Thermostat Bypass Housing Help

[jrocket567]

I'm having a hard time finding the inlet/spacer located below the thermostat on my '66 327. Does anyone happen to have a part number, or at least what it is officially called? Looks like the inlet is for the bypass, although not 100% on that either.

Details:
1966 C20
327, 99.99% original
Short water pump

Thanks,
Jay

[markeb01]

Interesting, I'd never seen or even heard of a bypass on a small block Chevy.

All I have to go by is the 1960 Chevy truck shop manual - on page 8-115 they do show a line drawing of a system similar to your picture. Apparently what you're looking for is called the Bypass Thermostat Housing. On page 8-116 there's brief disassembly instructions under the title: Thermostat by-pass cooling system (Connections for Engines Equipped with Automatic Transmissions).

I tried Google, EBay and Ecklers and don't find anything under bypass thermostat housing. This has got to be a rare piece.

[chevyguys]

That's a cool rare part... What's wrong with it besides the broken bolt? You can buy a 1" spacer that is threaded with one or two outlets at summit or jegs. CPP also makes one. Although it's not needed... you could just remove it and plug the waterpump housing.

[Captainfab]

It seems to me those were more common on Vette's. As was already said, you really don't have to have that, as there is already a smaller thermostat bypass internally. You would just need to plug the port in the top of the water pump. Unless of course you want to keep the truck original if it did come that way from the factory. I haven't seen one on an original truck that I can remember.

[jrocket567]

Thanks for the replies, almost glad to hear that its rare/wierd and im not just totally overlooking something stupid.

@markeb01- Thanks for looking through that book; I only have the 63 and 66 manuals. The name will give me something to run off of.

@chevyguys- nothing is really "wrong" with that part- missing some iron in areas due to 40 yrs of water sitting in it. The bolt that broke looks like it will not be fun to get out- water has been leaking around it for some time. Push comes to shove I can bore the whole thing out..

@Captainfab- Thanks for the Vette connection; just got off the phone with a friend of mine who has a 66 Vette and it does have something very similar.

I'm going to do a little more digging on it while I wait for a few more parts to come in, and if nothing, put a plug in the water pump.

Thanks,
Jay

[Eagar1]

Time to upgrade to an aftermarket intake, good used ones are really cheap.
Can't you lift the housing off over that bolt, exposing the rest of it? If it won't come out, just weld a stud to it, and grind it enuff to slide back down and use a nut and washer?

[NGN]

jrocket567, hope all been good. Well I came across this old post and found it interesting as I too have the same set up on my 1967 327, can't say I ever seen one myself or just never recognize it. Well in the interest of keeping my engine and bay area looking stock, I was wondering if you or anyone out there might of got more info on the uses of this thermostat bypass housing.
Thanks in advance to you and all .
NGN
Nick

[ray_mcavoy]

Originally Posted by NGN

I was wondering if you or anyone out there might of got more info on the uses of this thermostat bypass housing.

Dad and I recently swapped a 327 into his '66 C10 and it has one of those bypass housings. I believe they were original equipment on all 1967 & earlier 327's in truck applications. The ones used on Corvettes are similar, but not the same casting as the truck ones.

The purpose of the bypass is to allow some coolant to circulate through the engine even when the thermostat is closed. That continuous circulation helps avoid localized hot spots.

As Captainfab mentioned in an earlier post, the small block V8 already has a smaller bypass opening built into the block & water pump ... it's the extra hole on the passenger side below the lower mounting bolt. Although, I believe this passageway was blocked off with a metal dowel rod in the truck applications with the external bypass adapter / hose.

I've also noticed that the pick-up truck applications used a single bypass hose running from the adapter to an elbow fitting on the top of the water pump. While the larger truck applications used two bypass hoses going into a tee fitting on top of the water pump. The same bypass adapter was used for both so the pick-up truck applications have a pipe plug threaded into that unused hole on the driver side of the bypass adapter housing.

[Steeveedee]

I suspect that that housing was used in situations where higher RPM use would be expected. I have no proof of that, but just think about trucks being used to haul loads when still cold (and that little hole in the water pump maybe couldn't do the whole job), and everyone knows how people who drive Corvettes are. Like I should talk, since I revved the snot out of everything I ever owned, even when cold. Once it had oil pressure, it was game on!

[shortstep60]

I have a 1966 parts truck with the four barrel and that bypass it is a factory set up. You just don’t see very many of them.
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[macleek]

Originally Posted by shortstep60

I have a 1966 parts truck with the four barrel and that bypass it is a factory set up. You just don’t see very many of them.
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[shortstep60]

Sorry sold it on the for sale side of the forum.

[macleek]

Originally Posted by shortstep60

Sorry sold it on the for sale side of the forum.

Ok, thanks for the reply.
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