[xk-engine] 9:1 piston specs

XK-Engine
1

Does anybody have a listing of the specs, dome height, etc. needed
to make a .020 over 9:1 piston for a 3.4L, XK120 (’‘A’’ head)
engine? I’ll use a composite gasket. Thanks.

ASC–
asc
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2

In reply to a message from asc sent Wed 7 Apr 2010:

If you are ‘making’ a piston you can work out your overbore
cylinder volume, measure your chamber volume and allow for
compressed gasket thickness and a small amount of space
above the top ring and work out what dome volume you need
to make the effective chamber volume at TDC any ratio you
like. If you go for wild cams you can afford a slightly
higher CR as the filling (and therefore CR) will be as good
at low revs.

Pete–
The original message included these comments:

Does anybody have a listing of the specs, dome height, etc. needed
to make a .020 over 9:1 piston for a 3.4L, XK120 (’‘A’’ head)
engine? I’ll use a composite gasket. Thanks.

–
68 E-type OTS, 99 Daimler Super V8
Cambridge, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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3

ASC,

If you’re using that as a starting point for some exotic setup, fine, but if
you’re just recreating the stock 9:1 piston, check the archives. The
consensus on the lists over the time that I’ve read them is that it’s not
worth upgrading. The seat-of-the-pants power increase is unnoticeable
without other mods. I’m pretty sure there are 9:1 pistons and higher
performance, higher compression pistons available for the 3.4L XK engine.
When I rebuilt my XK120 engine about eight years ago, I couldn’t find any
new ones 8:1 .020 over, only .030 and .040. I didn’t want to machine my
block any more than I had to, and found a NOS .020 set, but that was luck.-----Original Message-----
From: owner-xk-engine@jag-lovers.org [mailto:owner-xk-engine@jag-lovers.org]
On Behalf Of asc
Sent: Wednesday, April 07, 2010 10:21 AM
To: xk-engine@jag-lovers.org
Subject: [xk-engine] 9:1 piston specs

Does anybody have a listing of the specs, dome height, etc. needed to make a
.020 over 9:1 piston for a 3.4L, XK120 (’‘A’’ head) engine? I’ll use a
composite gasket. Thanks.

ASC

asc
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4

In reply to a message from Mark Stephenson (J-L) sent Thu 8 Apr 2010:

AFAIK, OEM 9:1 pistons for the 3.4 are NLA. The dome is a
different design than the 3.8 piston.

They are being recreated;

http://www.rob-beere-racing.co.uk/engine6.html

Paul–
The original message included these comments:

If you’re using that as a starting point for some exotic setup, fine, but if
you’re just recreating the stock 9:1 piston, check the archives. The
consensus on the lists over the time that I’ve read them is that it’s not
worth upgrading. The seat-of-the-pants power increase is unnoticeable
without other mods. I’m pretty sure there are 9:1 pistons and higher
performance, higher compression pistons available for the 3.4L XK engine.
When I rebuilt my XK120 engine about eight years ago, I couldn’t find any
new ones 8:1 .020 over, only .030 and .040. I didn’t want to machine my
block any more than I had to, and found a NOS .020 set, but that was luck.

–
PS
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
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5

In reply to a message from asc sent Wed 7 Apr 2010:

Hello ASC (is that your name?)

I went through the same exercise with my 140. My engine came from
Coventry with a 9:1 CR, and when I blew up a piston, I knew it
would be a challenge. I ended up having improved, short-skirt
pistons made by CP Pistons in California. Same hemi-head design as
original, but upgraded technology. Here’s a link:

It’s an alternative to Rob Beere’s pistons for about the same
price, or maybe less because CP now has the ‘‘program’’ for the
pistons.

Good luck!

Dave S.–
The original message included these comments:

Does anybody have a listing of the specs, dome height, etc. needed
to make a .020 over 9:1 piston for a 3.4L, XK120 (’‘A’’ head)

–
1957 XK140MC OTS, 1964 E-type OTS, 1973 Maserati Bora 4.9L
Orange/CA, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php –

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