CRX Head Identification

[Domino]

Does anyone know how to identify a '90 CRX Si head from other years and models (except the HF for obvious reasons). I guess it's more of a camshaft issue then anything else. How do I know if I am getting a cam from a '90 Si as opposed to '88,'89 Si or worse, a DX cam without actually measuring the journals (since the cam will be installed).

[davew]

All Heads have a stamp on them that includes the chassis designation (PM6) for Si and a casting date stamp...the 1st is above the #3 exh port the 2nd is closer the the #1 port.

the date is not the model year, but is usually close...

-dave w

[Domino]

I had posed this same question to the cylinder head people. They do go by the casting numbers but said all PM3s were the same to their knowledge. My original head ('90 Si) is a PM3-8, the core exchange I got was a PM3-18.

[davew]

yes, my mistake...I meant PM3 for Si head, PM6 is the ecu code. The casting numbers are used by honda to track production runs not changes in the casting itself, though sometimes the two correspond (ie...some minor change is implemented at the start of a new run) but its not guaranteed. I have not studied these particular heads internally enough to say. But with the PR3 heads (from the DOHC B16A and Type R motors) there are some significant differnces in the castings. Honda made a number of improvements in the flow of coolant and oil through the heads after a certain point, which help keep #4 a bit cooler in harsh conditions and reduces headgasket failures from hotspots. The 2nd range of casting numbers can identify this...your average head machinist probably would not be aware of these differnces as they do not effect anything they do...all the tolerances are the same and all the parts interchange freely, so for all intent and purposses they would tell you they are the same head. Its only the race minded engine builders that can appreciate such fine details http://Forums.ImprovedTouring.com/it/wink.gif

-dave w