Classic cars forum & vehicle restoration.

jacks21 · Joined: 17 Jun 2014 Posts: 1

Hi I wonder if anyone could help. I have a 1948 morris 8 series e which was fine until this year it now has developed a strange noise from the engine when revved high or under load. When the noise is there a lot of smoke comes from the oil filler and breather tube but nothing out of the exhaust. It has no noise on idle or low revs. I have 140 psi on all cylinders and oil pressure is always over 50. Any ideals where to look.

47Jag · Posted: Tue Jun 17, 2014 8:27 pm Post subject:

Jack,

Heavy smoke from the breather usually indicates worn pistons and the noise you are hearing is piston slap although I'm surprised that you are getting 140 psi compression.

Art

goneps · Posted: Tue Jun 17, 2014 11:00 pm Post subject:

My first thought on reading this was, "broken piston rings". But 140psi compression pressure with a CR of 6.7:1 is surely defying the laws of physics.

Richard

ka · Joined: 03 Dec 2007 Posts: 600 Location: Orkney.

It is an impressive psi reading, I would plump for broken rings, worn bores, it may be the surplus of oil in the bores, giving an inaccurate reading.
_________________
KA

Better three than four.

Rusty · Posted: Sat Jun 28, 2014 3:17 am Post subject:

It shouldn't happen on a "low compression" engine like a Morris 8 but what's the chances of a severe carbon build up in the cylinder causing some sort of "pinking" or worse yet "detonation". If there was a hot spot of carbon it could cause "pinking" and if carbon was choking the combustion chambers it could cause a very high compression and "detonation" especially with the rotten fuels we are getting now, this would cause very high pressures in the cylinder and consequent overloading of the rings. Cylinder pressures of 140 psi sound miles too high for an "8" (although I don't know what they would normally be, maybe someone else can help there) Sometimes high pressure at cranking speed is just an over optimistic gauge.
Goodluck

Ashley · Joined: 02 Jan 2008 Posts: 1426 Location: Near Stroud, Glos

Sounds like piston trouble, so ignore compression tests, they're difficult to do and not reliable for this sort of thing.

Why not drop the sum and take the head off. It's a simple job and you can see the condition of everything that matters.

ukdave2002 · Joined: 23 Nov 2007 Posts: 4268 Location: South Cheshire

I'd do a vacuum test followed by a leak down test to try and pin point the problem, if still inconclusive, then as Ashely suggested, a sump and head removal is only a couple of hours work + the cost of some gaskets.

Cheers

Dave