Barrel and head flattening

[shane BBoys]

Before I re-install the barrel n head I intend on flattening them on some glass using some wet n dry which grade would be the best to use?
Cheers Shane

[missing lynx]

I would use medium grinding paste

[Warkton Tornado No.1]

Before I re-install the barrel n head I intend on flattening them on some glass using some wet n dry which grade would be the best to use?
Cheers Shane

I would use medium grinding paste

I agree course grinding paste will do the job. Doubt you'll need to go to fine as the paste soon 'converts' from course to fine

Of course, other than spigotting head or barrel, the best sealing method will be achieved by eliminating the head gasket.....

[Fast n Furious]

Not forgetting that you should maintain around 1.1mm of squish band clearance.

[shane BBoys]

I did have 1.45 on the 1st build using a 3mm base packer and a .5 head packer no gaskets so hopefully matting both surfaces won’t effect the squish too much! Mark 1 186 muggy 110/60 crank, reed valve.
Cheers Shane.

[coaster]

I did have 1.45 on the 1st build using a 3mm base packer and a .5 head packer no gaskets so hopefully matting both surfaces won’t effect the squish too much! Mark 1 186 muggy 110/60 crank, reed valve.
Cheers Shane.

As suggested by WT, best to lose the headgasket/packer completely really, one less thing to fail. Better to adjust to gaskets/packing at the base to achieve a good squish, 1.45 is a bit on the high side I think

[Warkton Tornado No.1]

As squish has been mentioned it's worth a reminder of the importance to achieve the closest safe amount.

Sorry for all those that know, but squish not only ensures the best combustion but is essential in the heat transfer process from piston to head. The head will 'soak' as much heat as possible from the piston & combustion process if the piston almost clouts it. Ideally, the profile of piston (crown radius) should be matched in the head, but few do so. Even with a lathe & a form tool, it is difficult to not get 'chatter' whilst machining, though I am no expert @ making tools

My interpretation of squish is to imagine feeling a very near miss on the chin from a boxing glove, & you won't be far wrong. The piston is hammering the heat into the head where it can be got rid of via the circulating air.

[shane BBoys]

Thanks for the advice, I’ll try without the head packer which actually measures .45 if my memory serves me well! How will this effect compression?
Cheers Shane.

[Warkton Tornado No.1]

Thanks for the advice, I’ll try without the head packer which actually measures .45 if my memory serves me well! How will this effect compression?
Cheers Shane.

A tighter squish will inevitably affect compression, but if you know what it was previously, it can be calculated.

Inevitably on any engine build, it should be checked & adjusted to suit based upon the desired squish. It is just a case of being methodical, though the majority of 'kits' these days have too high a CR, making adjustment just a case of metal removal from the bowl area. If you have a die grinder, Dremel type tool or even just an electric drill with various flap wheels, it is not such a hard job to do. The edges of the bowl to the squish profile should be kept sharp with a small radius IMO.

[shane BBoys]

It might be worth doing then I have no idea what the compression is but I do know it does take some kicking over!
Cheers Shane.