1957 Pontiac Star Chief - Page 2 - Pontiac GTO Forum
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post #11 of 15 (permalink) Old 03-08-2019, 08:29 AM Thread Starter
 
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Hi everyone. I might be closing in on a '57 StarChief, in the initial negotiations, and I'm trying to learn more and be as informed as I can. I'm trying to pick everyone's brain, not only here, but other sites also. My question is about the '57-347 cubic inch-270 hp engine. This would have a 4 barrel carb. I know a tripower setup was also offered as an option. Would anyone know what hp this tripower setup would be?? Other then the tripower, what else was done to the motor to make a hp increase?? There are alot of tripower intakes out there. Would anyone know what years might work on the '57 engine?? I tried to research this myself, but wasn't successful. Many thanks, Nicholas.
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post #12 of 15 (permalink) Old 03-08-2019, 09:44 AM
 
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We moved and most of my Pontiac reference books are in boxes. Let me look around this weekend for them because I know one or two of them have the info you are asking.
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post #13 of 15 (permalink) Old 03-08-2019, 09:05 PM
 
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Originally Posted by Nicholas View Post
Hi everyone. I might be closing in on a '57 StarChief, in the initial negotiations, and I'm trying to learn more and be as informed as I can. I'm trying to pick everyone's brain, not only here, but other sites also. My question is about the '57-347 cubic inch-270 hp engine. This would have a 4 barrel carb. I know a tripower setup was also offered as an option. Would anyone know what hp this tripower setup would be?? Other then the tripower, what else was done to the motor to make a hp increase?? There are alot of tripower intakes out there. Would anyone know what years might work on the '57 engine?? I tried to research this myself, but wasn't successful. Many thanks, Nicholas.
The Tri-Power was available on the "standard" 10.0 compression 270HP 347CI with Hydra-Matic transmission. The addition of the Tri-Power option increased the HP to 290HP. Was not available on the synchromesh transmission.

The next option was the Tri-Power on the "Extra Horsepower Engine" which was much like the 1956 316CI dual quad 285HP engine. Still 10.0 compression, this was basically a race engine with many different features than the "standard" engine. Horsepower was rated at 317HP. Available on either automatic or standard trans equipped cars.

The "Extra HP Engine" included the "886" cam of 1956, with slightly less duration. Int/Exh Lift .411", Int Duration 283, Exh Duration 293. 114 degree LSA. Valve overlap is 60 degrees.

Tri-Power Intake Part #528786 cast w/o number (528533).

Rochester Tri-Power Carbs - Standard & HP Engine w/Hydra-Matic
Front - #7011351
Center - #7011350
Rear - # 7011352

Rochester Tri-Power Carbs - HP engine with Synchromesh
Front - #7011351
Center - #7011500
Rear - #7011352

Generator was the same on both engines when equipped with the Hydra-matic, Serial No. 1100304, but the HP engine uses a larger pulley to slow it down at higher RPM's. Generator to crank pulley ratio on "standard" engine is 2.47:1 using the 2.875" diameter pulley, while the HP engine is 2.01:1 using the 3.5" diameter pulley.

Generator used on the synchromesh equipped HP engine used generator Serial No. 1100313, with a brush spring tension of 24-32 oz, cold output of 25 Amps @ 14 Volts @ 2750 RPM's, and a Field Circuit Draw of 1.5-1.62 Amps @ 12 Volts @ 80 degrees temp.

Fan Belt used on the "standard" engine have an outside diameter of 56.8". Fan belt used on the HP engines have a larger outside diameter of 57.5".

Timing on "standard" engine is 6 degrees BTDC @ 430-450 RPM's. HP engine is 10 degrees BTDC @ 630-670 RPM's.

Distributor is the same for both engines when equipped with Hydra-Matic. Serial No. 1110871. Centrifugal Advance begins 0-2 degrees @ 650 RPM. Maximum Centrifugal Advance is 24-28 degrees @ 4250 RPM. Vacuum Advance starts @ 6-8 in. of Mercury. Maximum Vacuum Advance is 22 degrees plus/minus 2 degrees.

Distributor used on the HP/Synchromesh engine is a dual-point unit, Serial No. 1110897. Centrifugal Advance is 0-2 degrees @ 800 RPM. Maximum Centrifugal Advance is 18-22 degrees @ 3600 RPM. No Vacuum Advance. Point Tension is 19-23 oz, Condenser Capacity is .18-.23 Mfd., Point Opening is .0125 - .0175 in..

All cars equipped with Tri-Power have the distributor positioned one camshaft tooth counterclockwise from the standard production distributor positipon.

Coil used for engines equipped with Hydra-Matic use Model No. 1115085.

Coil used for HP/Synchromesh engine is Model No. 1115099. Primary Resistance @75 degrees is 1.00-1.16 Ohms, Secondary Resistance @ 75 degrees is 7500-10500 Ohms. Amps with engine stopped is 4.0. Amps with engine idling is 1.8.

The Front & Rear Carbs are activated by a vacuum diaphragm via a vacuum switch mounted on the Center Carb. The choke on the Center Carb has a "lockout rod" that goes to the Rear Carb that keeps both the Front & Rear Carb from opening as long as the Center Carb choke is on. Vacuum is supplied by the vacuum pump (assume at the fuel pump as the fuel pump also supplied vacuum for vacuum wipers).

The HP engine also has special valve covers and crankcase ventilator inlet same as the 1956 engine. Special high RPM hydraulic lifters are used, and higher tension inner & outer valve springs are used without valve shields on the intakes.

Dual exhaust would have been used as well.
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post #14 of 15 (permalink) Old 03-09-2019, 12:24 PM
 
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Jim, you "tree'd" me. I'm still looking for my stuff and you have it all in post #13 . Appreciate you doing that.
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post #15 of 15 (permalink) Old 03-09-2019, 08:05 PM Thread Starter
 
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Yes Jim, thank you again for your #13 post. Alot of valuable info there. I appreciate your time and effort, Nicholas.
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