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A Boring Subject

To: mgs@autox.team.net
Subject: A Boring Subject
From: WSpohn4@aol.com
Date: Sun, 4 Apr 1999 12:14:09 EDT
<>

Greg - the original 1500 engines will take a bit less of a bore than the 
later ones, in my experience. They were the coolest running of all, being the 
last ones that didn't have 1 and 2, and 3 and 4 siamesed, i.e., the cylinder 
pairs look like an hourglass (if you machined the deck off so you could see) 
instead of 4 individual cylinders.

The blocks in general were pretty old tech agricultural, and boring to .060 
or more isn't usually a problem. I say usually, because with a minority there 
can be a serious problem. The cores for the block were held in place by 
little lead bits, and when the blocks were poured (i.e. cast) at the factory, 
there was no guarantee that a core wouldn't shift a little. A perfect block 
will have uniform wall thickness all around, while one that has experienced 
shift will be thicker on one side than the other, which means that some 
blocks will not take as much boring as others.

I have a fair bit of experience with this sort of thing over the years of 
racing, both in building them up and also after the fact when they have 
broken - in fact I often used to take written off blocks and break them up or 
cut them up and measure them just to learn about how they were made and what 
you could and couldn't do to them (hence my nickname "Boring Bill").

I have even had a B block take a very large rebore (over 2000 cc) and 
perforate the wall only when honing it!! (Better then than later). It's 
interesting, but some blocks seem to become a little coarser and porous 
toward the outside of the cylinder wall, as well.

Anyway - you asked about linering. There are two types - wet and dry. Dry 
linering is simply boring the cylinder out and then pressing a 'dry' liner of 
thin steel into the bore, after which it is again rebored or honed to size. 
This allows a repair of one damaged cylinder to match the other 3 undamaged 
one. There is some feeling, not backed up by any objective data that I know 
of, to the effect that a linered bore may not cool quite as well as an 
un-linered one, but for the street, any difference will likely be unimportant.

Wet linering is less common and more difficult. It is when you bore the old 
cylinder right out into the water jacket, and then press in a new liner. It 
is done, typically, only to save a rare and badly damaged block, or to bore 
an engine past it's normal limits for some other purpose. It has the added 
challenge of getting the liner to seal, i.e. so that it won't weep coolant 
under use. This can be accomplished with varying degrees of success with such 
methods as chemical bonding agents (glue) and my favourite, furnace welding, 
in which you actually arc weld the liner into the block after heating the 
whole thing up to a fairly high temperature. The liner gets welded both top 
and bottom, the block allowed to cool, and then the fun of re-decking the 
block, reboring or honing to get back to a truly cylindrical bore, align 
boring the main bearing saddles, and all the other fun stuff you have to do 
to make sure that the welding process hasn't deformed the block in any way 
that you can't live with. Fun and very expensive!

So for street use, the odd dry liner is perfectly acceptable, and about all 
you will run into. If you happen to run across a set of .060 or .080 pistons, 
that is an option as well, and will increase the torque of the engine to boot.

Hope that helped, and wasn't too - boring.
And now I have to go back out and rebuild my rear calipers from my A coupe 
that were leaking on the discs, and try and start it for the first time in 9 
years. Cross your fingers for me.

Bill S.

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