Quote Originally Posted by pdt View Post
what is the height and width of the exhaust ports on the bridge port engine ?
I will have to measure my oval spare block tomorrow as im sure its bigger, but you have worked on them so should know.
I am realy interested to know the differences now.

I do understand a bit about the port timming, but some of this is new to me that's why I am asking.
if you know the exact sizes outboard ,then please put them down here.
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Suggested reading is Gordon Jennings "Two stroke tuners handbook" where port-time-angle equations will help you understand one aspect of 2-stroke power delivery.

Specific to the topic at hand, manufaturers eliminated bridges because when overheated they expand inward and scuff pistons. As Fred points out, a common means of reducing the problem is oiling the bridge through drilled ports in the piston skirt. The factory method was to eliminate the bridge entirely, thus eliminating interference problems.

While reading Jennings, take time to study maximum port width as a function of bore diameter (there is a formula). I've successfully removed bridges from OMC Permold blocks and made more power the result of larger port openings with less restriction. Take care not to widen ports further as ring drop will be induced: Bridge supports rings.

Regardless, there are two major downsides to the OMC 56: Lack of sufficient cylinder cooling, and too long inter-cylinder merges. The Mod-50 and all late-model triple use shortest possible merges. Improving the exhaust would make more power than all the porting in the world.

Good luck with your project!

Tim