Thats not a bad cam for NA use, why not slap on the stock truck intake using the Radix injectors and see how its running without the blower. Same TB, same MAF, same Tune...

 

I don't think the Radix is too small to make a big performance difference on a 408, just too small to generate the 10 plus PSI boost Chris is looking for.

I say with a forged bottom end raise the compression ratio to 10-11:1 and shoot for 5-7 PSI and the thing will rock with monster torque everywhere. The Radix has limited capacity and seems to work best with stock and slightly higher CR's.

On a 408 I would go with the GT2-3 or any cam with high lift, big exhaust duration and very limited overlap. Exhaust duration is not the problem. With lots of air being forced in, you need time to scavenge it all out after combustion. Overlap is the problem. When the intake and exhaust valves are open simultaneously, the boosted intake charge leaks right out and you lose cylinder pressure. With force-feeding the intake duration is not as important as plenty of lift to allow in the maximum intake charge.

The bottom line is that the MP 112 blower was designed for engines in the 300 cubes range. On a 408 you won't be able to set up the traditional low compression/big boost combination using the Eaton. If, however you concentrate on maximizing cylinder pressure through a combination of compression, boost and valve timing I bet you will get great results in the 500+ rwhp range.

Chris: where is the AWD dyno that you use? Might be worth a trip for me some time as I am currently installing a Radix on the stock cubed LQ9 in my '04 Silverado SS. I hope you keep working and testing with the Magnacharger as I would love to have one of your 408's under it in my truck some day.

All of this just my $.02.

 

I guess the 9 psi I saw on a 427 was a dream

 

I'm not trying to be discouraging, BlownChevy. But with the MP 112 it's going to be tough to get there with ported heads and a big cam on any 400 plus cubes stroker.

I'm just saying stick with what is a very fine, intercooled blower for the street and work with the other non-boost variables to reach your goals.

 

And all I am saying is that if one does his research / homework the MP112 can and will feed the 408, if it is set up properly. I understand that folks just want to take the easy route with the hair dryer set ups, trust me I have been there. I just dont want folks to think it is not capable of doing it when it really is.

 

No argument here. I guess I just think concentrating only on the boost capacity of the Radix is a mistake. If monster boost is your goal get a Whipple or KB or centrifugal and shoot for 15-20 PSI. But, if you want a great, reliable, torquey, intercooled GM setup for the street you can go with the Magnacharger and adjust other factors to reach realistic objectives.

If I didn't think a lot of the potential with the Eaton blower, I wouldn't be putting one in my truck right now.

 

holla

 

Fo Sho

 

Hey Brian, what are the specs on this 427 you speak of? I'm not familiar with this engine. I think if we critically analyze this setup (emphasis on critically), then we can get an idea of what's going on with APE's 408.

Common sense tells me that since you're mechanically driving the compressor based of crank speed, then the blower will always be compressing air. It has to, otherwise it wouldn't be spinning. I also understand that a bigger engine needs more volumetric flow rate. Now with a SC, to increase the volumetric flow, can't you just spin it faster?

I'm not a SC guy, I've never owned one, but common sense tells me that a 6.0L kit with let's say 10psi is not going to make 10psi on a 408. Duh?!? But change the blower speed and it could be possible. The blower Q (vol. flow rate) should match the engine Q some how, so the engine is happy up top.

 

there is lots of information avaliable for this blower and if you crunch the numbers they sugest aproxamately 500rwhp max. i am not really up on outputs on stroker motors but i think a heads and cam 408 can make near500rwhp on it's own.

with an SS and a awd dyno the numbers will likely be a little lower. even though the radix may not be able to help peek hp much the are under the curve should be nuts

i could see geting some nice boost on a 427 but i dont think the blower would help with your peek hp much.

of course a hair drier or two would kick ***. a single t76 on there would spool almost instantly and make 600+rwhp on pump and 700+ with some good gas. there are many down sides to a turbo though like cost, underhood heat, more complex, harder to install, more maintainence..........

i agree with sslink, dont build an 8.5-1 408 boost motor and put a radix on it. if you want a radix and a 408 build a nice NA 408 and just put a few psi to it.