# Mk1 Cabriolet 2H digi vs JH CIS 8v engine up to 1993



## teknikALLEN (Jul 14, 2010)

VW transitioned to the 2H digi from the JH CIS 8v engine in about 1989-1990.
Outside of the fuel system, the head changed from a solid lifter JH to the hydro follower on the 2H. The compression went from 8.9 to 10.0. 
What accounts for that increase in compression?
Is if from the combustion chamber in the head?
Is it from different pistons?
Is it from "decking" the head?
Is it from all three?

Thanks to the old timers who actually check this thread.


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## WaterWheels (Aug 14, 2005)

teknikALLEN said:


> The compression went from 8.9 to 10.0.
> What accounts for that increase in compression?
> Is if from the combustion chamber in the head?
> Is it from different pistons?
> ...


.


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## Glegor (Mar 31, 2008)

WaterWheels said:


> .


x2


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## teknikALLEN (Jul 14, 2010)

So I could actually bolt a JH solid lifter head onto a 2H engine, and run it with the digifart? You may ask why... it's what I have.... looking for a 1.6l solid lifter cam "n" I think...
Thanks... if anyone has actually done this, I'd like to learn more.


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## WaterWheels (Aug 14, 2005)

teknikALLEN said:


> So I could actually bolt a JH solid lifter head onto a 2H engine, and run it with the digifart?


Yup



teknikALLEN said:


> .... looking for a 1.6l solid lifter cam "n" I think...


This one I'll ask why? Most used ones will be worn out or close to being worn out. You can purchase new ones but for about the same price you can get a better grind from some of the camshaft companies like CatCams or stores like TT or Autotech.


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## StealthVR6GTI (May 1, 2002)

*Mix and Match*

Hey there - I just converted my 83 GTI from a JH to a 2H. I'm running it as CIS rather than Bigi which required some injector spacers as well as the CIS intakes and goodies. The increase comes from the design of the piston top as well as the valve different head + valve design. 

I did this as it's a class legal mod for my SCCA class. If I were doing it simply for low buck power I would do something different. I would use either a 2.0 block from a MKIII or MKIV. These get you the best of the 9V world with a great power increase and the improvement to modern computer controlled fuel injection that is chippable. A 2.0 MKI is actually a very quick animal - we dusted a 2.7t with this swap in a pickup withou zero engine mods to the 2.0.

Or if you want it to be really easy you could do the Audi 3A bubble block conversion. That's a simple one that keeps it very OEM strighforward. You will will need the intake assembly, distributor setup (with a TT adapter plate), and the CIS injection setup over. Other than that it's easy and cheap power. I had this setup in a MKII beater Jetta for my college car and it was pretty quick.


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## teknikALLEN (Jul 14, 2010)

Actually I am trying to understand some of the SCCA builds I have seen and get confused on the classes.... 
For your SCCA class you just took the head and left the JH bottom w/low compression pistons? What class are you running?

I saw a 2H running 12:1 compression and I was trying to figure out what class that was, suposed to be a new thing...


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## rabbitnothopper (Oct 19, 2009)

i thought the 2H heads had different injectors, are the holes the same for CIS?


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## ps2375 (Aug 13, 2003)

rabbitnothopper said:


> i thought the 2H heads had different injectors, are the holes the same for CIS?


All you have to do is to have the correct inserts. My car has a solid lifter head that was on CIS and is now on MS. All I did to the head was change the inserts and attach the digi fuel rail.


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