So I'm knee deep in Oldsmobiles now, so I guess I should assimilate and figure these things out. For those of us running a hydramatic, in my case a Jetaway, behind a first gen Olds, swapping to an aftermarket carb is difficult for a number of reasons. The first issue, that is easily surmounted, is the small bolt pattern to the larger Holley or Edelbrock. Thankfully, that adapter is cheap and readily available. The bigger problem is how to make the TV linkage from the trans work with the new carb. On my '56 Holiday 98, my Rochester isn't quite up to snuff, and instead of rebuilding this carb, I'd rather swap on one of the good, newish Holleys I have around. If I'm ever out on a trip somewhere and need a power valve or something, I can saunter into any Pep Boys or Advanced and get whatever it is that I need, including a whole new carb if necessary. No such luck with an old Rochester. I chose a 600 cfm, single inlet, vacuum secondary, electric choke model I had on the 394 that formerly resided in my '61 Super 88. After staring at the factory setup, two things become clear; 1) I have to use the bottom portion of the throttle bracket on the carb since the Olds pushes instead of pulls, and 2) the entire linkage (literally) hinges on a stanchion off the left side of the carb, which mounts the bell crank for the throttle and TV link. I need that, except with a Holley. I decided to recreate the stanchion mount using a spacer underneath the Holley. First I started with a piece of basic 1/4" steel. Nothing fancy. I just used a carb gasket as a template and got to cutting and drilling. I hollowed out the bore with my Bridgeport but I'm sure you could do this with a drill, grinder, saw, or any number of other means. This doesn't need to be an exact science. I used my spare 394 as a mock-up motor for the mounting. Here is the adapter from small pattern to large pattern. And here's the plate with the stanchion mount I welded on. I found it helpful to take lots of measurements, but to use one spot from which all of your measurements are relative. I use the centerline of the left rear carb mounting bolt. Next I used one of my spare carbs to mock up the TV linkage One small modification that needs to be made here is to bend the throttle arm on the carb straight. The kick down hole at the bottom is actually in the right place, and is only negligibly further away from throttle shaft centerline than the Rochester. That way you still get full throttle range of motion. But the Holley has a small "S" bend in the lower portion of the throttle arm that puts the hole in a different plane than the TV linkage. I simply grabbed it with a pair of channellocks and a pair of linesman pliers, and bent the arm straight. To use the factory rod that connects the carb to the bell crank, I used this set, and turned it down by putting the ball so it stuck out of a hand drill chuck, and ran it through a best sander. The factory retaining clip even worked. Here's the part number. Here, mock up is successful and I'm getting full throttle range. I threw a coat of paint on the exposed parts of the plate and added a nylon locking nut on the stanchion to jam it solid. OK, now it's time to assemble on the car. I removed the Rochester and vacuum lines, and cleaned the surface with some lacquer thinner. I also removed the carb studs since the adapter has to go on first, and used the cap screws that mount flush. As always, use the utmost caution to not drop anything down the intake. Then install adapter Then install custom plate with stanchion Now add carb and reassemble linkage. And that's all there is to it. There's also plenty of adjustment in the idle speed, as well as the TV linkage itself to make fine correction if necessary. For less than $30 of gaskets and hardware, some steel from the scrap pile, and a few hours of measuring and cutting, this conundrum is easily resolved.
Going to pass on that job haha. Speedway sells a reproduction of the '56 Olds/Caddy air cleaner, except with a basic 14" paper element in the base. For the $109, it's money well spent.
Thank you so much for sharing this information. I made one for my 55 olds and it seems to line up perfectly. The true test will be next week when I take it for a drive.
Awesome work bro. And just to share some info from a previous thread, if you need to adjust the TV linkage a bit to get the trans to shift when you want it to, adjust it from the rod from the bell crank down to the trans first. The adjustment between the carb and the bell crank, because of the ratio, will give you much more change than you realize. And for myself, this setup has been rock solid (knocks on wood) ever since I put it together, and I have logged tens of thousands of miles without touching it. In fact I just had the car out yesterday.
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