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Water pump by-pass question

1002 Views 7 Replies 3 Participants Last post by  SnowScoutII
Why such a large bypass hose? I've noticed on virtually all SV's I've seen a large (1.5"?) bypass hose running from a "block" sandwiched between the intake and the water neck to the inlet side of the pump housing. My 1980 345 is different than this. It has the straight water neck instead of the long 90* bend water neck and does not have the "block" mentioned above. Instead of the large bypass hose, the pump housing is tapped for a 3/4" hose barb fitting. In the 4bbl spreadbore intake that came on it, there is a another 3/4" hose barb fitting tapped into the intake manifold right beside the thermostat. This fitting has another smaller hole tapped in it to accept the temp sending unit. My setup uses a 3/4" hose for the bypass instead of the short 1.5" or so bypass hose.

Now for the twist... When I swapped to the 2bbl intake, the tapped hole next to the thermostat is only a 1/4" NPT hole and too small to accept the hose barb fitting for the bypass hose. Now, does anyone see a problem with relocating the bypass hose fitting to the rear of the manifold between #5 & #7 intake runners (where the thermo-vacuum switch would go, yellow circle in pic below)? I'm not using the thermo-vaccum switch with my current setup. This is still in the same water passage as before, it's just not right next to the thermostat... I don't how important it is for it to be right next to the thermostat. What do you think? I suppose I could track down the "block" thingy and go that route with the large bypass hose if necessary.

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That's not possible in my orginal set up. Since the bypass water is being pulled off the intake on the ENGINE side of the t-stat, there is no way the bypass water can be shut off. Now this may very well happen with other bypass setup, but since I don't have one of those, I have no way of studying it to see how it would operate.

Anybody have an extra t-stat spacer block thingy laying around? If so, PM me if you want to sell it. thanks....
Well, to me it is/was broke. It came from the factory with a carb :barf: That's why I'm fixing it by putting EFI on it. That requires some things to be moved around a bit from where IH put them.:flipoff2: :flipoff2:
Pay attention Cheify.... look at the left edge of that pic and tell me what's under under the water neck. Now scroll back up to my pic and tell me what's NOT under the water neck. Like I said, mine is a 1980 setup.... the one in the pic you linked is not. 'Nuff said......

The site that has the pic you linked doesn't allow "outside calls" but here's the link: linkage pic
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