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MG MGB GT V8 Factory Originals Technical - Chevvy low oil pressure?

Hi All, Friend has a LR Vogue "Overfinch" fitted with a 5.7 Chevvy engine. Circa '91. Recently ran it for short period with a bad rad leak resulting in a knock when engine was hot. Local dealer told him that it would be more expensive to remove and overhaul engine than to replace the engine??Friend conceded and a new engine was fitted to LR but garage reported low oil pressure and blamed oil cooler (non standard fitment as prev engine was high performance) for this??? Uprated oil pump duly fitted with no effect. (thought the mains gave you oil pressure?) Garage now talking about returning the new engine under warranty to supplier?? Any views from the chevvy brigade/anyone?? Regards, Danny.
D R Smith

Danny,
How low exactly is the pressure we are discussing here?
In most US V8 engines the pressure is about 10 psi per 1, 000 RPM as a general guide. So look for about 30 psi at 3 000 etc.
Is this in the ballpark ?

Cheers , Pete.
Peter Thomas

Sure the gauge is accurate? And if it is, try bypassing the cooler and checking pressure, easier than yanking a motor and find out that's not the problem
greg fast

Of course if the garage is REALLY stupid, they might not have put in enough oil to fill the aftermarket cooler...
dave

Hi Pete and Greg, Dont know what figure garage thought was low oil pressure but your reply is really interesting cos my Rover V8 normally runs at 50psi at anything over tickover. They are LR dealers and wont be used to a chevvy engined car, so might have freaked at seeing only 30psi at half revs. Spoke to friend tonite and he'll pass that info onto the garage tomorrow. Does that mean that at 1k revs its only showing 10psi!! Greg, i already asked friend to query if garage had checked oil pressure against a known gauge. Many thanks. Danny.
D R Smith

Dave, Couldnt believe that they would blame the oil cooler for the low oil pressure. Wouldnt surprise me if they hadnt put enough oil in to compensate. Danny.
D R Smith

Danny,
The first time I came on this I too thought it was a mistake and contacted the printer of the workshop manual as well as a very reputable Chevvy place locally.
Both confirmed the pressure at about 10 psi / 1k RPM.

Having a background in the old type Mini Coopers I was loking for a fault as well and figured pressure at that low level could not possibly do the job. It does.

As an aside it is worth remembering the difference between pressure and volume in oil pumps. Chevvy oil pumps are low pressure but shift considerable volumes and go carefully on the subject of after market high pressure pumps since too much will blow seals etc.

Also it is worth having checked the basics like the oil pressure relief valve spring is seated correctly and is at the right rating and so forth. Anyone can make a mistake.

Cheers , Pete.
Peter Thomas

Pete, Further info from friend this am. Garage manager phoned to say that second engine is now in and running sweetly, although he did mention (why?) that the oil pressure on idle was only 10psi!? Again strongly suspect that garage had no experience of US engines and freaked when first new engine showed "low" pressure readings on start up and when running. He did remark that when running normally that it was indicating 40-50psi now. Maybe they are giving it stick on motorway to prove that it can get up to a "normal" pressure range,lol. Regards, Danny.
D R Smith

Hi Danny,
Sounds like all is well and yep perhaps a decent rev out on the motorway is giving the "right" reading at last.

Cheers , Pete.
Peter Thomas

This thread was discussed between 04/06/2005 and 19/06/2005

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