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Old 05-18-2021, 08:04 AM   #8
Jack Shaft
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Join Date: Dec 2019
Posts: 1,196
Default Re: High Compression Head Review

The reason you don't see much of a difference between 5.5 and 6 to 1 is based on two reasons.. one, there isn't that much increase in compression between the two.The second is a little more difficult to explain, it involves matching all the engines systems. The model a ford engine stock was detuned, its low compression and small carburetor (flows at about 80 CFM (cubic feet per minute air flow),the engine flows at about 170CFM) work together to keep efficiency down...so to gain maximum efficiency from the compression increase, you have to add fuel as well. Efficiency as stated implies use of the power the engine is capable of.
When you do raise the true efficiency of the engine, less heat is lost. Stock model a engines have exhaust manifold issues due to this, the engines efficiency is low, and that creates high exhaust temperatures, and ultimately higher engine temperatures if the timing isn't controlled correctly.
A modified flathead A engine, where fuel, compression, timing and cam design are improved will develop about double the stock horsepower through efficient use of its displacement. As a benefit, the engine runs cooler and uses less fuel.. hard to believe but true, performance and efficiency go hand in hand. Drivability? that wonderful low end torque that makes a stock engine so nice to drive is basically doubled, and with a a B profile cam it will develop it to 2900 rpm.. power to run suburban boulevards alone, power for safety without the protection of the convoy..
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