Thread: Filling Water Jackets?

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Hi there! I'm going to be having a 400ci Smallblock built for me in mid december to match a pair of Dart Iron Eagle cylinder heads I picked up just recently. I was shooting the breeze with a friend at work (and an experianced mechanic at that), and he advised me to fill the water jackets, noting that he had learned to do this the hard way with 400s. He cited that the cylinder heads are the component that require the most cooling, and that filling the water jackets with a block filler (HardBlok, etc) would reinforce the block.

I wanted some input from some of the experianced folks here at CHR. Do you agree with this advice? I doubt the motor will be making more than around 380 crank horsepower.

Does this technique significantly increase block strength? Will I notice a detriment in my cooling efficiency?

Thanks in advance, always appreciate a little help with these things.

-Rob

This pertains to SBC only as these engines I have this experience in.

The filler you are talking about is Moroso's "Hard Block" It is mainly used for completely filling a block on drag racing only engines. But can be used on circle track and high output street engines by partialy filling the block to the bottom third only. At what level of horsepower a block is considered high output varies among engine builders. To the level of the bottom of the freeze plug holes on the side of the block. This idea completely eliminates bore flex on the bottom third of the cylinder and therefore stiffens the top two thirds of the bore. As we all know reduced bore flexture improves piston ring seal and increases power.

Another advantage is that the filler (I will call it grout from now on) insulates the bottom of the block from the hot oil in the crankcase thus giving the cooling system a break. With a good water pump and radiator and 170 degree thermostat you can run the water temp at an optimal 170 degrees F.
Inversely engine oil likes running at a hotter temp of 210 degrees F because at the higher temp it flows better.

I have used this system on stock car engines and it runs perfectly. I am currently building up a 383 blown SBC and am filling the bores to half way with grout. So that the bores are really stiff.

Most of the heat generated from combustion is in the top inch of the bore, by the time the piston is pushed halfway down the bore most of the heat is dissipated. As for oil Temperature the oil being sprayed up against the side of the sump underside of the rocker covers, dissipate the heat through these thin metal surfaces. Painting these surfaces wrinkle coat black rather than polishing actually improves the radiating effect of the sump and rocker covers.

a few points to remember :


1 Hotter oil is thinner make sure your oil pump and bearing clearances are
right

2 Fill the block only to 1 third and do it with one mix only for a stong natuarally aspirated street or oval track motor.

3 If you are wanting to run polished rocker covers and sumps run a small oil cooler and oil temp gauge.

4 Ideally pour the block first. Wait for the grout to cure (3 weeks). Then do your machining on the block

5 On 400 SBC or any other siamessed bore block make sure that the cylinder heads have the extra water recirculating holes for the water flow.

While this is not a bad idea,if you keep a 400 cool it realy will be ok. I have had several 406's that would run 180 all day long.

Southerner, thanks for all the advice! That will pretty much sum it up I think. Bigdude, also thank you, that has been noted. Denny, I think I missed you on that one?

Anyways, thanks again. I'll look into it a bit further, and see what's going to happen here.

Originally Posted by SBC Maro

Hi there! I'm going to be having a 400ci Smallblock built for me in mid december to match a pair of Dart Iron Eagle cylinder heads I picked up just recently. I was shooting the breeze with a friend at work (and an experianced mechanic at that), and he advised me to fill the water jackets, noting that he had learned to do this the hard way with 400s. He cited that the cylinder heads are the component that require the most cooling, and that filling the water jackets with a block filler (HardBlok, etc) would reinforce the block.

I wanted some input from some of the experianced folks here at CHR. Do you agree with this advice? I doubt the motor will be making more than around 380 crank horsepower.

Does this technique significantly increase block strength? Will I notice a detriment in my cooling efficiency?

Thanks in advance, always appreciate a little help with these things.

-Rob

One area that is often over looked when you "rock the block" is the "rock" helps to control harmonics.
Denny is correct when he talks about "wavy" cylinders.
You may have some issues with this.
That is why I would only fill them to the bottom of the freeze plug holes.

I see, I see.

Well, I was going to buy a shortblock from a shop. I'll talk to them, seeing as it was reccommended to fill the block prior to machinework.

As with alot of things in engine building (or so I've noticed), alot of opinions severely differ from person to person. Let's see what the shop says when I talk to them about filling it 1/3

Thanks again guys, I appreciate it.

I filled my 400 two inches from the block deck. I run over 500 hp n/a plus a 250 shot and the engine runs cool. I have an engine oil cooler as well as a tranny cooler running through the rad. I run dual 14 inch electric fans. You might want to consider filling the block 3.75 inches from the top, seeing as that is your stroke. In this way the entire travelled cylinder gets cooling. I think the depth of the water jacket is almost six inches.

An issue of greater concern for me is the routing of the engine coolant. Edelbrok has a wonderful intake which allows for the coolant to travel past all the cylinders, then exit upward and return back to the thermostat housing via external hoses. I partially block the front two ports so that I only have one eighth size return holes which forces the majority of the coolant to the rear before coming back to the rad.

Having said that, running 375 hp is far from dangerous. It wouldn’t need the filler.

Denny,
Yea, absolutely. That's what I was getting at

Typhoon,
Thanks. If I do go the way of the filled block, I'll certainly keep that in mind.