Can someone, who is knowledgable on the topic, please give specifics on the differences between the three different head combinations on RSXs. I am trying to find out if it is just the valvetrain that is different or is the actual casting different. TIA!

 

the USDM Type S and the JDM Type R have the same casting.......the base model K20A3 is different/useless

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jdkindle &raquo;</TD></TR><TR><TD CLASS="quote">the USDM Type S and the JDM Type R have the same casting.......the base model K20A3 is different/useless</TD></TR></TABLE>

why is it useless?

 

Because it can not flow enough air, like the Type-S and Type R head does.

 

Useless for NA, maybe, to an RSX-S stunna.

VTC and boost will provide more power than a streetcar can lay down, on a stock engine... you can keep the VTEC, it's useless.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by J. Davis &raquo;</TD></TR><TR><TD CLASS="quote">Useless for NA, maybe, to an RSX-S stunna.

VTC and boost will provide more power than a streetcar can lay down, on a stock engine... you can keep the VTEC, it's useless. </TD></TR></TABLE>
what does this have to do anything with the question?

 

The port size of the A2 head is alot greater than the A3,but the A3 can be ported the same as an A2..the casting and material themselves are the same,but more material was added to the A3,which is why the ports are smaller..also...the split in between the ports on any cylinder is very different on the A3...it curves towards the valve that is active all the time,also making that side'd port narrower..and the part of the splitter closest to the bowls has an opening so the fuel doesnt pool up on the unused valve,its directed to the other valve...thats goes back to the curved splitter.Both the intake and exhaust ports of the A3 head are considerably smaller,but like i said before,thats not a big deal cuz it can be ported to the same size as any other k series head.The inside of the ports is large,its just the entrance...also...the combustion chamber of the A3 is different...the side arent completely round like normal port...(im not talking about the quench area)picture the quench area but add a 3rd quench area to only one of the sides...i beleive also that the valve length between the two heads is a few mm different...but valvetrain will swap between the 2...the exhaust side of the A3 has only 1 lobe per 2 valves(roller rocker also)..the intake side Has 1 lobe per 2 valves,but has sort of a "helper" lobe,for the"vtec" rocker arm..its only like 1 mm lift,just to keep the rockers aligned..i think for all out drag apps..the A3 valvetrain in a A2 head would be the best....ive got a few more things ive found out but dont want to reveal too much..PM me for more info about K series engines..