I picked up a 72 Stage 1 motor out of a riviera... It has a "stage 3" cam as stated by the owner and I can see dual springs on the valves. It didnt come with the carb as the seller kept the Holley that was on it. I was planning to use the carb off my 350 GS when the transplant occurs but I found conflicting information on the board. Some say a 750 carb is fine and there is no noticeable difference in going to an 800. Others say a 800 on a 455 is a necesity. Well I found what seems to be a good deal on a 74 800 CFM It has new Gaskets, New Float, New Bronze Bushings in the Base Plate, Bleeders have been Epoxied The set up is 73 Jets 43B Primary Rods CV Sec. Would this work nicely on my motor? Worth buying to use instead of a750 off a GS350? Right now there are no electronics on my current carb, all removed from by the previous owner. Here is a pic of the one Im looking at buying
You'll never know exactly what setup to use with the info you have given on the engine and drivetrain so far. It's possible that the carb you're looking at will run ok, but it's a shot in the dark and there will undoubtably be some adjustment required to make it run "just right". There are too many variables regarding a rebuild to tell if the purdy carb in your picture is built correctly. Best bet is to e-mail Cliff Ruggles to get his input. He's an expert who seems more than willing to give advice... although he'll probably give you a similar answer as above... It may be better to get a cheap core built exactly to your car's spec than to spend lots of $$ for a "good carb" and hope for the best.
Overall, if the carb is set up right, a 800 cfm will be useful on the 455. If it's not set up right, it won't make much of a difference if you've got a 750cfm or 800cfm
Makes sense.. I'm in no hurry so I'll pass on this one for now... Edit: Forgot to say...Thanks for responding!
Sorry for the late reply, but it is not so uch the extra cfm that will make the difference it is that the idle air passgaes are different in a 455 carb compared to a 350 carb. I have had good luck using 455 carbs on 350s but it is strickly not advised to use a 350 carb on a 455 it will not run right. If you complete extensive mods you can make any q jet work but for the best bet, find a virgin non rebuilt 455 core from 71-74 and have it rebuilt carefully.
If it's a good deal grab it. Either carb is probably going to need some help to work perfectly in all areas on the 455 with the Stage 3 cam, but the 800 is a better overall choice for it. Nothing at all wrong with a 750 cfm carb in that application, and tuned correctly there will be very little difference in overall performance. The larger "800" cfm carburetors have a slight advantage in the "normal" driving range as less throttle angle is required to acheive any particular rpm or vehicle speed. It's not all that noticable, but still makes the larger carbs the better choice for large cid engines......Cliff
