1) Will a tripower bolt onto my 455 with 6X heads?

First, a 455 has the same deck heigth as the 326, 350, 389, 400, 421, and 428. That said, the head is the critical factor. Heads from 61 to 64 have different water passages, a different bolt pattern, and a different angle where they meet the intake than do the 65 and later heads.

Therefore, what most people want is the popular 65 or 66 tripower to fit the improved and readily available 65 up heads. A 65 or 66 tripower will bolt directly to the 65 to 71 Pontiac heads. However, starting in 72, Pontiac has an extra exhaust crossover port in one of the heads. The 6X head is a mid-70s head and has this extra port. The 65/66 intake will not cover this port. There is no special intake gasket to accomplish this. The force of the exhaust is too intense for a gasket to stop. Best method is to have a machine shop fill this extra port while you are having the head work done. At least one customer filed this port while the head was on the car, using JB Weldand reports no problems. I am much more comfortable with the first method.

2) I am putting a tripower on my 78 Trans AM and the waterneck hits the timing chain cover. What is wrong?

Note that the waterneck on a tripower comes directly out of the front of the intake, compared to the top location for the thermostat on the 2 and four barrel intakes. Pontiac cast an indentation into the aluminum timing chain covers. I am not sure when this began, but I imagine it was as early as the first 389s in 59. In any case, Pontiac continued using the same castings for this cover until about 69. I have been told that a bit of grinding on the timing chain cover as well as a bit on the waterneck will make it fit. I recommend using the older style timing chain cover, though. Be aware that Pontiac used a different style waterpump after 1967. Make sure you brackets for the alternator, waterpump and airconditioning come off motor with the same style waterpump.

Also, do not assume your 65 motor has a 65 timing chain cover. The covers are interchangeable. I had a 65 timing chain cover on a 70 model 455. No problems.

3) I put a tripower on my 66 GTO that came with a 4 barrel. My throttlecable bracket bolts to the intake just fine, but the cable will not give me full throttle. What is wrong?

There is a differnece in the lengths of each throttle cable. The two bbl cars, four bbl cars and tripowers cars had different cables and different brackets. If you can locate a brakcet and a cable off, say a 66 LaMans with a 2 bbl, it will come close to working on the tripower.

You can make some adjustments in the bracket by either elongating the two mounting holes and/or altering the opening in the bracket that accommodates the flare in the end of the cable.

I carry, as do other suppliers, a reproduction tripower throttle cable bracket. However, I am not confident it will work perfectly with the 4 bbl cable. Some suppliers carry a reproduction throttle cable. It is rather generic, as it has several holes in the end to attach to the center carb. It would not be suitable for a "correct" car, but would work well on a driver. In any case, the tripower reproduction bracket will come closer to the mark than the 4bbl bracket. If you have experience with this, e-mail me and I will add information to this section.

4) My tripower leaks fuel out of the throttleshafts. Where can I buy new shafts and where can I get bushings installed in the throttleplate?

You are not approaching this from the correct perspective. First, fuel should never sit on top of the butterflies which is what is happening here. The problem is not your shafts, but the source of the fuel. See my answer to the next question for more information.

Regarding new bushings in the throttleplate....People who are familiar with the Quadrajets often pass along this advice. The Quadrajets have aluminum throttleplates which do wear out. Then, they leak air, essentially a vacuum leak that effects idle quality. Rochester 2 bbls have cast iron throttleplates that seldom wear out. The shafts are usually brass. So, any wear you might experience would be in the shafts. Reproduction shafts are available. However, they are usually not indicated.

Additionally, if you give it some thought, you will realize that the tripower end carb are not getting open often enough to wear out the shafts. I have taken apart 100s of end carbs and cannot recall a worn out shaft.

I have, however, replaced several shafts in the center carbs which, obviously, get most of the wear. For some reason, the 65 center shaft seems to wear out more often than the 66 center shaft.

5) My tripower leaks fuel. Sometimes it pours out of the top and I have to remove the airhorn because the float is stuck. Other times, it drips off the end of the throttleshaft. The car is hard to start and blows black smoke. What is wrong?

Boy, this is a problem that I get many e-mails about. There are many factors that contribute to these problems. First, you need to rule out dirt or rust getting into the carbs from the fuel system.

Here are several other items to check:

float is sticking......This typically will not happen if you have no debris in the fuel system. However, you may experience it within the first few days of getting you car running with the new tripower installed. Usually, you do not see the debris that makes the float stick. By the time you remove the airhorn and turn it over to inspect it, the particle has fallen out. Once, I did find what was causing needle to stick open. A very small sliver of rubber hose has fallen off as I forced the ruber hose over the fuel inlet line. It ended up in the front carb. Do not tap or hammer on the airhorn to "break the float loose." Many tripower carbs have scars from backyard mechanics with the hammer mentality. Respect these carbs. They don't make them anymore. If you damage the airhorn, you will be hard pressed to find a replacement.

faulty floats that leak......brass floats can and do develop leaks and fill with fuel. This is checked easily by removing the float and examining it to see if fuel is inside. Composition floats can absorb fuel and become too heavy. I don't think this happens often. However, I highly recommend getting new brass floats when rebuilding the carbs or trying to fight leaks. They are available through this page. They can be difficult to locate at auto parts suppliers.

floats need adjustment.......floats do not just change adjustment while on the car. If your car was fine with no leaks earlier, it is not the adjustment. Typically, the end carbs are set at 21/32" from carb airhorn gasket to seam on brass float, with 1 24/32" drop. Center carbs are 19/32" and same drop, 1 24/32"

needle/seat leaking.........I add this as it is possible that you could have a worn out needle/seat. However, unless your carbs are very old, I doubt this is the problem. See question #6 for information on an improved replacement for the needle/seat.

loose seat (check this out first!!).............I have run into this many times, especially if the carbs have been rebuilt recently. The seats can loosen in which case you will have a flow of fuel into the floatbowl whenever the motor is running, causing major flooding. The seats are not easily tightened as most have a slot for a very wide tipped screwdriver across the top. Unless you have the correct screwdriver, it is very difficult to tighten the seats adeqately. I recommend coating threads with liquid teflon, available at hardware stores in the plumbing section.

excessive fuel pressure......unusual, but possible. These Rochester carbs can only withstand 4 to 5 pounds of fuel pressure. I run mine with a regualtor at 4 pounds and it has not caused any problems. I do have an electric fuel pump, though. You typically will not need a regualtor with a mechanical pump. Excessive pressure forces fuel past the needle/seat and overcomes the resistance caused by the float pushing up.

6) I heard you carry a replacement for the needle/seat. Can you tell me aboout it? I don't really get this question, but put it in so I could answer it.

Glad you asked. I carry a checkball valve that has a pair of stainless steel checkballs in it. It replaces the old needle/seat and does a better job of regualting fuel. It will not stick as easily, especially after the car has been sitting for long periods. Sometimes the needle/seat will stick in this situation, while the checkball won't. Also, this valve can be installed with a 5/16" socket wrench. Consequently, it can be tightened more easily and is therefore, not prone to coming loose. I have them in my own car and have had no problems with them in last 7 years. I do highly recommend them. I carry a kit with three new floats, three checkball valves, and three quality rebuild kits that should solve your leaking problems.

7) Will an HEI fit on a Pontiac with a tripower?

The tripower intake extends further back toward the distributor than the 2 or 4 barrel intake to accommodate the rear carb. As a result, an HEI distributor will not fit. I have been toldthat some material can be removed from the back of the intake and some from the HEI unit and it can fit. I would not recommend it. There are indivviduals who will convert the points distributor to an HEI unit. I once had a website that offered this service bookmarked, but have lost the information. Let me know if you can refer me to a reliable sourc for this conversion and I will add it to links.

My own car actually turned its fastest time with the stock single point distributor, a 12.7 second quarter. I have since added electronic breaker for reliability.

8) What is the CFM of a tripower?

If you read this carefully, you will be surprized. And, you may learn a few things. I did as I did research to find the "real" answer to this question.

First, you must understand that flow numbers are estimates based on a mythical engine. Picture a 400 cubic inch engine running at full throttle. It is essentially sucking air through the venturi of the carb (or carbs). If this engine had a 2 barrel carb, the suction through each venturi would be greater than the suction through each venturi of a 4 barrel. The increased suction would actually increase the flow through each venturi. True, the 4 barrel would produce more CFM flow, but each barrel of the four barrel would produce less CFM than each barrel of the 2 barrel. Right?

Because of this, flow numbers based on venturi diameter have to be adjusted between the four barrel and the two barrel. The error many make is merely to apply a multiple to the four barrel numbers to yield flow numbers for the 2 barrel, then add the numbers up for three two barrels. This doesn't work. Why? Well, now, instead we are working with six open venturi, not two.

The flow numbers on Rochester 2 bbls are measured differently than a 4 bbl. Flow on 2 bbls is measured a 3" drop, while 4 bbls are measured at 1 1/2" drop. To make the numbers comparable, you must divide the 2 bbl flow numbers by 1.414. However, to convert to, essentially, 6 barrel numbers, you need to divide the two barrel flow numbers by ?. Doing so yields the following flow numbers for the various venturi sizes at each measurement.

In order to figure the cfm, you need to add up the cfm of each carb.

The 59 to 66 tripower end carbs have a 1 3/8" venturi. Center carbs of 64-65 tripowers have 1 1/4" venturi. Center carb for 66 tripower have 1 3/16" venturi.

Examine the above numbers. These are actual measurements I have taken. Note the difference between 65 and 66 center carbs. This is not a misprint.

I realize the throttle bore diameter is larger on the 66 center carb (1 11/16") than the 64-65 center (1 7/16') However, the venturi, which is the smallest diameter opening in each carb is actually larger in the earlier carb. I told you careful reading would yield surprizes.

CFM figures are not as meaningful as quarter mile numbers. Read answer to question 9.

9) Is a tripower better than a four barrel?

I take my information from the June 1995 issue of High Performance Pontiac. The article is entitled, "Four Barrel vs. Tri-power." The authors employed the services of Jim Taylor to assist. They took a well performing 68 GTO, 428 car, 4 speed with slicks. All launches were made at 1200 rpm and shifts at 5200. Car went throught the traps at 5400-5500 rpm.

The Q-Jet had was dialed in on the car. It was equipted with Edelbrock jets, rods, and high-flow needles. In other words, this carb was modified slightly to match the needs of the car.

The 66 tripower was stock except that the choke plate in the center carb was removed and the jets were replaced with 70s in the center and 72s in the ends.

Three runs were made with each set-up. Results:

The author calculates the 2.27 mph gain to a 22 hp gain over the 4 bbl. He attributes the gain to the tripower's shorter and straighter intake runners and its greater CFM flow.

10) I need a 1964 trpower front carb # 7024178 for my 64 GTO with automatic transmission. Do you have one you would sell?

Rochester did not start putting carb numbers on the 2 bbls until 1968. The numbers you find in restoration guides only appear on the carb tags attached to one of the airhorn screws.

Often people e-mail me giving me "carb numbers" that appear in a circle on the passenger side of the floatbowl section. These are casting numbers for the floatbowl section. Rochester used the same casting for several carbs, then machined them for specific applications.

There is one exception to this rule. If you bought a new Rochester carb at the dealer after 1968, Rochester DID stamp the carb number onto the passenger side of the floatbowl, horizontally. I have only seen 2 or 3 of these carbs in many years of restoring tripowers. Another diffenece I have noted about these carbs is that they also have phillips head screws holding down the airhorn.

So, since numbers non most tripower carbs only appear on the tags, and tags can be easily switched, beware. The only way to identify a tripower carb is visually. This really isn't too difficult after looking at these carbs and working on them for several years. However, if you are not familiar with how to identify them, learn before buying a unit.