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PostPosted: Wed Jan 23, 2013 6:16 pm 
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848cc
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Hi Matt,

Don't forget, when I had the oil returns in the head welded up they machined the head. So I'm assuming the chambers are less than the standard 28cc, but I will get them measured.

Thanks

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PostPosted: Wed Jan 23, 2013 8:41 pm 
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Re the cam mod, has the grove just been made bigger


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PostPosted: Wed Jan 23, 2013 11:16 pm 
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kiwiinwgtn wrote:
Re the cam mod, has the grove just been made bigger



The additional groove was machined in by Specialist Components, but after showing Matt R we decided it could be a bit larger. The groove is there to elliminate to pulse feed to the head and provide a continuous oil flow.

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PostPosted: Thu Jan 24, 2013 6:50 pm 
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TheMiniMan wrote:
looking good Steve,,, but it`s more like about 10.3:1 ,,, could do with more than that if you could lop some more off the head &/or block

the volume of all the fly-cuts ...plus the 8thou down-ness will make the capacity in the block about 5ccs-ish,,, maybe more actually (guessing)

add the head gasket (about 4ccs)

& the chamber (28ccs)

makes 37ccs all up,,, divided into 345 (1380 divided by 4) to give one cyl swept vol +1

& you have about 10.3:1

so,,,, more would be better,,, maybe try to get-rid-of another 4 or 5ccs from somewhere yeah?

well,,, sorry,,, best to make sure of it all first by grabbing a burette & cc-ing it all to make sure "Exactly" what you actually have there,,, but it`s lookin more like 10:1-ish than over 11:1-ish to me,,, ok?... & it will prefer 11:1-ish far better :-)

edit--> Looking real nice tho Steve,,, you`re doin well mate,



Chambers mearsured today. 22cc's, this being the difference between the standard head and a machined head.

So recalculated on Matt's formula is

the volume of all the fly-cuts ...plus the 8thou down-ness will make the capacity in the block about 5ccs-ish,,, maybe more actually (guessing

add the head gasket (about 4ccs)

& the chamber (22ccs)

makes 31ccs all up,,, divided into 345 (1380 divided by 4) to give one cyl swept vol +1

11:1

BUT, contacted MED to find out if they had a measurement on the fly cuts.

This was the reply.

"The total cc area is 9cc including the cut outs within the 73.5 x 7cc ‘K’ conversion pistons’

Not quite sure what the 73.5 x 7cc means. Matt, you could be right there may be a bit more than 5cc??? If 9cc is the figure i'm down to 9.8 :?

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PostPosted: Thu Jan 24, 2013 7:11 pm 
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73.5 would be the bore, 7cc could be the dome?


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PostPosted: Thu Jan 24, 2013 10:22 pm 
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A quick look on MED's site tells me that they have a die cast 73.5mm piston with 7cc dish and the flycuts add 2cc

However your pistons are the forged flat tops, so their reply means absolutely nothing to you.

So your compression is more or less what you thought


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PostPosted: Fri Jan 25, 2013 11:14 am 
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hee hee,,, we can get all muddled up if it`s not measured... measure it all Steve & then do the calcs

any guessing is just,,, well,,, guessing :-)

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PostPosted: Fri Jan 25, 2013 6:10 pm 
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TheMiniMan wrote:
hee hee,,, we can get all muddled up if it`s not measured... measure it all Steve & then do the calcs

any guessing is just,,, well,,, guessing :-)




Point taken!!!! Re-measured it again with a buret and dial gauge.

73.5 bore
Pistons 3 thou below deck (at top dead centre)
Fly cuts 3cc's (total of the four cuts in one piston) (flat top pistons)
Combustion chamber in the head 22 cc's

Correct me if i'm wrong :oops:

1cc (deck?) + 3cc (flys) + 22cc (c/c) + 4cc (gasket) = 30cc

1380 / 4 = 345 345 / 30 = 11.5 C/R

(I did guess 1cc for the 3thou below deck height, sorry)

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PostPosted: Fri Jan 25, 2013 8:00 pm 
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HI Steve
I think that may be 12.5 to one
Graham

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PostPosted: Fri Jan 25, 2013 8:56 pm 
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GR wrote:
HI Steve
I think that may be 12.5 to one
Graham




Thanks Graham, Wasn't expecting that. Is that the "swept vol +1"

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PostPosted: Fri Jan 25, 2013 11:41 pm 
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GR wrote:
HI Steve
I think that may be 12.5 to one
Graham


yep

again,,, just measure it all make sure

easy sorted now

edit-->... need to make sure of it now!!!

double edit--> ...altho,, 12.5:1,,, plus Av-Gas,,, plus some nasty cams,,, plus some decent injection/ignition tune & you got one mother of a thang :-)

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PostPosted: Sun Jan 27, 2013 7:09 am 
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Oh dear, worry, worry...

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Hi Steve
Run two head gaskets that will give you 11 to one.
Graham

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PostPosted: Tue Jan 29, 2013 9:18 pm 
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My math could be wrong here, but...

73.5mm bore
= 36.75mm radius
pi x 36.75^2
= 4242.92 mm2 area
x 0.0762mm (0.003") below deck
= 323.31 mm3 volume
÷ 1000 to convert to cc
= 0.3233 cc per cylinder
x 4 cylinders
= 1.293 cc total volume in your 3 thou below deck.

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PostPosted: Wed Jan 30, 2013 6:46 am 
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Oh dear, worry, worry...

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HI Simon
Your maths are fine but we are only talking about one cylinder.
Graham

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PostPosted: Wed Jan 30, 2013 7:56 am 
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Ah, there you go then. Happy days 8)

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