pressure testing the block

[Sailwood]

I plan on doing a complete rebuild winter 2005-06. I believe I have the early model (Prestolite distributor). How does one pressure test? A "shop" job?
What pressure? How reliable is the test? If it fails, I suppose I'm saddled with useless iron, or is there a way to salvage?

Help is greatly appreciated.

Doug Soden
Sailwood@aol.com
C29, 1965

[Don Moyer]

Doug,

I assume that you'll be taking your block, and other water jacketed castings to a local machine shop to be professionally cleaned and magna-fluxed for cracks during the rebuild. If your castings pass the magna-flux test, and there were no indications of leakage from any of your water jacketed castings (block, head, and manifold) before you started the rebuild, you're castings are probably OK.

It's always a good practice to test run an engine after a rebuild. During a test run, you can block off the water discharge coming off the back of the manifold for several 15 second pressure tests. A flexible impeller pump is capable of producing approximately 20 psi when deadheaded in this fashion, and if you missed anything during the rebuild, this amount of pressure will usually show up any leaks in any of the water jackets.

If you have a particular concern over your block, head, or manifold for whatever reason, you could perform a pressure test on your early model engine before removing it from the boat, using a bicycle pump with a built in pressure gauge as follows:

1) Remove the water fitting from the inlet to the water jacket side plate, and install a 1/4" pipe plug in the inlet.

2) Remove whatever fitting is installed in the outlet of the manifold, and install a reducer bushing and a Schrader valve in that location. A Schrader valve is the standard valve used on automobile tires, and they are available at any auto parts store.

3) Pressurize the block, head, and manifold to 20 psi. The cooling jackets should be able to hold 20 psi for an hour or more without a noticeable drop
in pressure.

Best regards,

Don Moyer

[redwitch]

water in oil

Well if been working a problem for severl weeks now. Water in 3&4, water in throut of carbuator, Runs bad. Also water in oil. Seems to all of started about the same time ???????. I pressure checked system, held 20 lbs for several hours. Replaced head gasket. Looked at manifold, can't really see much. My best guess now is that the Manifold is corroded threw and leaking manifold water get in threw the intake manifold, Any one heard of this?