Javelin engine oil pressure

[Forumadmin]

Moises, You should not worry about your oil pressure. At 1000 rpm hot that is good.

[Moises]

Thank you Keith

[David Morris]

Hi Moises,

Thanks for your very interesting posts. I would discount any worries about the oil pressure gauge. It's demonstrating quite well that the oil pressure rises when the rpm is increased, never mind that it might not be accurate. So, now we know that the engine oil is escaping within the engine. Whether this is due to worn bearings or a slack oil pressure relief spring, we don't know. I suspect the latter, as you were able to achieve 4500 rpm, so the engine noise must have been bearable!

Personally, I would stick a disc of cardboard over the oil gauge, with a smiley face on it, and just carry on! Until, of course, you decide to investigate where the oil is escaping internally?

All the best,

David

[Moises]

Thanks David, I will investigate. In the meantime I will listen to you and not look at the pressure gauge.

[David Morris]

Hi Moises,

Thank you! Sorry if I was being jokey? But seriously, you do have enough oil pressure for the engine to survive. It's escaping somewhere internally and I am sure you will find the cause. Perhaps a change to a higher viscosity oil might help?

I did learn some time ago that the engines that were intended for hydraulic tappets had much larger oil feed holes where the cam follower fits into the casting. You can feel the size of this hole if you remove a follower and feel inside the hole with your finger. The castings for hydraulic tappets had oil holes in the side of the bore about 7mm wide, whereas the later solid tappet engines had holes about 2mm dia. Apparently, using solid tappets in engines intended originally for hydraulic tappets would lead to problems similar to yours.

I also heard that Jowett's changed over to solid tappets due to the cost and availability of the hydraulic tappets, which were sourced from the USA. This change came about quite suddenly, and I am sure Jowetts has engine castings in the factory that had already been machined and you cannot put metal back, having already created the larger drillings! Jowett's were renowned, like most Yorkshire folk, for not wasting money!

If you are curious, it might be worth a bit of investigation?

All the very best,

David

[PJGD]

At long last I have got around to finishing my technical article on the Jowett oil pump and lube oil system that I mentioned back in September. At 13 pages, it has come out overly long but I hope that you find it a useful addition to the Jowett canon. Comments and critique are welcome.

To whet the appetite, I have added some the graphics here that also appear in the document:

[Forumadmin]

Philip, thanks for the excellent article.
Your comment about ' the point of oil pressure is to generate flow ' almost defeats the need to get the pressure correct. A tight engine needs more flow and thus more pressure, but a loose, worn engine needs less pressure as there will be lots of flow.

You really need to know the actual flow through the engine which you might be able to quantify by separately feeding the pump and collecting the flow through the engine into a separate container over a specific time. This is relatively easy to do with a static engine but more difficult with one that is running. Some sort of extended windage tray might do the trick. This could recirculate the oil back to oil pump feed sump if an extended test was required.

As I documented elsewhere on JT I spent many hours under and engine with the sump off but running an oil pump to find out where I was loosing pressure. Very messy, but found it was the camshaft housing that was worn. And then there is the case last year with the non standard cam followers uncovering the early crankcase oil delivery drilling.

The use of thinner oil for testing is reasonable but one with the same viscosity of SAE 30 at 90c but at 20C would be better in the UK!

[PJGD]

Agreed about pressure vs flow: a tight engine has more friction and therefore needs more flow, but actually gets less flow than the loose engine that has less need for it.

Actual flow through the engine is the point of the electronic flow meter. It can tell you the amount of oil that goes into the engine galleries, but of course is not able to differentiate the split between crankshaft, camshaft, and valve train , let alone a breakdown of each individual bearing.