Re: Head Milling: No help from the search button...

do it man!

 

Re: Head Milling: No help from the search button...

Put BUSA pistons in,and remove one layer of head gasket.

 

Re: Head Milling: No help from the search button...

Put BUSA pistons in,and remove one layer of head gasket.

more info please. what year busa pistons for 1st gen SV? what's the resulting compression ratio? what's the ultimate goal (more hp, more torque? why busa pistons!?) how do you swap them, is it a direct piston removal and swap? will this make your engine run hotter?

 

Re: Head Milling: No help from the search button...

You can get an idea of the resulting compression by assuming that the amount removed is a cylinder. So you take the stock SV compression ratio and swept volume and calculate the head clearance. Now assume that the change in head clearance is a cylinder same diameter as the bore, and as long as the milled amount. Recalculate the compression ratio.

You also need to know how much valve-to-piston clearance you have. Once you know that you need to figure out if you will have valve clearance when the engine is warm.

 

Re: Head Milling: No help from the search button...

Thanks. I just wanted to know if the ends justified the means. I'm clayin' the pistons anyway, do you know the expansion formula for when my bike is at operating temp?

 

Re: Head Milling: No help from the search button...

You multiply the length (in this case the longest distance along the rod from the top of the small end bore to the bottom of the big end bore) times 10 to the minus 6. Then you multiply that by the difference in temperature, ambient to running. For connecting rods in a street motorcycle engine I'd use 175 deg. F as the "high" temperature. The "low" temperature will be whatever the ambient temperature was when you measured the rod.

(thermal coefficient of expansion) X 10 to the -6 X length X (running temperature F deg. - ambient temperature F deg.)

Thermal coefficient for steel or cast iron is about 6. For aluminum it is about 12.3. Remember to keep all your dimensions in inches or you will get goofy numbers.

The reason you need to know the entire length of a connecting rod from the extremes of the bearing bores is because the bores expand also. This gives more clearance at the bearings making the piston approach the valves more closely. This is exaggerated when you have aluminum rods and cast iron cranks (rod bore grows more than crank diameter).

 

Re: Head Milling: No help from the search button...

Who has milled thier heads down, how much and what kind of compression did you end up with?

Forgive my ignorance, but what gets milled away, and what's the point?

 

Re: Head Milling: No help from the search button...

Wouldn't it be easier to call Suzuki get min valve clearance specs then clay the piston and mill from there?


Milling is a term, shaving or milling off of material, In this case it means shaving thousands off my heads in order to raise my commpression ratio. Like cutting a thin slice right off the bottom. Of course that means nothing if you don't know what a head is....

 

Re: Head Milling: No help from the search button...

shaving thousands off my heads in order to raise my commpression ratio.

A couple of thousands is not going to do much IMO. But it also wont mess up the cam timing. The easier and safer way to go about raising compression is with pistons and head gasket thickness. The busa pistons sounds pretty accesable, as stock pistons off busa's are often swpped out by week-end drag racers who race them.

If you want to, you can also shrink the quench area of the CC by welding extra material before resurfacing the head. This way you can stick with the stock pistons. Unless you are handy with a tig torch and die grinder, you can have this done in most reputable high performance engine rebuilders. But I'm sure you already know that.

 

Re: Head Milling: No help from the search button...

Yeah i was thinking more like 30 thou if I can get away with it but I have to wait to see what "the clay tells me to do". Just takin the time to do it right, hopefully.

 

Re: Head Milling: No help from the search button...

Wouldn't it be easier to call Suzuki get min valve clearance specs then clay the piston and mill from there?


Milling is a term, shaving or milling off of material, In this case it means shaving thousands off my heads in order to raise my commpression ratio. Like cutting a thin slice right off the bottom. Of course that means nothing if you don't know what a head is....

I know what milling is and what you're doing. My question, again, was what are you milling away. Note the use of the term 'away' points out that I know what the process of milling is...




So I'm assuming you wish to mill away the inside of the combustion chamber on the head?

 

Re: Head Milling: No help from the search button...

Ok then, I'm taking material off the bottom of the head, straight across the bottom, like slicin bread. The point is to make the combustion chamber smaller, sort of.

 

Re: Head Milling: No help from the search button...

Gotcha.

In RC airplanes, we sometimes add an extra gasket to do the opposite.

 

Re: Head Milling: No help from the search button...

my knowledge of the process is that the busa piston is about the same size as the sv piston, so you only really need a honing of the cyl wall to do the swap. the reason for the swap is that the piston is lighter than the stock sv piston, so it revs to redline faster.

if you search for busa piston you'll find all sorts of info

 

Re: Head Milling: No help from the search button...

And reduces stress on the engine a little, too. Plus, they're easy to find, since Busa people fit big bores and turbos a lot. For most people it's sort of synonymous with a compression bump, but I think any differences are negligible (not 100% on that), it's just that once you have the heads off, it's straightforward to deck them a little so you might as well.

I've got a set in the garage, which some day I might even fit ;D But I'm undecided whether to shoot for high compression, with all that implies as far as gauging clearance etc, and possibly retarding the ignition slightly to suit... Or to just lose a single layer of gasket, save a load of effort, and keep things in a more sensible tune. Probably the latter to be honest. It's a street bike so I'm not desperately chasing power, it's just a fun project.

The K7 Busa pistons are lighter still, but do they fit? WHo knows ;D