hello all, i recently thought it would be a "great" idea to upgrade to a offy 3x1 intake w/ 3 matched 1bbl rochester carbs for my 235. i bought the intake w/ carbs for 120 bucks, so i felt it was a deal i could not pass up. the only thing missing was the linkage which i am trying to find online or over the phone. well, needless to say it is a full time job in it self. does anyone have any info on where to find linkage? i would like to put a progressive set-up on, but if i need to, straight linkage will be fine. any info is greatly appreciated. thank you-DVZ
I just Googled "multi carb throttle linkage" and got 1,410,000 hits. You should be able to find some thing in there if you look. Might have to adapt a 3 deuces set up or use a universal kit.
go here: http://stoveboltengineco.com/index....:category=361512&mode=product&product=1222029 I'd suggest going with matched Carter WA-1 carbs though. Rochester's vacuum power valves will have you running super rich without a decent way to modify uniformly across all three carbs.
There is no progressive linkage available for 235 applications. Offy does make a cheap-ass direct linkage, though. Try Tom Langdon's Stovebolt Engine Co. Otherwise, I am currently working on a progressive setup for this (and other inline) application. I should have a finished version on my truck for testing in a few weeks...
Ain't that the truth. The dual solid linkage is bad enough and I think syncronization with the triple one would be hopeless. Seems to me the only way to get it right is with a pivoting rod. Will be watching for the progressive one you come up with.
The only way to get it 'smooth' is to turn the carbs 90 degrees - I spent over 2 years trying to make a 'sideways' progressive linkage and could never get a system I was happy with. The problems were binding and/or not getting WOT on all 3. Last winter I fabricated spacers to turn the carbs, and after making my own extended throttle shafts I was able to use 'V-8 style' progressive linkage. It works great.
Agree with a lot of the comments on here. First, dump the Rochesters. It is highly unlikely that they really match. Too many variants out there with different power restrictors, spring rates, and venturi diameters. The power valve issue is always a challenge and the usually-guaranteed leakage due to warpage between the airhorn and bowl castings will make you crazy. My dual carb set ups all use a siamesed shaft between the two carbs allowing for solid linkage. Progressive is another matter and much more complex. Going 90 degrees with elongated shafts is a good idea as suggested above. Adapting the manifold to allow the rotation will be a bit more difficult unless you have a way to cast an adaptor that matches the finish of the Offy. Otherwise, you can machine from stock but beware the billet aesthetic. The Offy does not have the capacity to run a countershaft. That is usually necessary for progressive linkage. You may need to weld some tabs on to do that. Hell...half the fun is getting there!
The adapters really don't look 'billet' - in fact, now I want to polish the Offy manifold - my 2 carb Offy was polished aluminum and I really liked the look. I started with a countershaft-type design but just on a bracket at the center carb; I was going to go with a long countershaft when I got the idea to turn them. You would still have to extend the throttle shafts.
Dave: Those adapters turned out nice. I am thinking of a way to do that and combine it with a phenolic spacer to serve two functions: Thermal break and 90 rotation. Here is my version of solid linkage for duals: Other side: My idea for a progressive triple would build on the concept above. Both end carburetors use a continuous siamesed throttle shaft. The shaft will pass through a spacer at the middle carburetor. Middle carb gets the throttle linkage and an extended throttle shaft. Non-throttle connected end gets a lever that feeds the end carb shaft. That is about as simple a system I can come up with. I will experiment with this idea over the winter...after I source a triple intake. Keep the ideas coming...
1931av8 - I was originally thinking of making the adapters from phenolic or a similar insulating material but was worried about strength. I haven't had any heat-related problems with the aluminum; my intake is water heated, not exhaust and I really haven't driven in any long, hot situations. Curt B - Nice brackets and levers/arms! Make your own?
The only concern I had was stud pull-out. That can be resolved with thread inserts like heli-coil. I don't think there is a lot of torque on the connection unless you have lots of deep potholes!
thanks for all the replies. i went to langdons and he said he did not have the linkage for a 235, but he did have linkage for the 250. he said it has about 95% of what i need. i may actually dump the rochesters, but for now i ordered 2 double carb linkages from summit (20 bucks each) and i am going to see if i can make it work. -DVZ
Yup. the fine threaded ball joints in my setup provide for extremely fine adjustability making it real easy to get them singing in harmony.
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