dimensions for water pump restrictor on 1966 and other small block?

[John M.]

Using the linked image, can anyone provide the dimensions of the cylindrical pin (between the pipe plugs and the gasket in the image)? Do you have one in use in your SHP 327? https://www.rockauto.com/en/moreinfo...322132&jsn=434 If link will not work it is Rock Auto 1966 corvette SHP 327 detail photos

[Joe L.]

Re: dimensions for water pump restrictor on 1966 and other small block?

Using the linked image, can anyone provide the dimensions of the cylindrical pin (between the pipe plugs and the gasket in the image)? Do you have one in use in your SHP 327? https://www.rockauto.com/en/moreinfo...322132&jsn=434 If link will not work it is Rock Auto 1966 corvette SHP 327 detail photos

John-----


The dowel pin used as a plug is 0.3707" OD and 0.75" in length. Is installing it absolutely necessary for engines with external bypass (like 65-67 L-79)? I don't think that installing it is essential and I'll bet there are lots of external bypass engines out there that don't have one. In fact, some rebuilt external bypass pumps were/are supplied without a dowel pin in the box. Without the pin installed the engine essentially has two bypass routes. The only downside I can see is that engine warmup might be very slightly delayed.

One other thing if it matters: once this pin is installed, the waterpump casting can only be used for external bypass type engines. If installed on an internal bypass engine (which is most small blocks), the engine would have no by-pass. Why is this a problem? If the thermostat should ever stick closed, one will find out why it's a problem. Actually, in such a circumstance, it might even be a good thing to have two by-pass routes.

[Duke W.]

Re: dimensions for water pump restrictor on 1966 and other small block?

The heater circuit is a bypass too.

Duke

[Joe L.]

Re: dimensions for water pump restrictor on 1966 and other small block?

The heater circuit is a bypass too.

Duke

Duke------


Yes, but for cars with a valve in the heater coolant flow circuit, only when the heater is on.

[John M.]

Re: dimensions for water pump restrictor on 1966 and other small block?

Joe, thanks for the information! I am going to remove my water pump and if that plug is missing will make one and install.Trying to divert more water to flow into the radiator rather than letting hot coolant by pass the radiator. May also put a restrictor in the shp bypass circuit on top of the water pump as well. Seems like a lot of coolant is able to bypass the cooling system in what I consider a marginal situation.

[John M.]

Re: dimensions for water pump restrictor on 1966 and other small block?

The hole in the water pump passenger side "leg" was a perfect size for a 1/8 NPT tap. After threading the hole a 1/8" pipe plug was installed and can be removed easily at any time in the future. Also used a 1/2" pipe plug with a 3/8 inch hole drilled in it to somewhat restrict water flow through the upper bypass hose. When warm weather returns will see if any improvements in cooling at idle are noted.