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beingblueeyes
08-19-2009, 02:13 AM
Iíve been stuck on the math on this for 2 days now. How much would a 3sge head need to be milled to have 10.5.1 cr on a 5sfe block?

Using this page (http://www.cbperformance.com/enginecalc.html) with
Bore: 87mm
Stroke: 91mm
Deck Height: 1.275 (I think this is the right number for a stock block 5s)
Combustion Chamber CC's: 60.6 (50cc for the 3sge head + 10.6 for the 5sfe dish pistons)

Gives me a 8.9 CR. By making the Combustion Chamber CC's 50cc it brings my cr up to 10.4

Using this: 1 cubic centimeters = 0.061 cubic inches I get
10.6cc X .061 = .6466 needs to be shaved of 3sge head to get 10.4 cr??
It just doesnít seem correct
any help would be great

MrWOT
08-19-2009, 06:25 AM
Gasket thickness needs to be accounted for, and on the deck height do you mean installed piston height?

Total chamber volume needs to be ~45cc's with 1.275mm in the hole for ~10.4:1

beingblueeyes
08-19-2009, 01:53 PM
Thanks for getting back to me Mr.wot, I did not take into account gasket thickness. Yes installed piston height. Is the cc to inches equation correct? Using that equation with 45cc total gives me .9394 to cut off (no way in hell is that or the other number correct)
So how do you figure out from total cc's of combustion chamber to how much you have to mill off to achieve the CR goal?

MrWOT
08-19-2009, 05:08 PM
simple, use a burrette, fill it with 45cc's of dye and see where it leaves you. And no, you aren't going to get where you want without at least flat top pistons. you certainly aren't going to get the head down to 35cc's (unless you weld it) :laugh:

As for calculating how much to shave, you can't, the chamber doesn't retain the same shape throughout.

nuclearhappines
08-19-2009, 05:33 PM
high compression (flat faced valves) and bosch +4 spark plugs help too (marginally)

beingblueeyes
08-20-2009, 01:36 AM
yea looking at the ge head and a fe head side by side your right MrWOT, there is no way i could get it down to 35 cc's with out welding. flat top pistons are also out on this "mod/head build"(donít want to spend the cash.) flat faced valves would be nice (but donít want to spend the cash on them) how do bosch +4 spark plugs stack up vs ngk irdm. Plugs nuclearhappines?

Also one fast question about cutting the valve guides down when porting the/a head good idea or bad? I know they smooth out the valve guides on sbc heads and completely grind them down on some motor cycles and they rev to 9k+ so why shouldnít I grind them totally out of the intake/exhaust ports because Iím only revving to a max of 7k?
(like this)
http://image.hondatuningmagazine.com/f/9346311+w750+st0/0607ht_21_z+port_and_polish+better.jpg.jpg

MrWOT
08-20-2009, 02:11 AM
You will gain nothing and lose longevity. In certain cases I might grind on the intake guide to contour it. I would never remove it entirely unless it was a race only engine with a big budget.

beingblueeyes
08-20-2009, 02:49 PM
i read you
thanks