Hey gang just a bit of trivea for you ? pulled my heads off this weekend only to find the back two water ports welded closed on my intake. WHY?

I never understood that. I believe they are all like that though. even my edelbrock intake IRC...

On an older type standard flow engine the cool water enters the front of the block and travels around the cylinders cooling them it then enters the heads at the rear of the block and is pumped from the rear to the front where it joins the flow from the other side of the engine to be returned through the thermostat back to the radiator for cooling---if the water was allowed to flow out the rear head ports the front of the cylinder heads would never get cooled and would melt ---its a complete flow path and there are some small holes along the block so a little flow enters the heads all along the path ---its an engineering attempt to balance the cooling so all parts of the engine cool appropriately---in a reverse flow engine like the new Chebbies the cool water enters the heads goes to the back of the engine down into the block and then back to the rediator---by cooling the heads more, detonation was held down so compression ratios and power could be increased even with today's fuels...................Dan

Mystery solved!

So would the addition of a reverse-flow pump convert the old style to the new? Surely nothing is that easy :cool:

So would the addition of a reverse-flow pump convert the old style to the new? Surely nothing is that easy :cool:

it's cam-driven. it may be possible with a cam swap and other parts.

I'm pretty sure I have heard of swapping to a serpentine belt and reversing the impeller. You would have to use the whole serpentine setup to run the belt on the "other" side of the pulley. I'm sure i have read where someone has accidentally installed a reverse flow pump. I dont think that would be possible if one was belt and one was cam driven? Stranger things have happened 8O

When you change to a serpentine belt you have to also switch to a reverse pitch impeller because you are spinning the water pump the other way---the water flow is still conventional---there is a whole lot of engineering to get the reverse flow cooling system and I don't know anyone that has ever reversed it sucessfully.................Dan

hmmm. maybe that ws something else? Northstar! that's it. okay disregard my other post.

Just when I thought I had learned something they change the question.

So if all you do is change to a serpentine belt on an older block what does that do to the water flow ??
Do you need to change the waterpump, cam, and heads also? to make water flow correctly?

All you need to do is change the waterpump to one meant for a serpentine belt when you convert to a serpentine belt ----everything else and the direction of waterflow stays the same----you are just spinning the water pump backwards to a conventional pump so changing the pitch on the impeller blades keeps the water flowing the same direction................Dan

Some GM vehicles may be equipped with a reverse-flow cooling system which operates differently than a conventional type cooling system. The specialized components of this system include a gear-driven water pump with cast internal cross-over passages, an inlet-side thermostat and a pressurized high fill coolant reservoir. In this system, coolant is routed from the water pump, directly to the cylinder heads. When the heads are adequately cooled, any accumulated vapors are vented off, and the coolant then circulates through the engine block. After the coolant leaves the engine block, it returns to the water pump, moving through an internal passage into the radiator. There is a thermostat on the inlet side of the pump which meters the coolant temperature as it flows from the radiator and tries to enter the water pump casting. The water pump, which is driven by the camshaft, which is the center of the system, has cast internal passages which route coolant through the engine without sending it through the intake manifold, eliminating possible leaks. The gear-driven pump ensures coolant flow even if the drive belt breaks. The reverse-flow cooling system is advantageous because it reduces the overall cooling system pressure and basically eliminates pitting or disintegration of the water pump and seal. In addition, routing the coolant to the cylinder heads first promotes higher bore temperatures and less ring bore friction, increasing output and horsepower. Due to the increased temperature of the cylinder walls, which created higher oil temperatures, engines with reverse-flow cooling systems may be equipped with an engine oil cooler or use synthetic oil.


Figure 3 Some vehicles employ a "reverse-flow" type of cooling system, which operates differently than a conventional system.

my mind went into overdrive trying to figure how you can reverse the flow when changing drive direction. If you draw a circular arrow with corresponding vains routing water in that direction then change the direction of rotation no pitch angle is possible to route water in the same direction. That is unless you remove the vains all together.

The other point Im stuck on is the cam driven gear in the reverse drive.
you have to have a total new block to reverse coolant direction.

there is a picture that goes with the above article. Cant post it so here is the link.

http://www.procarcare.com/icarumba/resourcecenter/encyclopedia/icar_resourcecenter_encyclopedia_cooling1.asp


Some thing's can not be had with old equipment.

the impeller on a serpentine belt type water pump is totally different as far as impeller angles are concerned almost nothing else was changed so you can bolt either to the old style blocks --the new engines are a complete redesign and there is almost nothing that will interchange with the old style small block and the new---there is as much difference in them as there is in one and a ford 302.

aoehero , I think your confusion is in the terms you're using. Reverse flow
means the coolant enters the heads first. Afaik The LT1 was the first small block to use this. Pump is driven by the cam.

The pre LT1 all used belt drive pumps. On the v belt setup the pump rotated in the same direction as the engine. When a serp. setup is used the flow remains the same(into the block,thru the heads, and out the intake thru the thermostat) but the rotation is reversed due to the way the belt is threaded. Thats why it uses a different impeller.





Rick

Totally missed your original question.
To prevent steam pockets and it's probably cheaper to cast it that way.







Rick

Only reason they are there is because Chevy Small block(and big block) heads are interchangeable from side to side. That means there is no left or right side heads so there would be need of the cooling holes on both ends as well as the bolt holes for the accessories on the front of the engine. No non LT1(93 up Z28, Caprices, etc.) ever had reverse cooling which has no bearing with the holes, they also had the same holes cast in them for interchangeability. The block on the other hand is different and the heads will not work on a regular pre LT1 block due to cooling passages in the heads.
Racers have used the rear ports on modified intakes or intakes with threaded fittings made into them for better cooling, it allows more flow and gets rid of air pockets that cause overheating. It will not burn your engine up, it does the opposite.
You do need a reverse flow water pump for factory serpentine belt systems but not all aftermarket serpentine belt systems. I have a March front accessory kit on my 350 and uses the regular water pump.
Not the best picture but this is what it looks like.

http://i57.photobucket.com/albums/g206/Mark_z28/R1Sielcamino013.jpg

We're talking about stock engines. They don't have threaded fittings to relieve the temp./press. Some may have a fitting to the heater on the pass. side.
The only other small block engine I've seen in that era was the L98 with aluminum heads that had the crossover ports at the rear of the intake.

So essentially, aluminum heads have the coolant ports at the rear of the intake and iron heads do not.

What you're seeing as welding might actually be corroded parts.


Rick

Thats what I was saying, racing engines use the back ports for extra cooling/air pocket removers. Has nothing to do with the holes being there though. They are there for ease of manufacturing or replacement costs.