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By BamaBob - 3 Years Ago
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Ted, which would be the best lobe center grind for the S-969 Isky cam installed in a 312 engine mated to a 1955 Fordomatic Transmission? Also, would a .030 deep center groove be enough for good oil flow to the top? Thanks.
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By Ted - 3 Years Ago
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For a F-O-M tranny, 112° lobe centers will work well. Install the camshaft with 4-5° of advance but a bit more than this will not be a show stopper. As far as the camshaft groove depth, 0.030” would be a minimum number but shoot for closer to 0.062”. That may require restrictors at the rocker arms to reduce the flow. The deeper groove is to simply compensate for the quicker wear that occurs with the softer cam bearings.
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By bird55 - 3 Years Ago
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Ted, I know that in the past you have ground a groove in the block behind the center cam bearing. Is this no longer a recommended practice? Or does it serve a different purpose?
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By Ted - 3 Years Ago
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I continue to machine the groove into the block behind the center cam bearing on all Y blocks as that is the ultimate fix for the long haul. But many shops do not have that capability so machining the groove deeper in the center camshaft journal is an alternative method to accomplish basically the same thing.
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By BamaBob - 3 Years Ago
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Ted (2/17/2022)
For a F-O-M tranny, 112° lobe centers will work well. Install the camshaft with 4-5° of advance but a bit more than this will not be a show stopper. As far as the camshaft groove depth, 0.030” would be a minimum number but shoot for closer to 0.062”. That may require restrictors at the rocker arms to reduce the flow. The deeper groove is to simply compensate for the quicker wear that occurs with the softer cam bearings.
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By BamaBob - 3 Years Ago
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Could the cam shaft be ground with the 5 degrees advance built in and the cam then installed at true TDC? Would this be a good install? Thanks.
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By Ted - 3 Years Ago
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As a general rule, I specify two degrees of cam advance when custom ordering camshafts. This amounts to four degrees of advance as measured at the crankshaft.
Keep in mind that camshafts are ground with cam degrees in mind and not crankshaft degrees. If you want the camshaft to install at 4° advance as measured at the crankshaft, then you must specify that the camshaft is ground on 2° cam advance. If you tell the cam grinder you want 5° advance built in and do not specify camshaft degrees, you could very well end up with a crankshaft that might install at 10° of advance as measured at the crankshaft. With that said, variances in how the camshaft is ground, where the crankshaft snout key for the crank gear is cut, where the slot is machined in the crank gear, and where the cam gear key slot is cut are all variables. When all these are off to some degree, some of those variances counteract each other and cancel out some of the positives and negatives. In rare cases, the camshaft is exactly where you want it.
When all the variances are negative or all are positive, then you have what is referred to as ‘stack ups’. I’ve seen those stack ups to be as much as eighteen degrees off in both positive and negative scenarios. For these reasons, camshafts must be degreed in to ensure they are installed at the appropriate position in relation to TDC. It’s also important that both a right bank and left bank pair of lobes be checked to ensure that the lifter bank angle has been taken into account when the camshaft was ground. In a sixteen month period here at the shop, there were three camshafts that did not make it into Y engines due to the lifter bank angle being incorrect when the camshafts were ground. These were found only by checking at least two cylinders that were on opposite banks. If it’s any consolation, none of those camshafts were Isky. On the Y, the #1 and #6 cylinders share the same TDC so it’s easy enough to check the lobe centers on both the #1 and #6 cam lobes without moving the degree wheel. Just move the dial indicator over to the #6 cylinder after doing #1 and check #6. By doing checks on at least two cylinders, you check your methodology, ensure that the camshaft is very similar on at least two cylinders, and ensure that the lifter bank angle has been taken into account when the camshaft was ground.
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By Florida_Phil - 3 Years Ago
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As a side note, I took Ted's advice and cut the grove in my new cam to .030". As it came from Isky, the oil grove was .018" deep. We put the cam in a lathe to deepen it. This substantially increased the oil flow to my heads. At .030" I did not have to use restrictors and my oil flow is perfect.
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By BamaBob - 3 Years Ago
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Thanks, Ted. I was just wondering about different installation scenarios. I think I'll stick to proven methods! Phil, thanks for your input as well. I think I'll do the same or maybe just a little more.
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