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Author Topic:   Any Suggestions
CrazyT
Dirt Forum Racer

Total posts: 79
posted April 24, 2005 03:51 PM  
I am thinking of building a 406 for my hobby stock. I have a 400 that was running when i took it out, so i feel like everything is ok just needs machine work. I am wanting to run the stock crank with scat 4340 6" rods and speed pro hyper 12.5:1 pistons. The engine won't see over 6000rpm with a 2 barrel rochester carb...will this motor live? What do i need to do to balance this engine...i always balance my 355s will need to buy a new flywheel or will the one off my 355 work? And what does everyone do for harmonic balancers i have a lightweight on my 355, i know the 400 has the big one for balancing reasons.

Thanks

STREET16
Dirt Maniac

Total posts: 158
posted April 24, 2005 04:14 PM  
You're going to have to clearence the rods if you go with the 6" rods, and I don't recommend going over 11.5 to 1 with hyper pistons. I ran a 12.5 to 1 383 with hyper pistons, after the fifth race the only thing we could salvage was the intake and the valve covers. As far as balance, you can use your 355 flywheel with a balance plate but you will still need a 400 harmonic balancer. I would recommend using a 400 flywheel over the balance plate if you're running a standard.

CrazyT
Dirt Forum Racer

Total posts: 79
posted April 24, 2005 05:26 PM  
What about moving up to the speed pro forged, are they any good? Are there any forged pistons that are in the $300-$400 range that are descent? Also what will i have to clearence on the block, and will i have to run a small base circle cam?
Thanks for the reply

BrianW
Dirt Freak

Total posts: 385
posted April 24, 2005 08:25 PM  
Personally I've run the Hyper pistons and have had great luck in the Factory Stock and modified classes when keeping them under 6500 RPM. (although they've been run up to 6700 a couple of times.)

I'd run a little less compression on the stock crank though - try about 11.5:1, run the 6" rods and the lightest piston you can find (hollow dome if you've got to have one) and then have the machine shop "internal balance" the setup - that way you can run the "neutral balance" 350 stuff (flywheel, balancer, etc.) Make sure you cam it to take advantage of the displacement and the restricted intake...

STREET16
Dirt Maniac

Total posts: 158
posted April 24, 2005 09:07 PM  
I've never used speed pro forged pistons, but i've heard that they're good. I would prefer that people that have actually ran them put in they're two cents worth on them though. What has to be clearanced on the block is the bottom of the cylinders and the oil pan rail. There was another post where someone posted a picture showing how much grinding has to be done. And another post where someone was concerned about getting too close to the water jacket. As for the small base circle cam - yes, you have to get one. Personally, I would leave the block work to the pros. If you can afford to have the motor balanced - do it. And if you can afford forged pistons - put them in. Of all the places to save money, your rotating assy isn't a good choice. I've had good luck with hyper pistons at 11:1 and nothing but bad luck with them above 12:1. You should talk to the people balancing your engine, and get they're recomendations. They will be able to go into more detail and probably even show you what's involved.

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