</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by VINCE:
<strong> Mellow made a comment in another thread that you do not need to spend the money on heads if you are going forced induction.. What do you guys think? Heads or just increase the boost? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">On my old Fbody, I added heads/cam to my blower and went from 12psi to 7psi. I lost a little bit of power. Then I upped the boost back up to 12psi again and <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

Lets just say assuming you can keep your boost levels and that your blower can support the power it is well worth it. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by VINCE:
<strong> It would work, but you will get better performance if you added a 2.02 x 1.60 to the equation or maybe even 2.08's.. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I think 2.08's are the better deal for FI setups.

 

I'm not sure I'd want to give up the lower end curve/rpm power by switching to 2.08's. SC's are weak enough at lower RPM's out of the hole as it is. Maybe 2.02/1.60

 

its all about what you want to run PRESSURE wise.

Here's a hypothetical situation to help you guys understand:

want 600fwhp?

ok...put 12psi through stock ls1 heads, ls1 intake.

OR

put 8psi through ported ls1 heads, ls1 intake

OR

put 6psi through ported ls6 heads, ls6 intake

--see a trend? Its all about the airflow you can move. If heads weren't important, even in a FI motor, then why are the big dogs running around with Yate headed fords and SB2 headed sbc with blowers/turbos? They are running 30psi through those heads. Could they run 50psi through lesser flowing heads and still go as fast? probably, would it be worth the hassle, tuning, octane, cylinder pressure? probably not

Take it FWIW, but you just have to decide how much horsepower you want and how much pressure you are willing to run to get it. THAT is what should be your determing factor on whether or not porting your heads when going FI

my .02

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 30thta436:
<strong> Well here is my experience. I was putting out 576RWHP & 530RWTQ with stock heads and 01 LS6 cam. I was seeing between12-13 lbs of boost.
I changed out to stage III heads and 02 LS6 cam.
Strapped it on the dyno. Put down 573 RWHP and 532RWTQ. And boost dropped to 8-9 psi. So I have $3000 lumps of aluminum to reduce boost by 4 psi. <img border="0" alt="[barf]" title="" src="graemlins/gr_barf.gif" /> .</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">This makes perfect sense. You had a fixed cfm rating going into your motor through your intake and heads. It made 576rwhp @ 12psi. You ported your heads to allow more efficient use of your blower and it responsed with a drop in pressure and almost the same power. To see the benefit of the heads you need to pulley up the blower to see the same psi reading again.


</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 30thta436:
<strong>
SJH tried to tell me that would happen. It's not that I didn't believe him, I just don't like theorys. His proved true. But I also have my blower maxed out. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">You need a bigger blower...if your blower is maxed out trying to ring anymore cfm out it will likely overheat the discharged air because its out of its effieciency range. If your blower had more room to pulley up, you'd see a gain from your heads. Read my post above for a better explanation

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by verbs:
<strong> On my old Fbody, I added heads/cam to my blower and went from 12psi to 7psi. I lost a little bit of power. Then I upped the boost back up to 12psi again and <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

Lets just say assuming you can keep your boost levels and that your blower can support the power it is well worth it. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">See? This correlates to exactly what i told 30th436

If you have to describe a FI motor in one word it would be

COMBO or PACKAGE

If you dont have your combo/package straightened out or know/realize what effects changing compression, pulley sizes, ported heads, etc etc will do a FI motor you are in for a heap of awakening.

Just do a little research.

 

Personally I would want to move the most cfm at the lowest boost level for a given RWHP target.
Lower IATs, less cyl pressure, easier to tune, less stress on springs, lower octane requirement.

I would like to see someone use the TEA 77cc heads (8.9:1) with about 15#'s boost. That would run its *** off if properly tuned and would make great power in a street tune as well with 94 octane at (~12#s)

I have considered a budget 370 iron block with 77cc heads. extra cubes would eat up a bit of the torque loss down low and make MAD power under boost...

Chris

 

I agree with you Chris.. I am thinking of 6.0L heads with a 77cc chamber myself. That is why I am running the bigger F1-SC blower.. I only want to push 12psi though..