[d1mbu1b]

At the risk of sounding ignorenter...

Can you add material to the to piston surface?

Instead of paying a machinist to zero deck your block,
can you add some material to the top of your stock
piston only at the minimal quench area?
Then just fit and shave until you get the desired clearance.

Kind of like a poor mans stepped dish piston on a
zero decked block without buying stepped dish
pistons and zero decking your block.

[Bill Hanlon]

You'd need something better than JB Weld to hold the new material in place.

[Half-Inch Stud]

You can add a DURABLE coating to the piston.
---------------------------------------------
Anthing fastened to the pistons by screws is fraught with thermal difference & tension problems. Fastening shim to head's quench area sustains a thermal problem.

Block decking sounds so practical in comparison.

[Mr. P-Body]

The only way to "add" material would be to weld it there. Not advisable. What are you trying to acccomplish?

Jim

[TIN TIGR]

the issue is metalurgy..the piston takes the most insane beating in the motor..ya need consistent molecular makeup ..if ya had 2 types of material it would be prone to hot or cold spots..i have seen it done however..and it lived at moderate power levels..more of a test of piston configuration than racing tricks..

[d1mbu1b]

Originally Posted by Half-Inch Stud

You can add a DURABLE coating to the piston.

is it possible to get a durable coating 030 thick?

Originally Posted by Mr. P-Body

What are you trying to acccomplish?
Jim

trying to achieve quench without paying money to deck the block by adding some "material" whatever that may be, by whatever means to mirror the quench area on the head; while not increasing the static compression ratio (too much) on a 428 with 72 cc heads without buying custom pistons. There are not a lot of 428 piston options available.

According to my calculations (red flag) decking the block 030 removes 6.7 cc's from the compressed volume on a 040 over 4.12 bore
this changes the static CR from 9.78:1 to 10.4:1
and changes the dynamic CR from 7.9:1 to 8.3:1

These numbers are too high for my novice (in)abilities.


I am building down low (~4500 rpm) for a daily driver with a 268-218(050) square cam at 110 degrees

I am a tire kicker back, yard guy, just trying to save money.

here are my calculations...

STOCK DECK
inches cm

deck height 10.250
bore 4.160 10.5664
stroke 4.000 10.16
rod length 6.625 16.8275
gasket bore 4.300 10.922
gasket depth 0.041 0.10414
actual piston height 1.595 4.0513
desired piston height 1.625 4.1275
deck clearence 0.030 0.0762

total sqush/quench 0.071

ci cc
chamber size 72
dish volume (neg. for dome) 12
gasket volume 9.757
ring gap volume 1.000
clearance volume 6.681884236
compressed volume 6.190 101.439
swept cyl vol 54.367 890.918
displacement 434.937 7127.343
total volume 60.557 992.357

static CR 9.782813355

intake valve closing event at 0.05 in degrees ABDC
64.000
cartesian crank position -26.000
x 1.798
y -0.877
theta 1.296 74.25633387
Y 6.376
piston pin height 5.500
piston height 7.125
piston to deck 3.125 7.938205092
actual swept volume in ccs 42.478 696.0914366
actual total volume 48.668 797.530
actual CR 7.862182451 7.862182451






ZERO deck
inches cm

deck height 10.220
bore 4.160 10.5664
stroke 4.000 10.16
rod length 6.625 16.8275
gasket bore 4.300 10.922
gasket depth 0.041 0.10414
actual piston height 1.595 4.0513
desired piston height 1.595 4.0513
deck clearance 0.000 0

total sqush/quench 0.041

ci cc
chamber size 72
dish volume (neg. for dome) 12
gasket volume 9.757
ring gap volume 1.000
clearence volume 0
compressed volume 5.782 94.757
swept cyl vol 54.367 890.918
displacement 434.937 7127.343
total volume 60.150 985.675

static CR 10.40214285

intake valve closing event at 0.05 in degrees ABDC
64.000
cartesian crank position -26.000
x 1.798
y -0.877
theta 1.296 74.25633387
Y 6.376
piston pin height 5.500
piston height 7.095
piston to deck 3.125 7.938205092
actual swept volume in ccs 42.478 696.0914366
actual total volume 48.261 790.848
actual CR 8.346076598 8.346076598

[Schurkey]

There is NO POSSIBLE WAY to add .030 to the pistons such that it would not be MORE EXPENSIVE than just decking the block.

Smokey Yunick wrote about welding up pistons that had been holed by detonation; he claims he was pretty good at it, but of course he had to heat-treat them afterwards. And you're also adding weight that's going to change the balance--although perhaps not enough to be concerned with.

Might as well put stone to block and carve off thirty. When you're done and the bill is paid...you'll be happier knowing that the job was done with no stress to any of your engine's internal parts.

[Half-Inch Stud]

You can run rich for about 10, 000 miles and that can develop a .080" thick carbon coating. Mostly develops around the outer 0.4" perimeter, not the central regions.
Ask me how I know.

With some effort I sure you could reach .030". Perhaps a Holley.

[Overkillphil]

Why not just use offset wristpins or even eccentric rod bearings?

[Red Coupe]

Originally Posted by Schurkey

There is NO POSSIBLE WAY to add .030 to the pistons such that it would not be MORE EXPENSIVE than just decking the block.

Smokey Yunick wrote about welding up pistons that had been holed by detonation; he claims he was pretty good at it, but of course he had to heat-treat them afterwards. And you're also adding weight that's going to change the balance--although perhaps not enough to be concerned with.

Might as well put stone to block and carve off thirty. When you're done and the bill is paid...you'll be happier knowing that the job was done with no stress to any of your engine's internal parts.

What he said. A good TIG welder and plenty of expensive machine work would do the trick, just at a much larger cost.....

[mkpontiac]

I have seen 0.021 thick head gaskets available from Summit. That would improve the distance by .020 over a 0.041 thick gasket. They are $120. Has anyone tried this? Are there any negatives to doing this?

Mark

[Schurkey]

Originally Posted by mkpontiac

I have seen 0.021 thick head gaskets available from Summit... ...Are there any negatives to doing this?

Originally Posted by mkpontiac

They are $120.

I'd say you answered your own question.

Originally Posted by mkpontiac

That would improve the distance by .020 over a 0.041 thick gasket.

.030 in the hole, plus .021 for the gasket results in .051 of quench/squish.

Do-able; but it's on the high side of preferable. Not my first choice.

Bite the bullet; deck the block.

OR offset-grind the crank for .015 more stroke...

[lust4speed]

If you are running a late open chamber head or milled dish pistons, is there really enough area left to provide quench? Also, for years I heard that opening up the chambers would provide better flame travel and more horsepower -- but this definitely reduces quench area. Now they say more quench area is desirable.

So what type of quench area does a hemi have?

[d1mbu1b]

Originally Posted by lust4speed

If you are running a late open chamber head or milled dish pistons, is there really enough area left to provide quench?

That's a better question.
Is very little quench area better than none at at?

So with that in mind which of the two is safer:
squish - The zero decked 10.4:1(8.3dynamic)
no squish - or the stock 9.8:1(7.9dynamic)


BTW I like all the ideas.

[Schurkey]

Originally Posted by lust4speed

So what type of quench area does a hemi have?

None. The difference is that it also has NO DEAD AREA--too tight to support combustion; but too loose to induce turbulence in the rest of the mixture.

If you really have an open chamber--fine. That can work. Apparently, it works REALLY WELL for combusting nitromethane.

If you have a closed chamber--one intended to have a squish/quench area--but the clearance is too great to be effective--all you have is excessive hydrocarbon emissions, poor power, and a tendency to detonate.