The original carb from my '70 Riviera has #67 primary jets. The carb I have been using on the car is from a '72 Electra that has #74 jets. As a side note, I see in the service manual that a '70 Stage 1 used #68 jets from the factory. I'm curious as to why the '72 Electra would use much larger jets? Does it have something to do with the air pump that was on it? And the fact it is an 800 cfm carb? I ask because now that I have the engine rebuilt, I can't seem to get the '72 carb in tune, it seems overly rich, and I have tried cleaning it, adjusting the float level, and everything I can think of to no avail. I'm wondering if I should switch it back to the to the #67 jets? Maybe it ran well on the engine before rebuilding because leaking valves and such compensated for the overly rich condition? o No:
The 71 and up 455 carbs are 800 CFM, and the have bigger primary venturi. They were jetted richer from the factory.
I thought as much. I'm going to go through the original 750 carb and see if it works better. I usually have pretty good luck working on these, I refuse to be defeated! I'm hoping to send one of them to John Osbourne this coming winter to work his magic on. From what I have read on this board it is money well spent. I doubt I would notice any real difference in performance between the 750 and 800 anyways. I won't be racing with it.
Keep in mind that the large disparity between jet sizes on 750s and 800s is accompanied by an equally big difference in primary rod sizes. You'll be super lean with a 67 jet and the much larger rod from the later carb!
Nicholas is dead on...lots of us forget about metering rod diameters when talking primary mixtures. Devon
:TU: I always keep them paired together. But thanks for mentioning it. I hope to get to it this afternoon. I'm on vacation from work this week, but of course there is work around the 'ol homestead to do. Paint touch up, etc. Still better than sitting at work!
