12 port are you talking about the "cadillac 261" engine? So what I am really understanding one of the main reasons you would increase the rods size is because of the design of the GMC rod is built stronger than the chevy, however if the rod is longer, then the added length of the rod would have to be subtracted by a shorter piston so it does not hit the head. The angle of the rod as 52Carl suggested I am sure has engineering benefits that i can almost visualize it I understand now how to get a longer stroke by offsetting the crank or putting a different crank that would work if that's even possible.
Now my next question since I put a stock 261 camshaft in my 235 engine, I was reading soup that chevy article that was published in May 1955 issue by hod rod magazine. Would the valve timing now be altered or the same as in the article? The article states the intake opens 11 1/2 degrees before top center and closes 52 1/2 after bottom center, duration 244 degrees and a lift at the valve .405
Exhaust opens at 51 degrees before bottom center and closes at 13 degrees after top center and a duration .244 degrees with a lift at valve .414 of an inch. Are these numbers the same with the stock 261 cam in the 235? This is stovebolt 101 for me. As I have mentioned earlier I have know rebuilt one motor. As I am reading the different concepts and thoughts I really can visualize what to do on my next stovebolt. I am taking notes all the way.
I think the "Cadillac 261" is along the same lines, but it makes a 261 cube engine out of a 235 block by stroking the crank to gain the cubic inch. Whereas Walt started with a 261 block and stroked it in a similar manner but arrived at close to 300 cubic inch because the 261 block has a lot larger bore to begin with than the 235 does.
Yes, the timing events would be the same regardless of the engine your installing the camshaft in, as long as you are able to "tweak" the cam by either advancing or retarding it to degree it in the same as the article, and of course as long as its the same cam profile as in the article as well. This may require a multi-keyway timing gear to accomplish though.
