SBC Heads (1 Viewer)

[DLB]

Cylinder Heads

I suppose LESS specifically, heads in general...
What's the "differences" in the various degrees of heads.
I just chose SBC because that's what I am most familiar with.
You can explain the difference on anything really.

But what's the advantages you gain/lose between the 12° - 18° - 23° heads?

Just something I have never really studied much, and kind of been wondering.

DLB

 

[Buzzz Miller]

Well, first of all, there are lots more differences than just the degrees. The shallower heads are designed to fit on a larger bore engine, and thus, really get big on the valve sizes.
The 23 is the standard heads. Replacements for stock, and some performance stuff. Iron and aluminum. Lots of makers, and lots of various applications. Anywhere from small cc intake runners for lots of torque, to big runners for racing applications.
Then you get into the shallower chamber stuff. There are all out racing heads. Designed for larger bores, like I said. Flow better with the shallower angles, and smaller chamber which does a few things. First of all, it has a quicker flame travel with the shallower chamber. Second, you can make as much or more compression with less dome on the piston. And thus, a lighter piston. Great for big rpms.
When you get to the 12 and close degree stuff, it is one purpose only. Horsepower at huge rpm. There is no use for these heads under about 6500rpm. Some of the heads are dead under 7000+. Lots of sprint car stuff, and other various circle track stuff. As they pretty much stay in the small block stuff with the rules.
Same stuff with the BBC heads. Standards, then the 24's that are stock, just rolled over. Then the 18 degree spread port stuff like Big Chief and DRCE. Designed for racing only. Then the 14.5 sonnys stuff and the 12 degree Brodix and Profiler for bigger inches and higher rpms. Then the 11 degree dart stuff. Just pushing for quicker flame travel, better flow at higher lift, bigger valves, lighter pistons, etc.
This is a very basic answer. If you are looking for a more in depth approach, let us know. But this should help with general understanding.

 

[DLB]

Thanks a lot Buzz - that's a great explanation.

I won't be offended at all though if anyone wants to take the time to put their knowledge through the keyboard though so I can read more.

That bit right there explained some things to me that I was wondering.
The quicker burn with the shallow chamber I understood how it worked, but just wondered on a few other points.

You said a stock BBC and SBC head is 23° - I suppose that is excluding any newer head design (LSX head, Vortec, etc.?)

BTW - You started out saying there were lots of differences besides just the degrees - I understand a lot of that stuff (not all by any means). This is just one area that I lacked some good understanding in. I know a (very) little (compared to most) about valving, chamber sizing, porting, and the top of the head, etc. If anyone wants to go in depth on anything though - hey, I am never to foolish as to think I know to much and try not to learn. Or if there are any trusty website - I'll just read those and save you the typing.

DLB

 

[G'ginna]

Mind if I ask my own dumb question?

I think I understand that the degrees are dependent on type of usage needed; but would you also make that choice dependent on fuel (for example differences in 85%-90% nitro) or would that (fuel) be strictly left to size, port, valve, etc?

Sorry If I sound stupid, but I am trying to figure out if I am thinking right or if I need to go back to reading.

 

[Buzzz Miller]

Fuel is really not a factor in making heads. It is more the induction, the rpms, and the rules. The heads that work the best with gas for a certain application, seem to work the best with alcohol for the same application. The ones for stack injectors, work with injected gas or alcohol, or ethanol. Nitro likes heads that are durable. Lots of the heads with large water ports, to keep away from detonation, are hurt easily with nitro, or large supercharged applications. That is why you see some dry heads. (Similar with blocks.) For big blowers and nitro. More durable. Easier to fix, etc.
Really, when you see the heads out there, you need to look backwards to see why they happened. For instance, the big dollar circle track stuff went shallow, big runner, far away from stock runners because they do not see under 7500 rpm. No need for a full range of a flat torque curve. AND, A Nostalgia Dragster, use their heads because rules mandate an iron head, but these guys stall their converters into the 8 grand area. Then shift them at 10+. Their design is very shallow and very large runners for this application with stack injectors.
When you understand how they will be used, you can see backwards, why they were designed the way they were. And what benefits.

 

[G'ginna]

Induction being carburation or injection with injection being the most used method currently for racing and most newer applications (until something better comes along)... right?

So that means size of the valves and type of injection system, porting, etc. as in previous posting. I think I am getting it.

Thank you.