Head Milling and what it does to you...

[regal81455]

Question: How Much do I mill my head?

Answer:
Base UCCR 9.84:1 = 135 psi = 22.06 cc's
-.010" off = 10.20:1 = 139 psi = 21.20 cc's
-.020" off = 10.58:1 = 144 psi = 20.35 cc's
-.030" off = 11:10:1 = 150 psi = 19.49 cc's
-.040" off = 11.47:1 = 156 psi = 18.65 cc's
-.050" off = 11.98:1 = 162 psi = 17.77 cc's

Question: If I mill my head, will it require me to run a higher octane gas?

Answer: Yes, Milling the head raises the compression. The more compression you have, the higher octane gas you will need to run. Anything over .035" will require race gas. .035" and below you'll be safe with 92-94 Octane Gas.

 

[flyers42091]

Very good post. Thanks

 

[blasterman312]

what part of the head do u mill, thats a weird term to use, when I hear the word milling, i think wood

 

[2stroke4life]

this is the same as shaving the head right?

 

[regal81455]

Yeah, milling would be the proper term for the machine work.

 

[hickskateboarder]

stock compression is 9.84:1? i thought i remember reading in my repair manual that it's only like 8.8:1.......

 

[hickskateboarder]

i just checked my clymer repair manual and a site on the net, both are saying stock compression ratio is only 6.6:1.....

 

[regal81455]

Compression ratio is determined by a myriad of things, most importantly piston selection. Much like a car, you can get pistons for the same vehicle but they can have different compression ratios. From there milling the intakes and heads can effect compression ratios as well and stock figures are always on the mild side...

 

[regal81455]

Use this chart as a guide to figure out your own compression ratio, do not use it as a tell all chart...

 

[regal81455]

Keep in mind that differents cranks will affect your compression ratio as well. If you truly need to understand and know where your compression ratio is here is the formula....

CR=(D + PV + DC + G + CC) / (PV + DC + G + CC)

CR = Compression Ratio

D = Displacement

PV = Piston Volume

DC = Deck Clearance Volume

G = Gasket Volume

CC = Combustion Chamber Volume

Hope that helps clear things up a bit...

 

[hickskateboarder]

i realize all of this, but i am talking about stock compression ratio.

 

[regal81455]

Yeah I understand, this chart is all figured using the Uncorrected Compression Ratio method ( UCCR )...see this website then maybe you'll understand it beter ....

How to Measure Your Uncorrected Compression Ratio...

 

[hickskateboarder]

ok, makes sense, but does the stock uccr reflect mathematically that the cylinder pressure is 135 psi, and it that what it actually measures?

 

[regal81455]

i do believe that to be true

 

[daniel3877]

i just recently sent my head to have it milled, im going .020 off, i didnt know i could go up to .035, should ihave more taken off? will i notice a diff in performance with .020?

 

[regal81455]

your still going to notice a bit of a difference becuz' your still raising your CR regardless of how much you take off...not taking off to much isn't necessarily a bad thing, it just means you can take off more next time if you were to damage your head in some way

 

[taekwondo dauber69]

hey regal your prettysmart i wish i new you 10 years ago when i was racing my 55 .so i didnt have to do everything lol.good to see someone like you in here

 

[bklinger389]

what does milling your head do to the performance of your blaster

 

[dblaster]

more compression = more power

 

[blastermaster85]

great post regal rep points givin