years ago.

 

[belmateo]

I found this article that is very clear about oil pressure issues and what to do.

The article is here:
team.net/www/rootes/sunbeam/alpine/mk1-5/techtips/techtips.html

Depending on the specific model relief valve, the regulated pressure should
be between 40 and 50 PSI at 2000 RPM and up.

If the pressure is much lower then that, then either the bearing clearances
are too loose, the pump is shot, the relief valve is stuck open, or the gauge
is not accurate.

The purpose of the modification is not to fix clearance problems, but rather
to increase pressure for modified engines.

 

[RootesRooter]

The stock PRV on Series I-IV is rated at 40 psi hot, at speed, on an engine in like-new condition. Series V PRV's, identified by a dimple on the face of the bolt, are rated at 45 psi.

The SV PRV's started sticking open randomly. A Service Bulletin came out before the mid-point of SV production instructing dealers to replace the SV PRV with the SIV part number if customers complained of low oil pressure. Although its likely, I'm not sure if the factory stopped installing SV PRV's at the same time.

The steel-cylinder Arrow Range PRV is also rated at 45 psi. Those turn up on ebay, NOS or used, but I don't know of a Sunbeam supplier who has them in their catalog. This PRV is a different design, so requires using an Arrow Range filter base.

 

[BEpine]

Thanks everyone for your input. I just drilled out the main oil galley with the 21/64 drill, and performed the oil pump Mod.
I will also remove the PRV and clean and make sure it moves freely in its bore. I do have the dimple on the bolt.