How much power can you wring out of a Pontiac Flathead straight eight? What are the significant differences between the HydaMatic behind this and the later slant pan trannies?
According to my vintage copy of .."the Complete Book of Hot Rodding".......the std compression ratio is 7.70 to 1. By milling.070 off the head you can bump it up to a whopping 8.5 to 1 !! The one I had in my 53 Pont was a stump pullin torque monster. I was 14 at the time and I picked up 20 horses from the Honest Charley decal in the window . I'm thinking the hydro was a 4 forward speed model but it's been so long I wouldn't swear to it. I know the one in our 55 Pontiac was a 4 speed and you couldn't tear that damn thing up. Hell a port & polish job, mill the head and a reground cam along with headers and dual carter 2 bbls ought to wake the beast up.
Like any other engine, these straight eights respond to all the usual performance modifications. Of course, they are limited in their breathing and RPM potential, but if you modify with an eye towards enhancing low-end torque you will save yourself a lot of headaches. Here is a photo of the modified straight eight in the 1954 Pontiac Bonneville show car. It's got four side-draft carbs and a header. Period materials claim that the engine produced in excess of 200 horsepower. While there were aftermarket parts made for them at one time, they are as rare as hens teeth these days. Personally, I am mulling over a draw-through junkyard turbo for mine. Prior to that, I am going to swap the Carter carb for a Rochester 2GC, convert to 12-volts, electronic ignition, larger exhaust pipes, a free-flow muffler and other little sundry items. I imagine that I will be able to raise the power from 122 to 150-160 and push the torque into the 250-260 ft./lbs range. We'll see.
'48-'51 use a single range hydro, while the '52-'54 has the dual range, a much better trans. When I was about 15, the neighbor's kid had a nice '52 Chieftain 4 door with an Edmunds 2-2 setup ... he traded it in on a '56 Star Chief Catalina, & said the '52 was 12 mph faster top end according to the state police.
I have a '46 Pontiac woody with a HydraMatic. Installed a K&N air filter and a Petronix 6v electronic ignition to make it a dependable driver. Since my Honest Charlie decal is a repro, it only adds about 12 HP.
i have a 51 with the manual three speed. would i be better to put a hydro under it and would the 52-54 trans bolt up to the 51 straight eight?
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