Hot Rod Forum : Hotrodders Bulletin Board

Hot Rod Forum : Hotrodders Bulletin Board (
-   Engine (
-   -   Combustion chamber shapes (

birkey 10-14-2012 09:55 PM

Combustion chamber shapes
Lets stray away from timing here for a second and talk about cylinder head combustion chamber shapes. I always hear people say many factors such as fuel, and timing (just to name a few) depend on the shape of the combustion chamber. Besides Hemi, which I have been told most new heads are technically "hemispherical" what are some others?
Along the lines of typical domestic v motors

techinspector1 10-14-2012 11:05 PM

The latest wowza seems to be the heart-shaped chamber that is closed enough to allow a generous squish pad on the underside of the head.
We went through what seemed to be a very short romance with Singh grooves a few years ago....

birkey 10-14-2012 11:21 PM

Advantages and disadvantages of each?

F-BIRD'88 10-14-2012 11:52 PM

Most combustion chambers on american V8's are wedge style.

Hemi good port to valve angle. big valves, central spark plug(s), valves open away from cylinder walls no shrouding around valves.
Disadvantage large surface to volume ratio. No effective quench (true hemi)
High compression ratio requires a big piston dome. High surface to volume ratio. Convoluted combuston
chamber shape with big dome. More expensive to manufacture Complicated valve train, rocker system. Most Hemi's are not a true Hemi head . But a modified hemi Semi hemi with quench like the new chrysler Hemi.
engine of present.

techinspector1 10-15-2012 12:24 AM


Originally Posted by birkey (Post 1599236)
Advantages and disadvantages of each?

Well, I'm no engineer, I can only read what engineers write and repeat it to others.
Time for links....Little rhyme or reason here, I just included what looked interesting and valid to me.....
Combustion Chamber Design
Design To Improve Turbulence In Combustion Chambers
Cylinder head design
Cute little video...
Wedge combustion chamber
Don't know who wrote this, but it's an interesting read....
Cylinder Head Technology
Cylinder Head Designs - Head Porter - Circle Track Magazine

birkey 10-15-2012 04:34 PM

I take it when you got to order a cylinder head, if it doesn't specifically say which shape it is, then it is the typical wedge shape?

cobalt327 10-15-2012 05:18 PM


Originally Posted by birkey (Post 1599405)
I take it when you got to order a cylinder head, if it doesn't specifically say which shape it is, then it is the typical wedge shape?

With a modern production and many aftermarket SBC heads, what you will be looking at in most cases is a fast burn combustion chamber. These are usually heart or kidney shaped and have quench pads on both sides of the combustion chamber. The Vortec (shown below) is representative of such a chamber.
Click on image for brief article on Vortec head

More info on one reason for the Vortec and other fast burn-type chamber shapes can be seen here.

birkey 10-15-2012 07:12 PM

These Singh grooves, are they a modification made after the fact. Or are they sold this way??

ap72 10-15-2012 07:23 PM

Here's what newer sbc heads are trending towards
R07 chamber image by performancecnc on Photobucket

that basic squished figure 8 is being used in a lot of aftermarket race heads, it works pretty well, BUT it creates a very high compression ratio with most shelf stock pistons.

pentroof 4 valve heads are also becoming fairly normal on OEM stuff.

true "hemi" haeds haven't existed fora LONG time, but there are many manufacturers who run "semi-hemi" shapes.

birkey 10-15-2012 07:45 PM

This is the kidney shape people speak of? With larger than normal squish pads, how much smaller are the combustion chambers?

All times are GMT -6. The time now is 05:45 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright 1999 - 2012. All Rights Reserved.