Thread:

Water routing - rear of manifold

Originally Posted by mpkardell

I wondered about this for years, and actually did something about it on the Olds I ran until last year: I removed the center freeze plugs and made inserts that allowed me to feed the pre-heated water off the logs into the center of the engine (in the center freeze plug location). I then drilled and tapped the rear bosses on my Torker intake so that I could dump water from all four corners. Just something that seemed like a "better" way to even out the thermal profile through the engine.

I've never seen a sectioned V-8 block, but I'm aware of nothing that separates or affects the in-flow and out-flow paths down the length of the block. With the freeze plugs out, everything looks pretty "open" in the water jackets. Seems to me that the bulk of the water would take the path of least resistance from the water pump inlets right back up to the thermostat outlet. That would mean most of it flows through the front portion of the block. Maybe it does, and the rear half of the engine gets by on some minimal flow circulation. Water is a very effective heat transfer medium, so maybe that's all that's needed.

Just thinkin' out loud.......

Something bout them olds motors.....I tore down the used 455 i bought that broke...found the spun brngs and broke main caps and the skirts on all 4 center cylinders were plenty torn up. As it was explained to me from someone at Mondello, 455 olds used in a marine application tend the run the 4 center cylinders cold...they sell, and i bought a set, of marine head gaskets and used them on my new build. I compared them to stockers before i installed them and the coolant passages were way scary small. I closed my eyes and installed them. Set up v-drive with a magnaflo i did have issues with building heat in the first motor....ended up using a drilled t-stat just to get 170*. Second motor ran kinda hot with the t-stat deal...pulled it out and the motor ran 160-170 all the time...even warmed up quicker.

As for how that applies to a BBC, it probably doesn't but if you check the head temp you might find 10-15* difference in the metal temp. front to rear.... (as it was explained to me long ago) Water moves in from the front plenty fast and fills the area around the cylinders. The head gaskets offer a minor amount of restriction to the flow to the heads...the water picks up a minor amount of heat from each cylinder...the water that gets to the rear cylinders is a little warmer and by the time it makes it back to the front the temp equalizes.

I do know a guy in utah who runs a 34 ford 530 8-71 aluminum head deal on the street. The intake dumps coolant out the rear.....because the radiator is in the trunk.....The thing that should be the radiator tucked neatly behind the grill is actually the condenser for the AC. I never thought to ask if it caused an issue but it was a full on 9.0 150+ street driver...that he let me drive around the block...one time....it was a freekin animal at half throttle!

edit:
And for a little more potentially irrelevant information
Early 90's GM decided it would be a good idea to pump coolant through a small block...backwards..iron head or aluminum...didn't matter....according to the engineer at tech school it was to reduce head temp so they could run more compression.

Older bbc installed in car/truck used to have a hose that ran from intake below t-stat to water pump...don't know if it was intended to bleed air or just recirculate during warm-up.

And i believe that by '88 all gm engines (v6-v8) pulled coolant for the heater from the rear of the intake..there was about a 1/8" hole in gasket to slow down coolant flow.

And someone correct me if i am wrong but years ago i was told that in an automotive application water pressure in the block, below the head gaskets runs considerably higher than a 20 psi rad cap at high rpm...

I did see a guy i worked with install a rubber freeze plug and used silicone to seal (great lubricant until it dries) it.....pulled it out on valley blvd in pomona and stood on it...pushed the plug out and did a couple 360's before he got it stopped...
ok..i'm done

Originally Posted by sunkisst

Seems to me, the water goes in the water pump inlets and just kinda roams around and eventually finds it way out the thermostat housing. Am I wrong? It seems to me, that if the water went in the water pump inlets, made its way to the rear of the engine and dumped out of the back side of the intake manifold, there would be more even cooling throughout the engine. Interesting , Hmmmm I am the one that asked John. AKA Mailman.

You absolutly cannot flow ALL the water in a BBC out the back. The most you should flow off the rear of the manifold is about a -6 from each side tee'd to a -6. This helps eliminate the chances of trapping any air in the very back of the head.
If you flow 100% of the water out the rear of the manifold, you WILL trap water over the entire front combustion chambers. If you block the front outlets, there is NO WAY for the water in the front of the head to exit.
Look at this pic and you will see there is no water passed into the head from the block until AFTER it has passed the front cylinder, with the exception of a very small passage to ccol the sprakplug. . The only way for water to flow thru the front of the head is for it to have a place to flow to. You can't flow water thru a Coke bottle.

There is no problem bleeding water off the rear. In fact there may be some benefits. But don't crazy with it. Like I said, I would never consider anything larger than a single -6 [B]DUMPED OVERBOARD[/.B] The more you flow straight out the back, is that much less that flowed over cylinders 1 and 2.

Originally Posted by 67weiman

So if water comes in the front and dumps out the front, wouldn't the path least resistance be out the front? I dump outta the rear. No t stat, four corner manifold. I plumber from the front to the rear, wit a t each side continue to a t to tie both aides together at the dump. Now, if the block fills with water, entering in the front, isn't more cold water going straight thru thread right back outta the dump at thefront? Head gaskets restricting flow yeah, but why wouldn't said hot spot be in the rear of the block if water enters in the front and exits in the front. Nothing forces water to the rear other than pressure correct? So if the heads have restricted flow and you are pushing water at let's say 18 lbs. Wouldn't it be beneficial to force into the rear to exit? How can it not flow across the head front to rear? Why are four corner manifold made?

Simple. water does not enter the head until AFTER the #1 and #2 cylinders. Explain how water entering the head will flow FOWARD if it has no place to flow to. Can you flow water THRU a Coke bottle?

Teeing the front to the rear will allow water from the front to exist. Thats not the same as BLOCKING the front, or flowing 100% out the rear.

I will repeat one part from my previuous post. EVERY single drop of water that exits the rear, is a drop that did not flow over the front 2 cylinders. If you choose to flow that much out the back, you are choosing to reduce the water flow over the chamber that has to deal with the hottest water in the motor.
Don't get the idea that the water in the head over #1 and #2 is cooler because its up front. ITS NOT! The cylinder walls are, the head IS NOT!

Yes, agreed. I'm not talking BLOCKING water from flowing out the front. I'm no expert. Just a hobbiest.