measuring piston dome volume

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
\" how do you measure piston dome volume"
I just bought a 454 from a yard sale,

the seller has no clue as to the pistons used"


ok you want to calculate your compression ratio,
be aware all BBC pistons will NOT work with ALL potential heads.
remember open and closed chamber heads on THE BBC.

yodam.jpg

rectvsoval.jpg


youll need to verify clearance in the combustion chambers and valve to piston clearance

http://garage.grumpysperformance.com/index.php?threads/vin-casting-info.10474/#post-44012

https://www.mortec.com/bbc.htm
and you bought a short block all ready assembled from some source that has no clue what the pistons used are.
they certainly have a dome volume that will take up space in the combustion chamber and raise effective
compression,
but are they 35cc-50cc, 64cc ?
you'll need a deck bridge and dial indicator lexan plate and cc burette


,
AARfHkwt7wIGydhoIaZQFVsTX-uJuCY4ccvEzsCzZlNDotRDDr2zTJsziRpxOcyLu3CtM1EWf3dCQhMy3o5CzO3RowgybguVQVJlhnizs5b2XuZt9Fd1tpJZYqUvwAkWq-IyDy-cpZiIFY2vTA0pbwPSp8yeKF70Y1rgiI3Kph5b570WaycI24JJ-RPzLWSQ5iqHBOKRW0LYfw=s512-rw-pd-pc0x00ffffff

66797proform32.jpg

dial indicator and ideally a lexan plate and a burret with cc measuring marks
watch the videos, the procedure is very similar to measuring combustion chamber volume
you push the piston down bore 1", using the deck bridge /dial indicator,
seal the piston to bore ring gap area with vasoline,over the rings, wipe excess away

the bore diameter must be measured accurately, a dial caliper can be used
13cal.jpg




but a bore gauge is much more accurate
owler Full Warranty Extender Dial Bore Gage Set, 52-646-400, 1.4-6" Measuring Range, 0.0005" Graduation Interval: Bore Measurement Gauges: Amazon.com: Industrial & Scientific

fowlerbore.png

chkbr2.jpg


Fowler Full Warranty Extender Dial Bore Gage Set, 52-646-400, 1.4-6" Measuring Range, 0.0005" Graduation Interval: Bore Measurement Gauges: Amazon.com: Industrial & Scientific
www.amazon.com

6 Pcs Professional Premium Outside Micrometer Precision Machinist Tool Set 0-1"/1-2"/2-3"/3-4"/4-5"/5-6" Measuring Range Included 0.0001" Graduation: Amazon.com: Industrial & Scientific
6 Pcs Professional Premium Outside Micrometer Precision Machinist Tool Set 0-1"/1-2"/2-3"/3-4"/4-5"/5-6" Measuring Range Included 0.0001" Graduation: Amazon.com: Industrial & Scientific
www.amazon.com


Lexan Polycarbonate clear 1 sheet - 1/2" thick x 6 " x 6"

lexan1.png



pdome3.jpg


I found two 1/2" thick 6"x 6" thick lexan clear sheet on scam bay for about $22 plus shipping that will allow me to fabricate,
TWO of the 6" x 6" COMBUSTION CHAMBER CHECKING AND CCING cover plates,
a step drill helps
http://www.harborfreight.com/catalogsearch/result?q=step+drill
by simply cutting into two equal pieces and drilling a counter sunk 3/16" hole in each half.
lexans a whole lot stronger than plexi-glass, and 6" x 6" allows more sealing surface options so thats the route I took
and its extra stiffness and weight helps seal the measuring fluids


measuredeck.jpg


measuredeck3.jpg




the formula for a cylinder volume is R sq times PI (3.147) times depth, 1"=25.4mm
R=1/2 the diameter of the bore.

yeah a pocket calculator may be helpful.
lets assume a 4.25" bore,and the piston 1" down bore,

4.25 bore x.5= R= 2.125 x 2.125 x 3.147=14.21067 cubic inches
theres 16.3871 ccs in a cubic inch, thus 14.21067=232.87 ccs



in this case lets say you fill the cylinder and it takes 189ccs,
you sub-track that from the potential max volume of 232.87 and see you have a 43.87 dome volume

screenshot_20220119-172210_photos-jpg.317101


related threads YOU'LL NEED TO READ,
don,t skip the info links it great related info












 
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