Head change

[Ross Clover]

my 90 engine is getting a new head . It just so happens that my 95 head measures up exact and is already rebuilt so it will fit what I noticed was the 90 head gasket only had really small holes in the water ports but the block and head have large triangle ports would it help to drill out the gasket so more water flows through the whole head instead of just the ends... does the 95 head gasket have better water ports or is it the same 1/4 inch holes as the 90?

[4.3LXJ]

That is about the same as for any engine. For better or worse, they all have small holes in the gasket

[BlueXJ]

Opening the gasket may increase flow but may compromise the gasket. Head gaskets have lots of pressure on them and when we alter them we may weaken them, so I would exercise extreme caution when contemplating head gasket surgery.

[Cheromaniac]

I'd leave the head gasket well alone. The same head gasket will fit on all 4.0L engines from '87-'06.
Keep in mind that your '95 head came from a High Output 4.0L engine whereas your '90 head is from a non-HO Renix 4.0L engine, so the intake and exhaust ports are in different locations. If you're going to use the '95 head, you'll also need the intake and exhaust manifolds from a '91-'99 HO 4.0L Jeep (except for WJ).
Then you'll find out that your '90 injector rail and throttle body won't fit on the HO intake manifold so you'll need more HO bits like the injector rail, fuel lines, and throttle body (TB). Your Renix TPS won't fit on the HO TB unless you modify it or make an adapter, so the list goes on.