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Re: head swap question HT/RD head to GX block



--- drew <drew@dyermaker.cs.uoguelph.ca> wrote:
> 
> I have a question for all of you gas motor gurus out
> there in
> Scirocco-mailing-list land.
> 
> I've been going through my inventory trying to come
> up with low-cost
> engine enhancements for an 87 Jetta GL with the GX
> (85 hp CIS, no cat/OXS)
> engine.  Rather than dropping in a complete RD/HT
> engine (cost $$ which I
> haven't got), or purchasing a tci-h knock for a high
> compression motor
> (same problem), can I put the big-valve GTI head on
> the GX block (which I
> do have...)

Yes, basically you'll end up with a motor with JH type
output. The RD/HT head has 40mm valves, compared with
the GX head, which has 38mm in valves.

> 
> Obviously my main concern is what kind of
> compression I would end up with
> if I were to install an HT or RD head on this block.
>  Do I end up with
> 10.1:1, 8.5:1 or somewhere in between?

8.5:1 - same as a stock GX or JH (i think)

It's the pistons that make the compression, as I
understand it (at least for U.S. VW 8 valve motors)

> 
> I'm assuming that installing this hydraulic head on
> a JH (solid lifter)
> block is out of the question because of the lack of
> large oil return port
> on the block?

You can put a hydraulic head on a JH (or about any
other 1.8), you should probably put a hydraulic type
oil pump on it at the same time. The oil passages are
the same.

HTH


=====
Mark Peele
1981 Scirocco, 1982 Scirocco, 1978 Scirocco, 1987 Golf GT
http://www.scirocco2.de/mark.htm
Direct Mail: SCIROCCO_GTX@YAHOO.COM
Need parts? try http://www.parts4vws.com/ (Potterman)
or http://www.germanautoparts.com/ (Adirondack)
or http://www.newdimensions.com/ (TurboTim)
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