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- - Max Rpm (https://www.offshoreonly.com/forums/general-q/138266-max-rpm.html)

Quote:

Originally Posted by SB

Even if they came with a spec, you need to find out. This goes with any cyl head from any manufacturer.

Without knowing this means you do not have any idea where the valvetrain will bounce and bust you up.

Therefore, no one can answer your 'where's my rpm limit' question. Not being a dick, but we just can't.

I DON'T THINK YOU ARE BEING A DICK. I JOINED THIS SITE TO LEARN ALL THAT I CAN. I REALIZE THAT WITH LIMITED SPECS NO ONE CAN GIVE AN EXACT ANSWER JUST TRYING TO GET A ROUND ABOUT ANSWER. I DO APPRECIATE EVERY ONES INPUT AND WOULD NEVER GET PISSY AT SOMEONE THAT TRIED TO ANSWER A QUESTION THAT I ASKED. OBVIOUSLY I DON'T KNOW THE ANSWER THATS WHY I ASKED. :D

Quote:

Originally Posted by SB

He asked for a max RPM rating for the 454 that he has. He didn't give detailed specs on cam/springs etc, but they aren't needed to give him a max number that the parts can run at with no breaking issues, unless the heads were assembled with some very poor/low spring pressures.

That's cool - same people hate when they get a 'I don't know' even if we don't know. LOL !!!

I looked up your valvespring:
p/n 12462970
Dual spring
140 lb/bs installed at 1.94 height
Rate 325 lbs (per inch)
solid height 1.20 "

============

Since these heads have been used for some time, and since they are apart I would just have the springs + heights checked. If one or more is 'soft' or not installed to waht your application demands, then now is definately the time.

I get paranoid over valvesprings so I even have new heads checked.

My rule of thumb is if the heads or head is off for any reason, let's check them out ! They get quite a beating in a marine environment.

Quote:

Originally Posted by SB

NOT TO WORRIED ABOUT THE SPRING THEY HAVE LESS THAN 20MINS RUN TIME ON THEM. I AM GOING TO MATCH THEM UP BEFORE I PUT THE ENGINE BACK TOGETHER. THANKS TO EVERYONE FOR HELPING WITH MY QUESTION.

SB WHERE DID YOU LOOK UP THE SPECS FOR THOSE HEADS. I HAD CALLED GM LAST WEEK AND THE COULD NOT TELL ME WHAT THEY WERE. THEY TOLD ME MY CASTING NUMBER DID NOT MATCH ANYTHING IN THE COMPUTER. (I LOST MY SPEC SHEET)

GM Performance parts catalog. Yes, they have misprints too, so we always have to check.

Duke - why doesn't valvetrain matter for rpm limit ? I did answer on the shortblock too.

Quote:

Originally Posted by SB

Duke - why doesn't valvetrain matter for rpm limit ? I did answer on the shortblock too.

In the specific, the valvetrain does matter. In the general, as he asked the question, it didn't, as I answered the question in general, with all the parts being as they should be the engine can run X rpm.

I understand now. Thanks.

Didn't want to see someone rpm into valvetrain issues. Very common for this to not be looked at / considered.

Check the springs - I found out the hard way. I had a Magnum motor set up almost identical to yours until I floated a valve at 5500 RPM. The valve took out the head, piston, 2 rods and split the block(junk). Ouch! - can you say new motor. It's worth the piece of mind.