Water Pump Bypass

Is a water pump bypass to the thermostat housing really necessary?
A lot of engines have them. They are mostly a small diameter, say ~ 1/2".

I'm tempted to bypass the bypass unless there's a compelling reason to use it.

The way I see it, the bypass actually diverts some of the cooler return water close to the pellet/sensor side of the thermostat rather than directing it to the block (or heads)...which is sorta counter-intuitive.

What's the opinion out there?

 

What engine are you talking about, they are all different.

 

The bypass allows coolant circulation while the thermostat is closed. If you eliminate the bypass you should drill the thermostat plate to allow some circulation. Usually three 3/16" holes will do.

 

this is for a 331 Hemi and a BB Chevy pump. (HotHeads adaptors) The old pump from the 331 has a cast-in-place internal channel that connects from the impeller chamber to right below the thermostat. The BB Chevy pump has 2 threaded ports at the top rear of the casting. Included with the Chevy pump are 2 socket pipe plugs & 1 short threaded hose barb. The hose barb would suit the bypass purpose alright. Was wondering if this is intended for the heater; but shouldn't that connection be at the intake side of the pump; aka the return from the heater?

 

"The bypass allows coolant circulation while the thermostat is closed."

Why?---So your heater will start working right away,(barely) before the t-stat opens,,nothing more.

They're not needed on older engines...unless your really need some heat right away.

 

I'm not sure it's just about a heater. Most of the circle track guys I know run either a home drilled or a Shaw vented thermostat. I thought the limited coolant flow was more about keeping air purged and preventing hot spots?

 

Dead heading the pump isn't a good idea.

 

I understand about not wanting to dead-head a pump. I'm trying to get my head around how the cooling system was/is designed.

This pic shows the cast-in-place channel that is in the original 331 pump.
It is below the t-stat..... what I can envision is that prior to the t-stat opening, the coolant is circulated through the block/heads, albeit in a limited flow because the coolant has not gone through the radiator yet.
The bypass is a much smaller path that still allows circulation, but slows down the flow until operating temp is reached; and then the t-stat begins to open; with coolant going to the radiator.


Or, am I all wet?

The 2nd pic shows the tapped ports on the BB Chevy that I mentioned b4.
The pipe cleaner just shows that the ports are common.

 

Big block chevys have a bypass hose from the intake manifold to the water pump. My guess is that you probably want to add that hose to your hemi, so coolant will circulate thru the engine before the thermostat opens. If you have a heater that gets coolant circulating thru it all the time, that should be able to take the place of the bypass hose.

Notice that I'm assuming you're running a thermostat.

 

That makes sense to me.

However,

The intake manifold on the 331 does not have any coolant passages at all; it's an Industrial engine, if that matters.
I'm going to make a "connector" that goes from head to head at the front of the engine similar to what is an integral part of the original 331 pump.
(see previous pic)

This connector will have a t-stat housing. I'm thinking of providing a bypass port on the underside of it to connect to the Chevy WP. I can always plug it if not needed.

HotHeads sells this aluminum cross-over, and what I've got in mind would be similar but with the t-stat housing facing up rather than forward




So, yes, I'll be running a t-stat.

thanks for the info.

gatz

 

I have the stock style 392 water cross over that goes from haed to head and holds the thermostat on my 354. It has a big block chevy water pump with no hose hooked up to the water cross over from the water pump like you are discribing. There is no cooling problems at all with my engine. Hope this helps.

 

gearhead....

If it's not too much of a bother, could you take a pic or 2 of that crossover?

thnx

gatz

 

I'm not surprised that you can get away without the bypass on a hemi...each engine is different.

 

One way or another, even with the t-stat closed you want the coolant in the engine to circulate.

 

-Could you pm me your e-mail so I can send you some pictures. I still suck at posting pictures. Drilling holes in the thermostat is a good idea. I have had two thermostats fail closed ,now I dont run one and have had no problems with cooling.

 

sent PM ^