I did some prowling around in the paperwork for my GS this weekend and found that what I have always thought was a '71 Stage 1 short block that we purchased and installed in 1981, is in reality a regular '71 short block, no Stage 1. :ball: It is still the ballsiest car that I've ever owned, so not too disappointed. My question is, I'm pulling the motor this winter and giving it a "once over", replacing the gaskets, cleaning it, painting, etc... I figure since I'm taking it that far, and had an issue with the lifters and will be replacing them, I might as well replace the camshaft. I'm looking at maybe a T/A C113 camshaft, but I don't know what the numbers on the spec sheet mean. Also, which numbers determine whether I would be able to be used with power brakes? The motor is stock, as far as being a '71, so I'm not sure what the compression ratio was for that, and the heads are from our original '70 Stage 1 Motor. I'm wanting to keep the torque converter and gearing original. Has anyone out there used this cam, and do you recommend it using a pretty much stock valve train? I can change the valve springs if need be, and will be using the T/A lifters anyway. Here's the specs listed for the camshaft, with the stock 1.55 ratio rockers, and the T/A Roller Rockers, as the first 4 numbers. I'm really interested in knowing what the lobe centers means and what effect this have on the power in the motor. TA C113 .478" .475" .494" .491" 228 247 276 295 113 2500-6000
Woah, lots to cover here... Are you running stock exhaust manifolds? That cam is about as big as you should go with manifolds. Lobe center, in conjunction with duration, determine overlap. Lower lobe center=more overlap. Longer duration also increases overlap. That cam has a fairly small lobe center, and lots of exhaust duration, for a good bit of overlap. Lots of overlap makes less vacuum and rough idle. That cam will idle with a noticable lope, and will work with power brakes. I gather your car is more of a street car. If so, I'd go a smidge smaller (no bigger than 226/238 at .050 duration), and keep the lobe center around 116-118, for more vacuum and better idle. With your low compression short block and 70 heads your CR is a little under 9:1
Thanks for the help!!! Yes, I'm running stock exhaust manifolds for now, but am looking at the Postons headers in the next year or so. It's mainly a street driven car, just looking for some extra "oomph" as I guess you can never have too much. :3gears: I do want it to be manageable though and use 93 octane gas. I am looking at maybe replacing the low compression pistons with the original Stage 1 10:1 (Or maybe it was 10.5:1) pistons, just to get it back to where it was when it was new. But if I could get it a bit better, that's even better.
Scott I don't believe that a stock replacement cast 70 (10:1) piston is available anymore. (could be mistaken...) The hypereutetics, that are advertised as "10:1", give about 9.5:1, I believe, with uncut heads/block. Thing is, they are really sensitive to detonation, due to being more brittle than a regular cast piston. Should be fine with 91-93 octane, just don't put in 87 and beat on it! By the way, all 70 455 pistons are the same. Stage 1 was rated at a quarter piont higher compression (10.25:1) on the theory that the larger valves took up more room in the combustion chamber.
