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Pistons for Lancia Vx CR increase
Posted: July 4th, 2006, 8:11 am
by Fingers
Are there any standard Fiat/Lancia pistons that can safely be fitted to the VX engine to raise the compression ratio, with a minimum of work eg machining deeper valve pockets. The delta 1600 turbo pistons for example. What cr will they give, and what's safe to go to on the VX engine?
Posted: July 4th, 2006, 9:02 am
by Guy Croft
hello Paul,
Me, FWIW I don't go for raising the CR, 7.5/1 is my preferred max. You don't tune them by raising the CR. I have heard of 8/1 and higher.
What fits? I have not seen a carb version Delta Turbo piston for years.
The availabilty of most of the old good stuff is er, pretty well zero.
It is not easy to match the piston bowl to the head and the sept volume. . The Vx has dunno, 53-56cc combustion chamber volume depending what you do to the valve seats. The later reversed port 8v head is 48.7 cc std and 16v head eg: 16v Integrale 40cc std.
A lot depends on bore size and esp the relative height of the piston to the block deck, not two setup heights are the same - if you e mail me I'll send you a Vx CR calculator in Excel, like the one below - you can have a play with the various CR parameters.
The last time I tried a swap was 5 years ago with Croma Turbo pistons, they were hard enough to find, more so now. I'd never do that again, bowl way too big, the Vx only needs about 11cc bowl, what a nightmare.
In my engines mostly I used my own design forged now.
GC
Thanks
Posted: July 4th, 2006, 9:14 am
by Fingers
Excellent, thanks Guy. It was more just to see if it could be done easily, and if so how. If you you don't really think it's worth it I won't bother. There doesn't seem to be much info around on this sort of thing for the VX. I'll email for that excel file.