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Oil pressure on the 4 cylinder cars? [1st post!]

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B

burgundyben

Jedi Hopeful
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Hi All,

Lots of useful info for a new Healey owner here.

We bought a very well restored BN1 about 2 months ago, it had done about 250 miles since the restoration was completed, the engine was rebored with HC pistons and crank reground.

Oil pressure was running at 5-10 hot at idle but not more than 20 at 3000 rpm.

I did find a stripped thread on the oil pipe banjo on the rocker pedastal, so replaced the pedastal and that got it up to 30 at 3000 hot, I replaced the releif valve and spring but despite the new spring being longer and stiffer it made little difference, the rocker gear appears very good order and not flooding oil all over the place.

By 900 miles the pressure dropped to nothing and a big end let go.....grumble grumble blast.

Today I got started under the bonnet and made good progress getting ready to lift it out. Hopefully next weekend I'll have it out.

I've no idea what the problem is....some careful investigation needed.

I'll keep you posted (and may ask a big long line of questions!!)

TTFN

Ben
 
Re: Oil pressure on the 4 cylinder cars? [1st post

As you know, there is a serious problem.
Some possibilities are:
1- The pressure relief valve is not seating due to a deformed seat or plunger, or contamination on the seat. Excessive friction in the plunger/spring could cause the relief valve to stick in the open position.

2- The oil pump internal clearances are excessive. The pump gear to gear, gear to housing, & gear to end plate clearances should be no more than about .002".

3- The high pressure copper pipe connection from pump to block could be fractured or it's connections leaking. I highly recommend a high pressure flexible braided replacement pipe here. There have been several accounts of this pipe fracturing & losing oil pressure. Denis Welch & maybe others have a replacement pipe.

4- The pump intake pipe may be loose or damaged.

5- One or more crankshaft or cam bearings may have excessive clearance.

6- One of the internal oil way plugs in the block or head may be leaking or missing.

From personal experience, a Hundred Four should have around 40 psi pressure at hot idle & rise quickly to around 60 psi at anything above 2,000 rpm even when very hot. Assuming that you are using a SAE 20W-50 rated oil.

I have attached a drawing of the oil system routing & connections.
D
 

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Re: Oil pressure on the 4 cylinder cars? [1st post

Dave,

thanks for the reply, useful info, I hope when I get in there I'll find something that is obviously the cause.

You say clearances in the oil pump should be .002" max, how bad is bad? if its .004 is that likely to be the cause?

This engine had a crank grind and all new rocker gear 900 miles ago so there must have been somethign very wrong in there...
 
Re: Oil pressure on the 4 cylinder cars? [1st post

Hi Ben,
I can't really say that .004" clearance is bad enough to cause a serious problem. It could cause lower pressure but I wouldn't expect it to be the main problem. Just carefully check ALL of the items I mentioned. Let us know how it goes.
D
 
Re: Oil pressure on the 4 cylinder cars? [1st post

Who did the rebuild of the engine, is there any recourse there?
 
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