Thread: Tri-Power Carbs build.
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09-30-2006 08:48 PM #1
Carb Selection
Carb Selection:
I’ve mentioned before that what I have found in the past is that a relatively stock engine under 325 cubic inches will work well with 3 small base Rochesters, but once over that displacement engines tend to prefer a large base center Carb.
If you building a setup with 3 small base carbs, the center carb gets a standard rebuild with no mods other than possibly jet and power valve change. All jets and power valves from large and small base carbs interchange so having an abundance of “junk carbs around to rob the jets from can be a blessing as I know of no readily available aftermarket source for Rochester jets.
If I’m using a large base center carb I generally tent to try to find one off an engine of about the same displacement as the tri-power motor I’m building so the initial jetting will at least be in the ball park. I also like to have an electric choke so in a lot of cases I will pick up Pontiac Olds and Buick carbs when I come across them (I’m particularly fond of 400 CI Pontiac 2 bbls.
Up until I started rebuilding the carbs for the Hemi I would have said that all large Base Rochesters used the same size throttle plates….and I would have been wrong. The large base carb I had set aside for the Hemi turned out to have throttle plates that were the size normally found in the small base carbs (needless to say I pick out another carb to build). The picture below shows the difference in the in the throttle plate size.
As far as the end carbs I try to match them as close as possible especially as far as linkage and jetting is concerned.
I saw last night on fb about John. The world sure lost a great one. I'm going to miss his humor, advice, and perspective from another portion of the world. Rest in Peace Johnboy.
John Norton aka johnboy