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my squish band and compression
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Posted by: lee37vernon

having just rebuilt my engine i come to sorting out the squish . the cylinder is at 265cc having been ported , the cylinder has also been machined for o -rings , when on the engine the piston does not come over the top of the deck , its running an 86 style piston with spacer plate .

i bought this set up from a guy who had it as a spare and cant really give me much info on it .

i can fit the head on ( std honda ) and with no gasket other than the o rings my squish is around .055 to .060 '' around the edge getting to maybe .070'' towards the centre . i had to use plasticine to take these measurements as all solder i could find was too thick or too thin .

i know a squish ideally is around .035'' to overlap the cooling layers , so , should i ---

1) just have this head milled by .020'' ?

2) have the top of the cylinder decked by .020'' ?

3 ) something else i have not thought of !!

what should the squish height be also ?

also how much compression can i get away with running 99 octane fuel ( maybe 97 but most likely 99) ?

how can i work out , if the compression is too much , how much material to take from the dome ?

Posted by: Zedicus

mill the head.

210lbs psi at 99 octaine... (roughly, variables envolved, if you detonate youve gone too far) for comparison im running 203lbs psi at about 97 oct.

Posted by: lee37vernon

ttt

Posted by: spanky101

dont bump threads.... unless its a bst... its pointless

Posted by: 86 Quad R

and what psi do you currently have with that squish setup?

Posted by: lee37vernon

the engine is on the bench so its an unknown , i see on mcdizzy there are some charts to work out cc for correct compression ratio but the examples dont give info for my 68.25 mm piston size. guess i'll just send it off to someone in the know ..