compression???

[awbr]

I'm swapping my 7 bolt for a 6 bolt, but I wanted to put a 2g head on the 6 bolt, will this change the compression of the block?? Or my better off keeping the 1g head on?? thanks alex

 

[LaN-]

Im swaping my 7 bolt for a 6 bolt, but I wamted to put a 2g head on the 6 bolt, will this change the compression of the block?? Or my better off keeping the 1g head on?? thanks alex

1g heads flow more then 2g's anyway, i think there are problems going backward, but i'm not sure.

The compression is really dictated by the pistons not the head. You will gain a little bit more compression if the head has been decked but its really all in the pistons.

2g pistons are 8.5 to 1 and 1g pistons are 7.8 to 1

 

[Locke]

The compression is really dictated by the pistons not the head.

Assume R=([pi*(b/2)^2*s]+p+k+g+C)/(p+k+g+C); where R=compression ratio, b=cylinder bore, s=stroke, p=piston volume, k=piston to deck clearance volume, g=gasket volume, C=combustion chamber volume.

If the volume of the combustion chamber changes, so will the compression ratio. A head with a bigger bowl will give you a lower CR, and a smaller bowl will yield a higher CR.

I am unsure if the volume of the bowls changed, though.

 

[LaN-]

Assume R=([pi*(b/2)^2*s]+p+k+g+C)/(p+k+g+C); where R=compression ratio, b=cylinder bore, s=stroke, p=piston volume, k=piston to deck clearance volume, g=gasket volume, C=combustion chamber volume.

If the volume of the combustion chamber changes, so will the compression ratio. A head with a bigger bowl will give you a lower CR, and a smaller bowl will yield a higher CR.

I am unsure if the volume of the bowls changed, though.

I understand that, but is there a difference between the 2g and 1g bowl in the head?

 

[JayRolla]

1g heads flow more then 2g's anyway, i think there are problems going backward, but i'm not sure.

The compression is really dictated by the pistons not the head. You will gain a little bit more compression if the head has been decked but its really all in the pistons.

2g pistons are 8.5 to 1 and 1g pistons are 7.8 to 1

This is true but cant the 2g head be ported to flow better than the 1g head?

 

[LaN-]

This is true but cant the 2g head be ported to flow better than the 1g head?

i don't know, but if you think about it. If a 1g head flows more stock, then when your port it i would imagine its going to flow more anyway. It really comes down to how thick everything is. If the 2g head has more material that can be ported away then the open would be better.

Think about it in terms of a 1g and 2g exhaust manifold. the 2g is better because the walls are thicker and it can be ported more. if you compared the opening of the 2 unported they would be the same, but the 2g has more potential.

Did i make any sense , i'm confusing myself.

 

[awbr]

Thanks for the help guys

 

[DirtyBirdRacing]

I believe that the combustion chamber has a volume of 47 cc's on both the 1g and 2g heads. So swapping the head will not change the compression ratio of your engine. So block with 1g pistons will be 7.8:1 and blocks with 2g pistons will be 8.5:1.

Bill

 

[oldman]

i don't know, but if you think about it. If a 1g head flows more stock, then when your port it i would imagine its going to flow more anyway. It really comes down to how thick everything is. If the 2g head has more material that can be ported away then the open would be better.

Think about it in terms of a 1g and 2g exhaust manifold. the 2g is better because the walls are thicker and it can be ported more. if you compared the opening of the 2 unported they would be the same, but the 2g has more potential.

Did i make any sense , i'm confusing myself.

You're forgetting velocity. A 2G head is better designed therefore it flows more efficiently.

 

[LaN-]

You're forgetting velocity. A 2G head is better designed therefore it flows more efficiently.

o ok, thanks