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Supreme Being
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What John said I believe is right on the money. For example the .234@.050 I referred to is a Comp tight lash solid .234@.050 with a rated duration of 264. valve lift with 1.6 rocker ratio is .528 minus lash. This seems to be a excellent street cam and should do well at the strip and a few upgrades on the engine will be even better.
-Gary Burnette-
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Supreme Being
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Getting some good advise here. Nathan mentioned the Isky RPM-300 cam. If I'm reading the numbers right it's just about the same as the 270 cam I'm running now except for the lobe separation angle. I think I've narrowed my choice down to 2. I'm looking for low end performance and the "sound". One is the CompCam I've mentioned here but I'd run it with a 4deg advance. The other is Johns 284 cam that I would also run a 4deg advance (is that too much for that one?). Any ideas guys.
Dan Gregory Mi. 48137
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| Dan, Puzzled some on your existing Mummert cam spec. The highest @50 cam Mummert lists is a Y-292S with 240* @50 duration. Your only data match to his Y-270S cam is your 108 LCA. Confused. That aside, I’d be concerned stock 113 heads have enough static compression to take advantage of cams over 270* advertised duration on pump gas. Maybe these two Vizard articles can help you decide. http://www.popularhotrodding.com/enginemasters/articles/hardcore/0606em_understanding_compression_ratio/index.html and http://www.popularhotrodding.com/tech/0311_phr_compression_ratio_tech/index.html I’ve a 56 Fairlane, estimated weight 3750 lbs. My 3.44” stroke, 3.860” bore, 312 (now 322 cid), zero decked forged flat top pistons, ECZ-G heads milled 0.060” (estimate 68cc), standard 0.040” Fel-Pro head gaskets (estimated 0.218” head gasket bore over size) calculates to 9.6 static compression. Back tracking that ratio through Vizard’s example in the second reference using 91 octane pump gas and 170*F coolant, allows an 8.1 dynamic compression. My static minus dynamic correction = 9.6 – 8.1 = 1.5 points. From his advertised duration data points (250, 275 & 300), the largest duration cam my heads support is 275* advertised duration. I consider 5500 rpm a safe redline for stock 312 rods, mains and valve train in good condition (has worked for me over 45 years on this 312 build). Any more cam than a Y-270S would lower dynamic compression and low end torque and ad nothing above (don’t ask how I know). I’ve good flowing exhaust ports and fenderwell exit headers. So split lobes might even hurt my situation. I’ve a manual 3 speed Borg Warner T85 with the R-11 overdrive and 3.89 rear gears. If an auto trans with even lower rear gear ratio, original vacuum wipers and all weather driving needs, I’d consider Mummert’s Y-265S cam. If you’ve any less compression than my build, I suggest keeping what you’ve got or moving down a notch for even better dynamic compression and street manors - unless you are hatching a 7000 rpm sleeper needing a power band above 3000 rpm and are willing to give up lots of 1500 rpm torque. Jerome
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Supreme Being
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Dan, the larger rated cams (286-etc) will not help you on the lowend torque. Keep the advertised(rated duration) short to help on the lowend torque. The @ .050 should work well in the .232 to .236 range for the setup you have. Call John M and see what he has that will work with your application or take another look at the one comp cam has I mentioned earlier. I would not go any larger usless you build the engine on up.
-Gary Burnette-
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Supreme Being
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| Bear with me guys I've been away from this stuff over 35 years. You guys have been very helpful. Jerome. I was only comparing the 270 cam to the Isky RPM300. I wish I could build a 7000 rpm sleeper. The last FE sleeper I built I brought home in a basket. It was fun while it lasted. Gary. If I read the cam numbers on both of your posts they look like the numbers on the cam card I have here from the CompCam I had to replace. If I go with the lower advertised duration and the duration @50 to around 230 I should either keep what I have or go with the CompCam. The few times it ran decent it did sound good. To this point I've only been looking at the @50 spec. Now I understand all the numbers a whole lot better. I wish I could get in a time machine, go back 40 years and pick up that Racer Brown cam I had in my 56 Ford.
Dan Gregory Mi. 48137
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