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#1 | |
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Location: Arkansas - In the middle of everything.
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#2 |
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Location: lyndon ky. ... louisville area
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elgin rocker arms, then ship to jim bailey he will harden and polish them... shazaam nice pieces and very reasonable pricing
captain jack
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Jack McCarthy 3609 STK "the Captain" |
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#3 |
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Any ruling on the ratio? I have an article written in Oct 1966 "What Makes Bill Jenkins' Chevy Run" He ran a Isky 550 flat tappet cam with a 108 centerline and Crane roller-tip rockers. Not real stock for a stock class but I guess those were the rules.
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#4 |
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You can run any ratio as all that is checked is lift as measured at the valve.
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Jeff Lee 7494 D/S '70 AMX |
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#5 |
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Jeff, thank you for the information. I was reading an article about a gent with a 409 that found a Canadian source for stamped steel rockers that were 1.7. It was a simple question and all I need was a straight answer. I guess it's an Arizona thing about looking a man in the eye and getting a straight answer.
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#6 |
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Im not sure you understand what Jeff is telling you, the cam still has to check at legal lift specs so theres no advantage with the higher lift rockers. Maybe Im misunderstanding him too, who knows.
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#7 | |
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If you have a "true" 1.5 rocker ratio, the lobe lift will be .333" if you have a cam spec of .500". If you still have the same cam spec of .500" and want to use a 1.6 rocker ratio, the lobe lift will be .3125". It's up to the racer to determine what rocker ratio he wants. That choice may be limited with a stamped steel ball stud arrangement. Maybe rocker to valve spring clearance comes into play as well. But a higher (numerically) ratio will open the valve at a faster rate. The bottom line is, it can't open the valve more than .500" in this scenario. You can juggle with Chevrolet ratio and Pontiac ratio if that's what you want to do. I found on the AMC which is advertised as 1.6 (also stamped steel ball / stud system) most rockers checked at 1.55 or so and a SBC 1.5 ratio rocker was around 1.45. Since I was always using custom cams, I had the lobe lift adjusted to compensate for the true rocker ratio. Keep in mind what was said earlier, your net valve lift can be adjusted by pushrod length (or even plunger height). The engines with shaft rockers like a mopar have it easy. The ratio is fixed. And with offset grinding of the shaft hole in the rocker, the ratio can be adjusted. I believe those racers are in the 1.85 range and I think they have been around the 2.0 range but I don't know as a solid fact. But it is allowable. I know this, when I switched from Stock to Superstock and having a shaft style rocker system from T&D sure made it a lot easier. Where I once adjusted valves every 2-5 runs, the T&D is set and forget (as long as there are no problems of course). And we tried different ratio's on the dyno. There is a difference that can be seen in RR both intake and exhaust. Hope all this helps...
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Jeff Lee 7494 D/S '70 AMX |
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#8 | |
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While it is true that the Tech Dept checks valve lift at the retainer, we can still check rocker arm ratio if we so desire. That could happen anytime we run across a set of rocker arms that do not appear to be correct. A racer was DQ'd a few years ago at Gainesville for using 1.6 rockers on a SBC even though the lift at the valve met the spec. Travis (Disclaimer: Opinions expressed by me on this forum are exactly that, my opinions.) |
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#9 | |
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And if the tolerance is "dead nuts", you would be able to throw just about everybody out. Right? My guess is somebody in Gainsville a few years ago must have really PO'd a tech guy off to get bounced for that... ![]()
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Jeff Lee 7494 D/S '70 AMX |
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#10 |
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I agree with you Jeff, if they did the lobe lift to the valve lift to check R Arm ratio.. everybodys out... good luck with that NHRA Tech...
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Bub Whitaker |
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