# High Comp 8V + 9A Block Build



## Stangy (Mar 16, 2007)

I hope all is well. I hate my free time and saving money so i thought i would have some fun this fall and use one of the 9a’s I have at my disposal. I am hoping to swap my current big cam 8V JH head onto a stock 16v 9a block. All of this will be going on my 1985 Scirocco. I know this will yield a high come of 13.5 which I am fine with. With my big cam (287) and 94 fuel, I am hoping to create a fun “semi reliable” track car and weekend bruiser. 

I have a lot of experience with the 16v 9A engine but this would be my first hybrid swap built- I am a boost guy. I know I will need to do the following:

•Use 8v JH head gasket
•Swap out 16v intermittent + water pump pulley with 8V 
•Block off 9A block breather + add freeze plug to block 
•Modify 8V JH distributor w TT adapter 
•Use 8v APR head studs in the 9A block.

Since the 9A is a “short block” AND if I remember correctly, I can use my current header and exhaust set up. If I read correctly I can also use my current transmission set up including flywheel, clutch and pressure plate- all should simply bolt up. I am also hoping to use the stock CIS system with slight tuning.

Am I missing anything? I am hoping to yield around 165hp. 

Thoughts?


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## Tomjr (Aug 8, 2012)

Stangy said:


> one of the 9a’s I have at my disposal.
> Am I missing anything? I am PRAYING to yield around 165hp.
> Thoughts?


:what:
Two thoughts, actually.
Sell me one of them, and tell me what you plan on using for management? :thumbup:


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## Stangy (Mar 16, 2007)

Tomjr said:


> :what:
> Two thoughts, actually.
> Sell me one of them, and tell me what you plan on using for management? :thumbup:


Stock CIS- crazy? Maybe 
Sell you one? Never! There has to be some available in your area. 

I will create a build thread once i get to it this saturday.


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## nairmac (Jan 22, 2004)

Personally i'd use a really good head gasket, like a Cometic, and for the 9A (doesn't really matter- Cometic has 9A ones though). Many thicknesses available, customize your compression. :thumbup:


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## Ol_Drippy_Beard (Oct 28, 2015)

I built one of these a while back, but instead of using the 16v block I used a JH and swapped in the crank rods and pistons (the 9a block was damaged beyond repair due to a disagreement between the valves and the #4 piston) I spent a lot of time porting the head and doing a pretty serious valve job. Anyhow, the motor wound up in a friends scirrocco, where it proceeded to destroy clutches and transmissions until it finally got a 9a trans and high pressure clutch/plate assembly. Ran fine on CIS with 94 octane or e85.

To get the most out of this engine you're gonna want to do a significant amount of machine work. Especially to take advantage of a really aggressive cam. Consider getting oversized, back-cut valves, porting the head, upgrading your valve springs and retainers, and having the crank knife edged. These motors will make power, but the more aggressively you tune them, the higher they have to spin to make it. You'll also want to install a knock sensor ignition of some sort. After all is said and done you can expect to produce over the 165 target range.


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## boopizi (Dec 1, 2008)

Im currently in the processes of doing something extremely similar. I started out with the same idea but ran into a few problems that made me go with a pg motor over a pl or 9a. 

First off the 9a will not accommodate the distributor from an 8v. For what ever reason the intermediate shaft between the 2L 16v and the 1.8 16v are different. The gears on the 9A are bigger, therefore render a bigger hole and block off plate making the 8v distributor fit in extremely sloppy. It could probably be done with some custom bushing pressed in to make up the slop. Another route could possibility be an aba distributor? I don't have any specs on the dizzy at all so I might be off on that. I know the blocks were taller, not sure if that altered the distributor set up. It didn't matter to me because I'm retaining the CIS lambda and needed a vacuum assist.

The other problem is that from my calculations (which could be wrong) a 92.7mm stroke x 82.5mm bore under a Pl head gave me more of 14:1 CR. Which IMO will need much more then 94 oct. Especially if you don't want to extremely sacrifice advancing your timing. ALSO could possibly burn up starters left and right. I know some Harley guys will machine relief valves in at 12:1 just to get the pigs started... Might be looking more at 100 oct or possibly E85. 

So, instead what I did was essentially a g60 16v hybrid but opposite. lol. I put the bottom end of a 1.8L 16v (PL) in a PG 8v block. That way I know my 8v distributor fits, and my compression ratio will be less. My calculations came out to be 13.28. Still too high for me! I know these factory internals can take a lot of abuse from my turbo builds, but I'm not sure the abuse is the same. Detonation is a bitch... lol. So I got a head spacer in there to drop me down another point. 

As of now the motor is in, I just need to put the front end back together and play with it for a little. There a lot of things that need cleaned yet as well, but honestly I'm probably not on this car. like yourself, my beater needed a fresh motor and I wanted an easy project... plus I can't put things back together stock. :screwy:

Sorry to thread-jack but wanted to share my experience. Ill let you know how it runs with what fuel and timing combo. Id like to experiment with E85 but that'll come later.


-Ausin


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## Ol_Drippy_Beard (Oct 28, 2015)

The starter is a good point. My bunny runs a shaved head @ 11:1 cr and I have a hard time starting if the battery gets cold. Tbh though, 8v are pretty durable under high compression. expect to have a short lived but peppy engine on e85.


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## nairmac (Jan 22, 2004)

As a counter point on the starter- I run a 10.8:1 compression ABA/JH (kinda) 8V and use a MK3 starter with a tiny 270 CCA battery to turn it over. Works fine every time.


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## Ol_Drippy_Beard (Oct 28, 2015)

I never thought about it, but is the mk3 starter heavier duty?


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## nairmac (Jan 22, 2004)

Ol_Drippy_Beard said:


> I never thought about it, but is the mk3 starter heavier duty?


Yes, and much lighter than a MK1 diesel starter. :thumbup:


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## a1aa1992 (Apr 20, 2013)

i run 10.8:1 C.R and i have alot of knock and the engine rev limt goes 5000 Rpm only on stock tune 2E engine :banghead:


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## Ol_Drippy_Beard (Oct 28, 2015)

You might start from the beginning with the timing. I also recommend installing a knock sensitive ignition from a later vehicle.


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## LT1M21Vette (Nov 25, 2015)

Running above 11:1 CR on the street... :screwy:

It is simple.
8V pistons with 8V heads.
16V pistons with 16V heads.

Anything else is just, well, good luck.


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