Combustion chamber

[goodnigh]

The book says my combustion chamber volume is 64 to 67.

What does that mean exactly?

mike

 

[Canted 393]

How many cc's of liquid a combustin chamber will hold. A smaller cc combustion chamber means higher compression ratio.

 

[goodnigh]

How many cc's of liquid a combustin chamber will hold. A smaller cc combustion chamber means higher compression ratio.

Please explain "combustion chamber".

I am trying to explain to a Dutch friend

and car enthusiast how my 4V D0AE

Cleveland works. 

mike

 

[Canted 393]

here is a closed chamber on a 351C 4V head

Having a problem adding an image, so a chamber is the area where the intake and exhaust valves are in the head. If it only holds 64cc of liquid it will provide a higher compression ratio than a head with a 72cc chamber. Hope that helps and I am sure someone smarter than me will chime in.

 

[rvrtrash]

Simply put, a combustion chamber is the pocket or recess in the head where the valves are, which would be over the piston when the head is on the block. They have different shapes which can be named closed chamber or quench which has smaller volume for higher compression or open chamber which has higher volume for lower compression. Even within a type/shape there can be different sizes, depending on how the head is cast.

Steve

 

[goodnigh]

So the combustion chamber is what is left when the piston is

in full compression cycle, top of stroke.

mike

 

[jbojo]

So the combustion chamber is what is left when the piston is

in full compression cycle, top of stroke.

mike

Yes, the heads will have a volume, 64 cc for example but I think you have to consider the type of piston too and thickness of the head gasket.  For example, are you using a dish, flat top or dome piston?  A dish will add to the total, flat top is essentially zero and a dome will decrease it some because it is above the block area and extends into the cylinder head area.  The thickness of the gasket will also add some volume though it is usually minute.  In general when talking combustion chamber size you are talking cylinder head but serious engine builders consider everything..

 

[c9zx]

How far the top of the piston is down from the top of the bore when at Top Dead Center (piston deck height) plays a very large role in the actual compression ratio. It is often overlooked. Chuck

 

[Don C]

You can use the spreadsheet in this thread to see what the effects of the above descriptions are.

https://www.7173mustangs.com/thread-engine-and-compression-calculations?pid=199290#pid199290

 

[Carolina_Mountain_Mustangs]

If you want to measure your CC on your heads you will need the valves in place and get you a piece of plexiglass or Lexan about a 1/4" or 6 mm thick big enough to cover one chamber and overlap all around. Set up your head level and take a little bit of grease and put on the head around the chamber. You will need a small hole in the plexiglass so you can add liquid until it fills the area and you can see thru the plexiglass that all air is out. You can color the water with food coloring to make it easier to see. You can use one of the glass lab tubes with markings or get a large medical hypodermic also. You can also use antifreeze and it will not rust the cast iron.

You can do the same with the pistons in the engine block. If you cc vary you might need to have the block decked to make the head surface parallel with the crank shaft bearings. If the head is off you might also need to cut but might also do some grinding to make the combustion chambers the same. If a valve seat is cut too deep it increases the volume and reduces the compression also.

An engine with all chambers equal will run smoother at idle due to volumes being the same. It is just one part of blue printing and engine.

 

[Stanglover]

I think that when the head CC's are listed as 64 to 67 cc, that represents the range across the 4 recesses. These are cast in, not machined as in CNC'd, so accuracy from one to another will vary. The patterns that were used were likely wood and they can change with wear or even temperature. On a set of '70 D0AE-"N" heads I had, these were supposed to be 62.8cc according to Mustangtek, but a rough check showed them between 61 and 64cc's on one head. I'm not claiming that to absolutely accurate numbers, but close, so 62.5cc would be the average and so on.

Geoff.