[Fot] TR4 Compression Ratio Calculation Question

[Steve Yott]

Steve,
In order to calculate the combustion chamber volume desired you need also know the bore, stroke, head gasket diameter and thickness, piston to liner clearance, depth of the top ring and deck clearance of the piston (or pop up if you are running any).  These all make up the total volume which you need to calculate the chamber volume you need for the static compression ratio you desire.  Also when doing a chamber volume test don't forget that the valve head thickness will affect this measurement.

There are a good number of web sites out there that will do all these calculations for you and give you a required chamber volume for the desired compression ratio.  There are various head castings out there so I would not take the thickness into account except for a rough idea.

This all creates a "static" compression ratio and will not mean much when the dynamics of the cam and valve overlap come into play and create the "dynamic" compression ratio.... wish there were a good method of calculating that!

Steve Yott



-----Original Message-----
From: Fot [mailto:fot-bounces at autox.team.net] On Behalf Of Stephen Borowski
Sent: Friday, September 23, 2016 6:45 PM
To: FOT Triumph <fot at autox.team.net>
Subject: [Fot] TR4 Compression Ratio Calculation Question

Hello All,
Does any one know the "chamber volumes" vs "compression ratio” for the TR4 high port head. What should the head thickness measure?

All comments welcome!

Thxs. Steve
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