Piston to wall clearance
Thread Starter
Pro
Joined: Aug 2008
Posts: 744
Likes: 19
From: Salzburg Austria
Piston to wall clearance
Hey!
Today I got the stroker kit for my 427 BB. Now I have a question about the piston to wall clearance.
I got a list from Scat that displays the clearance for several applications. My application would be "street naturally aspirated". The column next to right shows the ring end gap factor, in my case 0,004". But further to right there are two columns for piston to wall clearance, and I don´t know which to choose. What means "3,5" to 4,1" and 1,4" and up"?
Here is the list:
Thank you, Günther
Today I got the stroker kit for my 427 BB. Now I have a question about the piston to wall clearance.
I got a list from Scat that displays the clearance for several applications. My application would be "street naturally aspirated". The column next to right shows the ring end gap factor, in my case 0,004". But further to right there are two columns for piston to wall clearance, and I don´t know which to choose. What means "3,5" to 4,1" and 1,4" and up"?
Here is the list:
Thank you, Günther
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
You did get the part about the ring end gap factor? From your post, I'll guess you did, but just want to keep you from an expensive mistake in the event you missed it.
Drifting
Joined: Jun 2008
Posts: 1,565
Likes: 111
Typically, the oil expander support rings do not require gapping. They should already have a gap that exceeds your target first and second ring gap, but check them just to make sure.
Last edited by Neil B; May 20, 2017 at 05:13 PM.
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Melting Slicks
Joined: Mar 2008
Posts: 2,666
Likes: 289
From: Spring Park MN
Make it a couple thousandths larger than the top ring.
It used to be standard operating procedure to have more gap on the top ring than the second, but testing has shown that the pressure build up between the two rings cause the top ring to lift and flutter reducing ring seal. To fight this you now see grooves in the sides of the ring lands between the top and the second ring and larger second ring gaps to lower the pressure between the top and second rings.
Mike
It used to be standard operating procedure to have more gap on the top ring than the second, but testing has shown that the pressure build up between the two rings cause the top ring to lift and flutter reducing ring seal. To fight this you now see grooves in the sides of the ring lands between the top and the second ring and larger second ring gaps to lower the pressure between the top and second rings.
Mike