# Engine Block Options for 8v Digifant Head



## ON3WHLS (Jul 11, 2009)

Yes I did some research on here already.

I have a built 8v digifant head I'm considering swapping to a 16v 9A 2.0L block. Two reasons: more torque and higher displacement. The 9A block has a 92.8mm stroke vs the stock digifant stroke of 86.4mm and bore is 82.5mm vs 81mm. Any issues with doing this? 

Will Wiseco 8v 13.4:1 pistons work with this setup or do I need to get 16v specific pistons. I know the rod length of 144 mm is common between the 8v and 16v blocks, so I don't see why they wouldn't work?

Another consideration would be the diesel 95.5mm stroke crankshaft. Would I have to use stock diesel connecting rods in this case?

Anyone done this combination or similar? (digifant head+9A block with high compression and a diesel crank)

I'm going after torque, hence the 8v & largest stroke I can achieve combo.

Thanks fella's :thumbup: :thumbup:


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## ps2375 (Aug 13, 2003)

I think you will need custom pistons to go with the longer stroke and lower deck to get the CR you want. I wonder if this would be the same piston as the 3A block? As that is the only 8V short deck block that I know of that was of the 2.0L displacement.


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## Glegor (Mar 31, 2008)

ps2375 said:


> I think you will need custom pistons to go with the longer stroke and lower deck to get the CR you want. I wonder if this would be the same piston as the 3A block? As that is the only 8V short deck block that I know of that was of the 2.0L displacement.


should work.. i think the 3A may have had different sized small ends on the rods.. or something goofy with the rods.. i think the pistons should be able to be used tho :thumbup:


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## ON3WHLS (Jul 11, 2009)

ps2375 said:


> I think you will need custom pistons to go with the longer stroke and lower deck to get the CR you want. I wonder if this would be the same piston as the 3A block? As that is the only 8V short deck block that I know of that was of the 2.0L displacement.


3A piston would work with the stock 9A block/crank - is this what you mean? This wouldn't give a high compression though right?

Yeah after posting I realized the 8v 13.4 Wiseco pistons wouldn't work because of the longer stroke- the 13.4 CR piston is a + deck piston, I wasn't sure if a thicker head gasket could be used to correct back down for the larger stroke of the 9A short block.

Let's remove the diesel crank from the equation for a minute. Why is it that Wiseco makes the racing piston for the 8v (13.4 CR) but 'only' an 11 compression piston for the 16v 9A applications? Anyone else make a 13-14 ish range CR piston for the 9A 16v? JE maybe? Not sure swapping the diesel crank would net much more over the stock stroke of the 9A for the effort involved..

I am allowed to use any combination of blocks & heads from 85-92 Jetta/Golf in the class I run, but pistons do NOT need to be stock.


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## ON3WHLS (Jul 11, 2009)

Glegor said:


> should work.. i think the 3A may have had different sized small ends on the rods.. or something goofy with the rods.. i think the pistons should be able to be used tho :thumbup:


I'm not very familiar with the 3As- what compression was stock on those engines? The digifant head I'm running already had some material removed bringing compression on the 8v up a half point.


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## Glegor (Mar 31, 2008)

ON3WHLS said:


> I'm not very familiar with the 3As- what compression was stock on those engines? The digifant head I'm running already had some material removed bringing compression on the 8v up a half point.


3A is 10:1 compression..

had a weird head with Keyhole shaped intake ports, and fuel injectors were mounted in the intake, not head.


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## ps2375 (Aug 13, 2003)

3a was an Audi motor. The CR was prolly 10:1 or less. Foe the 9A with the 144mm rods, there should be a piston out there for you. Seems any 8V 83mm piston should work with the CR you want.

I also don't know if the 3A has the same oil returns as the 1.8L blocks.

And thinking about how you want to stay within the rules of EP, the 9A with the worked 8V head you have or to go 16V motor and build that.


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## ON3WHLS (Jul 11, 2009)

Assuming the 9A and digifant blocks share the same crank centerline and deck heights (maybe they don't?), it is obvious why a a 13.4 8v Wiseco piston wouldn't work- it would be taller and have a big +deck, with the longer 9A stroke. But I wonder what a 3A stock piston would give for CR? Is this what you guys were getting at? I really need to get a hold of a schemetic or actual blocks to compare..


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## ON3WHLS (Jul 11, 2009)

ON3WHLS said:


> Assuming the 9A and digifant blocks share the same crank centerline and deck heights (maybe they don't?), it is obvious why a a 13.4 8v Wiseco piston wouldn't work- it would be taller and have a big +deck, with the longer 9A stroke. But I wonder what a 3A stock piston would give for CR? Is this what you guys were getting at? I really need to get a hold of a schemetic or actual blocks to compare..


Ok, little more info. I looked at some specs on Wiseco's site. 

Compression height (distance from wrist pin to piston top) for the 11 CR 9A piston is 29.7 mm. For the 8 valver 13.4 CR piston it is 33.5 mm, so my assumptions above are correct. I can use the 9A 11 CR 'off the shelf' piston and achieve about 11.5 compression, but to achieve the 13-14 I'll have to either go the route of a custom piston or look into the option of a thicker (3 mm?) head gasket with the use of the 13.4 CR Wiseco.

I need to know the compression height for the 3A piston!! Anyone, anyone?? :thumbup:

So now the question is cost. As you go higher in CR, the returns are diminishing...we'll see!


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## ON3WHLS (Jul 11, 2009)

Cool website!

http://www.not2fast.com/vw/stuff/vw_engines.shtml

Of course the CH for the 3A isn't listed lol

The ABA piston has about the right compression height to achieve 13 CR, but a different wrist pin (21mm). Since the ABA rod is 159mm vs 144mm, not sure this will work w/o custom connecting rods lol. It does have the same journal diameter, though. ugh!


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## ON3WHLS (Jul 11, 2009)

I can't change the stroke in my class, so that simplifies things. 

I read an 8v head on the stock internals 9A gives about 13.5 compression. This might be the simplest and cheapest thing to do, in the end. 

What I need to do at this point is measure the clearance volume on my digi head, so I know exactly what it is to do the calculation. I have a feeling I'd be around 14 compression with the head being shaved a small amount. This might be too high..

I know I'm rambling on here today, thanks for reading and any inputs!


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## Glegor (Mar 31, 2008)

ps2375 said:


> 3a was an Audi motor. The CR was prolly 10:1 or less. Foe the 9A with the 144mm rods, there should be a piston out there for you. Seems any 8V 83mm piston should work with the CR you want.
> 
> I also don't know if the 3A has the same oil returns as the 1.8L blocks.
> 
> And thinking about how you want to stay within the rules of EP, the 9A with the worked 8V head you have or to go 16V motor and build that.


you can bolt a c-flow, or x-flow head on a 3A block no problem. all ports line up, both coolant and oil..

and yes, OP, an 8v head on a 16v bottom end yields ~14:1 compression..


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## ON3WHLS (Jul 11, 2009)

Glegor said:


> you can bolt a c-flow, or x-flow head on a 3A block no problem. all ports line up, both coolant and oil..
> 
> and yes, OP, an 8v head on a 16v bottom end yields ~14:1 compression..


That might work perfectly- how do I dial it back a point? Can I double up the gasket or is there a thicker gasket available?


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## ziddey (Apr 16, 2006)

How much head work are we talking here? I imagine it's pretty hard to compete with a 16v motor, even if you do have 14:1?


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## ON3WHLS (Jul 11, 2009)

ziddey said:


> How much head work are we talking here? I imagine it's pretty hard to compete with a 16v motor, even if you do have 14:1?


It is match ported, the valves are cut, high compression springs, and it is decked. 

You bring up a good point, _but_ you also have to realize what I'm after. Even if the head was stock, 8v's create more intake air velocity at lower RPM's, which is better for low speed engine work (aka torque). 16 valvers have better VE at higher engine speeds.

If it was a road racer and I was always keeping it in the 5000-8000 RPM band, you're absolutely correct. But I'm after the car pulling like a mule out of lower speed autocross corners in the 2000-4000 band. 

The larger 9A displacement/stroke, 8v head and high compression is the winner. :thumbup:


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## ps2375 (Aug 13, 2003)

Seeing as you can run any tranny, and going with a built 16V motor...low speed accel should not be an issue with the 16V motor. In the past I have seen dyno charts and claims that the 16V motor has as much or more TQ at 3000 rpm as an 8V motor. They seem to just "feel" softer in "normal" driving.


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## Glegor (Mar 31, 2008)

i would go full 16v..

~140hp stock, versus 100 TOPS from a stock 8v. 

i mean, im a die hard 8v fan. i love them, they are the toughest engines ive laid hands on..

but i would go 16v..

the 16v has no softer power, its just DIFFERENT.. and you can expect it to be..


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## ON3WHLS (Jul 11, 2009)

There are financial considerations, too. I already have a built 8v. Would the additional $1k (or whatever) to modify a 16v head be worth it? I'd have to buy new cams, machine work, etc etc. Unless I can find a built one cheap here. In contrast and on a relative basis, finding a stock 9A bottom end and running a thicker head gasket is cheap!

I _do_ like the fact that I can run Weber DCOEs that draw air from the front w/the 16v setup, however.

I'm just not sure the additional investment would be worth it when bumping the CR and swept volume are the biggies IMO.

But thanks for the advice and I will def put some thought into it! :thumbup:


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## ps2375 (Aug 13, 2003)

You would have the additional costs of header,fueling, 2X cams,lifters, springs, valves. The rebuild/freshening of the block should be the same as any other motor.

That said, a stock head 16V on a fresh bottom-end with header,cams, and what-ever management will generally make more power than most worked/warmed-over 8V's of the same displacement.


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## ON3WHLS (Jul 11, 2009)

ps2375 said:


> You would have the additional costs of header,fueling, 2X cams,lifters, springs, valves. The rebuild/freshening of the block should be the same as any other motor.
> 
> That said, a stock head 16V on a fresh bottom-end with header,cams, and what-ever management will generally make more power than most worked/warmed-over 8V's of the same displacement.


Right now I'm set up with a 38 DGES downdraft and a TEC-s ignition (has fuel capability too, but I'm only using the ignition portion of the ECU). If I went 16v head, I'd do fuel injection with ITB's or DCOE's. 

This thread is really about a longer term motor that I'm planning on building on the side, while I'm running the digifant 1.8L setup for a few years. Basically an "all out" motor for E prepared. That was the original plan, anyway. But I have 2 kids and a few house projects to finish up this summer, so I don't think I'll finish what I've started- which is why I'm kicking around the idea of building the longer term motor now.

Here is the car and my current setup:

http://forums.vwvortex.com/showthread.php?5105682-38-DGES-Good-Choice-for-Autocross-Racing


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## ON3WHLS (Jul 11, 2009)

ps2375 said:


> You would have the additional costs of header,fueling, 2X cams,lifters, springs, valves. The rebuild/freshening of the block should be the same as any other motor.
> 
> That said, a stock head 16V on a fresh bottom-end with header,cams, and what-ever management will generally make more power than most worked/warmed-over 8V's of the same displacement.


Don't forget $500+ for new 16v pistons to achieve the compression I'm after!


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## AnAgentOrange (Jul 14, 2011)

ps2375 said:


> You would have the additional costs of header,fueling, 2X cams,lifters, springs, valves. The rebuild/freshening of the block should be the same as any other motor.
> 
> That said, a stock head 16V on a fresh bottom-end with header,cams, and what-ever management will generally make more power than most worked/warmed-over 8V's of the same displacement.


More power, definitely. But it will still lack the low end oomph that a mildly worked 8v will have. You're talking about max hp, which means nothing. What matters is foot pounds and the torque CURVE.


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## ON3WHLS (Jul 11, 2009)

AnAgentOrange said:


> More power, definitely. But it will still lack the low end oomph that a mildly worked 8v will have. You're talking about max hp, which means nothing. What matters is foot pounds and the torque CURVE.


Kind of the lines I was thinking along, but I'll admit I haven't seen actual torque curve comparisons for both built engine scenarios. It would be nice if someone had actual data..


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## ziddey (Apr 16, 2006)

http://forums.vwvortex.com/showthread.php?5251337-2.0-CIS-E-16V-dyno-run&daysprune=-1
as you can see, 8v having more tq down low is a fallacy.

so you are restricted to a2 engines? i'm guessing you can't take the turbo and manifold from an a2 td.


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## ps2375 (Aug 13, 2003)

AnAgentOrange said:


> More power, definitely. But it will still lack the low end oomph that a mildly worked 8v will have. You're talking about max hp, which means nothing. What matters is foot pounds and the torque CURVE.


Gearing of the trans can overcome the so-called TQ deficit. We ran a car in SM with a mild 8V and when we went to a stock 1.8L 16V, we lost nothing at all. The car never had any problems getting out of any corner with more than enough twist to spin the tires if wanted. And we were running 13 X 9 wheels and "R" comp tires w/ a LSD.


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## ON3WHLS (Jul 11, 2009)

ziddey said:


> http://forums.vwvortex.com/showthread.php?5251337-2.0-CIS-E-16V-dyno-run&daysprune=-1
> as you can see, 8v having more tq down low is a fallacy.
> 
> so you are restricted to a2 engines? i'm guessing you can't take the turbo and manifold from an a2 td.


How is it a fallacy? There is no comparison to an 8v...the 16v torque curve is not flat, it is rising from 2500 to 4500 RPMs. Any 8v runs on the Tex?

I can use engine parts/backdate any 85-92 Golf/Jetta. But I cannot add a turbo to an originally non-turbo engine.


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## ON3WHLS (Jul 11, 2009)

ps2375 said:


> Gearing of the trans can overcome the so-called TQ deficit. We ran a car in SM with a mild 8V and when we went to a stock 1.8L 16V, we lost nothing at all. The car never had any problems getting out of any corner with more than enough twist to spin the tires if wanted. And we were running 13 X 9 wheels and "R" comp tires w/ a LSD.


I have a similar setup- 13x8 Keizer with Hoosier A6s, wavetrac diff. 

I guess my thinking at this point is that there won't be a big enough difference, other than top end _power_, to justify starting from scratch with a 16v head. Let's think in terms of benefit, highest to lowest: 1) increasing the size of the engine to 2.0L /higher stroke (accomplished by using 9A short block) 2) 13-14 compression ratio (accomplished by using 9A short block with 8v head- no need for a piston set) 3) volumetric efficiency is better for the 16v at higher intake velocities and up for debate /similar at lower flows. 

Maybe if I was starting with a stock 8v, I'd change over. But I have a lot of $ invested in the 8v head.

I agree w/your comments about gearing.


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## ON3WHLS (Jul 11, 2009)

Post 11 is interesting. The 9A 16v has smaller intake ports, relative to the 1.8 PL, giving it better low end torque.

Maybe the air velocity hypothesis holds true more so for the PL 1.8L 16v and not as much the 9A, when compared to the 8v..

http://forums.vwvortex.com/showthre...w-to-the-16v-forum-this-is-the-thread-for-you


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## ps2375 (Aug 13, 2003)

All true, but how much of the better TQ is due to the smaller intake ports and how much is due to the added cc's?

To prevent losing too much low-end with a 16V motor, I would not go with to wild a set of cams. But I seriously doubt you would see the diff with a 16V, except you would be faster due to the additional HP.


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## Glegor (Mar 31, 2008)

maybe a long runner weber/ITB manifold? something that will point the webers/ITBs towards the front of the car, and setting them above the valve cover/spark plugs?

thats the only thing i can easily come up with to improve torque on the bottom end..

if you need more torque yet, then bite the bullet, and drop a hotrod turbo diesel in it..

if you build a TD to produce 130hp, then you will probably have somewheres around 200tq. 

i have a K24 turbo on mine, witch is a stock sized turbo, and it spools nice and low, and pulls hard clear to 5800 rpms..

that also nets you a bunch of extra costs too tho, finding a turbo diesel engine..


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