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I have heard you can swap a A18 head onto a A20 and get a bump in compression. My thought is( i figure this to be so, just want someone with more experiance to varify) can a A20 head fit onto a A18 bottom end? with this combo bring the comp down to 8.5/8.6? or did I get that part wrong
 

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I have heard you can swap a A18 head onto a A20 and get a bump in compression. My thought is( i figure this to be so, just want someone with more experiance to varify) can a A20 head fit onto a A18 bottom end? with this combo bring the comp down to 8.5/8.6? or did I get that part wrong
That is basically correct on both counts. The A20s and the later 1.8Ls are interchangeable. The compression change would be minor though, 0.3 points at most. The older 1.8Ls have an oil port that is slightly different. You really don't want the 1.8L head though because it has a unique intake manifold that is compatible with nothing else. Best thing to do with an A18 head is to rob all the parts from it for spares.

However, if the 1.8L head in question happens to be from an ET1 engine the best thing to do is to pack it up and send it to me. The ET1 has evenly spaced small round intake ports that would be perfect for my ITB project. :D

C|
 

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lol, I thought it would make a good cheap high boost motor, being that a 2.0 head on a 1.8 would drop it. I have heard of 17psi on a factory A20, maybe 2.0/1.8 combo could yield 20+...
 

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boost

Not on stock pistons you need forged to take any kinda boost safely and realiably. Another option is too use A20A1 pistons which have 8.8:1 CR ratio but again not realiable the crowns are thinner than the others because of the lower cr ratio you really need forged for turbo for any kinda long term reliability.
 

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Not on stock pistons you need forged to take any kinda boost safely and realiably. Another option is too use A20A1 pistons which have 8.8:1 CR ratio but again not realiable the crowns are thinner than the others because of the lower cr ratio you really need forged for turbo for any kinda long term reliability.
you can say that again, especially with stock a-series rods they look more like toothpicks then connecting rods
 
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