# 1966 Pontiac Tri-Power



## maw2078826 (May 1, 2020)

Rebuilding my original 1966 Tri-Power. Noted that after market suppliers are offering needle & seats for the 2G Rochester in three different sizes: .101, .119, & .120...which one would my fellow GTO Tri-Power owners recommend?


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## Old Man Taylor (May 9, 2011)

I use these from Pontiac Tripower (Mike Wasson). I don't recall the orifice size.

Needle and Seat replacements.


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## PontiacJim (Dec 29, 2012)

Old Man Taylor said:


> I use these from Pontiac Tripower (Mike Wasson). I don't recall the orifice size.
> 
> Needle and Seat replacements.


Interesting. But, if I am seeing it correctly and it has a flat bottom versus the typical conical and tapered needle, I would be afraid that the stock fuel pump pressure of 5.5 - 6 pounds would easily raise the needle off the seat.

I keep reading that the tri-power fuel pressure needs to be set at 3 pounds, and this may explain that IF this needle and seat is being used - which is not being mentioned in that recommendation.

In theory, I get that it'll allow trash past the seat and not cause it to stick or be held open due to its flat bottom design, but then where does that trash go? ......clog up your jets? If you have a good fuel filter and change it regularly, you should not get any trash in the needle and seat.

This would also mean that you will need a fuel pressure regulator to bring the factory type fuel pumps down to a 3 pound fuel pressure level. I never seem to see this tidbit added when the 3 pound fuel pressure is stated.

The larger inlet will allow more volume at the lower 3 pound pressure, but you want to get a quality fuel pressure regulator that allows for good flow at lower pressures, and not one of the cheapo $8.00 units. I would also think I might want a 3/8" line from the tank to pump to replace the factory 5/16" line to provide more volume, and the 3/8" line from the fuel pump to the fuel block at the carb if they are not already this way.

When Milt Shornack of Royal Pontiac rebuilt his tri-power carbs in blueprinting them as part of the Royal Bobcat offering, he used the needle and seats from a standard 2 bbl carb, not the tri-power 2 bbl carb, because they had larger orifices and were cheap. 

I would do a little research, but any needle and seat you get, you will want to ensure it is ethanol friendly - which I am sure most are. Unless you have a big cam and the engine needs additional fuel because it runs out, ie "noses over", at the top end, I would stick with a factory sized needle and seat. If you are "nosing over", then go with a larger sized needle and seat.

Think of it this way, the larger the needle/seat, the more surface area the fuel pump pressure is able to exert pressure and the harder the float has to work to shut the needle/seat when the carb fuel bowl is full.........and you don't want the fuel pressure to overcome the needle/seat and flood the carb or spill out the top and catch fire (and I am not saying this to scare or discourage you). A fuel pressure regulator could be the answer as the needle/seat get larger so you can optimize flow, but keep fuel pressures in check.

I am presently setting up a fuel system for my dual fours. Been doing a lot of reading/research. I am going with an electric external fuel pump versus an in-tank set-up. The fuel pump is mounted at the rear in front of the tank to push fuel. I am not using the factory mechanical fuel pump. I have a BIG, and maybe too big, 140 gallon per hour @ 14 psi free flow pump that drops down to more like 120 GPH @ 9 PSI as used - so electric pumps have 2 ratings.


My carbs only want 5.5 pounds fuel pressure or I could have problems, so I have a fuel pressure regulator. I am using a 3/8" fuel line from tank to carb. However, in my instance, I must use a 3/8" return line to correctly set my fuel pressure adjustment per the fuel pump manufacturer. Some fuel pumps do not require a return line based on their output - this is termed "dead head". If I do not use the 3/8" return line, my fuel pressure at the regulator may not be set to provide a consistent pressure reading and may allow pressures to fluctuate. So a return line will help provide a steady flow of gas that can then be regulated by the fuel regulator without fluctuation. It also allows the pump to push gas at a steady state so as not to overload the pump motor and burn it out. I am also making my return line "convertible" in the manner that I can actually remove a small section of return line and replace it with a means to restrict the return flow with a smaller length of 5/16" line, or even braze a line up and use drill sizing holes to get the fuel pressure number at my carbs where I want them.

I point this out because this may be a consideration in your build if you do not already have the factory 1/4" return line from the fuel pump or up near the carb using the 3-port AC fuel filter. The 5.5 - 6 PSI factory fuel pressure rating will drop a little lower when using the return line and may provide a steady state fuel pressure to the carb's needle/seat. The AC equipped cars used the 1/4" return line to prevent vapor lock, but I see another advantage in providing a more consistent fuel pressure & supply to the carbs using the 3-port AC style fuel filter up by the carb when using the tri-power set-up.

Take all this with a grain of salt as I am by no means a fuel system expert. I know what I am doing with my fuel system, and won't know if it'll work as I believe it will or if I will have to make any changes. But, this is how I see it.


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## Old Man Taylor (May 9, 2011)

I never ran my tri-power as low as 3 psi. It was close to 5 psi before I added regulators. After that I set it between 4-4.5 psi.


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## maw2078826 (May 1, 2020)

Neither had I...have owned my 1967 GTO since 1968 and always run stock fuel pumps. I noted on you tube a professional Pontiac Tri-Power builder stating he recommends the 3 pounds pressure as noted within these posts...I think if GM thought that necessary they would have produced fuel pumps with that pressure!...Anywho, just rebuild my 1966 Tri-Power unit utilizing the standard *.119* needle & seats which I believe came stock...and the Tiger screams new life, idles perfectly, no flooding nor leaks. On a different subject is spark plugs, I've always been a GM AC Spark plug fan...HOWEVER...(like most products today) they're either made in China -or- Mexico...I've had many right out of the box that are DEAD...frustrating...I'm now using Autolite Platinum which are working fine (don't know where they're made)...have also been forced to buy NOS AC Plugs via ebay which work because they're made in the U.S...use those primarily for car shows. Sincerely appreciate Old Man Taylor (my Mother's maiden name), and Pontiac Jim for their input. P.S. Semper Fi to all my *USMC* Brothers out there for our upcoming birthday on *10 November.*


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## Old Man Taylor (May 9, 2011)

My grandson celebrated his 12 years in the corps while I was visiting him in Virginia about two weeks go.


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## PontiacJim (Dec 29, 2012)

And if you get the chance, you gotta visit the National Museum of the Marine Corps. Fantastic museum with tons of artifacts and diorama displays throughout going back to the colonial days right up to contemporary. Bring a camera and plan on spending some time there to really take it all in!









The National Museum of the Marine Corps


The National Museum of the Marine Corps Museum is located in Triangle, Virginia just outside the gates of Quantico. It's striking architecture is reminiscent of the famous statue of the flag being raised on Iwo Jima by the Marines during World War II.



www.usmcmuseum.com


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## Old Man Taylor (May 9, 2011)

Unfortunately we didn't make it to Quantico. I did get to tour Parris Island two years ago when I visited his family in Beaufort. He was a DI there for 3 years.


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## Old Man Taylor (May 9, 2011)

Matt finished (at Parris Island) as a Chief DI. He's in the middle of these two pictures.


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## PontiacJim (Dec 29, 2012)

Old Man Taylor said:


> Matt finished (at Parris Island) as a Chief DI. He's in the middle of these two pictures.
> 
> View attachment 138237
> View attachment 138238


I have not gone to Parris Island, but am well aware of its history. In WWII the Navy undertook a glider program that was to be used by the Marines, Glider Group 71. I had the chance to correspond and meet with several of the original members who supplied me with their stories, photos, and saved military documents for my WWII glider program research.


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## maw2078826 (May 1, 2020)

OOH-RAH......Absolutely awesome Mr. Taylor I know you must be very proud. My nephew joined two years ago, 0311 (Rifleman) with 2nd MARDIV...and he's already been all over the world. After returning from Viet-Nam I was stationed at Quantico in 1967-68...long before there was any museum there....when I was there we built the first Viet-Nam Village for training and obstacle courses for the "butter balls" as I was with engineers...gotta go see that museum. Semper Fi.


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