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Old 06-02-2010, 12:29 PM   #41
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last motor i built was a 408 ford small block and i put new pistons and rings in let it warm up then cool down changed the oil and stuck it on the dyno. We did one motor pass to make sure timing and a/f was correct which it was then we did about 4 nitrous pulls starting with a 150 shot ending with a 300 shot. motor ran perfect no leakdown and lasted longer then it ever should have with a stock 95 f150 block making over 700hp.
everyone told me i was an idiot for not breaking it in but i have witnessed that the rings continue to rotate around on the piston throughout the engines life so to think that the rings are going to wear into the slight groves that might be in the cylinder walls is incorrect.
our cam had been in the engine already but in the event that the valve train was new a few heat cycles and some time spent holding it at around 2k-2500 rpms would prolly have been a good idea. im not sure if this applies to miata cams though since they ride in the head with no bearings and there are no rockers. i would still do it though its not going to hurt, and heat cycling new springs is important in my opinion.
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Old 06-02-2010, 02:32 PM   #42
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The first heat cycle is key to the cams. Only takes once to work harden it. Many of us have broken the rules and gotten lucky. Sucks to be the unlucky one. As for Miata cams. Old pushrod v8s have higher stresses (stock). V8s have a much greater leverage disadvantage and much more weigh to manage. I have not done any Miatas so this is just an opinion, however I would expect to break these in as I would a bike. Managing RPM as the motor wears in. I have replaced more than one rocker assembly on a bike for this reason. btw - avoiding a set RPM on bikes is also for the cam to rocker pad/ bucket breakin.

I envy the 408. The terror I could have caused in high school with my 68 fastback.
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Old 06-03-2010, 02:16 PM   #43
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Corky's Procedure for breaking in a motor:

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