Hi,
I have some intresting new data based on a day of measuring.
Soo, I have dismantled a 29D engine, just to make some comparisions.
- rods are equal lenght
- pistons in the 29D engine are the same height as new pistons, soo differ
from the old pistons in the 26H engine.
- stroke is the same
- the difference is the block deck height. The 29D engine is 1.3mms lower
than the 26H block! Assuming that the 29D has a CR of 8.9:1, the 2mms taller
pistons in that "mysterious" 26H engine gives the same!
- Question one: why? As it is a "26H" aka "miscellaneous" engine, the answer
may be hidden forever. The engine has also got a nonusual camshaft with the
same lift, but greater duration than the 29D' camshaft (especialy longer on
the exhaust).
- Question two: where is that extra 1.3mm material? Unfortunatly definiatly
NOT on the deck, as the deck thickness is roughly the same as the 29D.
Somewhere below.
- Question three: wattodo? I can order special higher pistons, but they will
be aftermarket, unproven items. It means risk, if not quite high, but still
some. OR I can skim the block 2mms. OR I can skim the head. OR both. OR I
can order a special thin gasket (with 0.7mms compressed thickness) , skim
the block and the cylinder head to get the pistons were they belong.
One extra think I have uncovered today is, that the BMC 2639ccm engine
existed in low compression-form (Wolseley 6/90 for example). Theese engines
had only got 7.3:1 CR. Wich number is quite close to the one I get if I put
the new pistons in my engine.
???
BMC forever.
Gergo
2011/3/22 Magnus Karlsson <magnuskarlsson@bornet.net>
> I would definetely scrap/return those pistons and get some with the proper
> height.
>
> Magnus Karlsson
> Bores Motor Corporation AB
>
> www.concourshealeys.com
_______________________________________________
Healeys@autox.team.net
Donate: http://www.team.net/donate.html
Suggested annual donation $12.75
Archive: http://www.team.net/archive
Forums: http://www.team.net/forums
|