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BJ8 Oil Pressure

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Correct me if I am wrong but I believe that the purpose of the spring and plunger is one of by-pass. Isn't it true that the plunger is seated @ low oil pressure situations and as the pressure increases the plunger comes off its seat and allows the excess pressure to bleed-off or by-pass to protect the oil system including the oil pump (mouth-full). So if the seat/plunger is poor enough the pressure may not build especially @ low RPM. If the spring is weak then the pressure will prematurely find a relief path and thus not allow a pressure build up. So if you have a bad seat you have big problems. If you replace the plunger (inexpensive fix) you might improve the seal and maybe improve the pressure. If the spring is weak, replace it too as it is cheep. NET NET replace the plunger and spring. As for shimming the spring I have no personal experience but I do respect some who state that such a fix worked for them. I would not shim a new spring however as you would be changing the oil pressure control characteristics and covering up a much bigger problem elsewhere in the oiling system. If your oil pump is weak or your bearings are worn or your rockers are worn then your new plunger never comes off the seat and your oil pressure is low due to leaking clearences. The next easiest thing to do is to look @ the rockers and re-build if necessary. Or perhaps just do it as it too is cheap and easy. If you have done these three things and still don't like your oil pressure then you have three more choices; Rod bearings, Main bearings or the pump itself. Do it all or in sequence and you will eventually see the pressure you are looking for. When you are into the crank mic. it to be sure a new set of bearings will still seal. Keep going until you are satisfied @ the increase. When I get inside my pan I will do it all so I don’t have to open her up again. You may get by doing nothing as some have suggested but @ great risk. These fixes are nothing compared to broken internals and metal spread through out your engine. Peace to all!!
 
Hi Bob,
I pretty much agree with you. One situation comes to mind where oil pressure at hot idle was around 20 psi. Cold oil pressure & hot oil presure at speed was around 55 psi. To experiment, I shimmed the relief valve by about .060". Cold oil pressure was not noticeably increased but hot idle pressure increaed from 20 to 25.

The next step was to increase the spring shim to .250". This increased the cold & hot running pressure from 50 to 60. Surprise - the hot idle presure increased to 40 psi. Hot pressure now runs between 40 hot idle & 60 hot running.

I attribute this dispproportionate increase at idle to imperfect seating of the relief valve at low pressures which was overcome by the overall spring pressure increase. Likely any carbon build up & leakage on the seat was reduced by the higher overall spring presure.

To carry things one step further, I tapped the relief plunger firmly into it's seat via a wood dowel in the punger. Reult was an even greater hot idle pressure with the same 60 hot run pressure. I chose to use a spring which had already taken a set & was less likely to change in the future.

I can only assume that imperfect plunger seating can noticeably reduce hot idle pressure while not affecting hot running pressure to any noticeable extent.(Much more flow at higher rpm makes the plunger leakage less relevent).

In an engine with complete rebuild where the passages can be thoroughly flushed, lapping the plunger to it's seat will assure correct pressure relief operation. Guess it all depends on how perfect you want things to be.
D
 
Dave Great run down. I will try some of your suggested tricks prior to pan removal. Bob
 
Dave Great run down. I will try some of your suggested tricks prior to pan removal. Bob
 
OK Everybody...Here's the update, finally..Replaced the Pressure Relief set-up..no change...Placed a guage in-line to the dash guage and Duh,,Duh,,,DUH got a reading ten lbs greater than the original i.e. 14 lbs at idle, hot (water temp 175 , oil temp 190) . Does anyone think this is acceptable. Dash guage shows 25 lbs at 2500 rpm which would be 35 lbs if the discrepancy is consistent. Also read Geoff. Healey's fix for low OP which was to re-lap the pump. Thoughts? Cheers, David (actor 430) Lamb
 
Hi Bob, 14 Lbs at Idle is not characteristic of the BJ8 engine. A fresh BJ8 engine will show 55/60 Lbs hot running and 30/40 Lbs Hot Idle pressure. A worn engine that is still in good condition will show at least 20 Lbs oil Pressure at hot Idle. However, using the old British standard an oil pressure of 10 Lbs / 1000 RPM won't scatter the internals. On the curious side did you get the correct pressure relief valve for the BJ8. This valve has a recessed nose? The 3000 type valve does not and sometimes it functions OK and sometimes it does not. Just a passing thought.---Fwiw--Keoke
 
Not sure, but did you ever tell us the mileage on the engine? 14# at idle probably gets you through this season of driving with a rebuild over the winter? 14# is not good, but if you are careful you can buy some time.
Changing or rebuilding the oil pump might help. You can check the clearances. However, just an opinion here, if the oil pump is well worn, I would bet the bearings are too.
 
Thanks shorn . Mileage unknown (shows 48 thou.but I'm sceptical!!) Receipts for a top-end rebuild in '02 from Healey Werks but no bottom-end job!!! Looks like a "wait'll winter" (as people have been known to say here in Buffalo) by which time, since I have four shows coming up and don't posess the competence for a full engine rebuild, I'll be looking for a trustworthy engine wizard. Any suggestions??? Cheers, David.
 
Thanks shorn . Mileage unknown (shows 48 thou.but I'm sceptical!!) Receipts for a top-end rebuild in '02 from Healey Werks but no bottom-end job!!! Looks like a "wait'll winter" (as people have been known to say here in Buffalo) by which time, since I have four shows coming up and don't posess the competence for a full engine rebuild, I'll be looking for a trustworthy engine wizard. Any suggestions??? Cheers, David.
 
David,

a few quick thoughts for you.
1. can you contact Healey Werks in Iowa? They should have extensive history of their work for all cars. That can answer your question of bottom end rebuild.

2. When did the oil pressure drop? Was it a dramatic change or did it happen over a period of time?

These engines will run strong if put together properly and usual maintainence. . . Most of us have years of service / miles with no drop in pressure.

Please keep us posted,

Regards,

John
 
Cheers, John.
1) Will contact HW when I return from the UK on July 19th.
2) The car is fairly new to me and I noticed the 20lb pressure on the dial when driving it the 500 miles home from Boston in Feb. but only just noticed the 4lb pressure at idle recently since I have a Moto Lita wheel which conveniently covers the guage!!!! (and I was having too much fun controling the car while I got it sorted!!)
3) Yeah I know...This is my sixth (and best?!?!) big Healey since the sixties (when I drove a 100-6 without ever refering to the OP guage...not sure it even had one..ignorance used to be bliss..now I worry more!!

All The Best, David
 
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