Oil pressure advice

[Hugo 356]

I have conducted an oil pressure test on my 1956 T1 1600 Normal (engine warm) and am getting c. 30 psi at 2500 rpm. Both the A workshop manual and specs book give wear limits of 2 atmospheres (c. 29psi) at 2500 rpm. I do low mileage (maybe 1500 miles a year). Based on this info how long should I leave it before pulling the engine and putting in new bearings etc? Advice much appreciated.

[roy mawbey]

Hugo,

Years ago did some tests on my old and clattery 356C with the larger oil pump, The results did not compare favourably with the manual. I decided to run it as I didn't have the cash to rebuild it. It ran and ran for the next two years till I sold it. It did burn a bit of oil but reliable it was. And the green idiot light never came on when the engine was idling.

My 'A' I have never checked just use the green light and always have changed the oil every 1,000 -1500 miles and the filter every 3000 miles. And always keep a check on the level. My engine was split for overhaul in 1965 and this was a fully comprehensive job. Since 69 when I started driving it I have found out a lot of info on my small oil pump engine. I know I should have a oil pressure gauge but still rely on the idiot light on the dash and my engine has crankcases that have never been split since that 65 job.

I have read many comment on oil pressure and it would seem this rule seems to be the most sensible.

Small pump 'A' engines newly rebuilt and perfect might have 45 psi at 3K rpm engine warm and upto mid 20psi idle.

Average ( used ) 'A' engine when warm 25-30 psi at 3K rpm and 10-15 psi idle.

Cold engines of course might have 70psi at 3K.

If the engine runs well and doesn't smoke like a train then with your pressure I guess with your annual milage it has many more years to run before a problem. I presume your idiot light never comes on at 1000 rpm?

I reckon Mike at PRS might confirm his thoughts on this its so difficult to confirm engine life span as it depends on how you drive it and how much you go near the red line?

Someone said once with a warm engine 10psi per 1,000 revs as a rule of thumb excluding idle means the engine should be probably okay pressure wise.

Cheers

Roy

[simon james]

Hi Roy,(and Hugo!) Thats very interesting. My car (62BT6 S90) is running a BT5 S75 engine, with the larger pump.
I have noticed that on start up from cold there is a rumble for say 2 seconds, which I take to mean a worn bottom end and or LOW OIL PRESSURE? I was always told that engine wear occurred most when things were cold and the oil had not yet circulated. To counteract this I have been popping off the coil to Distributor HT lead and winding the engine over on the starter till the light goes out, then there is no rumble.
I realise that eventually it will need a rebuild or replacing but it goes like hell, indeed today we have been over The strines (hilly range on edge of peak district) and we were racing a guy in a Modern mini badged as a Cooper S (who to be honest was a sh*t driver anyway!) but the thing was that on the hills and round the corners I was pushing him!!! We were going way too fast for the conditions, but my wife did comment that I was driving it like it was meant to be driven!
Which was nice!
Anyway, I have now done the best part of a thousand miles since mending the box. I did change the oil and filter at this time but think I ought to do it again, although the oil is still golden.

What oil would the collective recommend? I am of the opinion that ASDA 20/50 changed every 1k or so is better than some "classic" 20/50 left in for years.
The Handbook recommends Straight 30 Diesel oil for S90 and hard driven motors (like mine!) has anyone ever used this as I thought the 50 component side of things was better for a hot (as in temperature) motor.

[pauldvern]

Hi Hugo,

I had a problem with the oil light coming when hot on on my small pump engine. This was strange as the engine had supposedly had a recent rebuild. In the end I had the oil pump surface skimmed. The two gears wear their way into the pump casing creating a gap between the pump cover and the gears. This allows oil to sort of leak back through the pump losing pressure. Haven't had the oil light on since.

Paul

[roy mawbey]

Simon,

Years ago Porsche would not recommend multi grade oil for 356 cars. I ran with Shell 'Rotella' S 30 for many years. This was a single grade 30 HD oil. In the 60's could understand why they called it a diesel oil. To be honest still don't.

Roll on the years and it became much harder to get hold of and further more they changed the specifications to Rotella T1 the type I should use. So yes, in the end I bought the oil from Halfords a multigrade for classic cars. Seems to have worked well but I think I will change back to Rotella once I find a nearby supplier. ( Porsche also seemed to accept multigrade as well maybe because it was developed further since the 50's and 60's?)

Rotella was used all the time at AFN back in 356 days. In saying all that, changing the oil regularly is in my opinion really sensible. The standard filtration we have is okay but not that perfect. So what you are doing makes sense to me.

I guess its true also the pumps even the large one like yours can wear over time so the delivery when cold is not so good as it was when new. ( Same for the small ones! like Paul and I run on our T2 cars )

Roy

[Hugo 356]

Thanks all for the advice. We have changed the oil pressure switch and the green light now stays off at tickover after a long run. The consensus seems to be that the early A cars with small oil pump make less pressure. Whilst I love working on the car I love driving it more, so plan to keep it on the road unless there're a risk to any of the expensive bits.

[neilbardsley]

I also was using the Halfords Classic Oil in my car but after exchanging an email with Mike Smith I source some off ebay and I used that during my last oil change.

http://www.maxted-pageandprill.com/prod ... aspx?id=26

Mike recommended Valvlene Racing 20/50

Here is the email from Mike. Hopefully he doesn't mind me sharing.

"Oil is a subject that is always raising its head and I sware that I would never try and get into a discussion over it

It is and always has been a real problem for the layman (and I am a layman) so a `Real` Oil Chemist may argue with some of what I am saying

It is complicate and the Oil companies also add the confusion by their Sales Hype

356`s `In Period` ran on Straight Grade Oils (the same as Diesel Engines of the period – Usually Rotella 30)

Oil companies are always changing the specifications of their oils but sometime in the last 10 years the majority of companies started to reduce the levels of Zinc and Phosporus in their oils, brought about by the `Green Movement` and the increased use of catalytic convertors

The Zinc and Phosphorus were primarily in the oil to cushion wear on the camshaft and our little engines need cushioning more than average

We have 2 x Cam Followers sharing each cam – i.e. twice the wear of a car with 1 x follower per cam

Our problem as a company is to supply the best products that we can at a price that people will pay

The best Oils for our engines come from the USA (Gibbs – Millers and Kendal) – with that said there is a trend at the moment towards Motul (French) but more of that in a moment

The American oils are expensive and the occasional delays in availability means that we would need to invest in large quantities if we were to use these all the time

I looked around some 10 years ago and Valvolene came up trumps as being an oil that gave us enough Zinc for an ordinary 356 engine at a price that does not hurt the customers wallet

I had excellent experience of Motul when we used in at a 12-hour race in France (Magny Cour) – 12 x hours on a new engine and at the end of the race we had to top up with 1.5 litres
I investigated it but at that time, it again, meant that I would have had to put large quantities into stock at a high price and Valvolene was satisfying our needs at a lesser price

Andy Prill is now the agent for Motul

As for the Halford oil – it will be being supplied by one of the oil companies and packaged for Halfords. I would need to know more about it BUT it will probably be OK

Hope this helps just a little – but try looking at The Web and looking for the arguments about `Zinc Comment in Oils`"