Piston to valve clearance
Thread Starter
Teching In
Joined: Feb 2007
Posts: 32
Likes: 0
From: Cape Town
Piston to valve clearance I have come up with this method for checking piston to valve clearance without stripping the engine, anybody think its ok or stupid? (I havnt tried it yet)
remove the rocker cover and install a dial gauge on #1 intake valve. Fit a degree wheel to the engine, and record the valve drop at several intervals 30 degrees either side of TDC, repeat this with the exhaust valve.(obviously not on the compression stroke)
put the engine back at TDC (compression stroke this time) and remove the valve springs from both valves on cylinder #1. let the valves drop onto the piston
turn the engine over again 30 or so degrees before and after TDC. Using a dial gage measure how much the valves have dropped from their seat every few degrees. now you can compare the 2 sets of figures and it will tell you what the piston to valve clearance is for the stock cam.
Now, using the rocker ratio, and some guesswork, you will have an idea what size cam you can fit before you have problems. Also once you have fitted the cam, you can check what clearance you actually have.
remove the rocker cover and install a dial gauge on #1 intake valve. Fit a degree wheel to the engine, and record the valve drop at several intervals 30 degrees either side of TDC, repeat this with the exhaust valve.(obviously not on the compression stroke)
put the engine back at TDC (compression stroke this time) and remove the valve springs from both valves on cylinder #1. let the valves drop onto the piston
turn the engine over again 30 or so degrees before and after TDC. Using a dial gage measure how much the valves have dropped from their seat every few degrees. now you can compare the 2 sets of figures and it will tell you what the piston to valve clearance is for the stock cam.
Now, using the rocker ratio, and some guesswork, you will have an idea what size cam you can fit before you have problems. Also once you have fitted the cam, you can check what clearance you actually have.
I find it easiest to just install a pair of "test" valve springs with ounces, not pounds of pressure, and valves adjusted to zero. Then, much like your method, with dial indicator on the retainer, bar the engine over, starting about 15 deg. BTDC. Depress the valve with your finger or whatever, and record the clearance. Then repeat every couple degrees though 15 deg. ATDC, or until you're comfortable that the clearance is out of the woods.
Scotty
Scotty
TECH Resident
Joined: Aug 2004
Posts: 875
Likes: 2
From: Portland Oregon
"I find it easiest to just install a pair of "test" valve springs with ounces, not pounds of pressure, and valves adjusted to zero. Then, much like your method, with dial indicator on the retainer, bar the engine over, starting about 15 deg. BTDC. Depress the valve with your finger or whatever, and record the clearance. Then repeat every couple degrees though 15 deg. ATDC, or until you're comfortable that the clearance is out of the woods."
Perfect Scotty.. That's how I do it, in the car or with a new motor on the engine stand.
Perfect Scotty.. That's how I do it, in the car or with a new motor on the engine stand.
