On ram engines, some of us like to control the amount of heat going to the rams. George Riehl said completely blocking off the heat was the best way to go. Other people prefer the way Chrysler built it (no restriction), and some people are in between.
When I was restoring my J, I investigated methods of heat control. One method is to install cup plugs in the header as shown below.

I thought that was a good idea until I had to work on the headers installed in the car.
I learned access to the plugs is a bear.

Style 1 Style 2

So I came up with two styles of stainless steel shims that would fit the junction of the heat tube and ram. The first style has slots so it can be installed and removed after loosening the heat tube bolts (nuts). With the second style, you would install in the normal way over the ram studs. With either style, it is a lot easier to get to these than dealing with cups in headers.

If you choose to "dial in" some degree of manifold heat, it is easy enough to drill a hole.


At a minimum, you will need one block off shim for each ram (or two shims per car.)
If you wanted to completely isolate the ram from exhaust heat, you will need 4 shims.

Note: for long rams with thermostatic chokes, block off plates are not recommended
unless you have converted to manual chokes or disabled your chokes.

Aug 2019

Style 1 or Style 2 are
$5.00/each + $5.00/lot to ship within US
Bob Merritt
PO Box 279
Auburn, NY 13021
email: bob@simplexco.com