Ok, stupid question here...can the base plate off a 70 455 carb be used on the bottom of a 1972 455 carb?? The throttle bores are the same size (in fact, 350 carbs have the same size bores), but any other issues to be addressed (passages, etc)? Later Tim
Tim, IMHO, you are asking for trouble when you mix parts from different years of Q-jets. Certain differences can possibly give you phantom vacuum leaks. Not saying that's going to happen, but it did to me many years ago. Yes the throttle blades are the same size, but other passages may not match up.
Not only the vacuum leak issue, but you may change your idle circuit. When you take the bottom off of both carbs and compare you'll see the different passages. You can even hold the gaskets together and see where they're different. I put a 76 800cfm carb on my 86 231 just for fun. With the idle turned all the way down it wouldn't go below 1200 rpm. It had everything to do with the idle circuit. BTW... just to make life with Q-jets simpler, get Doug Roe's book Rochester Carburators.
Just for some info, I pulled a 72 and a 70 carb partially apart. The base plate gaskets are identical, the main body bottom and all passages are identical, and the only difference in the base plates is the extra passage that was used on calif cars and manuals for the EGR system on the 72 version (it appears the 71 version used this section to pull in vapours from the fuel cannister, in 72 this was used for EGR on some carbs, the cannister line went o the air cleaner itself). Since its not even ported unless used for those apps, its just an empty spot in the carb base, all connections are blocked off with the gasket. I had asked this question because I had a 72 carb missing the base plate but also have complete 70 carb. I now have a complete 72 carb as well, but might try the swap next summer just for a laugh... Thanks for your help. Book is on my Christmas list! :beer later Tim
This is a good question for John Osborne. I had a question similar to this one about swapping a 70 air horn onto a 72 carb body. He said it would be fine. (both 455 carbs) Email him though...I'm sure he knows. JOP455@aol.com
Well I just wanted to swap the 70 455 base plate onto a 72 455 carb (missing base plate), I have more use for a 800 cfm than a 750 cfm.... I won't bother Mr Osborne, I'll just play next summer....I'm sure it will work ok, but like I said I have found another 72 carb anyway so it doesn't really matter anymore...I get a kick out of this stuff though... later Tim
