Comression ratio advice, 6 cylinder motor build |
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Comression ratio advice, 6 cylinder motor build |
team914 |
Apr 22 2023, 04:06 PM
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#1
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Newbie Group: Members Posts: 3 Joined: 5-April 20 From: Ireland Member No.: 24,102 Region Association: Europe |
Hi,
I am planning to build a 6 cylinder street motor for my 914/6 factory replica. My original 84mm barrels were worn, so I elected to machine the barrels to 84.5mm and have bought a set of 84.5mm Wossner pistons. With a 70.4mm crank, the compression ratio is stated at 10.11:1 with the pistons out of the box. I intend on using Weber carbs, E cams and an E distributor/123 Distributor. My machine shop engineer has recommended reducing the compression ratio from the 10.11:1 to a more suitable figure. The petrol quality in Ireland is poor, typically 95 octane, and we now have a compulsory addition of 10% Ethanol added (E10)! Any advice greatly appreciated |
gereed75 |
Apr 22 2023, 04:44 PM
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#2
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Senior Member Group: Members Posts: 1,250 Joined: 19-March 13 From: Pittsburgh PA Member No.: 15,674 Region Association: North East States |
The general wisdom says 9.5:1 is the max you can do on pump gas with a single plug.
Not familiar with the Wosners but it is fairly easy to remove material from the top of the pistons to adjust compression. Measure the volumes, do the calculations and then adjust. |
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