Thread: 427 chev ???
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Old 08-02-2004, 01:50 PM   #3
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Re: 427 chev ???

At the risk of opening a can of worms, I must disagree. The "high block" or "tall deck" is VERY popular among racers today. The 427 is a "big bore" version of the 366. They are bullet proof!
The only big block pickup engines I've seen have been either the 396, 402 or 454. I don't recall a light truck coming from the factory with a 427. That doesn't mean they never made one, just it must be rare.
The big advantage of the tall deck, is the ability to put much longer connecting rods in the engine, and use the good pistons available for the standard deck. Weiand makes spacer plates for both oval and rectangular port heads, allowing the use of standard deck intakes.
Tall deck blocks are ALL 4-bolt main. They ALL have forged steel cranks (3.76" stroke). They use the stock length rod (6.135") and the piston has an extra .400" added to the top, whcih allows the use of an extra compression ring (not uncommon in heavy duty applications).
Eagle and others, make a rod exactly .400" longer, making the swap easy. Even longer rods are more commonly used (6.7 and 6.8, respectively). We in the Pontiac world are grateful for this popularity, as it has significantly reduced the cost of good rods for the Pontiac. We use a ton of the 6.8 jobs. Adding to the rod length improves the rod/stroke ratio (not very good on stock BBs). it also reduces the rod angle, and allows for more "dwell" time (in degrees) at TDC and BDC. More time at TDC will give more cylinder pressure under firing, and it will fill better on the intake stroke, when it dwells at BDC.
The one negative (aside from sheer weight) is the exhaust. The headers will be up higher and further out with the tall deck...
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