Today I was at a car show and there where actually Oldsmobiles at it. I was looking at them and noticed about half had the rear of the manifold plumed to the front of the manifold. What does this accomplish, it looks like they are trying to even out the flow from the front to the rear of the head. Has anyone tried this and does it do anything?

 

It tells me they bypassed the heater core.

 

Probably too lazy to change it when it started leaking...

- Eric

 

There is belief that coolant flow is a bit stagnant @ back of heads leading to increased temperature @ cyls 7 & 8. The hoses help evacuate the area & route it to front of engine sending it to the radiator via front manifold cooling passage or stat housing. I had one engine that was always on the precipice of preignition, probably more prone to those cyls.

I plumbed only the left side of that engine figuring that if the heater core is hooked up than at least #8 is getting good flow, simply connected rear coolant passage & front passage. With no heater, one would connect the right side as well. IIRC it did help & remember shooting things w/ IR thermometer & it did cool that back corner better but don't recall by how much.

 

This is an ongoing debate on various automotive forums. Suffice to say that factory heater delete cars simply plugged those rear ports with no ill effects.

 

... And cars with A/C blocked those rear ports with a closed heat valve when on "Full Cold" A/C, presumably on the hottest days of the year, with no ill effects.

- Eric