I am at a point where I need to make a decision about a couple of things with my 408 stroker build. I have already gotten some good input and very good recommendations from some people, but would be interested in what you guys have to say.

The first thing is my heads. I have been told, just by my builder, that stroker motors like flow over 300cfm, intake, with around 315cfm being optimum. Of course, this is a NA scenario, but I am keeping my Radix. On my intake side, I am seeing a peak of 295cfm at .5500. I flow pretty good compared to the ones I have seen on my exhaust side with that being a peak of 243cfm @.6000. I have discussed the work with TEA (my heads are TEA stg II oring'd 6.0L heads 2.02/1.55) and they for sure tell me that they can get me well into the 300cfm area, and if I change to a 2.05, they can get me to about 315cfm. This would include their hand finishing. The cost of this would be about $400. Is my exhaust flow good enough, or does that need work, at a minimum? Maybe a 1.57 valve? Would you do it for the extra ponies?

The second thing is injectors. It wasn't until last night that it was brought to my attention that I may not have enough injector (42lb) for this setup. I just have not thought too much about that, honestly. Most formulas that I have used on the internet, say that I should have at least 50lbr's. So, what's the best place to get these things? Racetronix? How about low impedence vs high impedence? Connectors? I need some rudder. (Naval expression)

Whitt - didn't I read a while back you were going with 60lbr's and the Radix? Any info you have on how you're doing it would be greatly appreciated.

TIA for anything.

 

Thats a wicked setup man!! Sorry i don't know much about this field. You should try asking HitManX and or BigTex.

 

I think you are on the right track with your heads. Do you already have the heads or is this something you are going to order? Lots of the fbod guys swear by the TEA or the Absolute Speed heads. Myself, I don't think Patriot's are worth not considering either. I was reading something a while back about heads and valve sizes. bigger isn't always better.

You would definantly need bigger injectors I think. I don't think there are any of the truck size injectors that are bigger, so that would mean having to switch styles.

 

On the injectors you are most likely gonna have to modify your harness and rails to accept the LS1/SVO style injectors which can be had in every size under the sun. No biggies there.

You are going to need to look into the fuel system though. Bigger pump, possibly bigger lines etc. I would definately lurk inthe forced induction section of this board for more info on what guys are currently doing at your proposed power levels.

 

The RADIX comes with that extra pump, so he should be OK for a while with that.

 

That is good exhaust flow as it is. When they hand finish those exhaust ports, flow should increase even more. I think your exhaust porting is fine. You'll more than likely be restricted by your pipes, cats, muffler, and 2.5" header flange. Those need attention. With your motor out, its a perfect time to modify the headers to a 3" flange. I'll give you details.

Your cam has lift between .550 and .600, so flow above .600 is not used. The amount of time your valve is open @ .550+ lift is super small. If you can get 300+ at .550 lift, you'll be fine. I'm sure the Radix will feed those heads as much air as they want.

You stated .295 cfm @ 5500 intake and .243 @ 6000 exhaust flow numbers. Did TEA flow your heads when you sent them last time to open up the chamber?

I have the flow sheet sitting right here for those heads:
LIFT -- INTAKE - EXHAUST
0.100 - 072.7 - - 061.8
0.200 - 145.0 - - 124.1
0.300 - 210.9 - - 174.8
0.400 - 259.8 - - 212.9
0.500 - 290.2 - - 247.4
0.550 - 296.7 - - 253.0
0.600 - 300.7 - - 256.8

Also, let TEA know this is going on a 4.03 bore and have them reflow the heads on a 4.0 bore. They were originally on a LS1 with 3.9 bore so these flow numbers should have been flowed for that bore.

 

See what im saying BigTex knows his Sh!zn!t

 

Yes, I already have the heads.

So, are you saying to go ahead and send them in to TEA? My flow looked like this, after the porting (they did flow them after):

LIFT -- INTAKE - EXHAUST
0.100 - 073.1 - - 46.5
0.200 - 152.0 - - 105.8
0.300 - 215.8 - - 160.5
0.400 - 256.0 - - 198.8
0.500 - 284.5 - - 226.9
0.550 - 295.7 - - 237.1
0.600 - 290.1 - - 243.4

My exhaust work will be done after the motor gets back in. My header flange's are getting enlarged to 3", going to Random Tech 3" cats, and 3" all the way to the muffler. Possibly plans for 3" cutouts at the muffler.

 

Found some 50lb'rs from More perf. that they say should pop right in the Radix fuel rail. They put them in a Radix truck without any mod to the fuel rail whatsoever. Just a change of connector is needed. They are Rochester 50lb injectors.

 

Did they flow the exhaust with a pipe? The exhaust numbers are huge.
As far as the heads, I think that is plenty for a FI motor. Do some searchs in the FI forum, most of them think that spending money on heads is a waste. I don't think it is a waste but, those heads should be plenty good. Spend the $400 on a huge exhaust, not on the heads.
Just my opinion.