Checking Valve/Piston Clearance on stroker without Removing Head.

[AntParker]

Hi Guys,

Got my M20 Stroker up and running, now want to dial in some cam timing, so have added a nuke Vernier pulley (Annoyingly this wasn't on from the start) Got a Shrick 288 Cam, with Mahle Custom Pistons, 11:1 Comp, With the Vernier adjusted all the way and turning over by hand there is no interference, but I'm keen to check that there is a sensible amount of clearance (I'm under the impression 1mm is ideal)

Don't really want to pull the head and use Clay as motor is in the car and up and running etc.

Does anyone have experience or advice on the best/ easiest way to check on an M20, I'm hoping to get a bore scope in there, but not sure how much visibility there would be when at TBC, and ideally would like to measure it rather than 'Have a look'

Im thinking building/ making something to push the valve down and measuring with a dial gauge?


Never Stop Driving :)

[TobyB]

You might be able to place some play dough or similar, using the camera for guidance, and roll the engine over, and see what the result is.

But typically, once the springs are on and the head torqued, you've already done a cam timing sweep to make sure it's all OK for clearance.

I didn't- once. It was an engine that I just 'freshened up' and I figured, 'ah, it's all pretty much the same, it'll be ok.'
Well, with a cam with steeper ramps... it wasn't.

t

[digger]

i setup a lever to push down on the end part of the rocker and see how much it moves before the valve hits the piston. if needed you can bolt something on the pivot on using the valve cover studs

[mzollo]

you can replace the valve spring with a soft spring (toilet paper expander spring 2$) setup a dial indicator on the valve seat and rotate the motor to TDC and take measurements of much total travel you get. take a measurement of how much lift in inches you have with just the cam, then go past full lift until you feel the valve contact and subtract the difference. rinse and repeat for intake and exhaust side

[digger]

IMO easiest way is the push down the end of rocker, you just need a bit of mechanical advantage to push and a bar bolted to the valve cover rail using the studs to react against. it works easily have done it myself. you can also use a dial indciator to quantify but its not 100% necceasry as you will be able to see how much it moves and if its 1mm or more GTG



i did think about using the eccentric to open the valve and as you only need to makes sure you have a mm and there may be enough range. Obviously care would need to be taken to not force it. ive never checked this would work

[TobyB]

I'm ham- fisted enough that I'd be afraid I'd use too much force and bend the valve.
At least, the first time I tried it. But valves are tough, and if you have a good sense feel,
why not?

t

[AntParker]

Thanks for the help guys - i ended up pushing the valve down and putting a 1.5mm shim between the valve stem and follower, this allowed me to check the entire range of motion for both piston and valve.
Clearance was there but annoyingly the cam timing wasn't where I'm loosing power, this is still to be found !