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By joey - 16 Years Ago
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Hello gentlemen, There's probably a simple answer to this, but...on their '56 312 Y-block, how come Ford designates a 9.0 compresson ratio for an automatic tranny, but an 8.4 for standard? (in 57, those numbers are 9.1 and 9.7). Also...I have read where the baby Birds came stock with a pretty strong Dana 44 19-spline rear end. But in 'The Book of the Ford Thunderbird' by Brian Long, it says that they had a Spicer rear axle with a 3:73 on manual models and a 3:31 on the automatic. Any input is appreciated. Thanks.
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By Hoosier Hurricane - 16 Years Ago
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Joey: The higher compression was to help make up for some of the power loss with the early automatics. You couldn't lug the engine, so more compression and more spark advance was possible without detonation. Spicer and Dana axles are the same thing. Dana-Spicer was the name of the company that built them.
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By paul2748 - 16 Years Ago
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The Dana/Spicer rears also came in station wagons. As you probably know, all the cars, including the TBirds, went to the 9 inch in 1957.
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By joey - 16 Years Ago
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What method was used to achieve the differetn compression ratio?
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By crenwelge - 16 Years Ago
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Different cc in the heads. The smaller, the higher compression ratio.
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By joey - 16 Years Ago
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So what Ford did was to put different heads (or at least different grinds) on automatics as opposed to standards? To take it a step further...if you had a 312 y-block from a '56 but equipped it with the heads from a '57 automatic, you'd be generating the output (in terms of CR, HP, torque) of a '57 engine...all other things being equal?
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By pcmenten - 16 Years Ago
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56 engines came with Load-o-matic vacuum only distributors and either Holly 2100 or 4100 carbs, 57's had mechanical/vacuum distributors and different carbs. The cams were mostly the same, and both 56 and 57 had the high ratio rockers.
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By Hoosier Hurricane - 16 Years Ago
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Concerning, the cams, the '57 cam is slightly better than the '56, but nowhere near aftermarket grinds available today. On the street, you probably couldn't tell the difference between '56 and '57 cams. 4 barrel '56 312s were rated 225 HP, in '57 they were rated 245.
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By Johnson Rod - 16 Years Ago
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joey (1/27/2009)
What method was used to achieve the differetn compression ratio?
Good question Joey... I doubt Ford had different heads for the different compression ratios between manual and auto transmissions (in the same model year). Anybody got ideas??
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By pcmenten - 16 Years Ago
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Actually, it looks like that's exactly what Ford did. A 56 292 2bbl would have ECZ-B heads and the 56 4bbl had ECZ-C heads. They stopped that nonsense in 1957 - most engines had ECZ-G heads, including the truck 272 2bbl. The 57 F code engines had special heads, but they're rare.
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By Johnson Rod - 16 Years Ago
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Thanks for clearing that up, Paul. Happen to know which one is the 'high compression' head... Oops, never mind, I just looked it up on Mummert's site...
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By joey - 16 Years Ago
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Hoosier Hurricane (1/28/2009)
Concerning, the cams, the '57 cam is slightly better than the '56, but nowhere near aftermarket grinds available today. On the street, you probably couldn't tell the difference between '56 and '57 cams. 4 barrel '56 312s were rated 225 HP, in '57 they were rated 245.Actually, it looks like that's exactly what Ford did. A 56 292 2bbl would have ECZ-B heads and the 56 4bbl had ECZ-C heads. They stopped that nonsense in 1957 - most engines had ECZ-G heads, including the truck 272 2bbl. The 57 F code engines had special heads, but they're rare. Best regards,
Paul Menten. Thank you gentlemen. I am trying (if you haven't guessed) to estimate what my own engine's numbers are without dynoing it. We started with a 1956 312, bored 030 over, with chrome moly rings, new rocker assemblys, etc. It has the ECZ-C heads that have been ported and polished. The cam is from summit, it was a 275 duration .423" lift. I put a Speed Demon 575 carb on a stock 9425B intake (no headers), stock exhaust but without resonators. New Mallory YH dual point dizzy with high output coil. As was pointed out by John above, 1956 312s were rated at 225 HP and 1957s at 245 (torque 324 and 332). What numbers (ballpark) do you think my setup would yield? Any and all estimates considered.  Thanks, joey
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By PF Arcand - 16 Years Ago
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Joey: First the old H.P. ratings of the 50s & 60s were gross Brake HP. That roughly means sans generator,water pump & other accessories. In G.M's case the power was in some cases "calculated based on fuel consumption". Anyway, around 1971-or 72 Detroit went to net H.P. figures, which are somewhat lower (what percentage?) The point is that you can't take the old ratings to seriously as a jump off point for your engine. Your engine is about 317". The cam is advertised at 275 duration, but what is it at .50 lift? The lift is barely over that of a 57-312 cam. According to J. Mummert, "C" heads don't improve much from porting on the intake side. I'd guess that your at somewhere around the old rating of between 225-245 H.P. I'd be surprised if it was higher. But! it's only a guess...
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By joey - 16 Years Ago
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Thank you Paul.
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By Ted - 16 Years Ago
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joey (1/28/2009)
The cam is from summit, it was a 275 duration .423" lift.Do you have more information on the camshaft?. Specifically the lobe centerline the camshaft is ground on, the duration at 0.050”, and where it’s actually installed in the engine (intake lobe centerline). Also, when degreeing in the camshaft, were the lobes on more than one cylinder checked? All these are pertinent to achieving maximum output and/or efficiency from the camshaft as well as checking the accuracy of the cam grinder.
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By joey - 16 Years Ago
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I wish I did have more information on the cam, I looked for the paperwork but couldn't find it. My friend installed the camshaft and I'm not sure how he went about degreeing it in. I sure wish I had known about this board back then..
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