New here, 8v questions.

[jdbubb at verizon.net (Dan Bubb)]

Good morning to you too!

From: "Eric Austin" <ewaustin@gmail.com>
Sent: Thursday, July 13, 2006 12:52 PM
Subject: New here, 8v questions.


> I have:
> 1.8l 16v (pl code) engine, from the headgasket down.
> G60 engine from the headgasket up
> 8v digifant golf parts car, with engine and drivetrain intact.
> 
> 
> What I was originally thinking is that if I bolt the G60 head onto the 16v
> bottom end (with .040 shaved off the pistons) I would wind up with about
> 14:1 compression ratio.

G60 head, 16V short block will get ~14.7CR
G60 head, 16V short block w/1mm milled off pistons will get ~12.8. Probably a little higher since you won't be taking 1mm off of the entire piston due to the valve cutouts.
> 
> The Vortex said that if I use 9a (2.0l 16v) pistons, that the compression
> will drop to 13.5:1, and I won't have to worry about the reliability of
> modified parts.

Course, using the 9A pistons requires you to bore out the block to 82.5 so you'll have a little more displacement, 1847cc.
But, the 9A has a piston pin height 3.2mm shorter than a PL piston. In other words the piston crown is 3.2mm further down the bore at any given crankshaft position. That adds an extra 17.1cc to the compressed volume which is a lot in view of the 29cc volume of the 8V head and is almost exactly the difference in volume between the 16V (46cc) and 8V heads. So, not surprisingly, the CR ends up right back at the 16V CR of 10:1!!
And in the process you've also ended up with an effed up combustion chamber with no squish area.
So much for the Vortex Genie! ;^)
To me it's a non-starter.
> 
> Next question is the head, I was originally thinking that I'd just use the
> G60 head, but it sounds like if I get a solid lifter head I'll be able to
> rev it higher than with the G60 head.

Depends on how big of a cam you want to run and what RPM you want to turn. Anything below 7500 and streetable will probably be OK with the hydraulic head.

Dan