65air_coupe

I noticed in a pic John Z provided that the original setup for my engine (L79) includes a cooling system bypass hose. It's my understanding this function should always be in place so that water continually circulates through the block before the thermostat opens. And if I remember correctly, some thermostats in later cars had a bypass hole in it allowing some circulation past the thermostat but it was my impression that was a very small hole and was more for bringing the heated water to the thermostat so that it responded correctly then any significant circulation through the block, but I could be wrong (often am).

I never gave it much thought before, but my car doesn't has a bypass. I'm using a later model reverse direction water pump (serpentine belt setup) and an Edelbrock manifold with only the heater hose fitting on the front. And since my car is A/C equipped, no water is normally flowing through the heater (A/C is usually on).

So I guess that until the thermostat opens, I have no circulation in the block? Is this something I should be concerned about? And how many others that have non-original manifolds and/or water pumps have this situation?

ctjackster

if it makes you feel any better, the non-SHP C2s don't have the bypass, and about half the ebay SHPs I see have the by-pass by-passed, not to mention all the 44461 intakes on the 'bay with the by-pass hole permanentyly plugged with a pipe plug.

Does your intake have accomadation for the by-pass hose?

SWCDuke

When the thermostat is closed, flow to the radiator is blocked, so it recirculates back into the block through the bypass(es) This promotes quick and even warmup.

If you have no bypass circuit(s) flow is completely blocked, so the block will neither heat up quickly or evenly, and the pump will probably cavitate, which will erode the impeller.

Some engines are set up so that the bypass closes as the thermostat opens, but on vintage Chevrolet V-8s the bypass(es) remain open. As the thermostat opens more coolant will flow into the radiator (and less throught the bypass(es) due to increasing flow area.

These cooling systems work fine as built. I have never seen a need to re-engineer it.

Duke

SWCDuke

All OE coolant pumps/blocks have an internal bypass - the "third hole" in the pump and block. The heater circuit functions as a bypass on non C-48, C-60 cars. The external bypass on some SHP engines can mean up to three bypass circuits.

You DO NOT WANT a cooling system with no bypass at all. The bad effects are explained in my previous post.

Duke

65air_coupe

Duke, do later reverse rotation pumps also have the internal bypass?

JohnZ

GM reverse-rotation serpentine pumps have the bypass hole - don't know about aftermarket pumps.

ctjackster

yeah, the SHP bypass is redundant, that's why I was referring to the one SHP bypass that the original poster noticed was not present on his car, which many choose to live without without exploding

SWCDuke

I have no idea. You need to talk to whoever modified your cooling system.

Duke

65air_coupe

Thanks John, that's what I have on there.

Well, that would be me!