Don Terrill’s Speed-Talk

Looking at reverse cooling an LS engine with an open cooling system. Meaning now water pump just water supplied from an outside source and exiting back to that source.

I need to see who chimes in on this, cause I thought all LS engines
were reverse cooled, you mean though the heads first correct.

That is correct. The old lt1 was but that ended a while ago. Lots of issues doing it when using a closed cooling system apparently but I do not know of any when using an open system.

Lakewater cooled boat? That's my experience with open cooling systems. In my case, using a neoprene-vane positive-displacement water pump as well.

I'd expect MORE problems with a reverse-cooled engine with a cooling system that is "open" rather than closed. Especially if that system gets put on a trailer and drained fairly frequently.

Far as I know, the "big problem" with reverse cooling is that air (or steam) wants to climb to the cylinder head, and the coolant is trying to push it the other way.

If this were me--and it isn't--I'd consider having two separate cooling systems, one for the block (both banks) and one for the pair of heads. Close off the water passages in between the block and heads, run both from front-to-back, or as close to that as core plugs or drilled holes allow. You could direct more flow to the heads, keeping them cooler like a reverse-flow system; but hopefully without a problem drawing the hot water out of a high spot in the block on each side, and a high spot in each head.

Early Pontiac V8s were reverse cooled. Then switched to conventional cooling. I presume the extra cost & complexity of RC wasn't worth the improvement, if any, in cooling.

I did read an engineering paper once where the researcher got an old 1200cc pushrod Corolla engine and made up a special head gasket that blocked the coolant holes, and with a bit of external plumbing ran the block at normal temp and the head quite cold. Two completely separate cooling circuits. Can remember the temp but it did mention the ability to use low octane fuel with 14:1 CR.

What is the application? Two of the racers that I have rubbed shoulders with over the years have both logged data of the water pressure of their boats open cooling system. One was a drag boat and the other a circle sprint boat. Both were shocked to see water pressure well over 100 psi in the heads (and that was running standard cooling through the block first and then the heads). They both altered their water pickups and the drag guy also reduced the inlet line size to try and bring it down to reasonable levels. My point is that if this is your application that you may be able to force so much water through that it may not be an issue, either way you want to run it.

Paul

Circlotron wrote: ↑Wed Oct 02, 2019 9:59 pm I did read an engineering paper once where the researcher got an old 1200cc pushrod Corolla engine and made up a special head gasket that blocked the coolant holes, and with a bit of external plumbing ran the block at normal temp and the head quite cold. Two completely separate cooling circuits. Can remember the temp but it did mention the ability to use low octane fuel with 14:1 CR.

You're giving me very bad ideas.

Interestingly there is a similar trend in modern 4 cylinder engines, where the coolant route is gated so that coolant flow goes only to the exhaust valves, then the head, then the rest of the engine, to maximize warmup speed.

FC-Pilot wrote: ↑Thu Oct 03, 2019 3:17 am What is the application? Two of the racers that I have rubbed shoulders with over the years have both logged data of the water pressure of their boats open cooling system. One was a drag boat and the other a circle sprint boat. Both were shocked to see water pressure well over 100 psi in the heads (and that was running standard cooling through the block first and then the heads). They both altered their water pickups and the drag guy also reduced the inlet line size to try and bring it down to reasonable levels. My point is that if this is your application that you may be able to force so much water through that it may not be an issue, either way you want to run it.

Paul

The application is marathon river racing. Yes we can see block pressure of over 100 psi if the system is not designed properly. In the past we usually feed the engine through a single #8 line and have two #8 lines exiting. we usually see approx 30 psi doing that.