Arctic Chat : Arctic Cat Forum banner
1 - 8 of 8 Posts

·
Registered
Joined
·
352 Posts
Discussion Starter · #1 ·
Looking to get my heads machined down to take up a bit of the slop in my squish band. The question is how much of an increase should I expect to see in my compression ratio? Not looking to increase compression too much, I just want to lose a little from the .089 thou squish band I have. Looking to take about .029 thou off. What kind of compression increase will that give me. It's another 100.00 a head to have my combustion chamber machined to match and I would like to put that 200.00 somewhere else if I could.

Thanks all.
SPDFREEK
 

·
Registered
Joined
·
4,097 Posts
<div class='quotetop'>QUOTE (Bearcat-97 @ May 16 2007, 01:36 AM) <{POST_SNAPBACK}></div>
Don't take that much off. I think 0.02 (about 5mm) woud be ok and safe.[/b]
.5 mm, I presume???? Every engine is different and somebody has to know what is optimum for SPD's 700, but the optimum is going to change depending on the desired outcome, and other mods. The optimum squish may be different now that he has modified the porting of the cylinders.
 

·
Registered
Joined
·
197 Posts
<div class='quotetop'>QUOTE (SPDFREEK @ Apr 16 2007, 12:07 PM) <{POST_SNAPBACK}></div>
Looking to get my heads machined down to take up a bit of the slop in my squish band. The question is how much of an increase should I expect to see in my compression ratio? Not looking to increase compression too much, I just want to lose a little from the .089 thou squish band I have. Looking to take about .029 thou off. What kind of compression increase will that give me. It's another 100.00 a head to have my combustion chamber machined to match and I would like to put that 200.00 somewhere else if I could.

Thanks all.
SPDFREEK[/b]

I shaved 0.020 on my 550 a long time ago 94 i think and it is still running today with no problems on regular fuel. Now the compression went from 125 to 145 @ 2300 feet of elevation and back to 125 @ 7000 feet of elevation. I am going by memory so the numbers might be 120&140 but you have an idea where you will end up at . Hope this helps.
 

·
Banned
Joined
·
252 Posts
Every .010 ( 10 thou) will be 10 psi change. Same goes for your porting. if you raise port timing the psi will go down. .029 is alot to take off, and that would definately put you in race gas territory. I think if you rechamer to your needs from a reputable company like D&D or Speedwerx it should only cost 100-175.00 for both domes. Any machine shop will ony charge about 45.00-75.00 to just whack off a designated amount for decking. I've had it done for as cheap as 25.00 for a mono head. For trail friendly applications you need to keep your squish band in the .064 - .078 range for safe all season use. When and if you take that much off you HAVE TO rechamber to make any kind of real gains. Mostly low end grunt for 60's. If you took off .029 you would be reducing your volume by approxamately 5cc's per side and would put you around to 14.7 :1, if you don't rechamber. When you tighten up your outer squish band that much you increase squish velocity alot and also make pump fuels more unstable and create uncontrolled burn rates. Which leads to unpredictable detonations from day to day. Like I said check the 2 leaders in technology for cats. The last race head I had cut and rechambered from them was only 100.00 for a 118 octane head. And the squish band was close to what you want for a 700cc machine. It also made over a full tenth gain in the 60' times, with proper octane, with wrong octane it'll lose et.
 

·
Registered
Joined
·
352 Posts
Discussion Starter · #7 ·
Thanks for all the info guys....wanna keep the thing trailable . Don't mind running premium but race gas is out of the question. This 7 is allready brutal on fuel. I'll get a call into D&D and see what they recommend. Once again thanks for the info. This site is truley the best!!!!!!

SPDFREEK
 

·
Registered
Joined
·
362 Posts
Took 10,000 off my zr 8 before it was ever ridden back in 02. Never had a problem and today the compression is still at 152 both sides. Only 4200 miles on the sled. ZR
 
1 - 8 of 8 Posts
Top