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CycleSi
02-03-08, 09:47 AM
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
02-03-08, 10:36 AM
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
02-03-08, 10:42 AM
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
02-03-08, 01:20 PM
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
02-03-08, 04:10 PM
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?

http://th.physik.uni-frankfurt.de/~hossi/Physics/aero.jpg

mikey
02-03-08, 04:35 PM
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
02-03-08, 04:51 PM
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
02-03-08, 06:57 PM
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. :mrgreen:

mikey
03-03-08, 10:06 AM
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. :mrgreen:

Only for track use Wilf


:oI 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
03-03-08, 07:40 PM
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?

CycleSi
03-03-08, 08:08 PM
The engine has been built to rev to 7000rpm.

l haven't seen the torque curve myself probably because the engine builder in question tends to give just max. bhp and max. torque. Either that or my mate just hasn't read through the paperwork.

Did have an interesting and detailed reply from Dr Dee of Fastco fame and he made some sensible comments about looking closely at the cam and followers as it seems they are encountering more & more problems in the US with cheap Chinese made products.

As of today, a different engine builder has looked at the engine and can't actually find anything wrong with it yet so he's going to dig deeper.

Certainly is a weird one.....

Clarkson
03-03-08, 08:15 PM
I guess it's the strainer to sump pan clearance!

400ci= 540hp?? not so sure,but if it's making that power 7200rpm tops.

slogger
03-03-08, 08:21 PM
I guess it's the strainer to sump pan clearance!

400ci= 540hp?? not so sure,but if it's making that power 7200rpm tops.

Spoke to a mate of mine about this and the only thing he could come up with, if all is ok so far, was the oil pump mating face. If the pump was fitted with a bur the oil pressure could dislodge this and then oil could escape from this gasket-less joint. Just a thought!

Purple AK
03-03-08, 08:48 PM
The engine has been built to rev to 7000rpm.

l haven't seen the torque curve myself probably because the engine builder in question tends to give just max. bhp and max. torque. Either that or my mate just hasn't read through the paperwork.

Did have an interesting and detailed reply from Dr Dee of Fastco fame and he made some sensible comments about looking closely at the cam and followers as it seems they are encountering more & more problems in the US with cheap Chinese made products.

As of today, a different engine builder has looked at the engine and can't actually find anything wrong with it yet so he's going to dig deeper.

Certainly is a weird one.....
There goes any warrantee it might have had then :rolleyes:

mikey
04-03-08, 08:31 AM
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?


I know Wilf - and I know your knowledge on outputs and characteristics is at least comparable to mine.

The oil pressure is a mystery if it was actually showing that on the rig. You aiming to get some more smudge marks on the rear top panel again this year.

Why did you get another engine builder to touch the engine - is it from the states or something. This really could have blown your warranty chances. Best thing to do is if the builder is in the states agree that this option was carried out as an economical way of identifying a problem. If it is a professional builder that is looking at it now, the guyb should not have a problem.

Wish you luck with it.

By thwe way curves - Everest ascent and Killimanjaro (or however you spell it) I guess the useful power will kick in about 3000 RPM. If I was close to reality I would be tempted to advance the cam up to 8 degrees and bring it down say 800 RPM and still leave scope to give good power around 6000 RPM.

However it may have fuel injection that will have flattened out some of the low RPM fun!! - still be worth thinking about the cam advance. I got the Cloyes adjustable jobby with the inspection plate on the timing chain cover. Played about and ended up at around 7 degrees advance - fantastic difference in pulling from around 1800RPM and its still gouud to around 6500 RPM which is fine.

Mike