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I'm building a ls/vtec 84 mm 12.5.1 wiseco piston. I'm not running over size valve. Will I be ok with piston to valve clearance. If not what is the best and easy way to check it.
If you don't know how to do it personally I would have a professional do it. Last thing you want to do is experiment for your first time on an expensive build. Also this is very dependant on what cams you run as well.
You put clay on your piston 2 colors 1 exhaust 1 intake. Put your head on (using an old hg helps) Spin engine over 1x revolution cut clay in half where valves and valve reliefs are and measure your clearance.
There is no way to explain how to do this process correctly in 2 sentences. Seriously, get someone who knows how to do it RIGHT and has done it BEFORE so there are no discrepencies.
there are write ups all over the web, including honda tech. honestly its not very difficult and if you feel confident in your ability to follow instructions and have half a brain you will be fine. like mentioned the largest factor is the cam lift and timing. also, you will need to engage VTEC using some sort of manual method since it uses the large lobe profile.
that being said if you want to know how far you can adjust the cam gear timing without interference issues, which is pretty much the purpose of this check, to determine what range you have to play with, then you will need to be very meticulous in your measurement and calculations. It's a time consuming process.
The easiest and most accurate way to check this is to place strips of modeling clay on top of one piston, and then rotate the engine over by hand with the cylinder head bolted in place and all of the valve train components adjusted. If there is any resistance during rotation of the crankshaft, STOP! The piston has probably hit the valve. Then you must decide whether to fly cut the piston, or exchange the cam for a profile that will fit into your engine. Note: Minimum piston to valve clearance is .080” on the intake and .100” on the exhaust valves. If aluminum connecting rods are being used, add a minimum of .030” to these suggested clearance figures. Aluminum rods will stretch and expand more than steel rods.
Note: Be sure to check piston to valve clearance after the cam has been degreed. The positioning of the cam in the engine will greatly affect the piston to valve clearance.
With the camshaft installed, remove the cylinder head from the block. Clean the combustion chamber and the top of the piston and valve reliefs. The cleaner the piston, the better the clay will stick to it.
Apply a strip of model clay 3/8” to ½” wide approximately ¼” thick to the pistons. The clay strip should be long enough to run across both the intake and exhaust valve reliefs. Applying a small amount of oil to the clay will prevent it from sticking to the valves as they press into it.
Reinstall the cylinder head with the head gasket that is going to be used. It will not be necessary to torque the head yet. All head gasket manufacturers can tell you what the compressed thickness of their gasket will be. Measure the gasket before you install it permanently and add the difference to the piston to valve clearance. Install a sufficient number of head bolts to secure the head in place while you are rotating the engine. Install the pushrods, lifters and rocker arms on the cylinder you have prepared for the clearance check.
Adjust the rocker arms to their suggested clearance. If the camshaft you are checking uses hydraulic lifters, you must temporarily use solid lifters in their place. Hydraulic lifters bleed down and will provide a false measurement. Once the hydraulic lifters are replaced with solid lifters, adjust the lash to “zero.” Be sure not to pre-load the valve spring. Be sure to reinstall the hydraulic lifters before starting the engine.
Now turn the engine over by hand in the normal direction of rotation. Be sure to rotate the engine over two times. This will be one complete revolution of the camshaft and assure you of an accurate reading on both the intake and exhaust.* Remove the cylinder head from the block.* Do this gently, so the clay is not disturbed.* It may be stuck to the valves or combustion chamber, so be careful.
With a razor or sharp knife, slice the clay cleanly -lengthwise through the depression, and peel half of it off the piston.* The clay’s thickness in the thinnest area will represent the minimum piston to valve clearance.
To accurately check the thickness, use a set of dial calipers.* The clay can also be measured close enough with a thin steel rule.
For a pushrod but same idea... Now go clay your motor locked in vtec tell us what the dimensions are and we tell you if you are going to have problems
^^ I remember a long time ago checking the squish on my Yamaha Superjet heads that had been milled. I used solder down the spark plug hole till it butted against the cylinder. Then slowly cranked it over and measured the squished solder. I wouldn't try this method for p2v though. Now I have the tools to measure, so I just measure everything as I'm setting the engine up.
^^ I remember a long time ago checking the squish on my Yamaha Superjet heads that had been milled. I used solder down the spark plug hole till it butted against the cylinder. Then slowly cranked it over and measured the squished solder. I wouldn't try this method for p2v though. Now I have the tools to measure, so I just measure everything as I'm setting the engine up.
Welcome h2.4. I was hoping you would stop in and share some knowledge. Ive learned a lot from your posts throughout the years, thanks!
I've used the clay/playdoh method before. Time consuming but it works.
I assume you use dummy valve springs and dial indicators now for measuring PTV? Like the Belben kit uses?
Is this still the best way? What do you torque the headbolts to when mocking up, about half torque?
I got a b18a1 with 404 brian crower stage 3 cams what is the valve to piston clearance that it needs it's got a 12-1 compression pistons it is bored 30 over so yea let me know I would appreciate It
11-29-2011, 04:58 PM
Piston to valve clearance
