The Crossflow Chronicles

Crossflow Head Modifications - For the US 200 Block

Coolant passages

There are six coolant passages which have to be blocked off. These can be blocked by welding the holes shut, milling the openings to fit a pipe or freeze plug, or with a high temp epoxy. I chose epoxy. The Jeep crowd has to do the same mod to adapt a 4.0 head to a 258 and it seems to work well.

First, cover the head surface with masking tape (this could get messy) and cut out the openings. Use a file to thoroughly clean the opening. Next, stuff toilet tissue in the hole to support the epoxy as you pour it in. Not to worry, it will be "flushed" out later.

Mix up enough JB Weld or similar steel reinforced high temp epoxy and pour it in the holes. The tissue should prevent it from running into the coolant passages. Finally, take another piece of masking tape, cover the holes and the epoxy, and flip the head upright. Allow the epoxy to cure.

After curing, remove the tape and use a file to bring the epoxy to the same level as the head surface. Try to avoid scratching the head.

Coolant Bypass

A hole has to be added for coolant bypass. The Crossflow gasket has a position for this bypass, but it is not used. Open the gasket first by drilling a 3/6" hole. Lay the gasket on the head and mark the position of the hole. move the gasket aside and at an angle, drill a hole into the area just behind the thermostat opening, just like the picture below.

Finally, locate the three coolant passages on the pushrod side of the Crossflow head. The Crossflow gasket has positions for these as well, but they are not opened. Using a 3/16" bit, drill holes in the gasket to match these passages. One of these is visible in the picture below.

This completes the required head mods.