How much life, if any, will heads and a cam take away from a motor (35)?

Not enough to be concerned with for the performance gained

For every .001 lift you add, you lose an hour of life.

For every .001 duration you add, you lose two hours of life.

For every .001 you take off the heads, you lose 5 hours of life.

For real? ^^^


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It's highly dependant on what kind of oil you use.

Cb always has the answer haha

I figured I was. I just felt like blurting something out.:D

Oh, you were right in that post. I just figured that was an open invite. I'm sure you were wrong about something today..


Seriously, the simple answer is, there is no answer..

However, most would agree, on this particular engine, as long as you don't go with an extremely aggressive cam, and aggressive decking, the longevity of the engine is more likely to increase than it is to decrease... Properly sealing valves and a cam built to perform better in the desired rpm range is only going to help things...

This is something i have given a lot of thought to, also. I spent the last three years developing an equation. I have ran it against many real life examples and it has been pretty accurate. The Shaft Constant was the hardest thing to come up with because the horizontals were failing at various intervals dependent upon the builder and the cam. But, I was able to interpolate and extract the constants into this formula:




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I just put some numbers through Blue's equation there.... Friggin spot on!!!!

As you can see, the higher shaft constant for the horizontals creates a linear ratio with a higher denominator...therefore, this gives a shorter life cycle with all the other remaining constants.....even with the varying K factor of the oil.


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Makes sense. The verticals gotta have something going for them. It surely isnt speed. Haha sorry blu, had to

Considering these motors suck ass in stock form, modding them is like waiting for a bomb to explode

If its a time bomb either way, might as well have a better time bomb

Lol ^

Well, a buddy that I run with has put over 300 hours on his 45 mag. Stock crank, billet rods and Pistons. He had a rocker boss pull out of a stock head at around 200 hours. He swapped to iron mountain heads (we have decided that these are not the heads to go with) and has put over 100 hours on them. 3 out of 4 valves burned " boat still running 28 mph" but we cut the valves and seats at 4 angles to help heat dissipation and did some port work on heads and intake. Over 300 hours of load hauling and mud bogging and those were the engine repairs done so far. Can't say I don't expect head problems. Briggs heads are not tough at all. Just how it goes when you mod. My motor has chronic pan gasket leak, but I have 186 hours on it and have faith in the old prodrive. It's all about catching problems early and maintaining well. Keep your bolts tight, rockers adjusted, valves in good shape and oil changed.

My experience is more with ford small blocks and 2 strokes, but generally engines have 3 enemies heat, friction and operator. Mods just make it more efficient (but generate more heat), jetting and oil cooling help keep it cool and a loose nut on the end of the handle tries to tear the whole darn thing apart.

I would be willing to bet if you could increase oil flow and capacity, it would act like a liquid cooled system.

If it hurt reliability at all,,,you would see it magnified x'10 on this forum. If shit breaks,,,they run here and testify...

You don't see it much anymore. Most of the parts have been proven reliable.