Re: Tech: Cylinderhead question

[Brett Van Sprewenburg <brett@netacc.net>]

<x-flowed>>Attention all engine swap pros...  ; )


Well, I've reading up the theory anyway... Ok, so I've actually done it. :)

>  I am in the middle of installation of a 1.8 JH motor into my "new" MK1.
>I am using the standard 1.8 JH block but have a different head to use.  On
>the front of the head reads "3 ME".  I know that this head is a 1.8 8v
>head, but I don't know if it will be a direct bolt-on.  I think that this
>is one of those 8v's with hydrolic lifters.  Can someone tell me if this
>head has the same coolant channels and, basically, if it will have any
>problems to bolt to the JH block?

If it's the late model hydro head, it'll have only 4 cam bearings
holding the cam.  One was removed to make room for the oil feed.  If
you do have one, it was mated to the standard JH block so you'll have
no problems from that direction.

>  Also, I have talked to Potterman about shaving the head on a JH motor to
>up the compression... he said that this can be done safely to increase the
>compression up to about 9.3 or so.  So, my next question is about this
>head that I am going to use (the 3ME)....I was told that this head was
>used on the higher compression 8v engines(like, 10 to 1 compression).


Yes, basically the same head was used on the 8.5:1 and the 10:1 engines.
Engine code RD for example was 10:1 I believe. The difference was in
the pistons, as most (if not all) of the combustion chamber is in the
piston.  The 10:1 have less of a dish, smaller volume, so more 'squish'
going on == more compression.  So take .25-.3mm (.020+) off the head
(past min deck), and use a motorsports (smaller) head gasket.  I'll bet
you that getes you in the neighborhood of 9:1, probably 9.1-9.3:1.

>If
>I simply bolt on this head to a standard JH block, will there be an
>immediate compression increase or would I still bennefit from shaving this
>head?


I don't think so, as most of the combustion chamber volume is in the
pistons.  Shaving the head will raise the compression though.  Check to
see if the pistons come all the way up to the block deck...if they do not,
then you can shave the block deck a little instead to increase the
compression. However at some point (with a high lift cam) you'll be
creating an interference engine.

>I am just looking to increase compression a little...I'm not adding a
>knock sensor or changing pistons, just looking for a slight increase.  I
>would appreciate all help and suggestions... TIA!


Keep it comfortably below 10:1 then.  good luck!

==Brett


>
>Benjamin Harder

 \/  '84 Scirocco (ITB racer 2B) | "Hot VW's, take two home. They're small"
\/\/ '88 Scirocco 16v (Show), '85 Scirocco (Winter) | - brett@netacc.net

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