Exhaust Backpressure- 3" vs. 2 1/2"

[Hog]

Originally Posted by Hib Halverson

Mr. Hog gets a Beacon of Reality Award for that spot-in statement!


Point well taken but some of the supporting numbers puzzle me. Using the rating systems of that period, ZL1s made either 560-hp (if you believe unofficial "real" numbers) or 430-hp (if you believe the "official" power rating. No question that when a stock Camaro exhaust was attached there'd be a big loss, but a loss of more than 50%? Not sure I buy that. What testing done at Tonawanda are you talking about? I didn't think there were any dyno cells at Tonawanda back then which could accomodate a full OE exhaust system. Can you post the numbers and the testing method used? Or at least post the source for your info.

About the engine testing. I was confusing the ZL1 testing that went on at Tonawanda. After each Zl1 was built, it was run on a dyno in the Test Department where each engine was serialized and was run on a break in program. It was then packed up and taken down to the dynos operated by the Product Engineering Department.(all at Tonawanda). This is where each ZL1 was supplied with its dyno printout of exact engine output. Every engine that left the PED at Tonawanda produced between 500 and 535hp running on Sunoco 260 fuel.(as per Art Casper who worked with the MkIV since its inception at Tonawanda)

Some of these engine were sent to the Chevrolet Engine Center in Warren Michigan where Bill Howell was a development engineer and Tom Langdon(who was a dyno tech) took over for Mr Howell in 1966. Mr Langdon told the story stock Camaro exhaust being fitted onto a ZL1 during ZL1/Camaro development and cutting its power down considerably,

"We did run some checks to see what the performance penalty was. A good ZL-1 when equipped with a standard set of aftermarket headers, would produce somewhere in excess of 500hp, maybe 525hp, without any attention to detail whatsoever. In other words, taking the engine, putting it on the dyno, putting on exhaust headers, and making it run, you wound up with around 525hp, perhaps 600hp with some attention to detail with the cylinder heads, etc, etc. We took one of those engines and and ran it with the released Camaro exhaust system and got exactly half the power with the Camaro exhaust manifolds, exhaust system, manifolds and pipes. So you can see how sensitive the power was to the exhaust system when used with that ZL-1 racing camshaft. Power was cut to something like 275hp." Tom Langdon

The ZL1/Camaro dyno testing was done in Warren Michigan, not Tonawanda. It was other ZL1 dyno testing being done at Tonawanda. I can neiher confirm nor deny your assertion that there wasn't a dyno cell large enough to accommodate an entire Camaro exhaust and engine dyno at Tonawanda.