Combustion chamber CC variance

C

coronadon

New member
Just CC'd my 200 log head. Results as follows: Chamber# 1 2 3 4 5 6
44.5 45 44 46 46 45
I asked this question in a previous post but got no input. Is there an acceptable variance between chambers?
Also, if I do have to bring them all even across the board, is there a way to judge how much to remove to achieve balance?
 
Unless you have a target CC larger (or smaller) than within that range, the easiest approach is to make them all the largest volume measured - unless you are yet to deburr/smooth, at which point re-measure and equalise in a similar manner.

You won't need to remove much at all; a little trial and error wll show how readily 1CC can be picked up.
 
For grins and giggle calculate compression ratio for smallest and largest combustion chamber. That will give some idea just how much difference 1,5 cc makes.
And what is the variance in piston compression height? Would not have to be much to equal 1.5 cc. One cylinder volume is 550cc if my calculation are right so 1.5 cc is about a 3/10 percent variance.
 
JackFish":1g448q8g said:
Wow, mine measured around 52-54cc's.
How much has been milled of that head :unsure::
Click to expand...

Head was originally milled 5 thou after port and polish. Then the head gasket blew after 4200 miles. Since I am installing a Corteco gasket this time as opposed to the Felpro I took off another 15 thou to make up for the diff in crush thickness. Total 20 thou now.
 
Thad":2h2rkaab said:
For grins and giggle calculate compression ratio for smallest and largest combustion chamber. That will give some idea just how much difference 1,5 cc makes.
And what is the variance in piston compression height? Would not have to be much to equal 1.5 cc. One cylinder volume is 550cc if my calculation are right so 1.5 cc is about a 3/10 percent variance.
Click to expand...

Are you saying 3 tenths of a percent is alot?
 
addo":10yv8exu said:
Unless you have a target CC larger (or smaller) than within that range, the easiest approach is to make them all the largest volume measured - unless you are yet to deburr/smooth, at which point re-measure and equalise in a similar manner.

You won't need to remove much at all; a little trial and error wll show how readily 1CC can be picked up.
Click to expand...

Understood. Port and polish was done before I blew the head gasket this time. So I guess it is just a matter of micro surgery to bring the smaller chambers up to par.
 
No, was just noting how small, to the point of insignificantl 1.5 cc is in a cylinder of volume of 550 cc.
The affect is even smaller when the other varibles are consider such as individual port flow, etc.
 
coronadon":2bozrr5x said:
'68falconohio":2bozrr5x said:
Is that one of the 'kidney bean' heads?
Click to expand...

Not sure what that is. It's a 1965 non smog head.
Click to expand...

I've never saw one. Only read about them having a smaller combustion chamber size and 'kidney bean' shaped chamber.

Snooping a bit, it looks like they would've been a C4 casting from CZLN6's post HERE.
 
coronadon":1dmbe907 said:
Thad":1dmbe907 said:
For grins and giggle calculate compression ratio for smallest and largest combustion chamber. That will give some idea just how much difference 1,5 cc makes.
And what is the variance in piston compression height? Would not have to be much to equal 1.5 cc. One cylinder volume is 550cc if my calculation are right so 1.5 cc is about a 3/10 percent variance.
Click to expand...

Are you saying 3 tenths of a percent is alot?
Click to expand...
It is insignificant.
If it makes you feel better, go ahead and equalize, it certainly won't hurt anything. If you to do before/after dyno tests it would be virtually impossible to measure the difference.
Joe
 
Lazy JW":102agz3e said:
coronadon":102agz3e said:
Thad":102agz3e said:
For grins and giggle calculate compression ratio for smallest and largest combustion chamber. That will give some idea just how much difference 1,5 cc makes.
And what is the variance in piston compression height? Would not have to be much to equal 1.5 cc. One cylinder volume is 550cc if my calculation are right so 1.5 cc is about a 3/10 percent variance.
Click to expand...

Are you saying 3 tenths of a percent is alot?
Click to expand...
It is insignificant.
If it makes you feel better, go ahead and equalize, it certainly won't hurt anything. If you to do before/after dyno tests it would be virtually impossible to measure the difference.
Joe
Click to expand...

Do you think it would help to make the engine run smoother? Seems like balancing things out would cause less vibration.
 
It will not make any difference that can be measured or felt. It is not unusual for a combustion chamber to lose 1.5cc or more volume due to carbon deposits--- then regain as the carbon is burnt off..
 
Lazy JW":2ytjhqz1 said:
coronadon":2ytjhqz1 said:
Thad":2ytjhqz1 said:
For grins and giggle calculate compression ratio for smallest and largest combustion chamber. That will give some idea just how much difference 1,5 cc makes.
And what is the variance in piston compression height? Would not have to be much to equal 1.5 cc. One cylinder volume is 550cc if my calculation are right so 1.5 cc is about a 3/10 percent variance.
Click to expand...

Are you saying 3 tenths of a percent is alot?
Click to expand...
It is insignificant.
If it makes you feel better, go ahead and equalize, it certainly won't hurt anything. If you to do before/after dyno tests it would be virtually impossible to measure the difference.
Joe
Click to expand...

Well if nothing else, I have added one more ability to my amateur mechanics resume. Finished CCing the combustion chambers today. All balanced out to the largest chamber at 46 CCs. Thanks to all who chimed in on my post. Your thoughts and suggestions are much appreciated.
 
You must log in or register to reply here.
Back
Top