What the heck is going on here?

[Spassmacher]

So this is my first time assembling an engine, and I'm now getting to all the hoses and fittings and such. This is a picture of my engine as it was before I pulled it and rebuilt it. I'm trying to hunt down the fitting that is going from the top of my water pump to my thermostat housing. I'm not sure why that thermostat housing has an add-a-piece and goes down to the water pump, I'm pretty ignorant about all the passageways for coolant and fluids and such. So far I haven't been able to track down the fitting or the hose at any parts house. Anybody know what's going on here?



http://www.flickr.com/photos/72744831@N05/7227843970/

[Weasel Diesel]

It is a bypass used for fast warm up. Never seen it used on a chevy pickup smallblock though. Usually seen on marine engines. My Crusader marine engine had one on it and I did away with it when I rebuilt it and put it in my C10.

[Captainfab]

I have seen a couple in pickups, but mostly in medium duty trucks. But it seems like the Corvette's may have had that also? Did you loose the original fitting? There are a couple on this page, but since they are stainless they are spendy.

http://www.summitracing.com/search/P...nless+fittings

You could just eliminate the riser under the thermostat housing, and plug the port in top of the water pump, and be just fine. That is how most engines are.

[truckdude239]

jus cap it off you dont need it

[butch86]

if i was you i would cap it off...... it really serves no purpose in your application.

thats just my vote and opinion on the deal.

[Lee H]

Originally Posted by Captainfab

I have seen a couple in pickups, but mostly in medium duty trucks. But it seems like the Corvette's may have had that also? Did you loose the original fitting?

You could just eliminate the riser under the thermostat housing, and plug the port in top of the water pump, and be just fine. That is how most engines are.

Captainfab is correct, medium duty trucks and cars of the 60s and very early 70s with SHP engines got the bypass. It was a safety precaution in case the thermostat stuck closed. Usually the bypass hose went into a nipple in the intake, not a spacer.
Posted via Mobile Device

[ray_mcavoy]

Hi Spassmacher,

That looks like the stock bypass hose/adapter setup that was used on many 60's truck 327's. The pickup truck applications like yours used one bypass hose. While the medium duty truck applications used two hoses.

If you want to keep the stock bypass setup, the parts you need are still available. I recently went through tracking them down for the 327 we're getting ready to put in dad's 66.

The correct moulded rubber hose is Gates #20566. It's available from www.rockauto.com if you can't get it at a local auto parts store.

The 90 deg fitting that screws into the top of the water pump was a bit harder to locate. The original has a 1" hose barb and 1/2" NPT threads and is used in conjunction with a 3/4" to 1/2" reducer bushing in the water pump. The closest thing I could find were these fittings on ebay --> http://www.ebay.com/itm/5-FITTING-HO..._Parts&vxp=mtr They're nearly identical to the original except they have 3/4" pipe threads that go directly into the water pump (eliminating the need for the reducer bushing).

Originally Posted by Lee H

It was a safety precaution in case the thermostat stuck closed.

I've also heard that the bypass helps prevent localized hot spots inside the engine by allowing a small amount of coolant circulation while the engine is warming up with the thermostat still closed.