Low compression and burning oil

I don't think the spigot recess in the head will make the engine burn oil but you can turn a ring up to fit this and make the comp std.

If the barrel has been rebored I assume it was honed correct and if you fitted new rings it should not use oil. Are you sure the engine is scavenging, does it smoke?.

Tony

Worn or loose inlet valve guides can cause oil burning. The spigot recess will fill with carbon deposit in due course. Nothing to worry about there.

The last time that I was involved with a similar problem to that of Chas, the owner also had recently rebored the barrels but fitted cheapo pistons. Adding to his misery, both oil rings were inverted and pushing oil up into the combustion chambers.

You have to be very careful with the choice of piston, as badge engineering has changed some of the previously good brands into money wasting rubbish. Some are poorly manufactured.....being grossly over-standard weight and often round instead of oval.

The lack of spigot will only be a problem if the head gasket is leaking ......which does occasionally happen with the solid copper version. The lower compression should give the engine a slighly easier time when swallowing our grotty Ethanol laden petrol.

My 99 has done a few thousand miles since a rebore many years ago,Since then It burns a bit of oil and a little smoke along with some piston slap . Some hard use in the IOM has changed everything. No slap ,smoke and an impressive increase in compression. Its now run in!!.

Here you go, Chas....http://www.rgmnorton.co.uk/buy/alloy-recess-ring-for-converting-spigoted-cylinder-head-to-non-spigoted_171.htm

These will resolve that issue. With regard to blowing head gaskets, it may be that the head needs skimmimg, as they can warp. I have just had mine done. It was .008" out. Ian

Previously ian_cordes wrote:

Previously ian_cordes wrote:

Here you go, Chas....http://www.rgmnorton.co.uk/buy/alloy-recess-ring-for-converting-spigoted-cylinder-head-to-non-spigoted_171.htm

Will this ring fit a Mercury? The number 025494 is that needed for the early 750 Atlas engine.

You are right Phil, my mistake. Best check with RGM, or the other suppliers, to see if they do one for a 650. Alternatively, check out Norvil's part #990613 'Ring - Cylinder Head - Early 600/650 to Fit Later Plain Barrel'.

That sounds like it, doesn't it? I knew I had seen one somewhere!

Yes, you can lift the head and barrels as one unit. Not particularly easy though. The fun bit is replacing them without damaging the piston rings. A helpful, strong, patient friend would be useful - the combined weight of head and barrels is considerable.