The next step is to measure exactly how much clearance
you have between the piston and valve - a function which
takes into consideration your camshaft specs and rocker
arm ratio. This can be done with clay, or with a pair
of lightweight checking springs in place of an intake
and exhaust valvespring as we prefer. Temporarily bolt
the head to the block, there is no need to torque it down
for this check. Use an old headgasket to simulate the
actual spacing conditions.
Ideal piston to valve clearance is minimally .100"
on the intake side and .080" on the exhaust side.
We only had .40" on the intake side. It's important
that you should measure for this clearance at both top-dead
center (valves closed) as well as when the valves are
open during the overlap phase of the cam - since this
is actually when the valve is hanging open and the piston
is approaching the top of the stroke. Learn
more on checking piston to valve clearance.
Once you have determined your clearance, or lack therof,
it's time to mitigate. Big valves are no problem when
you have the Isky
cutting tool. Isky rents the tool for a deposit. Order
it in the valve guide diameter and valve head diameter
you need. Shows is a 2.02" tool.
The tool installs in place of a valve. The valve head
and stem snap together and are installed as shown. IF
you need to cut your exhaust side make sure you order
an exhaust notcher. We're just about ready to make the
cut. More
Bring the piston you are working on to top-dead-center.
Bolt the head back on the block with the tool installed
The supplied collar acts as a stop so you don't cut through
the piston. We set the collar .070" above the top
of the valve guide. With the .040" clearance we already
had plus the .070" we'll cut into the piston we'll
achieve .110", right at the desired saftey margin.
Be sure to use a head gasket when cutting as this accounts
for .040" of your real clearance.
We spun the tool using a standard electric drill. Start
off slow, you'll hear and feel the tool cutting. Watch
the gap between the collar and the top of the guide and
stop cutting when the collar bottoms out. You'll hear
a change in the sound as well once the cutter hit's the
collar stop and is no longer contacting the piston and
cutting.
Pull the head off and check your work. Do not turn the
crank until you've verified the cut to be accurate and
have cleaned out the shavings.
The freshly cut valve relief looks as good as any machine
shop could achieve.
We used a shop vac to clean up the shavings before moving
on to cutting the next piston.
Turn the crankshaft as shown until the next piston in
line is at top-dead center. Because the cutting tool head
is significantly thicker than a standard valve you may
need to bring the piston some distance below deck to allow
the head to bolt on. Just be sure to cut each piston at
the same position in the bore or your valve relief depth
and locations will vary!
We used a set of calipers with a depth gauge to ensure
the pistons were at the same location below the deck surface
prior to installing the head and making the cut.
The first couple of pistons take the longest as you get
the hang of things. After that you'll buzz through the
others in under an hour. We installed the head and rechecked
piston to valve clearance to confirm we had gained over
0.100".
The next step is to measure exactly how much clearance
you have between the piston and valve - a function which
takes into consideration your camshaft specs and rocker
arm ratio. This can be done with clay, or with a pair
of lightweight checking springs in place of an intake
and exhaust valvespring as we prefer. Temporarily bolt
the head to the block, there is no need to torque it down
for this check. Use an old headgasket to simulate the
actual spacing conditions.
Ideal piston to valve clearance is minimally .100"
on the intake side and .080" on the exhaust side.
We only had .40" on the intake side. It's important
that you should measure for this clearance at both top-dead
center (valves closed) as well as when the valves are
open during the overlap phase of the cam - since this
is actually when the valve is hanging open and the piston
is approaching the top of the stroke. 
Once you have determined your clearance, or lack therof,
it's time to mitigate. Big valves are no problem when
you have the 
The tool installs in place of a valve. The valve head
and stem snap together and are installed as shown. IF
you need to cut your exhaust side make sure you order
an exhaust notcher. We're just about ready to make the
cut. 
Bring the piston you are working on to top-dead-center.
Bolt the head back on the block with the tool installed
The supplied collar acts as a stop so you don't cut through
the piston. We set the collar .070" above the top
of the valve guide. With the .040" clearance we already
had plus the .070" we'll cut into the piston we'll
achieve .110", right at the desired saftey margin.
Be sure to use a head gasket when cutting as this accounts
for .040" of your real clearance.
We spun the tool using a standard electric drill. Start
off slow, you'll hear and feel the tool cutting. Watch
the gap between the collar and the top of the guide and
stop cutting when the collar bottoms out. You'll hear
a change in the sound as well once the cutter hit's the
collar stop and is no longer contacting the piston and
cutting.
Pull the head off and check your work. Do not turn the
crank until you've verified the cut to be accurate and
have cleaned out the shavings.
The freshly cut valve relief looks as good as any machine
shop could achieve.
We used a shop vac to clean up the shavings before moving
on to cutting the next piston.
Turn the crankshaft as shown until the next piston in
line is at top-dead center. Because the cutting tool head
is significantly thicker than a standard valve you may
need to bring the piston some distance below deck to allow
the head to bolt on. Just be sure to cut each piston at
the same position in the bore or your valve relief depth
and locations will vary!
We used a set of calipers with a depth gauge to ensure
the pistons were at the same location below the deck surface
prior to installing the head and making the cut.
The first couple of pistons take the longest as you get
the hang of things. After that you'll buzz through the
others in under an hour. We installed the head and rechecked
piston to valve clearance to confirm we had gained over
0.100".