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-   -   Crankshaft harmonics? (https://classracer.com/classforum/showthread.php?t=47335)

art leong 05-18-2013 02:33 PM
Crankshaft harmonics?
 
Can crankshaft harmonics/vibrations cause anything to happen in the valve train?

SSDiv6 05-18-2013 02:42 PM
Re: Crankshaft harmonics?
 
Quote:
Originally Posted by art leong (Post 381981)
Can crankshaft harmonics/vibrations cause anything to happen in the valve train?
Yes it can.

art leong 05-18-2013 02:53 PM
Re: Crankshaft harmonics?
 
I'm wondering if harmonics had a hand in my rocker to valve wear.
That is another thing that seems to be specific to my motor. Others have run same cams and springs trouble free.

SSDiv6 05-18-2013 03:09 PM
Re: Crankshaft harmonics?
 
Quote:
Originally Posted by art leong (Post 381985)
I'm wondering if harmonics had a hand in my rocker to valve wear.
That is another thing that seems to be specific to my motor. Others have run same cams and springs trouble free.
Art, although you have a timing belt, the harmonics and frequencies will transmit to the valvetrain due to the lack of dampening from a crankshaft that lacks counterweights.
I believe that a crankshaft with counterweights and the right harmonic balancer will solve a lot of your problems.

art leong 05-18-2013 05:25 PM
Re: Crankshaft harmonics?
 
Quote:
Originally Posted by SSDiv6 (Post 381988)
Art, although you have a timing belt, the harmonics and frequencies will transmit to the valvetrain due to the lack of dampening from a crankshaft that lacks counterweights.
I believe that a crankshaft with counterweights and the right harmonic balancer will solve a lot of your problems.
Even though the crank checked fine I'm going to put in a stock crank. I don't believe 8 pounds will hurt me that much. And maybe I'll get rid of these "one of" problems.
My other motor with less cam, less compression, and a stock crank. Responded to rpm a lot better than this motor. It was half a second between bracket mode and race mode. This motor was only two and a half tenths. That's shifting 1000 rpms short and running taller tires.
It might go quicker with the stock crank.

SSDiv6 05-18-2013 05:45 PM
Re: Crankshaft harmonics?
 
Quote:
Originally Posted by art leong (Post 381996)
Even though the crank checked fine I'm going to put in a stock crank. I don't believe 8 pounds will hurt me that much. And maybe I'll get rid of these "one of" problems.
My other motor with less cam, less compression, and a stock crank. Responded to rpm a lot better than this motor. It was half a second between bracket mode and race mode. This motor was only two and a half tenths. That's shifting 1000 rpms short and running taller tires.
It might go quicker with the stock crank.
Art, I believe you will not notice that much of a change in performance.
Nevertheless, if you want to get the best out of the crankshaft, I would suggest your crankshaft to have some weight removed and probably change the shape of the counterweight and have the lightening done properly.
My choice and recommendation is Shaft Tech:
http://www.shaftech.com/modification.html

art leong 05-18-2013 06:10 PM
Re: Crankshaft harmonics?
 
Quote:
Originally Posted by SSDiv6 (Post 381999)
Art, I believe you will not notice that much of a change in performance.
Nevertheless, if you want to get the best out of the crankshaft, I would suggest your crankshaft to have some weight removed and probably change the shape of the counterweight and have the lightening done properly.
My choice and recommendation is Shaft Tech:
http://www.shaftech.com/modification.html
Thanks for that, but I think I'll just use the stock crank and leave the trick stuff for a new owner. I went to the Billy Nees academy of race car finance (actually he might have got it from me LOL). I don't want to spend $1,000 or more on a crank.
The whole car is for sale for $12,500 LOL

tj310 05-18-2013 08:14 PM
Re: Crankshaft harmonics?
 
Does your 2.4 engine have a separate balance shaft ?---Trevor

art leong 05-18-2013 08:17 PM
Re: Crankshaft harmonics?
 
Quote:
Originally Posted by tj310 (Post 382011)
Does your 2.4 engine have a separate balance shaft ?---Trevor
It was removed. Just about everyone that runs a 2.4 removes them. Without any problems.

THoagland 05-18-2013 11:20 PM
Re: Crankshaft harmonics?
 
Which damper you running?


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