Page 1 of 2
cylinder head reprofiling
Posted: Fri Dec 04, 2015 4:35 pm
by holty
Hi folks,
im just building up a budget 200cc lammy engine, its a smallblock conversion, it came without a head so ive got a 150 head which is the correct stud pattern, but the wrong diameter combustion chamber, anyway ive had it in my lathe and opened it out to 66mm, my question is, should the machining of the head be exactly the same curviture as the piston crown, or should i leave a larger gap as i move away from the gasket, hope ive not confused everyone there.
holty
Re: cylinder head reprofiling
Posted: Fri Dec 04, 2015 5:26 pm
by eden
Depends what squish velocity your aiming for.
Re: cylinder head reprofiling
Posted: Fri Dec 04, 2015 5:32 pm
by holty
was aiming for a squish between 1 and 1.5 mm roughly.
Re: cylinder head reprofiling
Posted: Fri Dec 04, 2015 6:06 pm
by eden
I wasn't referring to the size of the squish.
Re: cylinder head reprofiling
Posted: Fri Dec 04, 2015 7:44 pm
by holty
did you mean that the angle/ profile determines the squish velocity, does that mean theres angle best suited to a lambretta? or more to do with the piston crown shape ?
its not a subject a know a lot about, other than it can make a big diffrent to how an engine runs.
holty
Re: cylinder head reprofiling
Posted: Fri Dec 04, 2015 10:40 pm
by fairspares
without getting technical basically you have the squish band and combustion chamber , have a read at mbs info it may help
https://www.lambrettaspares.com/info/ty ... -x+54.html
Re: cylinder head reprofiling
Posted: Fri Dec 04, 2015 11:06 pm
by eden
predictably no mention of squish velocity there
this guy touches on it though
http://www.macdizzy.com/update39.html
this is very good for head design
it wont tell you what to aim for but it makes it much easier to get what ever you do decide on
http://bimotion.se/Head/BimotionAdvancedHead_Manual.pdf
Re: cylinder head reprofiling
Posted: Fri Dec 04, 2015 11:27 pm
by Muppet
have you downloaded the software?
Re: cylinder head reprofiling
Posted: Fri Dec 04, 2015 11:28 pm
by eden
its one of the ones I have ye
Re: cylinder head reprofiling
Posted: Fri Dec 04, 2015 11:29 pm
by Muppet
msv meters per second formula?