Early Model Enging + new WaterJacket = No Diverter cap?

[smithla]

This seems almost silly to ask but I want to be sure. I have an early model engine where all the water enters through the water jacket side plate. This plate has rusted out. I replaced it with the newer "flat" style plate and I'm guessing I don't need a diverter cap. Or should I have a cap with multiple holes drilled in it?

Thanks,

Lance Smith

[Don Moyer]

Lance,

The full flow cooling system in early model engines provides somewhat better circulation within the block and head, even without a diverter cap. However, and while there's no rush, I recommend that at some convenient time in the future, you plan to add the diverter cap.

Here is a recent Q&A we prepared on installing diverter caps:

Q: What is a diverter cap, and how do I install one?

A: In late model engines, the diverter cap is a standard brass 3/8" hex-headed pipe cap installed on the stem of the "T" fitting inside the center of the water jacket side plate. Diverter caps are also used on early model engines when their cast iron side plate is being replaced with a late model style side plate. In the case of early model "full flow" cooling systems, the "T" fitting used on late model engines is replaced with a 3/8" 90 degree brass fitting in the following instructions.

The cap is modified after installation by drilling a 3/8" hole on the side, to divert water aft and down approximately 45 degrees; and a second 1/4" hole in the original top of the cap to divert some incoming water directly across to the manifold side of the engine.

INSTALLING A DIVERTER CAP:

1) If the "T" fitting does not extend in past the back of the side plate by at least three threads, the hole will have to be opened up a bit, using a 3/8" tapered pipe tap. Don't overdo the enlarging process in the beginning, and try the "T" fitting frequently to determine the fit of the "T" fitting.

2) After getting three or four threads of the "T" fitting through the side plate, dry-fit the diverter cap on the end of the "T" fitting, tightening the cap until one of the hex sides faces aft, and down about 45 degrees. Remove the cap and drill a 3/8" hole in that hex side, and a second 1/4" hole in the front of the cap. The 1/4" hole should face in the direction of the manifold side of the engine.

NOTE 1: Because the stem of the 3/8" "T" is a tapered pipe thread, it is not possible to know on which side of the hex head the 3/8" hole will need to be drilled until the cap has been actually "dry-fitted" to the "T".

3) Reinstall the cap on the end of the "T" fitting using a good sealer. Permatex cold-weld works well on the stem of the "T" fitting and on the inside threads of the cap itself.

NOTE 2: As an alternative to dry-fitting the cap and removing it for drilling the holes as per step (2) above, the cap can be installed using JB Weld, making sure that one of the flat spots in the hex head faces aft and down approximately 45 degrees, and then drilling the two holes with the cap
mounted on the back of the plate.

Don