Hey, I just recently had the block of my Dohc F20B milled .020", I've put new pistons and h22 flat faced vlaves in to bump up my compression for when i recieve my JUN cams, now I'm in the process of claying the engine to make sure that the vlaves and pistons are kept form having a brawling match at 8200rpm , now I put a 1/2" wide 1/4" thick strip of clay across the piston on each side of it and when I cranked it over by hand 2 times and checked it the vlaves didn't even touch the clay, now I tried it again with vtec engaged and the same thing, I have the cam gear arrows both pointing up along with the crank being at #1 TDC.


How much do I have to change the timing on the cams if I have milled the Block .020"? Do i have to Advance it or Retard it or can i leave it alone?

I want to make sure I have it set up right so it doent run like crap and so i can be 100% sure the valves wont engage with the pistons

thanks


Modified by AlmostJDM at 8:38 PM 6/19/2008


Modified by AlmostJDM at 8:05 PM 6/20/2008

 

Anyone at all? come on some one has to know how much i have to change it if any

oh wait lol i just reread my question and it was supposed to be like this

How much do I have to change the timing on the cams if I have milled the Block .020"? Do i have to Advance it or Retard it or can i leave it alone?


there we go


Modified by AlmostJDM at 8:03 PM 6/20/2008


Modified by AlmostJDM at 8:04 PM 6/20/2008

 

You shoud "degree" the cams instead of guessing, however here is an aproximate for you...

The H22/F20 is 105mm diameter. So the circumfrence of the cam gear is 105mm X 3.14 = 329.7.
Divide 360 by 329.7 = 1.09 degree per mm

So for every 1mm milled the cam gears will roll back (retard) 1.09 degrees at the cam or 2.2 degrees at the crank.

Example....So you have a 0.030 milled meaning 0.76mm = about .828 degrees retarded, so advance your gears 1.1 degree to compensate for the 0.030" mill

1mm = .040"

25.4mm = 1"

I am going to let you do the math yourself for the .020" mill.

 

ok thanks 2point6, I just couldnt find the word lol I ment degree, ok now I have to search to figure out what degree each of JUN's marks are on their cam gears

thanks again

 

woot ok I found it out now time to clay the engine again ....tomorrow

oh and if anyone wants to follow up on my build heres the link to it

http://www.cb7tuner.com/vbb/showthread.php?t=87076

 

just remember that one tooth on the cam gear is about 10.5 degrees

 

k ...yea I have a set of JUN cam gears, I just have to go buy some keys for them because my f20b cam gears have the keys molded into the gear.