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Old 03-11-2013, 07:53 AM
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Well, I guess it doesn't mean much, experience... It takes a LOT more than 375 HP to move a 3,500 lb. car into the 11s. NOT an opinion, a mathematical fact. My '70 GTO ran 13.60s "stock" (@ Orange County, 1973). It was a "Ram, Air" car. No 396 of any description ever beat it in a race while I was in it, including at least 5 "375 HP" versions. Never saw a real L-78 (425 HP) "in person" (VERY RARE). When Rick Holladay first broke into the 10s (10.80s, pump gas, TriPower 434), he dynoed 435 RWHP, which is well over 550 at the crankshaft (GBHP).

Building pump gas engines to make power, using antiquated parts and methods is a serious challenge. This is why we don't do it. The ONLY things we "keep" are the block, crank and head castings. Everything else gets changed, including the rod length (if a "racer").

Taking the "dome" off a piston and updating the heads and using a modern cam grind, is daily proceedure around most good shops these days.

Jim

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Old 03-11-2013, 08:23 AM
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Building pump gas engines to make power, using antiquated parts and methods is a serious challenge. This is why we don't do it. The ONLY things we "keep" are the block, crank and head castings. Everything else gets changed, including the rod length (if a "racer").

Taking the "dome" off a piston and updating the heads and using a modern cam grind, is daily proceedure around most good shops these days.



I agree. I am also a fan of the 396. Raced them "back in the day".
The problem I have is I've been there and tend to be a realist.

I see guys with great expectations and little experience trying to build these motors. Because their grandpa or buddies say it is the great way to go. GM did a good job advertising the SS396! Still in peoples' heads.

Compression is major problem. To build compression you need tall dome or small combustion chamber. Tall dome conflicts with flame travel/power. Small chambers are not really available bolt on aftermkt and the old stock stuff doesn't flow air. Plus the small bore shrouding really screws up the air flow into cylinders. Especially on the two bad cylinders on each side of a BBC.
Then to get decent valve lift, the piston valve reliefs have to be cut, thus lowering all important compression ratio.

It may rub some people wrong but the facts are there. If you want horsepower on a "reasonable" budget. Pass on the small bore BBC.
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