Adding rear boost ports to a US820

mcbob · Post by **mcbob** » Tue Mar 10, 2009 6:37 pm

Well fellas .............. how hard is it To add rear boost ports to the US820 is there special tooling needed and how deep can i make them and whats the angle of the top of the boost port so the boost is directed correctly ?

I was told that some actally fit a window like in the Mac's and fit a closing plate over the window's to reseal the crankcase .............

Any hints would be great and if possible pic's would help this old fella.

Mc Bob.

mcbob · Post by **mcbob** » Wed Mar 18, 2009 9:10 pm

Well fellas since this thread has turned into a real weath of info i have gone and done my own thing i have copyed the Copperhead boost ports into my normal 820 but i started by drilling small holes straight through the crankcase and filing them till they have formed vertical slots now there not as wide as the Copperheads but i ground the outside the cylinder to get a smooth flat surface and i'll bond on a cover plate i won't fix it in place with small metal theads as i feel the threaded holes will only prove to be a point of stress and could lead to a factured case.
My next line of thought besides trying to avoid a quick hip replacement is to fit a cage having the adaptor i have made to mount the Mac SP125C oil tank to the Westbend engine do a double job of providing anchorage for a couple of long bolts travelling down the side of the outside the cylinder from a second plate above the cylinder head. Now i should be able to play with the ports a little more.

Mc Bob.

" I feel the need for speed "

mcbob · Post by **mcbob** » Thu Mar 19, 2009 2:03 am

Thanks Enzo for the Ackermam article ..........................

Mc Bob.

Butch Kavanagh · Post by **Butch Kavanagh** » Tue Mar 31, 2009 8:58 am

mcbob, sorry, had read your thread when you had posted but i am no machinest, i just drove (somewhat questionable at times) these engines mid to late 60's. i was loking in my scrapbook and and old thread dated dec 14 2007 by roger mulkey 1-diagram and port layout of a 'big j' 820 lay out.2-i quote "the boost 8 ports are done with a 1/2 ball end mill on a bridgeport with head at 20degrees off vertical". i was based out of ohio (as was bob jefferies) and ran against his and other great engine builders of that era, my engines were built by wiseco piston and they were just as equal. i was just a tier 2 driver who was fortuante to be in this sport.......hope this answers your question......butch

mcbob · Post by **mcbob** » Tue Mar 31, 2009 1:58 pm

Thanks Butch

When you have the URL to those pic's you wrote to me about send me the link as i cannot find them on my space.

Mc Bob.

Adding rear boost ports to a US820

Adding rear boost ports to a US820

Re: Adding rear boost ports to a US820

Re: Adding rear boost ports to a US820

Re: Adding rear boost ports to a US820

Re: Adding rear boost ports to a US820