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#1
08-06-2025, 04:14 PM
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Tri Power Power Valve
Read many items about modifying the power valve spring. Cutting coils, but everyone seems to have a different amount. Others say by weight 150grams, 1 60 grams. It probably is trial by error. As a starting point anyone know the weight of an original assembly for a 66 center carb?
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#2
08-07-2025, 06:44 AM
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Cutting coils is normally a trial and error to failure procedure.
You "trial" by cutting a couple of turns at a time, until you "error" by cutting too many turns. Your "failure" is trying to glue some of the turns back.  There is a kit available with different weight springs. Jon
__________________
"Good carburetion is fuelish hot air". "The most expensive carburetor is the wrong one given to you by your neighbor". If you truly believe that "one size fits all" try walking a mile in your spouse's shoes! Owner of The Carburetor Shop, LLC (of Missouri). Current caretaker of the remains of Stromberg Caburetor, and custodian of the existing Carter and Kingston carburetor drawings. |
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#3
08-07-2025, 02:18 PM
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I measure the spring pressure with a gram scale. The number I use is the amount of pressure to JUST push the rod into the spring.
A stock '66 Tri-Power center carb will measure about 200 grams. For a cam such as the RAIV, 150 grams seems to work well, since there is less vacuum to overcome the spring and close the power valve. To achieve 150 grams, five turns of the spring are cut off. I have checked and noted that even only 100 grams of spring pressure is enough to push the power valve open, but this would be for a really radical cam.
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BONESTOCK GOATS '64 GTO Tripower Hardtop (Wife's Car) '64 GTO Tripower Post Coupe (My Car) '99 Bonneville SE Sedan |
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#4
08-07-2025, 02:40 PM
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1966 center carbs uses spring 7012265 Oz 8-8.5 Color (green) (227-241 grams) on the Power Piston Assy: 7012266.
Cut-In down at: 11 "Up" at: 8 all in at 6" hg. |
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#5
03-07-2026, 08:58 PM
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Just to revive this thread whats the correlation between the power piston assembly length and the power valve. I see power valves with short and long needles and long and short rods/spring assemblies. Lastly any advantage to opening the idle mixture screw holes?
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#6
03-10-2026, 10:56 PM
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There are two lengths of power valve rods--a longer length for the center carbs up to 1965, and a shorter length for the larger 2G used in 1966 only. The rods are within 1/8" of each other.
With a lumpy cam, cutting five turns off the spring is a good guess. Stock spring pressure is about 200 grams. Cutting off five turns reduces it to 150 grams. The power valves I use have the short actuating pin. I have also used the longer pin with similar results. I enlare the idle mixture screw holes in the base to .078" for most setups. Contact me at 920-450-1040--call or text.
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BONESTOCK GOATS '64 GTO Tripower Hardtop (Wife's Car) '64 GTO Tripower Post Coupe (My Car) '99 Bonneville SE Sedan |
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#7
03-12-2026, 01:29 AM
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For the Tri-Power ('61 SD) in my GMC, I built a variable spring seat for the power valve which is externally adjustable. The range of settings is about 5-13 In.Hg. I set it at 8 in.Hg. and haven't changed it in the 10,000 miles I've put on it.
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Anybody else on this planet campaign a M/T hemi Pontiac for eleven seasons? ... or has built a record breaking DOHC hemi four cylinder Pontiac? ... or has driven a couple laps of Nuerburgring with Tri-Power Pontiac power?(back in 1967) ... or has a Pontiac born the same year as Jim Wangers? (1926} 
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| The Following User Says Thank You to Jack Gifford For This Useful Post: | ||
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#8
03-12-2026, 03:17 PM
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TRIPOWER POWER VALVES
1957 (S) 7009349 1957 (A) 7006331 1958 (S) 7009349 1958 (A) 7006331 1959 (S) 7009349 1959 (A) 7006331 1960 (S) 7009349 1960 (A) 7006331 1961 (S) 7017950 1961 (A) 7011989 1962 (S) 7017950 1962 (A) 7011989 1963 (S) 7017950 1963 (A) 7011989 1964 (S) 7017950 1964 (A) 7011989 1965 (S) 7017950 1965 (A) 7011989 1966 (S) 7011989 1966 (A) 7011989 7006331 long plunger (4) #55 orifices 7009349 short plunger (4) #53 orifices 7011989 long plunger (4) #54 orifices 7017950 short plunger (4) #52 orifices Jon
__________________
"Good carburetion is fuelish hot air". "The most expensive carburetor is the wrong one given to you by your neighbor". If you truly believe that "one size fits all" try walking a mile in your spouse's shoes! Owner of The Carburetor Shop, LLC (of Missouri). Current caretaker of the remains of Stromberg Caburetor, and custodian of the existing Carter and Kingston carburetor drawings. |
| The Following User Says Thank You to carbking For This Useful Post: | ||
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#9
05-11-2026, 01:34 PM
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Nice work, Jack
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