Yes the A4 head will bolt onto a K20A3 block, the issue is the pistons in the A4 block.
BUT the A4 head flows worse than the A3 head, it is the chump head of the Kseries engines.
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I thought there was more to this....
Does the stock A3 intake bolt on? What about any water, hose, misc connections that the stock A3 has compared to the A1 head? Any jimmy rigging have to be done? sanding?
The a1 head is exactly the same as the a3 head except it flows much better. You need a new a3 head gasket and use the k24a1 exhaust gasket. Deck the k24a1 head before puttin it on to be safe but that is it sir. Very simple. The k24a1 head is the only plain ass bolt on head from a k24.
seeing how we are talking about rebuilding the head...
How can a machine shop destroy the flowing properties of the k24a1 head?
What is the proper way to port the k24a1 head?
Does polishing the exhaust ports give better results?
Is there an advantage to using an OEM s2k valvetrain compared to k20a2 aftermarket valvetrain?