old cars and duration...
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From: AustinTexas
old cars and duration... A buddy of mine has a 1959 Chevy Apache truck wit ha 400ci SBC. We were talking about old motors and cams and he was telling me how his trucks cam had 272/272 duration and I forgot the lift. My question is, how come alot of the older cams have alot of duration compared to the LS1? Can it be because of the way the heads are designed? Thanks in advance.
-Brent
-Brent
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From: LaConner WA
He's talking about advertised duration, not duration @ .050 . It used to be popular for cam manufacturer's to list the duration numbers at zero lift which made them sound bigger. Kind of a gimmick thing. Anymore they are listed at .050 lift which makes the #'s seem smaller compared to the old way of listing them, but it's much more accurate and easier to compare one cam to another.
Originally Posted by Racehead
He's talking about advertised duration, not duration @ .050 . It used to be popular for cam manufacturer's to list the duration numbers at zero lift which made them sound bigger. Kind of a gimmick thing. Anymore they are listed at .050 lift which makes the #'s seem smaller compared to the old way of listing them, but it's much more accurate and easier to compare one cam to another.
His duration ato .50 is more like 224/224. He is talking addvertise duration. Not only that but he probably runs a hydrolic cam which has a lot less lift and a lot less aggressive lobes. His lobes will resemble a V while our lobes resemble a U. He would need to run a much larger cam to allow the same amount of air and fuel into his cylinders compare to a 224/224 hydrolic roller. Also, a 224 will resemble a 218 in a 350 because of the cubic inch difference. Trust me, I have a .030 over 400 in my 72 SS. Advertised duration is 282/292 but my duration at .50 is 226/234 w/ a low lift of .465/.473. I hope this helps. Later!
