N/A vs Nitrous vs FI cylinder heads
 

I was just wondering.....

I was thinking and doing some reading, and was wondering what distinguishes these type heads from one another? I was on the Brodix and TFS websites and some heads are noted to work with nitrous or n/a or FI but could still work with any setup. What makes a FI head work better with a FI setup than a nitrous or n/a setup or visa versa?

I bought my heads for n/a but when I read the material when the shipment arrived with the heads it said, "These heads were designed for forced induction". I thought I was screwed until I actually went FI which now seems to be a perfect match.

Im really seeking for detailed responses on why.

So who wanna drop some knowledge on me?:cool:

Thicker head decks that aftermarket heads have (some have) area major benefit in a boosted/nitrous application. I guess they're a benefit NA as well, but more so for boosted/nitrous applications.

Thanks for your input.

What about valve angle? I know that good NA heads have a certain degree valves FI have a certain degree and nitrous has there own. Just wondering what was the theory behind the idea

I don't think that's a true statement. The only real difference might be the chamber sizes so you can get lower compression without a dished piston. What works for NA engines works with boosted engines. As you turn up the power on either, you start to need the same thing anyways. NA heads are just more reliant on how well the port works than a boosted engine because an NA engine relies on the meager pressure differential between the cylinder and the atmosphere to make power.

The way I see it is if you're running a NA setup, and want to make as much power as possible, the cylinder heads are the focal point of that setup. With that said, you need to match parts around the heads in order to have a well rounded combination that's going to work together, but on a FI setup, tons of guys run stock 317 casting heads and make anywhere from 700 to over 1,000 rwhp with those heads. Could there be more made with say a set of TFS or MAST heads (different valve angles and thicker head decks), sure, but is the cost worth the HP gain? Probably not in most cases. In most of those cases, the guys just turn up the boost, but then you have the issue of pushing water with heads that don't have the thicker head deck surface. A lot also depends on your budget and what your intentions are for the car. Is this a fun, weekend cruiser that you're going to track/street race from time to time, or is this an all out race car that's being built for a class?

You need to remember that an engine has no idea if it's boosted or not. All it sees is a intake manifold with a higher air density ( not pressure) than NA.

So in other words if you make more power NA with a set of heads you will probably make more power boosted. :)

Have a look for LME on youtube. They dyno a lot of their boosted engines NA to see what power they will make.

Agree with the above, but increased boost can make up for not so great heads, while on a NA engine, well, you can't turn anything up to compensate for bad heads. I don't think anyone is going to argue that a set of 317 castings on a well built turbo engine is going to be down on power as opposed to the same setup with a set of AFR or TFS heads. But, it the increase in power worth the dollar amount, or is it just better to turn up the boost. Again, maybe the OP will let us know what his intentions are for the car.

I understand the CC being a big factor. But one can also spec out specific pistons to compensate for the CC of heads. Whether you have 72cc heads or -32 dish pistons to achieve a certain compression.

So why does valve angle matter so much when choosing heads? You can get heads from 10 degree all the way up to 24 degree? I think that it matters more than just achieving a certain compression. Especially when head selection on a N/A setup is not as critical as a boosted setup.

Just wondering

My car is boosted and also have heads that were for "Forced Induction". But looking at various heads on various site, some seemed to be labeled as Good Nitrous heads, Good Forced Induction Heads and Good NA heads.

I was just doing some reading and researching and was wanting to know some things. Im probably going to be FI Till I Die but was wanting to know the "WHY?" of some things.

Some main differences you may find in a FI or Nitrous head can include valve seat angle differences, exhaust valve material, and maybe in some cases different chamber designs.

A wider seat angle on the valve will put more valve surface area against the cylinder head. This means heat transfer from valve to cylinder head which is cooled by water. Cooler valve means less likely to have valve failure/burning/breaking etc. heat in chamber is a major concern on high hp boosted or nitrous motors.

Some head guys may also propose slightly larger port size for boost but not all will agree with this.

Port velocity and flow quality can become a concern on higher boosted applications or more race oriented builds. Most shelf heads tend to back up in flow around .600-.700" lift. Not a huge deal on most street builds but a high density boosted application can have turbulent flow issues in the ports. Could cost some hp. Engine sees variety of depressions across the port that flow benches cant mimick. So flow stability to higher lift ranges tend to matter even if your cam lift isnt that high.

High density charges in chamber can be more detonation prone. Chamber burn rate can be controlled by removing some of the chambers quench pad areas. This squish action of piston to flat portion of head chamber in the bore increases mixture motion and can accelerate flame front. You dont necessarily neeed this in a high boost application or heavy spray. Control the rate of burn to control pressure rise and resulting heat in the cylinder. Heat is the enemy in high boost heavy spray type deals

Thank you so much for explaining that. Thats what I needed! Thats why some heads are labeled FI friendly and NA or Nitrous Friendly.

Great post! I was reading about Ken Blocks mustang. They use NASCAR heads on the sbf. The article said that the heads are great at removing heat from the chamber and they can run a 240-250 f all day without problem!

Any idea what they would be doing different than what most other matter market heads are?