Quote:
Originally Posted by Formulajones
A lot of the big HP muscle cars of the 60's had similar small exhaust.
The OEM system on our Z is just 2 1/4" head pipes, intermediate pipes, and the tail pipes are 2" That same system is what was used on the COPO camaro 427's and even the ZL1 camaros. Even if you opted for the Chamber exhaust the sizes were the same. Firebirds of that era would have been very similar. In fact I'm restoring a 68 400 Firebird now and it still has it's original system intact, and it's pretty small by the naked eye. It sounds nice and mellow, but I just cringe looking at it thinking of the HP that's soaking up LOL
Dad's GTO had small exhaust very similar, with little 2" resonators at the end of it.
There's a reason why these cars pick up so much with just the addition of a nice 2 1/2" mandrel bend system and some free flowing mufflers.
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from Motor Trend Archives; Pure Stock Prep School Part 2- Pontiac Tech
Learn What Makes Them Really Run
Mark Weymouth writerDan Jensen photographer Aug 1, 2008
"ExhaustThe exhaust system is your last drivetrain issue to address. How important is the exhaust? Very! The Ram Air IV Judge in the lead shot of the last installment is a good example. The previous owner used it as a show car and we were going to use it as a race car. Its NOS exhaust system and factory-spec engine only allowed 13.90s at 105 mph. With a change to an X-type pipe system, the car went 13.13 at 111.8 mph.
To achieve the best results, you'll need to start with an all mandrel-bent 2.5-inch exhaust. Next, you need to decide whether to use an H-style pipe or an X-type pipe. Each has its own merit.
Most racers have adopted the X-type pipe system. It provides excellent scavenging in the low to upper midrange. At very high rpm, it's not as effective. Most PS cars run completely in the rpm range, where it does its best work. The one exception is the Ram Air IV, but even this motor, overall, is well served by the X-type, as it provides additional bottom end and midrange that the engine lacks on its own."