g'day people,
quick one for someone to explain to me, i'm very close to buying an alloy head for the motor i'm building. Question is how does te chamber size have an effect on the running of the engine?? is bigger or smaller better?? ie close to 40cc higher or lower comp than 50cc???
cheers
chamber size
Started by
_micksgtr_
, Jan 04 2006 08:51 PM
2 replies to this topic
#2
J-Rod
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Posted 04 January 2006 - 11:25 PM
bigger chamber = lower comp ratio
smaller chamber = higher comp ratio
Whether a bigger or smaller chamber is better will depend on your specific application. If you provide some detail on the engine then im sure someone here will point you in the right direction
smaller chamber = higher comp ratio
Whether a bigger or smaller chamber is better will depend on your specific application. If you provide some detail on the engine then im sure someone here will point you in the right direction
#3
_Sammy_
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Posted 11 January 2006 - 01:02 PM
my opinion is that you want to get the chamber size to suit the compression ratio you will be running ....
for example, i got a stock VK EFI 202 head serviced and cc'ed, the chambers were 54cc after a light skimming of the head, so with this figure and all the other figured of my motor i can work out the compression ratio will be 9.5:1 which is spot on what i was looking for .... so in the case of an alloy head you can probably run 10:1 or 10.5:1 so you'd probably want 50cc chambers for example ....
you really need to know all the numbers and do your homework in this area because too much compression for pump fuel is the last thing you want ....
having said all this, if you have the option of a larger chamber head get it and then get it decked to bump the compression up later if you need it ....
i have a head which has 44cc chambers and they are just too small (previous owner had high compression for speedway car) and so i have to run a decompression plate to get the comp ratio right, not a real issue but i'd prefer to have a motor which didn't need a decomp plate.
for example, i got a stock VK EFI 202 head serviced and cc'ed, the chambers were 54cc after a light skimming of the head, so with this figure and all the other figured of my motor i can work out the compression ratio will be 9.5:1 which is spot on what i was looking for .... so in the case of an alloy head you can probably run 10:1 or 10.5:1 so you'd probably want 50cc chambers for example ....
you really need to know all the numbers and do your homework in this area because too much compression for pump fuel is the last thing you want ....
having said all this, if you have the option of a larger chamber head get it and then get it decked to bump the compression up later if you need it ....
i have a head which has 44cc chambers and they are just too small (previous owner had high compression for speedway car) and so i have to run a decompression plate to get the comp ratio right, not a real issue but i'd prefer to have a motor which didn't need a decomp plate.
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