what are heads? sounds stupid, but i read/hear about and see pictures of head setups all over this forum, and it seems like every other car has a set. but what do they do? how do they work? there is no head write up sticky (like the cam one) and maybe a breif overview will help me out a lot. from what i figure, u can manipulate the c/r, which would obviously directly influence hp, but thats about all i know. what are the differances between "stages" (i.e. stage I, II, III). how should flow rates be matched with cam specs? yeah im completely in the dark here, but im sure im not the only one. im sure people could write novels on this, but something breif would be awsome. thanks guys!

 

WELL..i am by no means even like a 1/10th of a head expert..but heads are a very very very important part of your motor....in the heads you have your valve train..rockers/valves/valve springs/push rods/retainers? and probably more??? im not sure about all the flow information, im a newbie to that stuff too..someones guna say use "search" but this can be a very helpful thread to some people like me and you but all those parts in your valve train can be matched to how safely you can run a certain amount of lift/duration of a cam..heads are just as if not more important than a cam. i think you usually match your CAM to your HEADs stats etc...but someone with more experience/knowledge will probably chip in...hope this helped you a little!!!

 

i believe porting/milling heads raises the compression?

 

thanks! i knew i wasnt the only one

 

With all these head manufactures out, how do you choose which one to go with? They all seem to have these great innovations and great numbers, is it simply close your eyes and pick one?

 

unfortuantely, no, you just dont close your eys and choose one.

You have to look at a few things when choosing the proper heads for your application. Budget, what kind of motor (FI, NOS, N/A), where do you want to make your power, aggresivness of your package, cam spec, compression, quench, port cc, port flow efficiency, etc.

It sounds a bit complicated and if you really want to get started, head on over to the advanced section and spend a few days reading through those posts.... fun stuff!!!

basically, your heads are responsible for the induction and expulsion of the gases to and from your motor. A combustion engine is basially a large pump. The more air in and the more air out, the more power it can produce. Your heads, yes got two!!! hehehe!!........... also holds your valvetrain. The valves open and close becuz of the cam pushing up and down on a lift, which pushes a "tada!!"...pushrod, which pushes a rocker up and down while it in turn compresses of decompresses a spring that is locked into the valve. The pressure of the spring is necesary to maintain a tight seal and velocity of the valve, among other things.

GOT IT? With out your heads, how will you get the air in or out of your motor?

So, a good set of ported heads, that are matched well to the overall system (motor) is crucial to power production and that is why it is important to pick the correct heads for your application. Without a well balanced flow of air, you motor will choke, and produce as much hp per liter as a my old 92 hp sohc eclipse motor, well, that is until i swapped it out for a 1gen motor with a t3/t4 turbo.

good luck and welcome, pm jrp and ask him about wat are heads, im sure he'll help you out!! HAHAHAHA!!! dont do that, just messing with ya!!

 

so a cam controls the duration of which the valves are open, and the heads determine the size of the "hole" so to speak?

 

Thanks for the lesson (seriously), but I still don't understand with all these new and improved heads how would you go about choosing from different manufactures. Kind of like xbox is a video game system and playstation is a videogame system you can play on both so what's the difference (by the way I don't play either so this could potentially be a bad example if you don't get what I am trying to say.)

 

There are a couple of books out that were written by David Vizard, one on Chevy Valve Trains and one on Chevy Heads. They are easy reading and very informative. You might want to consider purchasing them for reading. I have found them to be immensely useful and full of excellent information. They are written for the small block, but the principals are the same.

 

theres all types of heads for all types of things...theres some like AFR that are very good heads (bro has them on his stang) but are VERY expensive, then there are some budget heads too...Heads/Cam are my next performance mod and ill prob get them during the end of this summer so i too am researching about this stuff.

 

i know every third person on this site has a set of aftermarket heads, and i know you didnt buy them without learning a bit about them, share the wealth guys! thanks for all the info so far guys.

 

Okay, I'll give this a shot. One way of splitting the head choices up are ported GM castings, and aftermarket castings.

1. GM castings & ported GM castings: Some heads that came on later lsx motors flow better than previous years. Also, some aftermarket companies take GM cast heads, then port them for better airflow.

2. Aftermarket castings: Companies like Dart, AFR, and ETP make new castings, with better airflow and improved features. Features like: thicker deck (better for nitrous or FI applications) or smaller valve angle (ETP's are 11° if memory serves me correct, versus standard 15°)

You have to remember that engines are basically air pumps, and the more air and fuel you can get in the cylinders, the more power you will make. This is a very simplified view.

Depending on the shape and size of the intake, heads, and exhaust, and cam profile, your engine will be better suited for lower rpm or higher rpm use. The goal of a good street car would be to breathe well at the higher rpms, but not sacrifice too much low end torque, when compared to a race motor.

 

One other thing - if you are trying to decide on which head to buy, it is best to view results in the dyno section of this board. Many companies have flow bench numbers for heads, but this is decieving. You can only compare two different heads properly if they are flowed on the same bench, under identical circumstances. This gets even more complicated when comparing heads that are made for "smaller" or "larger" bore sizes. My best advice - don't be the guinea pig, and choose a head/cam combo that a lot of people have had success with. If I had the money I would buy aftermarket AFRs or ETPs. A lot of people like TEA heads as well. I would also keep an eye on the cheap CNC ported PRC heads for around 900 bucks. However, there are not that many dynos out for them yet.