Head hasket help

[Jdeac]

Hi all. Need a little help working out what thickness head gasket I need to order. Pictured Is what I have so far. Measurement wise. The old head gasket is long gone and this is a new head going on the motor.

I keep getting wierd results on ratio calculators.

[Jdeac]

This is how I've entered the info on a calculator 

[Gixer1460]

When you've measured piston dome volume was that at max stroke? If so, i'd omit the 'deck clearance' figure as it would be included already in the dome volume? Sorry, thats my best guess but Bus pistons reknowned for dropping CR but that number does seem low!

[Jdeac]

2 minutes ago, Gixer1460 said:

When you've measured piston dome volume was that at max stroke? If so, i'd omit the 'deck clearance' figure as it would be included already in the dome volume? Sorry, thats my best guess but Bus pistons reknowned for dropping CR but that number does seem low!

Not sure what your saying. I've never done this before. Tha calculator asks for the height and the volume. Can I leave the height out.

The old head was heavily skimmed  compared to the new one.

Intercooled turbo on race fuel. If that makes any difference

[Jdeac]

Comparison of the old to new head.

[Gixer1460]

Isn't a 'std' 1100 head volume about 26/27cc? If so, it can't have been skimmed very much? I think the Dot 750 heads volume is around 23cc for comparison! What happens if the 0.74mm is omitted?

[Jdeac]

Yes I belive so. The head was refreshed for me by @clivegto

the original head was on the bike already. Its cracked which is why the change. This is the motor from my drag bike pyro.

As said I'm new to all this. And what do you mean the .74 omitted??

[Gixer1460]

In the calc you've got a figure of 0.74! Set it to 0.0 and see what result is?

[Jdeac]

Like this?

[Jdeac]

I also just put 1mm for head gasket. As I can't seem to find specs for thicknesses 

 

[Gixer1460]

5 minutes ago, Jdeac said:

I also just put 1mm for head gasket. As I can't seem to find specs for thicknesses 

Won't be far off maybe a little less is possible, otherwise it looks like thats your CR - low - so off boost will be like a greyhound on Mogadon, but will probably take more boost than the turbo can make! Have you removed the detonation causing edges around the valve cut outs ?

[Jdeac]

4 minutes ago, Gixer1460 said:

Won't be far off maybe a little less is possible, otherwise it looks like thats your CR - low - so off boost will be like a greyhound on Mogadon, but will probably take more boost than the turbo can make! Have you removed the detonation causing edges around the valve cut outs ?

This motor was built by fbm/loopey has been a drag bike for many years. I'm just refreshing it. As I had gearbox issues last season. Pulled the head for oil drain oring change. Saw the cracks around plug holes etc. So decided to swap the head. Thanks @clivegto

So I now need to work out how to get the comp ratio in the right place.

Is there different thickness ones available etc. Do I need to get the head skimmed.

Again all new to me this turbo stuff

Pic of the bike that I ran last year. And I'm trying to get sorted again

[colinworth79]

On 8/13/2023 at 5:48 PM, Jdeac said:

I also just put 1mm for head gasket. As I can't seem to find specs for thicknesses 

 

When I built a motor with busa pistons I skimmed a  bit off the block .

I  do have a ported and skimmed 1127 head going cheap if you want ? 

Edited August 21, 2023 by colinworth79