What is happening here?

[CycleSi]

A mate of mine has just had a new SBC 400ci engine from a very well respected UK engine builder. However, he has a problem with oil pressure and we now totally perplexed as to what the problem is and we're now questioning our sanity. Have we missed the bleedin' obvious as they say?

It was run on the engine builder's dyno and was fine - it made 540 bhp and similar torque so it's a bit of a beast. Dart heads, Lunati solid cam, forged pistons, etc.

He got it home, filled it to the correct level with 20/50 oil and drove it. Noticed the pressure seemed low (around 20 psi) and it didn't rise much even when revved. When it was warm the pressure dropped and the oil light came on. Rechecked the oil level and topped it up a bit (less than a litre) and started it. This time it seemed better - 40 psi on idle but again it dropped right down as it warmed up.

We then questioned the gauge as it was an electrical gauge and not mechanical. He then bought a mechanical gauge and the pressure readings were the same as the new gauge so we have ruled that out.

Next, the engine came back out as l wondered if the oil pump pickup had fallen out or if the pump drive from the distributor had broken, but again nothing obvious.

We're now stuck as we have run out of ideas. The car is an Ultima by the way.

The problem seems to be a combination of low pressure AND erratic pressure too.

Any ideas, what else should we check, are we just barking mad?

Thanks Guys, (l feel a 'Wilf' moment coming on).

[Purple AK]

Hi Si. You really DO NEED to be talking to the engine builder not us If you're lucky if could be something simple like a dodgy oil pressure relief spring. But.........................!!!!!!!!!

[CycleSi]

You're absolutely right of course - l've told him he needs to go back to him and get it sorted but it's not as easy as that geographically and in terms of time, etc.

[wilf]

So many things it could be, but my money would be on an oil gallery plug having come out, or some other similar issue.

This engine HAS to go back to the builder, sorry. The more you play around with it, the more leeway you are giving them to wriggle out of a fix. Assuming they are the wriggling kind, and not all are, of course.

The only other non-mechanical thing that might just give this issue is a much too high oil level, leading to oil aeration.

[dave]

Originally Posted by wilf

The only other non-mechanical thing that might just give this issue is a much too high oil level, leading to oil aeration.

What, like this Wilf?

[mikey]

Dont touch it leave it to the builder. If he hasn't trashed the bearings which you should hear if he has, it is more than likely the pump that is at fault.

There is one other thing I can think of - does it have a deep or kicked out sump or non original. If it has the standard dip stick markings are useless and if you have a high volume high pressure pump fitted and are not putting sufficient oil in, it may be evacuating the sump and drawing air.

Bet thats a bit of a pig to drive on the road with those figures from a 400.

Hope you get it sorted.

Mike

[johannlitherland]

Sounds like a daft one but is the engine angle radically different when in chassis/ requiring a re-callibrated oil fill guide, as you did mention the problem getting better with more oil?

[wilf]

Mikey - you are a pussy, those output figures are luvverly...........makes one treat the throttle like it could kill you at any minute, just how it should be. And just how the originals were.

[mikey]

Originally Posted by wilf

Mikey - you are a pussy, those output figures are luvverly...........makes one treat the throttle like it could kill you at any minute, just how it should be. And just how the originals were.

Only for track use Wilf


I wont be wound up as I know you are more inteligent than that Wilf.

Its about the power curves and not the BHP - Those figures are best for the track or motorway whereas you would design a more sensible setup for fast road, certainly if you lived in Yorkshire and travel mostly on the country roads.

Every man for his own, it is probably built with the track in mind.

By the way I think to qualify for the pussy level it will sit more happily when we have finished the shootout.

Should be easy as I am only knocking out around 500BHP but the powers not banded its in from the bottom end.
Mike

[wilf]

Aah! Yorkshire roads-why didn't you say so?

Seriously - only funnin', and anyway, we haven't seen a torque curve for the motor in question here, so we don't really know its true characteristics - mind you, 540bhp out of 400 nat asp ci might just give us a clue...........revs anyone?