Piston dome
Banned
Joined: May 2018
Posts: 4,576
Likes: 978
From: Viet Vet, crossroads
That is a million dollar question!
There are many ways to do this-
There are people out there that know math tricks that I will never comprehend.
For the stupid as in me,
KISS-
I use dental material as i can make a mold of the piston top and then CC it.
Simple.
Domed pistons usually have more than enough material so some can be romved to help adj the CR ratio too.
It is done all the time
There are many ways to do this-
There are people out there that know math tricks that I will never comprehend.
For the stupid as in me,
KISS-
I use dental material as i can make a mold of the piston top and then CC it.
Simple.
Domed pistons usually have more than enough material so some can be romved to help adj the CR ratio too.
It is done all the time
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,899
Likes: 8,005
From: poway
That is a million dollar question!
There are many ways to do this-
There are people out there that know math tricks that I will never comprehend.
For the stupid as in me,
KISS-
I use dental material as i can make a mold of the piston top and then CC it.
Simple.
Domed pistons usually have more than enough material so some can be romved to help adj the CR ratio too.
It is done all the time
There are many ways to do this-
There are people out there that know math tricks that I will never comprehend.
For the stupid as in me,
KISS-
I use dental material as i can make a mold of the piston top and then CC it.
Simple.
Domed pistons usually have more than enough material so some can be romved to help adj the CR ratio too.
It is done all the time
Last edited by Max Headflow; Dec 25, 2018 at 10:47 AM. Reason: )
Tourer
Joined: Apr 2007
Posts: 412
Likes: 281
From:
That is a million dollar question!
There are many ways to do this-
There are people out there that know math tricks that I will never comprehend.
For the stupid as in me,
KISS-
I use dental material as i can make a mold of the piston top and then CC it.
Simple.
Domed pistons usually have more than enough material so some can be romved to help adj the CR ratio too.
It is done all the time
There are many ways to do this-
There are people out there that know math tricks that I will never comprehend.
For the stupid as in me,
KISS-
I use dental material as i can make a mold of the piston top and then CC it.
Simple.
Domed pistons usually have more than enough material so some can be romved to help adj the CR ratio too.
It is done all the time
Tourer
Joined: Apr 2007
Posts: 412
Likes: 281
From:
Banned
Joined: May 2018
Posts: 4,576
Likes: 978
From: Viet Vet, crossroads
One could use Bondo if they wanted to.
The dental impression material will hold shape and is more EZ to work with than Bondo.
They make purrfect teeth with it every day. (copies)
If you get the impression of the dome plus head gasket (grease to seal it)
All that is left is to CC it.
It is a funny looking cup to measure.
Just keeping it simple here.
Like i said B4-
There is a LOT of other ways to do this, But I have found this one to be the most EZ and foolproof.
The dental impression material will hold shape and is more EZ to work with than Bondo.
They make purrfect teeth with it every day. (copies)
If you get the impression of the dome plus head gasket (grease to seal it)
All that is left is to CC it.
It is a funny looking cup to measure.
Just keeping it simple here.
Like i said B4-
There is a LOT of other ways to do this, But I have found this one to be the most EZ and foolproof.
Last edited by Kingglide549; Dec 25, 2018 at 06:14 PM.
Grand HDF Member
Joined: Nov 2009
Posts: 4,315
Likes: 1,663
From: Tampa
Similar to how you do a head. Lower the piston down about half way, put assembly lube around the cylinder, raise the piston back up to 1/2" from the top of the cylinder.
Wipe the assy lube up and check cylinder volume just like on a head.
Then do the math for the volume of this 1/2" tall cylinder and your bore, minus how much fluid you put in there = piston dome volume
Wipe the assy lube up and check cylinder volume just like on a head.
Then do the math for the volume of this 1/2" tall cylinder and your bore, minus how much fluid you put in there = piston dome volume
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,899
Likes: 8,005
From: poway
Similar to how you do a head. Lower the piston down about half way, put assembly lube around the cylinder, raise the piston back up to 1/2" from the top of the cylinder.
Wipe the assy lube up and check cylinder volume just like on a head.
Then do the math for the volume of this 1/2" tall cylinder and your bore, minus how much fluid you put in there = piston dome volume
Wipe the assy lube up and check cylinder volume just like on a head.
Then do the math for the volume of this 1/2" tall cylinder and your bore, minus how much fluid you put in there = piston dome volume
That's the way I used to do it. Now do the John Sachs / WFO Larry way.
Banned
Joined: May 2018
Posts: 4,576
Likes: 978
From: Viet Vet, crossroads
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Known volume, then subtract the difference.
Easy, peasy.
As far as reverse domes, S&S offers pistons configured that way, and as long as you maintain .190" dome thickness, you can pull cc's from a flat top piston if needed, in dedicated soft jaws that hold the oil control ring surface, in a lathe.
A 45 degree tool with an approx. 3/32" radius does a nice job.
Glory of a soft jaw is that if ever under suspect they are not running true, you simply load the scroll in the direction of the clamping load with an adjustable spider or ring, and bore, face, turn as needed.
They will stay running as true as a collet.
Scott
Easy, peasy.
As far as reverse domes, S&S offers pistons configured that way, and as long as you maintain .190" dome thickness, you can pull cc's from a flat top piston if needed, in dedicated soft jaws that hold the oil control ring surface, in a lathe.
A 45 degree tool with an approx. 3/32" radius does a nice job.
Glory of a soft jaw is that if ever under suspect they are not running true, you simply load the scroll in the direction of the clamping load with an adjustable spider or ring, and bore, face, turn as needed.
They will stay running as true as a collet.
Scott
Banned
Joined: Sep 2009
Posts: 3,569
Likes: 624
From: deland,florida
I also made fixtures for measuring dome volume,also have used modeling clay,both work fine.its really not rocket science.we pretty much use only CP pistons here and have found their dome volumes to very accurate to the advertised dome volume (everything is still checked though,never assume anything)