Tri, Tri Again
Detailing the correct restoration of a Pontiac Tri-Power Part I: Teardown and evaluation
From the January, 2009 issue of High Performance Pontiac
Jim Taylor, HPP contributor and the proprietor of Phillipsburg, New Jersey-based Jim Taylor's Engine Service, remembers the days when Pontiac's Tri-Power setups were plentiful. It wasn't uncommon for him to get a unit in for repair that needed only a rebuild, which was completed with little labor and few problems.
Unfortunately, those days are over. With Tri-Powers becoming more and more scarce, those correct assemblies that needed only a freshening have been replaced with beaten-up, cobbled together collections of parts that would make the most well-tuned Pontiac stumble. Carbs that have been swapped from the center spot to an end; incorrectly applied gaskets that create major vacuum leaks from improper sealing; linkages that are homemade or from other vehicle;. and botched repairs to the carb body, throttle shaft, and throttle plates that threaten to leave these highly sought-after symbols of Pontiac's heritage in the junkyard for good. It's not a good situation.
But there are solutions to these difficult problems. Taylor is still fighting the good fight and restoring Trips to their former glory, so we traveled to Phillipsburg to observe how he does it. As we walked into the shop, we found a dirt- and grime-covered 1962 manifold with three deuces sitting on a table. Jim needed a core to build a 1965 spec. Tri-Power (he already had the intake manifold) for a customer so he found this assembly at a swap meet, and he knew that it would be a doozy to work with.
But it was only after he tore it down that we saw just how bad it was. Follow along as we tackle the first part of a multi-part series on how to correctly restore a Pontiac Tri-Power.
Jim found this Tri-Power setup...
Jim found this Tri-Power setup on the ground at Carlisle in the spring of 2002. At first glance, we can see that the air filters are incorrect and so are the throttle linkages--but it's really not that bad, is it?
Taylor opened up his Rochester...
Taylor opened up his Rochester service manual to the Brass Tag Identification page and inspected the unit's carb tags. The front and rear carbs proved to be a matched set from 1959, but there was no ID for the center carb. Taylor thinks this is what restorers are likely to find while searching for a Tri-Power unit to rebuild.
The manifold has a build date...
The manifold has a build date of March 8, 1963. Here, Jim is pointing out a homemade thermostatic vacuum switch blockoff plate, which is much thinner than the original Pontiac unit.
The Tri's incorrect center...
The Tri's incorrect center carb is supposed to have two complete metal choke tubes that draw air, via vacuum, to release the automatic choke. The two external tubes (one of which is connected to the choke, the other which draws in air) are the visible pieces that fit into an unseen loop in the exhaust crossover portion of the intake manifold. The exhaust warms the tube, as well as the air passing through it that was drawn in by vacuum, which releases the choke spring and the choke plate. The rubber tube is incorrect, and heat will get to it eventually.
This 1963-model carb in the...
This 1963-model carb in the center uses a ball-rod linkage, seen on the right side of this photo, which isn't correct for a 1965 Tri-Power. The '65 carb will accept the Tri-Power actuator linkage, which uses the throttle cable for 1965. Our '63's throttle shaft could be changed, but that's a lot of work when Taylor already has a carb to use.
At this point, Jim and Mark...
At this point, Jim and Mark Erney began the disassembly by using 1/4-inch drive swivel sockets to remove the carb bolts on a workbench.
Here is a shot of the nearly...
Here is a shot of the nearly bare manifold. These are 5/16ths studs with fine threads on the top, and coarse threads imbedded in the manifold. They can be tough to remove because they have been in all of those years.
It was apparent that flying...
It was apparent that flying insects had made this pricey assembly home, as evidenced by the mud nests built into the manifold's runners and the carburetors. Every bit of this contamination must be cleaned out to ensure a properly functioning system.
The front carb has a linkage...
The front carb has a linkage that doesn't belong on there. This appears to be a piece of Pontiac linkage that was welded onto a homemade rod. It's a big benefit when buying a set like this if the throttle pump and shaft are free moving.
An incorrect gasket between...
An incorrect gasket between the carb's body and base will cause a vacuum leak--it's likely that this gasket came from a universal GM 2-barrel carb rebuild kit.
This photo shows how easily...
This photo shows how easily the X-Acto knife slips between the assembled base and body where there is a gasket void.
Here is a disassembled carb,...
Here is a disassembled carb, from left to right: bowl cover (or airhorn), body, throttle flange (base), and venturi cluster. Two jets are in the foreground.
After the manifold has been...
After the manifold has been completely disassembled, it is cleaned in a caustic cooker and beaded, then washed with mineral spirits. This finished manifold was born on May 25, 1965, and is being used for a customer's project. Jim Taylor Engine Service is using it with carburetor cores from the '63 manifold--evidence enough about the scarcity of these parts. "We're scrounging," Jim explains.
This 1965 Tri-Power center...
This 1965 Tri-Power center carb will be used on the restored unit. It originally actuated the secondary carbs via vacuum linkage. Manifold vacuum is high at idle and diminishes as the throttle blades open so Pontiac took advantage of that fact with this system. . . .
. . . A screwdriver is showing...
. . . A screwdriver is showing the arm in a position that sends vacuum to a diaphragm that holds the secondary carbs closed. The next photo shows that when that arm comes down, it cuts off the vacuum to the spring-over-vacuum secondaries actuating diaphragm, allowing the spring in the vacuum diaphragm to open the secondary carbs. Jim will convert this system over to actuate the secondary carbs mechanically. He will also have to change the accelerator pump arm to a mechanical-type arm and then attach the mechanical linkage.
Here are the top and bottom...
Here are the top and bottom components, post-soaker. The can from NAPA is carburetor cleaner, and comes with a parts basket. Taylor took the parts and soaked them for a couple of hours, then scrubbed them clean. You need to scrub the parts and not blast them, because you run the risk of getting blasting media into those veins and contaminating them. After the cleaner, the parts get rinsed with mineral spirits in a parts washer with a brush, then are allowed to air dry.
Jim used a pencil blower to...
Jim used a pencil blower to blow out the veins in the venturi cluster and the bowl immediately after washing them. You can put compressed air in one end of the fuel vein and check to see if it comes out on the other end--hopefully, a little residue will come out with it. A good way to check the venturi cluster to make sure that all of the fuel veins are indeed open is to run various sizes of copper wire through them--this is .017-inch electric motor winding wire. The wire is flexible enough to make 90* turns through the small passages, and Jim can squeeze the wire with pliers to add texture, which will help remove stubborn deposits. "Here is where patience will pay off," Jim reveals. "If you do all of the veins except for one, you know that's the one that is going to be clogged when you put it back together--so you might as well do the work now."
Taylor's next move is to repair...
Taylor's next move is to repair a carb base. Someone had attempted to fix this base, with bad results. First, it was a center carb that was switched to an end, and they plugged the idle mixture screws. They then took the springs off and turned the idle mixture screws in real tight and ground the ends off to make a secondary base. In doing that, they buggered up the body, and the throttle plates are bent and not sitting flush. This low-light photo shows light seeping through the blades, which are definitely not mating up with the bores. To save it, Jim will have to get the plates out and straighten the throttle bore. Note the protruding throttle blade screws.
The factory intentionally...
The factory intentionally distorted the ends of the throttle blade screws so they wouldn't work themselves loose, get sucked between a valve and a seat, and send you in for a new engine. This was probably done with a four-pronged tool at the factory. So how do you get them out, you might ask? Jim grinds off the ends of the throttle blade screws, then unscrews each one from the shaft. This method prevents broken-off screws and a lot of headaches. Once they were removed, Jim found that whoever put the throttle blades back in didn't have them positioned properly. There was a bulge at the idle mixture screw side of the bores, so to save it, Jim has to take the shaft out. While it is out, the base will receive new throttle shaft bushings. Now that Taylor has the Tri-Power completely disassembled and cleaned up, we will be focusing on rebuilding, assembling, and testing our three carburetors in the second part of our series. Tune in next issue as we continue the restoration of a Pontiac Tri-Power.
Jim Taylor Engine Service
120 S. 5th St.