would a shaved head just at .010 and a big cam in the 410 range cause my intake valves to just barley kiss the piston running 13.5 comp.
RAGE 522
This write up has help me out alot...
Re: Racer's Edge Performance (REP)
If you don’t mind donating a little time and being resourceful you can complete the steps necessary to know what is needed to set up your head, for your particular bike and your desired octane requirements. This is going to be more benificial then sending it to someone for a cookie cutter job on a "typical" bike.
First you’ll need to make a few measurements so that you can do the math and find out where you’re at, and eventually where you want to be. Production tolerances can leave quite a bit of untapped potential hiding in your engine especially in regards to the squish band. Taking the production tolerances out of the equation and fine tuning the squish and compression ratio(s) to suite your available fuel can make a difference.
If you choose to continue make sure to double check your measurements and once you’re confident be sure to record them.
I would first measure the squish clearance with the head on. To measure the squish clearance you need to first find yourself a roll of 0.125" diameter solder (look at an electronics store like Radio Shack). Next bend a small length of solder into and "L" shape with the leg being about as long as 1/2 the diameter of the bore. Insert the solder through the spark plug hole making sure that the end of the solder contacts the side of the cylinder bore, preferably the left or right side of the bore (as opposed to the front or rear of the bore which may give a false reading due to the piston rocking on the wrist pin). While holding the solder against the side of the bore slowly cycle the kick starter so that the piston rotates near TDC, crushes the solder and descends enough to get the solder out. Be careful to only cycle the piston once so that you don't pinch the solder multiple times which could skew measurements. Remove the solder and measure the crushed thickness. This will be your squish clearance! Accuracy does count so try to use a measuring tool that will read down to 0.001" (dial calipers).
Next I would remove the head to measure the squish band. The squish band has two physical dimensions, the height and the width. The height is the distance between the gasket surface of the head to the top of the squish band. Measure the height (actually it’s a recess) in the head and the head gasket thickness. Measuring the squish height and head gasket thickness in conjunction with your total squish measurement will help you determine what the deck clearance is (height from top of cylinder to top of piston, can be + or - or even 0). Total squish - (squish height + head gasket thickness) = deck clearance. This is only easily determined when working with flat topped pistons. Next I would measure the width of the squish band (the flat portion from the edge of combustion chamber to the opposing edge where it starts to recess into the combustion chamber). Be sure to record each measurement.
After these measurements I would then measure the volume of the head, otherwise known as "cc-ing" the head. Again, accuracy counts so being able to measure down to 0.1 cc is to your benefit. If you can beg, borrow or steal an accurate measuring device (like a burette, syringe, etc.) that will allow you to meter down to 0.1 cc and a small piece of Plexiglas with a hole in it then you can do it yourself. Yes, you will need to fully install a spark plug, turn the head upside down and seal the gasket area of the head to the Plexiglas with a small amount of grease. Use your measuring device to fill the head with the liquid of your choice (water works) until it's full and record the amount it took to fill the head.
This measurement will only be the volume of your head if you do not use a head gasket and run 0 deck clearance. If you have + or - deck clearance and/or a head gasket (and/or a domed piston!) this will have to be figured into the equation to come up with total head volume.
Since you have the head off I would take two more measurements on the cylinder. The first would be the distance between the top of the cylinder and the bottom of the exhaust valve (with the exhaust valve closed) and the second from the top of the cylinder to the top of the exhaust port (with the exhaust valve open).
Knowing your head volume along with the two exhaust port measurements you can figure your actual compression ratio and see how close you are to the manufacturers advertised compression ratio. This will also allow you to crunch numbers and figure compression ratios for different octane gas.
Re: Racer's Edge Performance (REP)
If you don’t mind donating a little time and being resourceful you can complete the steps necessary to know what is needed to set up your head, for your particular bike and your desired octane requirements. This is going to be more benificial then sending it to someone for a cookie cutter job on a "typical" bike.
First you’ll need to make a few measurements so that you can do the math and find out where you’re at, and eventually where you want to be. Production tolerances can leave quite a bit of untapped potential hiding in your engine especially in regards to the squish band. Taking the production tolerances out of the equation and fine tuning the squish and compression ratio(s) to suite your available fuel can make a difference.
If you choose to continue make sure to double check your measurements and once you’re confident be sure to record them.
I would first measure the squish clearance with the head on. To measure the squish clearance you need to first find yourself a roll of 0.125" diameter solder (look at an electronics store like Radio Shack). Next bend a small length of solder into and "L" shape with the leg being about as long as 1/2 the diameter of the bore. Insert the solder through the spark plug hole making sure that the end of the solder contacts the side of the cylinder bore, preferably the left or right side of the bore (as opposed to the front or rear of the bore which may give a false reading due to the piston rocking on the wrist pin). While holding the solder against the side of the bore slowly cycle the kick starter so that the piston rotates near TDC, crushes the solder and descends enough to get the solder out. Be careful to only cycle the piston once so that you don't pinch the solder multiple times which could skew measurements. Remove the solder and measure the crushed thickness. This will be your squish clearance! Accuracy does count so try to use a measuring tool that will read down to 0.001" (dial calipers).
Next I would remove the head to measure the squish band. The squish band has two physical dimensions, the height and the width. The height is the distance between the gasket surface of the head to the top of the squish band. Measure the height (actually it’s a recess) in the head and the head gasket thickness. Measuring the squish height and head gasket thickness in conjunction with your total squish measurement will help you determine what the deck clearance is (height from top of cylinder to top of piston, can be + or - or even 0). Total squish - (squish height + head gasket thickness) = deck clearance. This is only easily determined when working with flat topped pistons. Next I would measure the width of the squish band (the flat portion from the edge of combustion chamber to the opposing edge where it starts to recess into the combustion chamber). Be sure to record each measurement.
After these measurements I would then measure the volume of the head, otherwise known as "cc-ing" the head. Again, accuracy counts so being able to measure down to 0.1 cc is to your benefit. If you can beg, borrow or steal an accurate measuring device (like a burette, syringe, etc.) that will allow you to meter down to 0.1 cc and a small piece of Plexiglas with a hole in it then you can do it yourself. Yes, you will need to fully install a spark plug, turn the head upside down and seal the gasket area of the head to the Plexiglas with a small amount of grease. Use your measuring device to fill the head with the liquid of your choice (water works) until it's full and record the amount it took to fill the head.
This measurement will only be the volume of your head if you do not use a head gasket and run 0 deck clearance. If you have + or - deck clearance and/or a head gasket (and/or a domed piston!) this will have to be figured into the equation to come up with total head volume.
Since you have the head off I would take two more measurements on the cylinder. The first would be the distance between the top of the cylinder and the bottom of the exhaust valve (with the exhaust valve closed) and the second from the top of the cylinder to the top of the exhaust port (with the exhaust valve open).
Knowing your head volume along with the two exhaust port measurements you can figure your actual compression ratio and see how close you are to the manufacturers advertised compression ratio. This will also allow you to crunch numbers and figure compression ratios for different octane gas.
of course many factors come in to play... brand/design of piston, size of valves, valve lift 410 but at what timing? valve timing CAN certainly cause an issue, but would probably require to be at least a tooth off.... .010" off the head is barely noticeable... since a normal setup with HCIII and 13.5:1 piston would yield about .080-.070" clearance, I cant imagine an extra .010" making a huge difference... but if you couple that with a 2-layer vs 3-layer head gasket, oversized valves, worn crank bearings and wrist pin, etc.... there may be a chance of the piston touching the valves... but it would still be rare... what makes you think this is happening? visible marks? or just the noise? jmho...g
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