Thread: Filled Blocks

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Read an article put out by David Vizard on partially filled water cooled blocks

His words : The question is, does such a move have a place in high output street and circle track motors.

By pouring block filler up to the freeze plug holes, the bottom third of the block is prevented from flexing, leaving the top 2 thirds of the blocks stiffer as a result. With this process, it is possible to generate more horsepower from the engine. This obviously improves ring seal and power due to less bore flexture.

However, we also get an advantage in temperatures. As much as 2/3 of the block can be filled before it has a significant effect on water temeperatures. The reason for this is that most of the heat in an engine occurs within the top inch or so of the block. From there down, temperatures drop considerably. Water temp can be kept down to 170degree fah. As a result of the block filler insulating the crankcase the oil temp is raised to 210 deg fah. Having oil and water at these temps is worth a measurable amount of horsepower. Eg a 300 hp chevy has up to 12 hp increase.


I have a few questions of my own:
- I recall on these forums that iron head small block chevys are prone to detonation at 1 full point of compression ratio as compared to the aluminium heads. So I am reasoning that if I can pull the water temp down to 170 deg f will this ward off detonation?


- I feel that this area of partially filled blocks needs more scrutiny from the more knowledgable members of CHR.

Thanking you.

S

Never ran one in anything but an aluminum head drag car. The theory is good, wonder if it's right on the heat issues???

Originally posted by southerner
:

I have a few questions of my own:
- I recall on these forums that iron head small block chevys are prone to detonation at 1 full point of compression ratio as compared to the aluminium heads. So I am reasoning that if I can pull the water temp down to 170 deg f will this ward off detonation?

Your question is about detonation as opposed to "spark knock", is that correct?

Originally posted by j*b
Your question is about detonation as opposed to "spark knock", is that correct?

I would be interested in an explanation of the difference between the two

Pat

Originally posted by Stu Cool
I would be interested in an explanation of the difference between the two

Pat

Hmm, actually, in this context there isn't any real difference, I misspoke, I was thinking about pre-ignition.

That being said, spark knock is the result of detonation, it is the sound of the fuel/air mixture exploding (instead of burning) and echoing off the cylinder walls, piston and combustion chamber.

Once the burn goes supersonic it is detonated so it's a matter of burn rate and the myriad of materials, geometries and processes that affect that aspect of the combustion process.

Thanks J*B

Pat

Originally posted by techinspector1
I've witnessed example after example of iron head street motors running at up to 11:1 on pump gas with tight (0.035"- 0.040") quench and cams with delayed intake closing points.

Quench, we used to refer to it, in the old days, as mechanical octane. Its main purpose is to provide a more homogeneous mixture around the plug. A homogenous mix will burn more consistent and" smoother" therefore lessening the chance of spark knock.

Later intake closing is crucial in controlling detonation in an engine like you describe. The later intake closing reduces cylinder pressure and in effect makes the engine " think" it has a lower compression ratio. Conversely, an engine with a lower compression ratio, say 9-1, can use a tight quench area and a cam with earlier intake closing events and generate the same cylinder pressures as the 11-1 engine in your example. This latter combination works well in low RPM street engines.

Aluminum heads reject enough heat, which also reduces cylinder pressure, to allow an increase in static compression ratio (usually .5 to 1 point), which restores the lost cylinder pressure due to the aluminum material.

I agree that the tighter the quench the better it seems to work. In our race stuff we usually stumble on to the point where the piston just touches the head and then back off a couple of thousandths.

Modern diesels have done away with cooling in the lower portions of the block. Only the upper most portion of the cylinder and all of the cylinder head are cooled. Some cylinders are even insulated in the lower portions. All of this is done because of a high sulfer content in the fuel and the cylinders must be kept hot so sulferic acid cannot precipitate out of the combustion processes and corrode the cylinder walls. This is refered to as low temperature corrosion. There is also a high temperature corrosion in which vanadium deposits form on the valve seats and get hammered into the seat causing pits. Cooling water is ciculated through the valve seats to prevent the formation of vanadium deposits.

Of course, none of this has anything to do with gas engines because there is no sulfer or vanadium in gasoline.

Originally posted by 76GMC1500
[B] Cooling water is ciculated through the valve seats to prevent the formation of vanadium deposits.

(/B]

Do the valve seats actually have cooling passages inside them? If they do, that's pretty trick.

We initially filled the blocks we used for racing to support the cylinder walls. We really weren’t all that concerned about the effects on cooling. We just wanted a bigger bore so we could stuff a bigger intake valve in the engine. Another way we used to "stiffen" the cylinder walls was to run high pressure in the cooling system, and it worked well. A buddy at Ford told me about it, it was kind of a serendipitous find for them and is the reason Ford engines had screw in freeze plugs. It seems this solved a lot of problems they were having with the old 427 NASCAR engines.

Originally posted by j*b
Do the valve seats actually have cooling passages inside them? If they do, that's pretty trick.

We initially filled the blocks we used for racing to support the cylinder walls. We really weren’t all that concerned about the effects on cooling. We just wanted a bigger bore so we could stuff a bigger intake valve in the engine. Another way we used to "stiffen" the cylinder walls was to run high pressure in the cooling system, and it worked well. A buddy at Ford told me about it, it was kind of a serendipitous find for them and is the reason Ford engines had screw in freeze plugs. It seems this solved a lot of problems they were having with the old 427 NASCAR engines.

Right, so it's coming back to the point where you have more control over cylinder flex, the more horsepower you can extract from the engine.

I may mention that Mr Vizard was supporting the idea of these partially filled blocks for street use. The block filler acted as an insulator between the crankcase and the water jacket thus getting different temperatures for the water and the oil, the oil by the way was a synthetic brand, probably something like mobil 1

Originally posted by techinspector1
In my experience, cooler water temps (160*F) will reduce the tendency of the motor to spark knock, however this is a band-aid fix in my opinion. The most important aspect of engine building to preclude spark knock is the quench dimension (piston crown to cylinder head measurement at TDC). I've witnessed example after example of iron head street motors running at up to 11:1 on pump gas with tight (0.035"- 0.040") quench and cams with delayed intake closing points. With lightweight components and reasonable RPM limits, I think this dimension could be tightened up even further.

On that quench dimension, most chevy SB's are at a deck height of 9.025 - 9.035 in deck height, so allmost any piston sits down in the bore .o25 of an inch, then you have your compressed composition gasket at .o38. So therefor if you add .038+.025 you get a whopping .063 clearance between the top of the chamber and the piston top. So I am reasonig after maesurig the same piston rod assembly on all 4 corners of the block get your dimensions and if the clearances check out, deck the block down to 9.000 deck height and any piston top slightly proud of the deck, say up to .008 of an inch leaves .030 clearance and a little safety margin for eventual wear and piston rock. I figure that with the 462 heads with a chamber capacity of 64 cc's will give an approximate c.r. of 10.25 - 1 with a 350 + .030 (4.030 bore ). Okay so how much more can that quench dimension be closed up ?

Cams, I have degeed 3 different cams with different lifts and durations, and have made a note of what height the piston is ascending in the bore when the intake valve closes, it measures out that the more duration the cam has, the intake valve closes with the piston further up the bore, Now if the cam is advanced say 4 degrees the piston will be slightly lower in the bore when intake valve cloure occurs, this will of course have an effect on dynamic cylinder pressure. The other thing I have noticed is cam lobe seperation angle. The llarger the dispacement of your SBC the tighter you can run the CLS angle, for example 350 - 108 degres, 383 - 106 D, and a 400 say 104 D.

To get all this, it took a lot of internet reading and even more degree wheel turning with different cam duration and stroke combinations to understand the relationship between cam and compression ratios and where you want the power in the egine rev range.

Hmm looks like tem pics did'nt load up.

Originally posted by southerner
different cam duration and stroke combinations to understand the relationship between cam and compression ratios and where you want the power in the egine rev range.

Static compression ratio, cam timing, flow capacities, rpm...etc are all components of cylinder pressure. The way these components are utilized in an engine combination determine the overall cylinder pressure of that engine and at what rpm peak cylinder pressure occurs. (Peak torque) An engine with 11-1 static compression ratio can easily have less cylinder pressure than an engine with 10-1 static compression ratio. Cam timing, particularly intake closing, has a large impact on cylinder pressure, but so does exhaust valve closing. Look into lobe separation and the effects it has on cam timing and cylinder pressure.

At the end of the day all these events relate directly to piston position/time, which of course are determined by the crankshaft stroke and connecting rod length.

Originally posted by southerner


I may mention that Mr Vizard was supporting the idea of these partially filled blocks for street use. The block filler acted as an insulator between the crankcase and the water jacket thus getting different temperatures for the water and the oil,

Hmm, I generally run the water temp at 180° and the oil temp at 220°. I would never run a filled block on the street unless someone could prove to me they had a material that would “move” exactly the same as the block and that wouldn’t eventually plug my radiator.

Originally posted by j*b
Hmm, I generally run the water temp at 180° and the oil temp at 220°. I would never run a filled block on the street unless someone could prove to me they had a material that would “move” exactly the same as the block and that wouldn’t eventually plug my radiator.

Heard of a product called Hard Blok from race engineering in California