# Differences in ABA cylinder heads. OBD1 vs OBD2?



## secondgen (Jan 9, 2004)

So I picked up a second ABA head at the junkers a week or so ago, got it back to the shop and cleaned up and was comparing it to the other head I had (that came off the bottom end that's in my carat ATM), and the valves are completely different looking:
Head one:
















Head two:
















Any idea if there's any performance difference between the two? The heads, other than the faces of the valves are IDENTICAL. 
Head #2 was an OBD1 head, and I'm not sure what the second head is (OBD1 or 2)


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## Longitudinal (Nov 13, 2004)

*Re: Differences in ABA cylinder heads. OBD1 vs OBD2? (secondgen)*

Hey,
First off, NEVER whiz wheel a head or top of a block. A hand-held tool like that might leave a shiny surface and remove gasket material, but it leaves a far from ideal sealing surface with lots of peaks and valleys. Don't believe me? Run a sanding stone over the whiz wheeled surface and see what happens.
As for differences in the heads, around 1996 VW tried a high-swirl design. You can see the difference in the shape of the inlet ports. Other than that, I don't know about differences between OBD1 and OBD2 heads.


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## secondgen (Jan 9, 2004)

*Re: Differences in ABA cylinder heads. OBD1 vs OBD2? (Longitudinal)*


_Quote, originally posted by *Longitudinal* »_Hey,
First off, NEVER whiz wheel a head or top of a block. A hand-held tool like that might leave a shiny surface and remove gasket material, but it leaves a far from ideal sealing surface with lots of peaks and valleys. Don't believe me? Run a sanding stone over the whiz wheeled surface and see what happens.
As for differences in the heads, around 1996 VW tried a high-swirl design. You can see the difference in the shape of the inlet ports. Other than that, I don't know about differences between OBD1 and OBD2 heads.

You are observant.







Don't worry it was just to clean everything up, the head will be decked before i use it. And for the record if i wasn't going to have the head decked, i'd have used my sanding stone. http://****************.com/smile/emthup.gif 
Good catch and excellent point.
What do you mean by swirl design? And what's different about the inlet ports? I'm prolly just not catching it....


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## Longitudinal (Nov 13, 2004)

*Re: Differences in ABA cylinder heads. OBD1 vs OBD2? (secondgen)*

Swirl: you know how on GM SBC heads, they cast in a little wedge to induce tumble? Well, on the swirl ABA heads, VW changed the shape of the intake port to induce swirl. The swirl heads have a noticeable lack of symmetry down the vertical centerline of the port--kind of a turn to the side as the port bottoms out into the valve pocket. The '95 and earier heads have a more or less symmetrical port. Look closely at your two heads. If one is a swirl head and the other not, the difference will be clear.
I do not know how long VW used this design or if they are still using it.


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## secondgen (Jan 9, 2004)

*Re: Differences in ABA cylinder heads. OBD1 vs OBD2? (Longitudinal)*


_Quote, originally posted by *Longitudinal* »_Swirl: you know how on GM SBC heads, they cast in a little wedge to induce tumble? Well, on the swirl ABA heads, VW changed the shape of the intake port to induce swirl. The swirl heads have a noticeable lack of symmetry down the vertical centerline of the port--kind of a turn to the side as the port bottoms out into the valve pocket. The '95 and earier heads have a more or less symmetrical port. Look closely at your two heads. If one is a swirl head and the other not, the difference will be clear.
I do not know how long VW used this design or if they are still using it.

Cool, I'd have neer known that. http://****************.com/smile/emthup.gif I guess I'll have to check them out.


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## fast84gti (Mar 2, 2003)

*Re: Differences in ABA cylinder heads. OBD1 vs OBD2? (secondgen)*

On the exhaust port there may be a hole for exhaust gases to go to EGR. I think the OBD1 don't have the same holes in them. For porting and flow, the obd1 is better in the long run. You can port an obd2 to run the same, but it is just more work. The swirl can be removed during porting process. I only have obd 2 heads, but I have been told the OBD1's don't have the port. The ports go to a tube that is part of the exhaust manifold... 


_Modified by fast84gti at 2:10 PM 12-3-2006_


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