After talking to people until I was blue in the face about this, I have decided to just put the information on my blog for all to see. 3-2’s have a bad reputation for being troublesome. Some is well deserved, some isn’t. Let’s start with the way Pontiac did this.
The original 3-2 setup was vacuum operated, which was just fine if you didn’t mind the 3-2’s kicking in about 2 to 3 seconds AFTER you romped on the gas. They were slow and beyond silly. 1961 to 1965 basically used the same carburetors. The end carbs had a bigger base with the center carb having a regular base like your normal 2 barrel carb. They were all Rochester 2-Jet carbs. Being that the car normally ran on mainly the center carb, that was the only one to have a choke setup. 1961 to 1965 used the “black wheel” twist to adjust choke with two tubes going into the intake to gather heat to tell the choke when to ease off. 1966 3-2’s went to the much better choke “stove” which was a little metal box with a Bi-Metal spring inside. They worked much better and were not affected by carbon buildup as the “black wheel” types were. Remember also that almost every year, the 3-2’s got better as more was known. Also, 61 thru 64 fit only 64 on-back. In 1965 Pontiac changed the head design and the intake design and therefore they do not interchange with 64 on-back units. You can put 65 on-up heads on an earlier engine and then you HAVE to use the 65 on-up intake manifold. You can also put 64 on-back heads on a 65 on-up engine, but again, you HAVE to use the 65 on-up intake. Either swap also involves some heater hose rerouting. Understand all of this?
OK, so what do you do for carbs? First off, DO NOT buy anything off eBay. 9 times out of 10, you are buying somebody’s problem they could not fix. In other words, leaky carbs. GM & Rochester found it to be acceptable to use cast iron carb bases and simply drill a hole thru the base to hold the throttle shaft. They did not use any bushings and eventually, the rod would wobble out the holes drilled in the cast iron bases, thus allowing gas to pour out. Many 3-2’s were pulled off cars because of this. Current carb rebuilders will usually drill out the bases and install bushings to solve this problem. Also, finding the correct end carbs is becoming tough and expensive, especially when you are buying a problem child in the first place. So what can be done?
Two companies have pretty much solved your problems. Some three years ago, Speedway Motors started reproducing the correct end carb bases for Chevy and Pontiac 3-2’s. They are cast iron however they have bronze bushings on the bases and use stainless steel throttle shafts. And as the originals, they do not have metering jets in the bases. They are about $90 each. The other company, Carburetor Restorations, started to reproduce the correct carb tops. Remember that these DO NOT have any provisions for a choke unlike the center carb. A lot of the old crap carbs have either cracked or weak top bridges where your air cleaner bolts went thru the top. Some are even missing. The reproductions have the fittings in the correct places. They are around $80. Some the suppliers that carry these items are Speedway, Ames Performance and The Parts Place out of Chicago. But here is the really good news….you can take almost ANY old Rochester 2-Jet carb and just use the center part with these two reproductions and make almost new front & rear carbs using a fresh carb kit and do so for less than $200 a carb! You can use any Pontiac 2 barrel carb for your center carb, but remember that 66 center carbs are 66 only and have the same size base as the end carbs. 66 was also the best 3-2 design that Pontiac had. The Parts Place also sells a reproduction ALUMINUM 3-2 66 intake manifold for around $350 plus postage. This intake is 100% correct AND shaves 45 pounds off your front end! If you paint it blue, nobody will ever know. It even has the correct casting number!
While we are on the 3-2 subject, the correct carb fittings are at 105 degrees, not 90 degrees. Ames sells the fittings and line kits for both. However, I am not a fan of the aluminum line kit currently available as they are too soft and prone to leaks. One more thing about lines…..DO NOT bolt your carbs down UNTIL you have connected all the fuel and choke lines. DO NOT tighten them but do get them started first. THEN, you can bolt the carbs down and then tighten the lines. I spent four hours trying to mount my first set of 3-2 lines not knowing any better.
One last thing….unless you are doing a 100 point show car, forget the vacuum system. Take it off and sell it on eBay. For performance, go with the progressive linkage sold by Ames. I set mine up to where the end carbs start coming in at about 5/8th throttle. The instructions are somewhat poor and have been copied too many times. Look for close-up photos on Pontiac sites or on setups for sale on eBay.
The rear carb MUST have an 8/32″ threaded screw hole drilled in the end (drivers side) carb shaft, so be very careful. Put the linkage on last and do not force anything. If you have to force it, something is wrong.
I have a retired Rochester carburetor engineer who does all of my carb work. He is a really stickler on dying parts correctly. He advertises in Smoke Signals and does excellent work. He name is Bob Campbell and he can be reached at 248-310-8740. I stock a number rebuilt carbs that he has done for me over the past five years. I do hope you have enjoyed all of this as with most info on big Pontiacs, it’s hard to come by. LK 4/2013
