low oil pressure

[Hoghead]

My new to me BJ8 has 20 psi at hot idle and 25 psi at hot running.
Cold idle is 40 but once warmed up it is down to 20
Oil is Mobil 1 15/50 synthetic
Oil filter is stock
Miliage is unknown but I suspect approx 110,000 miles

Just back from a 800 Km trip and it consumed 1 liter of oil which seems a bit excessive.

I have been reading about worn rocker shafts and related low oil pressure issues. Will pull the valve cover and take a look when running to see if this is the problem

Also reading on this forum about the oil pressure releif valve is this not for excessive pressure by-pass.

After all it still has a lot of miles and an engine rebuild may well be required. Any good Healey rebuilders in Vancouver Canada.

 

[John Turney]

.... Will pull the valve cover and take a look when running to see if this is the problem ...

Don't pull the valve cover to look. Just take off the oil filler cap. If it's bad (and after 110,000 miles it probably is) and you take off the valve cover, you'll have oil all over the engine compartment.

 

[Johnny]

Not sure about the Mobil 1 synthetic 15/50. Is that equilivant to Castrol 20w X 50w??

When cold I usually am reading 50+ at startup and around 30 when warm using the Castrol. My car has only 45K miles on it with good compression.

I would remove the pressure valve and clean thouroughly and replace the spring. You could try and re-tension the spring by stretching it a bit then install and check oil pressure again. If it's better, replace the valve and the spring.

If there's no improvement from above, most likely the cam bearings, rod bearings etc. need to be replaced.

 

[Patrick67BJ8]

Not sure about the Mobil 1 synthetic 15/50. Is that equilivant to Castrol 20w X 50w??

When cold I usually am reading 50+ at startup and around 30 when warm using the Castrol. My car has only 45K miles on it with good compression.

I would remove the pressure valve and clean thouroughly and replace the spring. You could try and re-tension the spring by stretching it a bit then install and check oil pressure again. If it's better, replace the valve and the spring.

If there's no improvement from above, most likely the cam bearings, rod bearings etc. need to be replaced.

Instead of trying to stretch the spring it would be easier to put washers in the "cup" area. Do one washer at a time until you get the pressure "up". And like the oil feed tube on to of my rockershaft...it was creased with a hammer & screwdriver to decrease the oil flow through the tube to raise the oil pressure. I found this out only when rebuilding my engine.

 

[twas_brillig]

Here's a list of threads on both the Healey and Sprite (and I think there's one from the MG) regards oil pressure. There'll certainly be some redundancy, but they're worth skimming.

https://www.britishcarforum.com/bcforum/u...Issu#Post749802

https://www.britishcarforum.com/bcforum/u...lief#Post749796

https://www.britishcarforum.com/bcforum/u...oo_l#Post704207

https://www.britishcarforum.com/bcforum/ubbthreads.php/topics/701646/1

https://www.britishcarforum.com/bcforum/u...sure#Post640232

https://www.britishcarforum.com/bcforum/ubbthreads.php/topics/576358/1

https://www.britishcarforum.com/bcforum/u..._pre#Post551682

https://www.britishcarforum.com/bcforum/u...mon_#Post548043

https://www.britishcarforum.com/bcforum/u...lief#Post532542

Doug

 

[Hoghead]

Compression test 140 - 150 with a 30 psi increase when squirting in 50W
Worn rings and probably worn in general

Oil dribbles out the rocker hole at 40 psi cold idle and a 2 inch gyeser at 20 psi hot idle
Seems like worn rocker shaft

What thinks the list on the lowish compression

 

[John Turney]

...

Oil dribbles out the rocker hole at 40 psi cold idle and a 2 inch gyeser at 20 psi hot idle
Seems like worn rocker shaft

...

Yep

 

[RAC68]

If your compression is within 10% between pistons, I’d say you’re all right there. From your description, I’d say your valve train needs to be rebuilt.

One other place that pressure can be lost and is easily overlooked is the timing chain tensioner. When the chain elongates, the tensioner foot can be pushed out of the boor and fall to the bottom of the cover. This allows oil directed to pressure the foot to flow unabated and reduce pressure.

Hope this helps,
Ray (64BJ8P1)

 

[EV2239]

My father had one in the sixties as did my wife and I and the best they ever seemed to manage at about 80mph was just above 40 psi.

I've just bought another BJ7 with a lovely smooth and quiet engine, absolutely no knocking on start up after a week of not running, nor when hot, engine sounded really good and rocker shaft looked good enough, but I was lucky to get 25 PSI when hot, so I bought an exchange rocker shaft assembly from AH spares (I'm in UK) and now it's just about 40 when hot and I'm doing around 70.

The engine sounds sweet as a nut too, but it's alarming after a TR3A than holds between 60-70 most of the time!

 

[Randy Forbes]

...

Oil dribbles out the rocker hole at 40 psi cold idle and a 2 inch gyeser at 20 psi hot idle
Seems like worn rocker shaft

...

Yep

I usually weld up the fitting feeding the rockershsft oil tube, then redrill it "slightly" smaller. All the engine needs in this area is a steady oil film, not a flood.

Note too, how this was assembled: thread the Banjo-Bolt fully (but not tightly) into the aluminum riser block, carefully aligning the stub end into the locating hole in the rockershaft. Lower the rockershaft assembly into place and start the flare fitting on the tube onto the (male) fitting threaded into the head casting.

Too many people get the bottom fitting started first, then try to force the Banjo-Bolt into submission, resulting in stripped threads in the aluminum riser block.

This riser had to be repaired with a ReCoil insert (BSP 1/8-28):

 

[TimK]

I have 100,000 miles and a rebuilt rocker shaft and new bushings. I have 60lbs at cold idle and 20lbs at hot idle. On the road (at about 2,500 rpm) I have 60 lbs when cold and 40 lbs when hot. I use 20w50 No smoke at all, no loss of oil (except a few oz. to leaks.) I have a new oil relief spring not yet installed.

 

[Hoghead]

Randy - Thanks for the tips

Rebuilt rockershaft ordered from AutoFarm in Canada and will fit it next week and report back. Relief valve will also be fitted and see if there is any incremental change after the new rocker shaft

Thanks to all for the help

 

[EV2239]

Very nicely done Randy, size do you re-drill the rocker feed fitting union to?

Ash

 

[Randy Forbes]

Very nicely done Randy, size do you re-drill the rocker feed fitting union to?

Ash

I don't remember off the top of my head, but somewhere near 60% - 70% of original area.

You're not trying to starve it, so much as limit the flow at high RPMs (when the oil pump is producing maximum output).

 

[EV2239]

Makes sense Randy, they do pump an enormous amount of oil up there.

Ash

 

[Randy Forbes]

Makes sense Randy, they do pump an enormous amount of oil up there.

Ash

I know, right?! With a badly worn rockershaft, you can really flood the rocker area, leading to seeping around the valve cover (since 99% of them have been deformed from over-tightening and incorrect fasteners...).

I still have eight or nine (8-9) of those BSP 1/8" X 28 ReCoil inserts left, if somebody has a stripped pedestal they want saved. E-mail me: erandyforbes@aol.com

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