<Expletive> oil pressure still lacking

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Zaphod
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Re: <Expletive> oil pressure still lacking

Post by Zaphod »

DavidOliver wrote:
Sat Dec 31, 2022 13:29
Zaphod.
With the auxiliary housing off you can check to see if your cam bearings are shot allowing a lot of oil to go up there, without knocking noises from below.
In the same way we bleed brakes with a pressure bottle you can set up a pressure feed to the cam bearing inlet from the exposed engine block and see what pressure you get. This will be independent of crank oil feed.

There is also a 6mm plug on the front of the block to seal the oil gallery, I doubt you are losing pressure there as you would see oil spirting at the engine front. Worth checking.


Dave the cog.
I would have noticed the oil leak by now! it seems free of those apart from when I didn't have the gauge properly screwed in.. I do seem to have a lot of oil getting to the top of the engine so this may be the issue. I do have a silly question however.. where is the cam bearing inlet? I am guessing it's in the recess that runs over the top of the aux housing?
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1957 MGA 1500
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel

Pete Boole
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Re: <Expletive> oil pressure still lacking

Post by Pete Boole »

The cam bearing surfaces are fed via the drillings in the cylinder head from the block (this is where a restrictor is often fitted), into the cam housing and then into a reduced-diameter void space around the belt end of the cam itself. From there oil travels through the central bore of cam itself to the bearing surfaces.

Pete

Zaphod
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Re: <Expletive> oil pressure still lacking

Post by Zaphod »

Hi Pete,
The head is still fitted, what I am uncertain of is as to where I should force oil to check the cam bearings are not too slack, I can see how this could cause low oil pressure if the bottom end is not so bad, previously having had low oil pressure on a rover V8 that was eventually tracked down to worn rocker gear!
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1957 MGA 1500
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel

Pete Boole
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Re: <Expletive> oil pressure still lacking

Post by Pete Boole »

There's no way to pressurise the top end only. Oil flows freely from the pump to the main bearings and cam housings. The only place to interrupt it is at the junction between the head and block, unless you get very creative with some dumbbell-style cylinder head oil gallery plugs. Even then you wouldn't know what "normal" was for flow in the cams/cam housings.

I'm well on the way with my oil pressure relief valve testing rig - just need to order a new pressure gauge and some hose after the weekend, and do a bit more fabrication work. I'd be happy to test yours once it's set up, unless you're certain that it's OK.

Pete

Zaphod
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Re: <Expletive> oil pressure still lacking

Post by Zaphod »

That would be great, but in the mean time I have taken the PRV apart and I started a washer to pack it out, it now feels much more like Mike’s description of the effort required to open it (needs my palm rather than just a finger to open) however I pinched the o-ring putting it back together and lost two of the oil pump bolts… so stopped there.
What size is the o-ring?
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1957 MGA 1500
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel

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Hawaiis0
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Re: <Expletive> oil pressure still lacking

Post by Hawaiis0 »

Hi Stewart
I have come across my old oil pump with a stripped locking thread.

Happy for you slave in if it helps.

Stu
Nothing is fool proof. Fools are clever!

Pete Boole
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Re: <Expletive> oil pressure still lacking

Post by Pete Boole »

Just a thought - do you have the o-ring on the distributor shaft? Is it in good condition? What are your measurements for the oil pump clearances?

Pete

Zaphod
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Re: <Expletive> oil pressure still lacking

Post by Zaphod »

Yes I did replace the O ring on the distributor as it looked a little 'flat'. Currently taking the sump off to change the infamous nylon olive and check the state of the big ends as it has run for some time now with little to no oil pressure so I'm thinking i really do need to inspect them as a minimum before going any further. I know I was warned to do this when I first got it! I have also found my plastiguage kit so I can check the running clearances. Would be nice to do the mains but I don't think that is an easy task with the engine in
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1957 MGA 1500
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel

Zaphod
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Joined: Mon Aug 23, 2021 21:38
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Re: <Expletive> oil pressure still lacking

Post by Zaphod »

OK, the sump is off, worryingly there was a fine layer of grey removed with one sheet of toilet roll in the lowest part of the sump, however every other part of the sump was spotless, as is everything else. As the engine is at TDC and the belt is off I can’t take a big end cap off to see what its like yet. Img going to remove the pick-up pipe and replace the olive tomorrow, then when the aux housing is back on and the belt tensioned I can move the crank to get the caps off and take a look. One question, should it have what appears to be a fabricated baffle plate?
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1957 MGA 1500
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel

Pete Boole
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Re: <Expletive> oil pressure still lacking

Post by Pete Boole »

Yep - sheet steel baffle plate is sandwiched between sump and main bearing panel, but is bolted to the sump prior to assembly - make sure all the bolt holes line up. If the engine was assembled with Graphogen paste it leaves grey crap everywhere.

Pete

Zaphod
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Re: <Expletive> oil pressure still lacking

Post by Zaphod »

How ever all is academic now. What I have found out is my engine is one which should have 0.0015" oversized main bearings (that is the outer diameter not the inner) and the main bearings in it if the part numbers on the receipts are to be believed are standard outer diameter This is almost certainly the reason for its near zero oil pressure. The crank has been reground 0.0010" So what it should have had were 0.0015" over sized outer diameter bearings with a 0.0010" under sized inner. Unfortunately such things are now made from purest 24 carat unobtanium and have been for some time and the blocks best use is as a coffee table.. I am to put it mildly disheartened, any spares worth grabbing off it before the scrap man comes?
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1957 MGA 1500
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel

Pete Boole
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Posts: 3711
Joined: Tue Apr 04, 2006 21:28
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Re: <Expletive> oil pressure still lacking

Post by Pete Boole »

Have you seen the stampings on the main bearing panel? I thought the engine had been rebuilt - can't remember now :roll: . I might be interested in buying the engine - pm me before you scrap/sell it.

Pete

Zaphod
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Re: <Expletive> oil pressure still lacking

Post by Zaphod »

Yes it had been rebuilt, but not very well, all the tappets were out which I have sorted, and yes it has the 15 stamped in the bearing panel and the receipt from QED for the main bearings is for the standard OD bearings. The crank has been reground 10 thou. If I can get the bearings I will pull it apart and fix it but it seems that is unlikely
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1957 MGA 1500
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel

Zaphod
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Posts: 242
Joined: Mon Aug 23, 2021 21:38
Model: Excel SE
Colour: Blue
Year: 1990
Location: Uffington

Re: <Expletive> oil pressure still lacking

Post by Zaphod »

Just had a chat with PNM, seems they can make the bearings, at a cost about 66% over the standard ones. So the plan of action is get the crank out and check the mains and go from there
Of all the things I have lost I think I miss my mind the most...

1952 MG TD
1957 MGA 1500
1959 Austin Healey Sprite
1975 MG Midget 1500
1990 Lotus Excel

Pete Boole
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Posts: 3711
Joined: Tue Apr 04, 2006 21:28
Model: Elite
Colour: Monaco White
Year: 1974
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Re: <Expletive> oil pressure still lacking

Post by Pete Boole »

66% on top is fine! Good news. It's still staggering that anyone could build an engine without measuring it at any time :roll:

Pete

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