I've always liked multiple carburetors. My first car in 1963 was a '55 Pontiac. By 1964 it had a 1958 motor (370 cubic inches) with a tripower sitting on top. The truth is, I never did get that tripower working correctly.
In 1986 I restored a 1966 GTO and, of course, put a tripower on it. I began buying, selling, and restoring these set-ups in 1987. on a limited basis. Over the years I have become very familiar with the Pontiac tripowers from 1957 to 1966. The 1964-66 units are, by far, the most popular.
First, let me dispel some myths:
MYTH Tripowers are always problematic and hard to keep in tune.
FACT I don't know where this started, but you hear it often repeated at car shows and swap meets. Think about it--a tripower is made up of 3 very simple 2-barrel carbs. The center carb supplies the fuel at all times, except under full throttle. The end carbs are extremely simple. They have no idle circuits, no choke.
I do believe that even when these units were new they freightened many merchanics and owners. I remember taking my '55 Pontiac to several garages back in '64-'65. They wouldn't touch it! The truth is, they didn't know about them and didn't care to learn. My current car, a '65 GTO, has a '66 tripower that has been on 5 years with virtually no problems--none. Update: I restored a 1965 GTO in 1994. The tripower on that car was trouble free until 2004. At that time, I had a float stick. The unit was looking shabby, so I pulled it off and restored it again.
MYTH The carburetors have to be "calibrated."
FACT What? Maybe a set of Weber side-drafts. I've got an original motor manual from GM--no mention of calibration. The only adjustment on end carbs is the float, and I suppose the rod to the accelerator pump. You adjust the center carb exactly as if the car had a 2 barrel. When functioning properly, the end carbs sit there, dead, until wide open throttle.
MYTH Tripower cars are prone to catching on fire.
FACT Well, there is some basis for this. Notice that Pontiac (as well as Oldsmobile and Cadillac) used metal fuel lines. When owners rebuilt the carbs, these had to be disassembled. There are many opportunities for leaks. On a '64-'65-'66 Tripower, I count 8 sites for possible leaks, versus 2 for a 4 barrel. I believe many owners were unwilling to go to the dealer to purchase new lines and fittings when needed. So...here come rubber lines and chrome fuel blocks. BAD IDEA!!!
Most tripowers I buy at swap meets or from individuals have rubber lines or evidence of them. Don't ever use rubber ruel lines on a tripower.
Never use Teflon Tape on fuel lines or fittings. I do recommend the use of Teflon Paste only on the threads of the brass fuel fittings.
The reason there are more bare intake manifolds then carbs is due to the fact that intakes survive fires, carbs don't.
MYTH I can take my tripower carbs to the local carb rebuilder, he can rebuild them, he said so.
FACT Don't let anyone who isn't familiar with these carbs touch them!! Yes, they can put in new gaskets and set the floats. But, unless they specialize in Pontiac tripowers, they won't know if your carbs are right in the first place. They can't offer you any advice. I have re-rebuilt many tripower carbs. Don't pay twice
Did you know that each major section of the carburator (air born/float bowl/base plate) is different? There is a difference between front and rear air horns. E-Mail me and I'll tell you. There is a difference between the center sections (float bowls) of the front and rear carbs, usually. They wouldn't know this. The throttlebodies are different, too.
It is not unusual to find Chevy 2bbl parts inside your carbs. Would a typical carb rebuilder recognize this. Would they replace worn out shafts? Would they examine your jets to determine if they are right for your modified or stock application? Would they recognize an incorrect lever or rod? Would they install a bushing if there was wear in the accel. pump pivot? They are offering a simple rebuild that worked when these carbs were 5 to10 years old. Your carbs need restored, not rebuilt.
Yes, internally the carbs are simple. But, when you put them on the car and find your reproduction linkage won't fit-they can't help. Neither can anyone since the linkage isn't the problem. Don't waste your money on a local carb rebuilder who isn't very famliar with Pontiac tripowers.
MYTH The tripower isn't really much better than the 4 barrel for performance.
FACT The '64 Pontiac 389, 4 barrel, had 325 HP -- the tripower, 348. In '65, the tripower 389 was rated at 360 HP. Pontiac discontinued the tripower in 1967 for 2 reasons that I am aware of. Primarily, GM came out with an edict that from '67 on, the only multiple carb car would be the Corvette. And, the Quadrijet, first introduced on the 1966 OHC 6 flowed 750 cfm, vs 550cfm for the previous 4 barrell, the Carter AFB. For those never to the hobby, the AFB (aluminum 4 barrel) is now copied by Edelbrocks 4 barrel. The famous 409 had a pair of them. Very nice. Remember I like multiple carbs.
My '65 GTO--421, tripower, automatic--turned a 12.7 quarter mile at 108 mph the second time out. I drove it 200 miles to the track and home. For those planning to run in the 11s, the tripower isn't for you. But, a tripower properly jetted can supply adequate fuel for most street driven cars. I have never seen accurate firutes on the CFM ratings on 65-66 tripowers. But, the figures I have seen are in the 700 to 800 CFM range. On my car I did remove the casting flash in the venturi and gasket matched the intake. Otherwise, the unit is completely stock. UPDATE....I sold this car in the summer of 2008. Building a 1969 Firebird with no carbs. A 2004 GTO driveline will power it.