4.0 head gasket query

Yanked the head off the '93 XJ searching for my overheating problems... gasket looked all good. fire rings intact, no apparent leakage anywhere. damn.

So, looking over the head, block and gasket I noticed a whole row of water ports along the left side of the head and block that are blocked by the head gasket. OEM and aftermarket gaskets are the same.

Coolant flow runs from the waterpump, rearward to the back of the block, though and up into the head then forward to the t-stat.

the right side has six holes that allow coolant up into the head.

Has anyone heard of modifying the gasket to allow coolant passage though the gasket at these points?

Wondering if this would be a good mod, or would it decrease flow to the rear of the block, causing a new set of problems?



What say the masses? links?

The head and block are designed that way for a reason. Changing this will make things much worse.

speaking from experience? have you tried this and it failed or?

I realize how they were designed, but as we all know the design of the XJ cooling was poor at best from the get-go.

Hence the question about drilling some small holes in the left side water ports to facilitate more coolant flow into the head.... if I can enhance the cooling of the head, now is the time to do it, while the head is off.

Maybe there is an aftermarket gasket designed with the ports open?

Digger87xj said:

speaking from experience? have you tried this and it failed or?

Click to expand...

When I had my head off I talked with several engine builders and they all agreed that you shouldn't alter the factory design.

Digger87xj said:

Maybe there is an aftermarket gasket designed with the ports open?

Click to expand...

No such gasket. All the 4.0L head gaskets I have seen have had the same size cooling ports. Felpro, Mopar Performance, OEM, Victor Reinz, etc.

Maybe Hesco would have some ideas on this.

being that the water flows through the block to the back, then up through the head from the rear, and out the front at the t-stat; i would think any holes made to allow water to go "straight up" into the head without circulating properly through the motor, would have a SERIOUSLY adverse effect on the efficiency of the system as a whole.
they're just casting holes, i would leave them be...

Thanks for the replies.

I'll leave it alone, as was pretty much the plan anyhow.