Base gasket thickness

[gsx1100e]

My GSX cylinder block is rather low so pistons hit the head if I use original base gasket. I have Wiseco 1134cc 10.25:1 pistons.
Is there an easy way to measure thicknes to base gasket?
Block is not on engine now and I?m not too enthusiastic to install it back on without any base gasket, measure height between piston and block, take block of, install new thick gasket, and block back on.

 

[Dink]

Vernier calipers will do, you need to take the measurement at about 2/3rds thickness to allpw for compression, you can always stack a few gaskets on top of each other to build it up to the level it needs.
Dink

 

[gsx1100e]

Yes, but can I measure that height whitout installing that cylinderblock?
2/3 for compression was good information I will remember it if I dont use copper gasktet, thanks.

 

[Dink]

Yes, but can I measure that height whitout installing that cylinderblock?
2/3 for compression was good information I will remember it if I dont use copper gasktet, thanks.

Yes if you take the measurement at 2/3rds of what it is to allow for it being compressed you dont need to install the block to measude them.
Dink

 

[Paul]

Put the block back on without any piston rings, gaskets etc.
Then rotate engine so that pistons are at TDC, measure how much they are protuding from block.
Using this measurement, you can work out how many base gaskets you will need, using Dinks 2/3rds gasket thickness.

 

[gsx1100e]

...of course without piston rings, it will make things almost easy.
I was remembering last time I installed that block and those broken fingertips and for some reason removing piston rings was not the first thing in my mind. Hopefully I dont break any of those rings, thanks

 

[cbxchris]

Paul is correct in his way of measuring. The only differnce is I like to put on the top ring only to make sure the piston centers itself but I have done it both ways with good results. You want a minimum of 35 thousandths...42 is better.

 

[gsx1100e]

...35 thousandths...42 is better. you probably mean thousandths of inch? Just to make sure that I dont make that same mistake that NASA did few years ago.
Is that 35-42 thousandths from block down to piston or between head and piston?

 

[cbxchris]

When you get your pistons completely flush with the top of the cylinder at TDC (you have shimmed using the correct base gasket thickness). You should use a head gasket no less than 35 thousandths thick. Most stock head gaskets are somewhere between 35 to 42 thousandths thick. That leaves you that much clearance for rod stretch. If using copper 42 is a common thickness. On a plain bearing engine like a GSXR or hayabusa you can get by with 35. A roller bearing crank has a little more movement and 35 is not enough sometimes....42 is better. The closer you get that piston to the top of the cylinder the better your bike will run. The cylinder walls are not the combustion chamber and hurt performance. I have run mine down 5 thousandths in the bore when being totally safe but no more than that. If you for some reason were using aluminum rods you would need around 60 to 75 thousandths due to rod stretch. Hope this helps. Also when you shim that base gasket you are affecting the cam timing and will need to degree your camshafts for good performance.Normally if you don`t degree you will retard the cams.

 

[cbxchris]

When you get your pistons completely flush with the top of the cylinder at TDC (you have shimmed using the correct base gasket thickness). You should use a head gasket no less than 35 thousandths thick. Most stock head gaskets are somewhere between 35 to 42 thousandths thick. That leaves you that much clearance for rod stretch. If using copper 42 is a common thickness. On a plain bearing engine like a GSXR or hayabusa you can get by with 35. A roller bearing crank has a little more movement and 35 is not enough sometimes....42 is better. The closer you get that piston to the top of the cylinder the better your bike will run. The cylinder walls are not the combustion chamber and hurt performance. I have run mine down 5 thousandths in the bore when being totally safe but no more than that. If you for some reason were using aluminum rods you would need around 60 to 75 thousandths due to rod stretch. Hope this helps. Also when you shim that base gasket you are affecting the cam timing and will need to degree your camshafts for good performance.Normally if you don`t degree you will retard the cams.

 

[cbxchris]

sorry for the double post...

 

[Anonymous]

This is really interesting stuff. It's not something I could afford to learn through trial and error. Too bad my 400's cam sprockets have dowels holding them in place plus the two bolts in non-slotted holes.

Steve