My question is about the main bearing "girdle" on a D16A6 motor.

I have a few of these around and was just looking one over today and this one has a 1 piece casting that covers all of the main bearings. Another one I've had apart has separate main bearing "caps" and a bridge/girdle that goes over the top of all of them. I don't know the history or vintage of either of them, but the blocks both read D16A6. In my '88 OEM manual it looks like the 1 piece bearing cap is an HF part, but the HF motor isn't a D16A6 is it? Were the bearing caps different over the years?

Any help info/clarification would be appriciated.

Thanks

I sent your question to a honda tuner friend ... his answer :

I am unsure, but early '88 year D16A6 has some quirks I do know of - early cam is cut on the D15 index and has a different cam gear that "corrects" this so that the cam is in the same alignment as the later 88 through 91 D16A6.

This may well be an early '88 quirk. Also, RT4WD sourced parts can be different - ask the gentleman if the engine with the odd girdle has the bolt hols drilled/tapped for an intermediate shaft?