Revelation222

if which ones? and what makes a head better or worse for FI? im lost

JimmyKash

the short and sweet of FI heads.....

stock heads with 10psi = 500hp
ported heads with 6psi = 500hp

turn the boost back up to 10psi and now you're at 600hp.

Get the idea? Ported heads just allow you make more power on less boost

if you'd like a more detailed explanation on why heads are still a good investment on a FI application...do a search. I've explained it a few times and i think VINCE started the thread

Revelation222

thank you very much...hard to get an answer around here. i was reading about how ported heads cause you commpression to go up, isnt that somthing you have to worry about when you boost?

JimmyKash

in general ported heads DO NOT raise compression, in all actuality it LOWERS compression (sligtly)

first: the only way to rasie compression through the cylinder head is to 1) weld up the combustion chamber and shrink the size or cc of it 2) use a thinner head gasket creating less volume or total cc 3) milling the entire bottom surface of the cylinder head (imagine the head being put on a huge belt sander)

Second: When you port the combustion chamber part of the cylinder head you are removing material from the head and thus increasing the volume of it. Just like when you'd bore a standard SBC...taking off .030 off the cylinder walls gains you about 5". Now even with a full-out port job on the combustion chambers i wouldn't expect much more than 3-5cc added.

may i ask what kinda combo you have? imo heads really aren't a bang for the buck when it comes to FI. It is either more of a maintenance thing (to help you make the power at the lower boost level since LS1s have head gasket issues still) or two it is more for the guys who have built race setups already making over 15psi who need the extra flow to make the hp

Revelation222

well i want to go heads cam first then go to supercharger, but i didnt want to spend 4k for my set up for it not to work well with a blower, or not as well as some other heads cam combo. i think milling the heads is what i was thinking about in raising commpression. some guys have them milled so they are getting like 11:1. this i good for making HP but i thought i was bad combo with a SC? i heard it was harder on the life of the engine. i guess its about long term reliability but i want to hit 500 hp at least.

jrios

I'm running TEA stage II heads with the chambers opened up to 73cc. This dropped my compression to 9.4 to 1

LuvmyC5

iTrader: (1)

In my opinion, the best heads for FI,come off of the 6.0 liter motors. They are called #317 heads (last three digits of the part numbers). They have 73cc chambers, and LS6 ports. The bigger chambers lower the compression, and the LS6 chambers are GM's best flowing factory LS1/LS6 port. Very little port work is needed out of the box. Best of all, you can pick up a set for just a little more than a pair of LS1 heads (about $500 a pair). Porting the head doesn't change compression ratio, unless you play with the chambers, or mill the heads.

Pro Stock John

iTrader: (34)

How I would look at this...

You can make 500rwhp with stock heads and cam, forced induction, a good tune, and a good fuel system.

To make 600rwhp with stock heads and cam would be difficult, you'd have to boost the heck out of the motor and the stock head bolts might stretch while trying to contain that much cylinder pressure. Basically your stock motor won't be able to take that power level very long.

Now, you could throw a new cam and set of ported heads onto a FI motor... but why. To make more power on motor, to drop the compression ratio, and to make the motor more FI focused.

Stock our motors are 10:1. Also, our motors are all aluminum. That means that our motors don't retain as much heat as say a 10:1 all iron motor. We can get away with more boost with comparable fueling (and octane).

I am a fan of 6.0 heads, they are 71cc stock vs our 67 cc heads. That's not a huge compression drop but it's a step in the right direction. If you ever change your piston, you can further drop your compression. I have not seen a 73cc'd LS1 head so I cannot comment to how reliable they are, and how they are changed, though it's obvious that they must be enlarging the combustion chamber.

Revelation222

So basically, if i get heads, dont mill them?
Also, if you ported the 6.0 head, would that more HP than the stock LS1 head? Just asking b/c i would probably buy the heads cam first then wait a while for the funds to kick the FI. So, I guess I want to know if ill get any significant HP gains before I go boost. Thanks

chasgiv3

iTrader: (1)

I bought the 6.0 heads myself for my buildup. Reason is
1. Slightly structurely stronger (watch for too much porting)
2. Great flowing (when ported properly)
3. Lower compression to start with

BIGBOS

I got a set of TEA's Stage II 73cc heads....we will see how they work on my new motor...

I was originally running 10.6:1 compression heads on my 346 motor, then I popped a head gasket @6psi...after that I switched to TEA's, and that dropped my PSI to 4, and had no problems there...

ChrisB

If both cars are making ~600rwhp with similar torque curves then cylinder pressure (peak) will be effectively the same (as cylinder pressure = torque, with @ rpm = hp). Sure, the cylinder pressure of the pre-ignited charge may be greater, but this is irrelevant from a durabiliity standpoint when compared to the pressure of the ignited charge.

Now the blower will be more effecient working at a lower pressure @ the same CFM rate - meaning the charge will be cooler, and the blower will take less power to spin - and it will be easier on all the intake tract tubing, etc. (and with the plastic manifold boost pressure could be an issue).

What you have to remember with a blower is that your CFM is essentially fixed now (for the motor) by the pulley combination - it's your manifold pressure that varies from seutp to setup. With a NA motor your inlet pressure was fixed (atmospheric) - it was your CFM that could vary.

SSHOTROD

iTrader: (5)

ARE stg II heads/ 550 rwhp