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Author Topic:   Crankshafts???
Dirt Newbie

Total posts: 4
posted September 25, 2001 05:43 PM
I have talked to a couple of reliable friends of mine and they tell me that a knife edged chankshaft and lighted will make more HP than a Std. cast Crank, see my problem this year is the other guys are constatly getting me on the straits and sometimes off the corners, so I'm looking to make some more HP right now. The motor I have is a 355 and it has a stock crank and stock rods with a .100 dome forged dome pistons. And so far throughout my whole racing career I 've never blown a motor with stock crank and rods.
Also I would like to stay with the 355 motor because I have another motor in the corner just like and I have a spare blcok, crank and rods and other misc. stuff.
And now I'm trying to put a good combo together and was looking for some insight, also here is another ? the camshaft that I'm running only has .535 int. and .555 ex. and this is a solid cam. But I'm thinking of putting a roller cam kit together to put it in the motor.
And money is an issue here. Any info. would be greatly appreciated.

[This message has been edited by WILDphil (edited September 25, 2001).]

Dirt Freak

Total posts: 222
posted September 28, 2001 10:16 AM
Phil, Your friends are right about the light weight stuff being a big help.....
Here is how I look at spending money on racing, because I have a budget too....
I can spend $1800 on a crank shaft or I can have fresh tires all year......which one of those two is going to help me go fast....I say the new tires. If I had the money we would have both. I need to spend my money where I can get the most out of the money as far as winning goes.

With that said, there are other ways of making a car fast. tires, shocks, fresh springs, new ball joints and suspension parts.

I don't realy understand the question you were trying to ask. If you want to stay in a cheap motor deal, a 305 crank works good because it's a few pounds lighter then a 350.
I wouldn't run a roller cam unless you got the rest of the motor to use this advantage.
I like to run a bunch of compression.....14 or 14.5 that's too much for stock parts.
But, a good steel crank and rods aren't too much money in todays world..........and then make sure you run the best bearings. With too much compression if you try to save a few dollars on cheap bearings you end up pounding out the bearings on ruining everything...........

I don't waste money to knive edge the crank, the sharp edge creates windage in the pan. This will keep the rings from doing their job.........a radius edge on the front of the crank is better, not the flat stock edge, and not a pointed knive edge......
You can due this yourself with a little time and work. Just due this before you balance the crank.

The reason the light weight stuff helps soo much is this.........take a 1 pound weight, try swinging it take a 5 pound weight and due the same thing.....
the light weight will excellerate faster, and decellerate faster.........the motor will go from 3000 rpms to 5000 rpms much faster with the light weight stuff.........this is true at the other end also, when driving into the corner the motor will shut down faster, allowing the driver to stay in the gas just a tick longer.
I hope this helps you in some way.


Dirt Newbie

Total posts: 4
posted September 28, 2001 10:07 PM
Yes, Jeff you did answer some of my ?'s. You were very informative. You answered my main ? which was : Is a Std. wieght crank better or a Lightweight forged crank better.
But I have another ? that you might be able to provide some insight to.
Here it I have been looking at 2 scat cranks the one is a 43-44 lb. crank and they want 1200.00 for it and the other crank that I'm thinking about Is another scat crank *(LW) that is suppose to only was 47-50 lbs. but it has the knife edge on it and it is only cast Iron I believe. And they only want 289.00 for this one. Which of these would be better for my application. I'm Still planning on running a roller cam, and also I might be moving up a class to Limited Late Models if I can find the right deal.
Thanks jeff For all the info you have gave so far, and Thanks in advance for this ?.

Dirt Freak

Total posts: 222
posted September 30, 2001 02:36 AM
Phil, I can't tell you what is best for you, I don't know how much money you have laying around to spend on a motor. And what you have sitting to use today. If you already have a set of pistons, and rods sitting there now you need to know the BOB weight of the crank.

Cranks are made with different counter weights for a reason. The reason is the size of the stroke and the weight of the rotating/recipcating........see a light weight crank will need the light weight pistons and the light weight rods......then you can get thin wall wrist pins too......
the light weight crank for the big bucks may cost you $300 more just to balance it to some heavy pistons and rods.....then when you get all done and said you have the cost of the crank and balancing added together to get a crank that's only 2-3 pounds lighter then the cheap crank..........remeber with the heavy crank you need to take metal out of the crank to get the balance but the light weight crank you will need to add heavy metal to get to balance.........unless you spend big bucks on light weight pistons/pins and rods

In my opinion, unless you got EVERYTHING else you need the light weight crank is NOT the way to spend money.

Remember, I talked about I like to run LOT'S of compression..........well, that works like a light weight crank.....makes more power to get off the corner, then at the end when you shut the motor off you have more holding you back........this allows you too achieve the same thing as for driving in the corner a little deeper. Compression COSTS money also.........just no nearly as much as a new light weight crank kit.

Also with a light weight crank you can plan on the life span being about half as long as the standard weight crank.........that tells me it cost twice as much as i just explained to you...............unless this would be your last year racing and you planned on tossing it away in a year........

do you see how much money you need to run the light weight trick stuff????

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