how feasible is an 8v piston swap?(8.5:1 to 10:1) (fwd)

[drew@scirocco.cs.uoguelph.ca (Drew MacPherson)]

Sorry for the multiple messages - bum mail client config...
....

I did the same thing with the engine in my winter-beater Jetta last year.  
I took 4 pistons from an RD engine, re-ringed them, lightly honed the
cylinders on the JH, and threw the bottom end together with new rod
bearings.  I rebuilt the head and installed a G-grind cam, and threw a
knock sensor ignition on (maintaining the car's stock CIS fuel injection.)  
It works very well, the result being a "DX"-like engine (a 10:1 CR version 
of the JH)

I have a dual-outlet manifold (A2) and a stock turbo diesel exhaust which 
is a litle loud above 3K, but flows quite well, a must for the g-grind.

As far as power goes, I'm impressed (of course, my summer car is only 
70hp... :)  The car pulls like mad to 6K in 3rd, and probably would in 4th 
if I had enough road to do it in (7A gearbox) and still gets about 44mpg 
imperial.

If you choose not to go with the knock sensor you'll likely need to stick 
with high octane to avoid pinging.  I run E10 blended 87 octane and 
haven't had any power/knock issues (at least no power issues since I 
replaced the bum knock control unit.)

I say go for it, if you can get the pistons cheap (make sure they're from 
an 8V - either digifant or CIS-E (HT/RD))  You can use the rods that come 
with the pistons as long as the piston bushes aren't worn.  Make sure to 
install them the right way and don't mix the caps though.

HTH,

Drew

On Fri, 13 Dec 2002, Robbie Cotner wrote:

> 
> Hey all, I rebuilt my 1.8 JH 8v engine about 8k ago.  Now I wish I
> would've installed some 10:1 pistons.  I recently came across a set for
> $50(is that a good price?), and was wondering how feasible it would be
> to install them in my '83 Scirocco.  Can I just remove the head and oil
> pan, disconnect the rods, push the old pistons(not oversized) up out the
> block, then put the 10:1 pistons(think they're from a GTI) with new
> rings onto the old rods and reassemble?  Would I have to rehone?  
> Should I replace the rod bearings and bolts even though they only have
> 8k? How much more HP can I expect by going to 10:1?  Should I use the
> 10:1 wrist pins or the current ones?  Is this a very common mod?(that's
> usually a fair indicator of if it's worth it or not).  Wow that was a
> lot of questions!  thanks in advance, every little bit of info/opinions
> helps!- Rob
> 
> 
> 
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