6 replies to this topic

[superzorg1000]

Just a hypothetical question. (for now)

 

Does anyone know if a 1275cc head would reduce the compression ratio for a 998cc block with standard pistons and con rods?

 

Thanks in advance.

[coopdog]

Pretty sure 1275 chamber volumes are less than a 998s

[Cooperman]

If you are considering doing this learn how to do the calculations regarding CR's. Then measure and calculate again.

[Spider]

As it's a hypothetical question, a hypothetical answer is no.

 

Nominally, the 998 head has circa 24.5 cc and the 1275 around 21.5 cc. This would increase the static CR.

 

But, as Cooperman has suggested, measure what you have and what you're contemplating and run the numbers.

[superzorg1000]

Thanks for all the help. When I get round to taking the head off the 998cc I will check the numbers.

 

After doing some more research it has only confirmed what you have said.

 

Thanks again.

[Stiggytoo]

If you are going to fit a 1275 head be aware of the possible clearance issues between valves and block face. Again, you may need a different water pump and pulley and coolant hose routing :)

[OzOAP]

Measure head cc difference.
Pockets in block 0.200 wide/0.200 deep = 1cc
1275 head gasket 3.8cc. 998 gasket 2.7cc