from what I know you can use clay. you'd have to put some oil onto the valve and the piston so it doesn't stick. use a very small amount just where you would think it'll squish the clay the most. obviously you'd have to have the heads off and then put the clay down and install the heads. turn the engine to get past TDC and then pull the clay piece and out and measure the thickness.
ive seen tootsi rolls used. leave it in the wax paper and just set in the valve relief. the wax paper keeps it from sticking and you have a treat to eat when done.
To check V/P clearance with clay...you need to use a solid lifter and push rod on 2 valves of the same cyl(one intake one exhaust)Hydraulics will deflect and your reading will be inaccurate.Also you need to use the proper head gasket(the ones you will be useing when you assemble the engine)Place a 1 1/2 inch square of clay approximately 3/8" thick over each valve relief.Install head and torque to spec.Install pushrods/rockers on valves to be opened.Adjust rocker to remove lash only(do not over tighten till valve opens) Slowly turn engine through 4 revolutions.Pull head... Cut clay impression in half vertically(so you have a cross section to measure) Measure depth of impression in clay left by valve.Now remove clay from piston and discard.Compare measurement to allowable tolerance and you will have your answer.Minimum clearance is "usually".80 for intake valve and .100 for exhaust.Good luck!!!!
Thanks, guys. Good info. I was hoping for some answer that didn't require assembly/disassembly/assembly of the heads and valve train. Looks like an opportunity for some clever tool maker to make something that could be inserted in the spark plug hole.
You can do it without touching the engine but...It requires you to know the many mathematical variables necessary to do the math and figure it out.Such as piston compression height...engine deck height...how far below the deck the piston is at TDC.. and things of that nature...
(Got the following email notification but don't see this post in the thread. Here is the message that has just been posted: *************** I use to use a couple of light springs from the hardware store in place of the valve spring and a dial indicator. Killed 2 birds with one stone using the degree wheel to double check the cam and checked clearance at the same time. The light springs allow you to push the valve down to contact the piston at max valve lift. The clay is easier if the heads are assembled already. *************** I was thinking along that line but wondered if minimum clearance occurs at max valve lift or at TDC? Or somewhere between those degrees? Guess it would be easy enough to check points around max valve lift and TDC.
Max lift isnt really the issue... its the timing events.For the intake valve...as the piston approaches TDC on the compression stroke.The piston basically chases the intake valve to its seat.The two get close around 30deg BTDC.As for the exhaust valve.The valve chases the piston down the bore.They get close starting about 15 deg of crank rotation ATC on the beginning of the intake stroke(this is the area of "valve overlap") where both valves are off their seats to aid scavenging of the exhaust and help to pull in the fresh intake charge.
The valves are usually the closest during "split Overlap". This is on the end of the Exhaust stroke and the beginning of the intake stroke. As stated before use some light springs and a solid lifter with a dial indicator. Roll the motor Thur till you get about 30 degrees before the ex closes then start checking ever 5 degrees crank rotation. Normally on most cams i have checked it will be the closest at around 15 degrees before till 15 degrees after TDC. It is very easy to check just at ever 5 degrees push down on the rocker and note dial indicator reading. When you touch the piston note reading. This will be how much clearance you have. Intake should have a minimum of 80 thousands and ex should have 100 thousands min. If you load the lifter more than 1 turn then you will need more unless you are sure you will NEVER float the valves. I have ran tighter clearances than this but you must be very careful as valve float can cause problems. These measurements is assuming you are using steel rods and not aluminum.
Thanks for the great answers. When I have my cam I want to measure with my stock E7 rockers, where I don't expect any problems, but then I'll know if I have clearance enough to install 1.7 rockers. There's another thread here that states the increase in lift from 1.7 rockers. Appreciate the help. Jim
