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Author Topic:   400 rpms
Burque
Dirt Forum Racer

Total posts: 98
posted December 13, 2004 12:39 PM  
Ok guys will be ordering new parts for next yearís motor. What rpm can a 408 with Scat 9000 crank, Sir 5.7 rods, flat tops, with 462 heads handle on weekly racing with out blowing up? It will have a solid cam havenít picked one yet, the heads have screw in rocker arm bolts, 1.6 rockers, .600 lift springs, and 2.02 1.5 vavles.

The intake is Super Victor, Holley 750 Double pumper, the exhaust headers with crossover pipe. This will be run on 3/8 Med banked track in a street stock weighing 3000lbs with Hoosier tires.

Xtreme12x
Dirt Forum Champ
Total posts: 874
posted December 13, 2004 12:54 PM  
keep her around 6700 and she should live for a long time

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted December 13, 2004 01:11 PM  
6" rods would be better yet

Burque
Dirt Forum Racer

Total posts: 98
posted December 13, 2004 02:19 PM  
What would the 6-inch rods do in comparison to the 5.7? 6700 with a cast crank I thought 6500 at best. Any cam recommendations for this combo?

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted December 13, 2004 03:05 PM  
6" rods will take some rod angularity out. Takes some of the angular or side load off the rod, loads the rod more vertically. Less thrust on the sidewall of the cylinder for reduced wear and friction. Now you can start to see how the longer rods help with higher rpms. The rod length to stroke ratio of your 5.7 combo is 1.52, compare that to the ratio of a stock 350 of 1.64 and stock 327 of 1.75, the old 302's were 1.9. The 327 and especially 302 were high rpm screamers.

Not that the 5.7 wouldnt hold up. In fact I would say the crank would be the weak link, especially with a 4 barrel carb. But if you are getting new parts then i think you would be ahead in the game to go 6" rods and pistons to match.

[This message has been edited by dirtbuster (edited December 13, 2004).]

Burque
Dirt Forum Racer

Total posts: 98
posted December 14, 2004 10:16 AM  
Thanks guys! Dirtbuster do they sell a 6 inch rod that is ready to fit a 400? Would I have grind them to make them fit? What would a 6 inch rod rpm be over a 5.7?Thanks again!

iowatoolman
Dirt Freak

Total posts: 369
posted December 15, 2004 10:56 AM  
i have a 406 that i ran last year and ran 75-7800 rpms one night i turned it 8300 it is a 5.7 rod

drive hard or drive home

are you scared of RPMS ?
then you need a drag racer to build your motor LOL

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted December 15, 2004 11:05 AM  
I dont know whether they sell one that would fit without grinding, but I doubt it. You would prob have to clearance the block.

The 6" rods wouldnt necessarily rev higher, it would just put less strain on some of the parts, more of a longevity issue. Longer rods will tend to help move the power band up in the rpm range which may help it pull harder/longer at upper rpms.

Burque
Dirt Forum Racer

Total posts: 98
posted December 15, 2004 11:14 AM  
Thanks dirtbuster!!! I will look into the 6 inch rods and what can be done with my budget.

Burque
Dirt Forum Racer

Total posts: 98
posted December 15, 2004 11:28 AM  
Toolman it's not Iím scared of rpm's it's just the thought of it blowing up! I have heard many people say 400 can't handle rpms. I have a nice vortec 406 in a streetcar but it does not see the abuse like on the track. So thatís hard to compare too.

The one guy who does run a 406 in my class is only running about 6300 rpms and won the championship this year. He was running a 6.20 when most other guys run 6.50 and up turning 6800 rpms. So I am just trying to see what would work for me and if I could turn 6700 rpm and still have great torque then I should be ahead of the game in my book!

speedy46
Dirt Maniac

Total posts: 165
posted December 15, 2004 11:45 AM  
that is a classic example of a old saying "horsepower sells motors torque wins races" and it is very true enspecially on dry tracks

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