402 vs 408
#1
402 vs 408
Im planning a new 6.0 iron block build but i'm on a budget. Are there any big differences in the 2 besides the 408 is bored .030? So my question is wouldnt it be cheaper to just get the 402 rotating assembly instead of the 408 to save money on the extra machining?
#4
Staging Lane
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do what they said i wouldve if my block permitted but chose 408 bcuz needed to be bored .30 over to clean it up but i recommend a wiseco/eagle for motor/n20 motor as i bought a stroker from tsp :-) but for some reason any type of failure in a 402 allows u to go up to 408 no problem
#5
11 Second Club
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There's pro's and con's to both. With the 402 you have futher options for re-freshening the motor. With the 408, the increase in bore size can increase air flow by decreasing valve shrouding. There are better options for cyl heads with a 4.030" bore. Personally, I would choose the 408 as you have the ability to create a more efficient combo.
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#10
TECH Junkie
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Like Conan said going 4.005 now gives you the chance to go farther later if you need to.
Al block sure, once you get past 4.010 you're kinda done, but not so with iron blocks.
It all depends on what heads you go with and the size of the valves. If you're running stock sized 2.00 valves then no need to go bigger than say 4.010.
But if you're going with some LS3 heads and their 2.165 valves, then it might be better to bore it out to a 408 for added clearance to the valves.
#11
Once you go larger than 4.030" piston choice becomes minimal until you hit the LS3 sizes 4.065"<. I am not saying they are not out there but just that you will have a more difficult time finding them. If you do not have a requirement for the 4.030" bore save the cyl wall and material for strength and go 4.005" 402ci. It is always nice to be able to say oops with a piston vs a piston and block combo. Neither size should effect price, It certainly will not with us at Thompson Motorsports.
#12
thanks for all the info guys. just trying to save money here. What if I went with forged 364 internals instead of 408/402? Whats the power potential with a 364 vs 408? My goal is at least 500 RWHP and like i said, just want a nasty street car, not an all out drag car. I just bough the block today from TSP, next up is which assembly i want!