Neil,
There is a "cheap & dirty" way of approximating CR that only requires a set
of calipers. This way involves measuring the head from the valve cover
surface to the combstion chamber face. According to the Triumph TR6
Competition Preparation Manual:
8:5-1 = 3.460" thick
10.0-1 = 3.375" thick
According to the manual, some low compression heads are even thicker than
3.460. Anyway, using these figures, you can interpolate them and roughly
figure out how much to mill from the head for your desired CR. Its not
nearly as accurate as Ted's "proper" method, but unless you've got all the
stuff required to cc your combustion chambers, its more "do-able"
Hugh Barber
Hollister, CA
'73 TR6
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net]On
Behalf Of Neil Wehmeyer
Sent: Saturday, February 01, 2003 2:34 PM
To: Ted Schumacher
Cc: 6pack@autox.team.net
Subject: RE: Machining head for compression ratio
Thank you. I have just this afternoon installed the partly striped engine
back into the chassis, I will now be able to pull the head and make the
measurements. I can visualize how to compute the CI displacement of the
cylinder bore, but how is the displacement contained in the head arrived at.
Plugging the spark plug hole and pouring measured amounts of fluid into the
area comes to mind, but I'll bet there is a more elegant way
-----Original Message-----
From: Ted Schumacher [mailto:tedtsimx@q1.net]
Sent: Saturday, February 01, 2003 12:45 PM
To: Neil Wehmeyer
Cc: 6pack@autox.team.net
Subject: Re: Machining head for compression ratio
neil, you cannot come up with an arbitrary amount to mill. you have no
idea what has been doe to the head prior to your custody. yo cc the
block adn teh head, work out the formula for compression ratio ans see
waht you have in the present form. then reduce the head cc to achieve
the desired compression. it's safe, accurate adn the only way youcan
knwo for sure what you have. please let meknow if we can help. ted
Neil Wehmeyer wrote:
>List:
>Can anyone help me understand compression ratios and head thickness? I
have
>a '69 with engine #cc26944HE. The compression ratio of pre 1972 models is
>stated to be 8.5 to 1. According to the TR Repair and Operation Manual the
H
>in this serial number is for high compression. I have a core engine
>#cc53580E. The head from this core engine measures the same thickness as
my
>'69's head.
>
>Question numbers one and two:
>Are these two engines of the same compression ratio, or were compression
>ratios changed by differences in the pistons?
>If they are the same compression ratio, what does the H in the serial
number
>of my '69's engine stand for?
>
>Question number three:
>How do I determine how much to skim from these heads to increase the
>compression ratio by a set amount. I would like to bring it up to 9.5 to
1.
>
>Thanks for any insight provided.
>
>Neil Wehmeyer
>ngwehmeyer@attbi.com
>CC26859L
>
>
--
Ted Schumacher
tedtsimx@q1.net
http://www.tsimportedautomotive.com
108 S. Jefferson St.
Pandora, Ohio, USA
Fax: 419.384.3272 (24 Hrs.)
Phone: 800.543.6648 (US & Canada)
Tech/ Gen. Information/ Worldwide: 419.384.3022
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