I am looking at a comp cams 268H cam for a 1971 olds 455.
Stock pistons, 68 C Heads, stock everything else.

Is it safe to use the 268H cam with stock internals or do I risk damaging my pistons and rods?
I will be buying the kit with the springs and stuff.

I was considering the comp cams next size up cam but I don't want to stress my internals to much.

 

You're not going to hurt anything and with your compression ratio you should be just fine with that cam, just don't go any longer with the duration.

 

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which est. compression he has ???????

 

Is that to keep the valves from touching the pistons?
Or is it because of the stock springs?

I'm replacing the springs with matching springs, I found the cam as a set with new springs and things.

 

Longer duration cams close the intake valve after the piston starts to move up in the bore. This late closing reduces peak cylinder pressure. These cams need a higher compression engine to maintain decent cylinder pressure (and power) at lower rpm.

You have a lower compression engine; the longer duration cam will not damage it, but the low cylinder pressure will make for weak power until the engine turns at higher speeds. You would not be pleased with the poor power off idle and at low engine speed.

 

Ok I understand.

The company says the cam is made for 8:1 to 9:1 compression ratio engines with stock components, so I hope its a good match.

 

Unless you have 9:1 compr. i would go with the 260H...
I drive this cam for 10 years in low comr BB with 3:55 rear and headers /Intake...the cam is GREAT for low comr. BB!
company´s want to sell ´...never forget!

 

With those factory "soup bowls" (deep dish) the valves won't be hitting the pistons. Detonation, too much timing and/or low octane gas is a piston killer. If your timing is right at that C/Ratio you can get by on medium grade. With the thicker Felt-Pro gaskets and a valve job, you'll probably be a low 8 to one engine. Have Mark recommend a torque cam. My 1971 Delta has a similar C/R. She pretty pepe for a big boat. Jmo

 

would it even be possible to kill your pistons with the wrong cam? despite from valve to piston clearance...

 

Thanks all for the info, I have the new parts I am planning to put together soon.
Info helped a lot.