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View Full Version : How many RPM is safe for a genIII truck engine?


Wasted Income
February 16th, 2006, 01:28 AM
My brother wants me to bump up the rev limiter in his 5.3L 1999 Sierra to 6500 rpm. Can the 5.3 spin 6500 on occasion (for a second) without coming unglued??

Thanks guys,
Jeff
Redline Motorsports
February 16th, 2006, 03:05 PM
Jeff,

The only thing that limits the motors rpm limits is the valvetrain. The stock pushrods should be replace and a good set of valve springs with Ti retainers and locks. If you are going to bump the REV limiter more then likely it will see that rpm more then a few times!

No sense spinning it up to to much as there isn't too much power up there with the stock camshaft.

Howard
wait4me
February 16th, 2006, 03:09 PM
It will valve float that high. 5800 is about max. I wouldnt want to go any higher.
dfe1
February 16th, 2006, 03:11 PM
The lower end will probably handle 6500 with no problems, but the valvetrain is questionable, because the stock springs probably aren't up to the task-- especially if the engine has a lot of miles on it. A bigger question is "Why". Assuming a stock cam, it's pretty much all done by 5500 rpm, so why push rpm to the point where horsepower really drops off? I think a bump to the 5800-6000 range is a better choice.
MN C5
February 16th, 2006, 03:16 PM
Thats my experience as well 5800 for shift points max...
Wasted Income
February 16th, 2006, 06:27 PM
Great, that's exactly the info I was looking for!!

Thanks guys!
Redline Motorsports
February 17th, 2006, 04:19 AM
The lower end will probably handle 6500 with no problems, but the valvetrain is questionable, because the stock springs probably aren't up to the task-- especially if the engine has a lot of miles on it. A bigger question is "Why". Assuming a stock cam, it's pretty much all done by 5500 rpm, so why push rpm to the point where horsepower really drops off? I think a bump to the 5800-6000 range is a better choice.

Hey! Thats what I said! :exactly:
dfe1
February 17th, 2006, 06:35 PM
Hey! Thats what I said! :exactly:

What can I say great minds, etc. When I started typing my reply, no one else had answered. But then I got side-tracked and when I finally got back to it, you had already replied. Didn't mean to step on your toes.
Redline Motorsports
February 18th, 2006, 04:52 PM
Oh no bad intent here!:coool:

I figured we must have past threads! At least he got the same answer twice!