[East]

When my 428 engine was being built in the late 1980s, I had asked the machine shop to enlarge the dish on the .030 TRW forged pistons. It's been a long time and I don't remember exactly what I was told.

I am thinking about switching from cast iron 16 heads to Edelbrock D ports and wanted to get the proper range of compression to operate with the aluminum heads.

The TRW pistons had the same dish that the factory cast pistons had for 428 pistons and with them being modified, I am having to guess at the the dish capacity when I use the Wallace Racing compression calculator. I drive the car so I don't have the luxury of measuring.

All that I can say is that the dish was enlarged to approximately a quarter on an inch away from the circumference of the top of the piston, and there is a little bit of the valve reliefs remaining. The dish was not cut any deeper than what was originally there.

The picture is the only one that I found on the Internet to use as an example. I added the red circle as best as I could.

[Stan Weiss]

It is all guess work and does not take into account some of the dish was there in valve relief to start. A 2.3" dish 0.100" deep is 6.8 cc's A 3.5" dish 0.100: deep is 15.8 cc's.

Stan

[gtofreek]

To calculate CC's of a circle.

Diameter x diameter x .7854 x depth x 16.3871 = cc's

Using the example Stan gave above.

3.5" x 3.5" x .7854[to make a circle out of a square] x .100" x 16.3871[to convert square inches to cc's] = 15.7662747165 cc's or 15.8 cc's rounded off.

This formula can also be used to determine the weight of a particular material removed from a hole if you know the specific gravity of that material. For example, the average weight of steel is 7.83 grams per cc, so the above example, if it were steel, would weigh 123.45 grams. Aluminum at 2.6 grams per cc would weigh 41 grams.

[steve25]

To do things right and in the simplest way you need to get a short type plastic CC Bueret and some clay.

Pull a head and pack the excess clay down into the Pistons dish and slice off the clay with a single edge rasor blade such that its level with the top of the piston.

Next pull out the clay and roll it into a ball, then fill up the Burertt half way with water and drop the clay into it.

The change in the Buretts CC level is the CCs of your Pistons dish.

I would run the high comp version of the E D-port heads and have the dish made for the CCs needed to end up with a 10.6 to one compression.

Remember that when you figure out your compression that there is always a extra 1.5 to 2.5 CCs that people never add into there compression formula .

This comes from the back clearance of the 2 compression ring grooves, the running piston to Bore clearance from the top of the piston on down to the top of the first compression ring , and lastly that same gap between the bottom of the top ring and the top of the second ring if your not running a gapless ring, which is another thing you should be addressing in your rebuild!

The deck clearance makes a minimal change in the compression ratio and as long as your not bigger then 050" I would not sweat it , if your at .030" to .050" then your golden!

The Fel Pro 1016 head gasket checks in at 6.9 CCs just for reference.

[Formulas]

Or you can figure compression with the standard dish and valve reliefs and realize that a 72- 75 cc head will be in the neighborhood of 10.60 - 1 AREA depending on a multitude of small variations

.

[tc]

You can place the modeling clay in one of these
https://www.amazon.com/Measuring-Cyl...qid=1568551414

[Cliff R]

It's been quite a while since I did a 428 with factory or TRW replacement type 428 pistons but I believe they are very close to 12cc for the dish......Cliff

[AIR RAM]

Originally Posted by steve25

To do things right and in the simplest way you need to get a short type plastic CC Bueret and some clay.

Pull a head and pack the excess clay down into the Pistons dish and slice off the clay with a single edge rasor blade such that its level with the top of the piston.

Next pull out the clay and roll it into a ball, then fill up the Burertt half way with water and drop the clay into it.

The change in the Buretts CC level is the CCs of your Pistons dish.

I would run the high comp version of the E D-port heads and have the dish made for the CCs needed to end up with a 10.6 to one compression.

Remember that when you figure out your compression that there is always a extra 1.5 to 2.5 CCs that people never add into there compression formula .

This comes from the back clearance of the 2 compression ring grooves, the running piston to Bore clearance from the top of the piston on down to the top of the first compression ring , and lastly that same gap between the bottom of the top ring and the top of the second ring if your not running a gapless ring, which is another thing you should be addressing in your rebuild!

The deck clearance makes a minimal change in the compression ratio and as long as your not bigger then 050" I would not sweat it , if your at .030" to .050" then your golden!

The Fel Pro 1016 head gasket checks in at 6.9 CCs just for reference.

I have never heard of this approach however its ingenious in its simplicity!!!

Thanks for sharing this tip!!!

SPEED SAFE, NICK

[gtofreek]

Originally Posted by steve25

To do things right and in the simplest way you need to get a short type plastic CC Bueret and some clay.

Pull a head and pack the excess clay down into the Pistons dish and slice off the clay with a single edge rasor blade such that its level with the top of the piston.

Next pull out the clay and roll it into a ball, then fill up the Burertt half way with water and drop the clay into it.

The change in the Buretts CC level is the CCs of your Pistons dish.

I would run the high comp version of the E D-port heads and have the dish made for the CCs needed to end up with a 10.6 to one compression.

Remember that when you figure out your compression that there is always a extra 1.5 to 2.5 CCs that people never add into there compression formula .

This comes from the back clearance of the 2 compression ring grooves, the running piston to Bore clearance from the top of the piston on down to the top of the first compression ring , and lastly that same gap between the bottom of the top ring and the top of the second ring if your not running a gapless ring, which is another thing you should be addressing in your rebuild!

The deck clearance makes a minimal change in the compression ratio and as long as your not bigger then 050" I would not sweat it , if your at .030" to .050" then your golden!

The Fel Pro 1016 head gasket checks in at 6.9 CCs just for reference.

I think you mean 9.6 cc's. It's a lot bigger than 6.9.

[steve25]

Yup, thanks for catching that Paul!