Straight-6 Oil pressure

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Old and Slow
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Straight-6 Oil pressure

Post by Old and Slow » Thu Apr 06, 2017 8:32 pm

Does anyone know what the length of a new oil pressure relief valve spring in a 213E engine is?
Mine has the vane-type oil pump fitted, and was running at 30 psi; the spring length is 1.965"
Calculating the spring force and piston area meant that adding in a 0.96" spacer between spring and piston would raise the oil pressure to 37.5 psi, which it has done (i.e. the calculations were correct). :)
My Zodiac handbook states the oil pressure should be 50-60 psi (but.... Richard Prosser, PO confirmed he drove the car hard, and the engine rebuild was years ago so the low pressure could be easily explained by worn mains, big ends etc).
If no-one knows what the spring length should be, what pressure are other Sabre Six & straight six coupes getting?


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Re: Straight-6 Oil pressure

Post by chrisgallacher » Thu Apr 06, 2017 8:58 pm

Mine runs almost exactly 50 psi hot at pretty much anything over say 1500 rpm. It drops down at hot idle, to say 20-25 psi-ish. It was rebuilt about 5 years and not that many thousand miles ago, but it was always pretty good on pressure. Can't help with spring lengths I'm afraid.

You're not using a Flexolite spin-on filter conversion kit by any chance Philip? If so, and without modification, the central threaded boss which comes with the kit - with the oilway down the middle - is too long on the engine block side and largely obscures the internal main oilway in the block to/from (can't remember direction of oil flow) the oil filter. There's a thread on here somewhere all about this in detail: it can reduce oil pressure substantially. Flexolite knew about this but for a long time chose to ignore the problem - no idea if they've corrected things now or not.


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Re: Straight-6 Oil pressure

Post by Oaksey » Thu Apr 06, 2017 9:30 pm

All i can suggest is give Iain a ring. All my pumps are the 'normal' kind so spring lengths are probably irrelevant


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Re: Straight-6 Oil pressure

Post by Old and Slow » Thu Apr 06, 2017 10:55 pm

Hi Chris,
Thanks for the feedback: I'd already picked up on your comments re: Flexolite threaded boss lengths when searching the archive.
Mine's fitted with a take-off boss and separate "Purolator" filter holder. That doesn't mean the thread isn't too long though. I've just changed the oil, so I guess I'm a bit reluctant to take the filter take-off to bits, however I might have a look.The oil pressure was a steady 30 psi across the rev range even on tick-over (around 1300 rpm; high to avoid stalling before fully warm, because the Webers have no choke) which implied to me the relief valve was always operating. Having upped it to 37.5 psi this afternoon I'll have a run out at the week-end and see what happens.
Hi Josh,
I'm not sure why some engines had vane pumps and others gears, and it probably means they had different characteristics needing different relief valve designs etc. Yes, Iain Daniels did the rebuild for Richard, but it's so long ago now I doubt they'll have records. I might try Kevin at Zodiac to see if he stocks the springs, if they are cheap I might buy one, just so I can measure it.


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Re: Straight-6 Oil pressure

Post by heathsabre » Thu Apr 06, 2017 11:13 pm

Our Sabre Six runs at about 40psi hot. We use straight 30 grade oil as recommended many years ago by Robin Rew. I initially thought the oil pressure was low. Iain, who built the engine, assured me that it was OK. And it has remained so for 7 years and 11,000 miles.


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Re: Straight-6 Oil pressure

Post by Old and Slow » Mon Apr 10, 2017 8:14 pm

Thanks for all the feedback. Here's the result of a drive at the week-end:
The pressure is now 37.5 to 40 psi, it doesn't drop on tick-over, but as I said above, tick-over is around 1300 when warm. To me this implies that the bearings are OK and it was only the pressure relief valve that caused the low reading.
I'm using Classic Oils Heritage 20W50.
I made a sump gasket using 3 mm closed-cell neoprene, it appears to have cured oil leaks, but there is a drip from the oil cooler take-off pipe and I can't easily get to the jubilee clip to tighten it! Drat.


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Straight-6 Oil pressure

Post by daveb » Thu Jun 07, 2018 8:23 pm

Re length of centre bolt on filter or adaptor, think if you remove either oil gauge take off pipe or small blanking off screw on top side of engine casting where filter fits and insert and apply finger pressure on say an 1/8"- or perhaps a slightly larger 1/4" piece of rod whilst loosening and retightening the centre filter/adaptor bolt the rod should not be clamped by the filter bolt, if it goes tight then centre bolt is too long. Its been a while since I checked this. If you want I can recheck the procedure and put on forum.


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