Squish Clearance Question

[jradnich]

I'm building a Suzuki RM500 engine (bore dia is 84.5mm). Any ideas on what I should set squish clearance to? I'm assuming a bigger bore needs more clearance to account for greater expansion. Or am I overthinking it?
Thanks, John.

[scully]

I'm building a Suzuki RM500 engine (bore dia is 84.5mm). Any ideas on what I should set squish clearance to? I'm assuming a bigger bore needs more clearance to account for greater expansion. Or am I overthinking it?
Thanks, John.

Over thinking

[racerclam]

not over thinking . The big bores are more prone to detonation becauce of the large diameter there for  squish is very important . Ifyour racing you should adjust the squish . You can normall cut about .020" off the head without any issues , this will help but not be optimum of  probobly around .050" squish but way better than what is stock which is probably around .090" the tighter the squish the more mix is sent to the combustion chamber to be used at the right time rather than burned later on down the power stroke or worse yet to create detonation.  Here is another good mod the reduce the chance of detonation as well as improve combustion eficiency and power . I do this if your interested. Torque grooves. One again this site wont let me post pictures  It always says too big . I can post anywhere else with no problem , what is messed up with this site ? I dont get it

Rich

[racerclam]

If anyone want to see the torque grooves Im trying to post give me a call and I can text pictures

Rich

[racerclam]

Ok so I forgot the number 702-858-9177

Rich

[teazer]

I'm building a Suzuki RM500 engine (bore dia is 84.5mm). Any ideas on what I should set squish clearance to? I'm assuming a bigger bore needs more clearance to account for greater expansion. Or am I overthinking it?
Thanks, John.

Both over and under thinking it.  Bore size is really not the most important variable.  There's a concept known as MSV or median Squish Velocity and it's more of a rule of thumb as to how the squish affects performance. The key variables seem to be percentage of bore (ie width of the squish band) and thickness of the squish band.  Obviously RPM is another variable, as is piston and squish band angle as is piston weight and con rod rigidity but no one has that last piece of data, so we assume that all rods are created equally tough.

Check out the THEORY tab on http://bimotion.se/ for a more comprehensive explanation. 

If you have a stock motor, you should measure the squish band thickness so you know what your baseline is and if you choose to modify the motor, you will have a basis for comparison.

[~JM~]

If I recall correctly, domestic V-8 engine building strives for .035"

[m in sc]

what is messed up with this site ? I dont get it

Rich

nothing, reduce your image size. ive increased it from the default 650 to 1200, so that's 1.2mb If oyu have issues you can PM me.

on the topic of the 'torque grooves'  are you talking about singh grooves?

[racerclam]

I completly agree with you .

Rich

[jradnich]

Thank you for the input. I probably should have been a little more specific. I want to reduce squish clearance to reduce the chance of detonation. It looks like from your info I should use the same clearance recommended for RD's. I was worried the possibility of a larger displacement cylinder expanding more and having the piston contact the head when hot.
The engine is going in a 72 TS250 IF I can get it to fit without chopping up the frame. The biggest issue I'm having is clearance for the carb. Assuming I'm successful I'll post some pics.

[racerclam]

tes you are correct that bigger bore increases chance of detonation.  Torque grooves help with this also , every engine I por gets them also  small or big bore . They work. If you go on my web site  richstaylordporting you can see a picture of a head done



Rich

[m in sc]

Nice work looking at your site, Richard.



http://www.richstaylordporting.com/index.html

[SoCal250]

Nice work looking at your site, Richard.
http://www.richstaylordporting.com/index.html

I agree. Nice builds in the gallery, both bikes and cars.

[racerclam]

thank you. For the compliments . I just came in for a break . Right now Im porting a Suzuki TS 400 for a Bonneville . Now back to work

Rich

[pdxjim]

I went over how to post pics off your website in the other thread.  Not so hard.