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P6 1953 Chieftain Engine HC or LC with 2 bbl Carby ?


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Hello all

Im a new member from Australia, with a 1953 Chieftain in partnership with my Dad.

Our vehicle has only 53000 miles on the clock so far and is original.

Its a P6 straight six -239 CID and obviously RH drive for us here, with the 3 spd Synchro gearbox fitted.

I have just had the engine and gearbox out for some reworks and a paint job.

My question is as this vehicle has the 2 BBL Carter 2010S carb fitted as standard, would it be the High Compression Cylinder Head fitted as standard (7.7:1) or the Low compression unit ( 7.0:1) Compression Ratio.

When I look in the shop manual, my interpretation of the engine spec sheet shows the Hydra-matic transmission unit was fitted with the HC engine.

I have the numbers in the 53 parts book ( Original GM book ) but I don't have access to the vehicle at present as its 2 states away.

The engine specs show 115 BHP for the LC unit and 118 BHP for the HC engine. Apart from removing the cylinder head and CC'ing the chambers to clarify the Compression ration, maybe some of you experienced guys can help here.

I am also seeking a replacement clutch for the car as the existing driven plate has not far to go before she is down to the rivets. Does anyone know of a lining supplier in the US or otherwise a reputable supplier for the manual clutch kits. E-bay is a good source for me in AUs but no one seems to list a clutch for the P6 driveline.

Thanks :)

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the two different cylinder heads have two different part numbers, on the straight eight, the HC head said HIGH COMPRESSION, i don't know if the six HC head says the same. standard or LC head p/n 517261, HC head p/n 517290. charles coker, 1953 pontiac tech advisor.

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the two different cylinder heads have two different part numbers, on the straight eight, the HC head said HIGH COMPRESSION, i don't know if the six HC head says the same. standard or LC head p/n 517261, HC head p/n 517290. charles coker, 1953 pontiac tech advisor.
Thanks Charles - I have the OEM part numbers also ( same as the ones you quoted above ) but the numbers cast into the top of the head didnt match any in the Pontiac Master Parts Catalogue, hence the question on the forum. I also have an original 53 Pontiac Catalogue hard copy and will check the numbers on that also when I return. I have 2 spare P6 engines in my workshop, but as the car is 2 states away I dont have access to the original engine installed and as such are unable to check the number on it as yet. The number on the 2nd spare engine i have was found to be different to the catalogue numbers as above. Im away from the workshop now but will get back to this when I return from work. These P6 engines from what I can see from other owners, all appeared to have 4 welsh ( freeze ) plugs on the distributor (RH) side of the block, as our original '53 does, as I not long ago replaced them all (1-15/16ths is not a common cup plug size!! ) The first spare P6 i purchased has only 3 plugs on that side of the block. Also - On the harmonic balancer retainer bolt, it has the one way claw type bolt ( as opposed to the standard hex head bolt ) retainer to allow the use of a hand crank handle. This leads me to believe its a much earlier model . Any clues to that ?? Sorry I dont have any pics of that with me at present but will post when I do. The spare engine/ gearbox in the pic is one I recently purchased out of Sydney for $100 from a guy who was rodding his 53 :( - it needs a valve grind as the leak down test results werent ideal but would still be a runner with a few accesories installed. But it still rotates freely & none of the head bolts snapped when i undid them so thats a good sign. :)

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