Classic cars forum & vehicle restoration.

Uncle Joe · Guest

Can we not wait until one of the other oldies sees this? There is one in particular that I would love to see opinions from, mainly because it will prove me right or wrong!

ukdave2002 · Joined: 23 Nov 2007 Posts: 4104 Location: South Cheshire

Picked up the blasted chassis yesterday, the place that did it is first and foremost a garage, mentioned the bore wear to the owner who quickly calculated that amount of bore wear in my engine would equate to an increase in ring gap of over 0.020" and that anything over 0.015" on that size of cylinder requires a re-bore.

The block is bored out to its maximum so will require a liner, which suits me as I have new set of standard pistons and rings in stock, at the same time I‘ll have the valve guides replace with K-Line Bronze Interrupted Spiral Guide-Liners as they have much closer tolerances which is useful as the Morris sidevalve engine does not have any additional valve stem seals, so were always a bit prone to using some oil via the inlet valves. The camshaft has no bearings I’ll let the machine shop decide if it needs some fitting.

The one thing that does concern me is the crank; I have not looked at it yet. It was not uncommon on these engines for the crank to need regrinding a couple of times, before a re-bore was required, so fingers crossed there is enough metal left on it!

Uncle Joe · Guest

UK, the only reason to worry about a crank is if it is cracked. That is something that should be checked. Wear on the crank is no problem whatsoever. Every crack free crank in the world can be restored, irrespective of the amount of wear. Biggest problem is to find a workshop that knows what a fillet radius is. Believe you me, in my time, I've seen a lot that dont....

Ray the rocker · Joined: 01 Aug 2008 Posts: 187 Location: south wales

Interesting debate about engine smoke---testimony of compression pressures usually determine either top end-ie---valve stem seals or guides--or bottom end-ie--worn rings plus bore wear and breathing badly.
Any deficiency in cylinder p.s.i. can be caused by both.
A simple test for piston ring wear can be determined by decelaration going down an incline and accelarating after say 100 yards.If a plume of smoke appears---it`ll be rings worn or broken,worn bores or both.
The problem with reboring tends to put extra pressure on a three main bearing crank so a full overhaul is vital.
I can remember a customer of mine with a 1952 austin somerset 1200
o.h.v. came in with the same problems and we removed the cylinder head.The bore wear was over limits,but he was strapped for cash ! You could actually see the arc of the top rings staring back ! As money was tight---he was a poor student in those days:- i opted for a set of standard
"cords" which took up the piston slap.Many painstaking hours to refurbish the ring grooves and slicing my fingers to boot!
Nothing was done to the bottom end---rebuilt making sure the bores were
"glaze busted" thoroughly.
Anyone know if "CORDS" are still around !! They were the king of reringing pistons in the fifties and sixties when budgets were tight.
I`ve also done a side valve morris series E with excellent results.
"Blue haze" on most side valves determine a sweeter running engine every time --but legislation will kill off most with stringent MOT regulations.

cheers----Ray the Rocker.

peter scott · Joined: 18 Dec 2007 Posts: 7118 Location: Edinburgh

ukdave2002 · Joined: 23 Nov 2007 Posts: 4104 Location: South Cheshire

have just dismantled the engine, pistons 1 & 4 both have broken top rings .The centre main bearing is breaking up others had normal wear, the crank is only -0.020" so hopefully will be ok for a regrind .

Jim Walker · Posted: Thu Oct 02, 2008 4:16 pm Post subject:

I'm a new member just browsing.
Reading this thread I am surprised that no one has directly commented that compression rings and oil control rings have different functions. The compression rings seal against compression loss (and you seem to have lots of compression). The oil control rings (sometimes called scraper rings) clear oil from the cylinder walls thrown there by the rotating crank. Oil rings can wear to the point where they cannot do their job even when compression rings are still good. They can also get clogged with carbon along with the holes/slots on the piston which discharge the excess oil to the inside of the piston, or swamped by excessive oil flow through the big ends (catherine wheel effect). Excessive big end oil flow means excessive big end wear.
Significant oil loss via the stems of side valves is unlikely because the oil has to defy gravity unless the engine breather is blocked..

Jim.