Valve travel variances. Is this normal

[Stapes]

I'm in the process of checking V to P clearance on my 200 head to determine whether if I need a stock head gasket or the oversize one. The short block was skimmed but don't know how much and the head measures 4.925".

Out of curiosity I measured how much each valve travels past the bottom of the head into the cylinder by drawing each valve's profile into a piece of hard wood. I noticed a few things:

1. Intake valves would travel longer than Exhaust valves
2. Travel range was very inconsistent.

On this last one, intake valves would travel anywhere from 0.327" to 0.356" (0.029" min to max range) past the bottom of the head while the exhaust valves would do 0.278" to 0.321" (0.043" min to max range).



Measurements were taken with a micrometer and there is the issue of how accurate where my pencil marks and whether if the camshaft loft was at its highest point.

I also think some of this variations are introduced by wear on the valve stem.

I recognize that the variances are nothing more than 1.09 mm and this is probably very OCD but since I'm a newbie I thought of asking for feedback on this. Plus, I've already spent some much time and money on the rebuild that I would hate it if I have to go back and redo the head.

Thanks for your thoughts.

[redlightpete]

This measurement would only be useful for determining piston to valve clearance if you know where the piston is in the bore at the valve lift you are measuring. Then you also need to know what combination of valve lift and piston position creates the least clearance.

That's why clearance is generally checked by putting clay or solder on the piston, correctly timing the cam, and turning over the motor.

Your variation is probably coming from your 'measurement system', the unknown cam angle, and worn valve guides allowing the valves to tilt.

[E30SPDFRK]

Also the valve clearance between the rocker

[digger]

Normally a good machine shop would cut the seats with respect to the semi-finished head face so each of the inlet valves are the same distance from the face and each of the exhaust valves are the same as each other, otherwise some valves could be more sunken than others.

What was the machine work done?

If the head was warped a lot more material gets removed from some parts compared to others if the head isn’t straightened as best as possible first.

What pistons are you using and what camshaft?

[Stapes]

Normally a good machine shop would cut the seats with respect to the semi-finished head face so each of the inlet valves are the same distance from the face and each of the exhaust valves are the same as each other, otherwise some valves could be more sunken than others.

What was the machine work done?

If the head was warped a lot more material gets removed from some parts compared to others if the head isn’t straightened as best as possible first.

What pistons are you using and what camshaft?

Since this was a 200 head I wanted to do just basic work on the head, new springs, seals, skimming, and valve seating. The machine shop is pretty involved with Pro3 cars so I trusted them. The head was pretty straight thus not a lot of material was removed. The dimples on its face are still there.

I'm also keeping the stock pistons (M20B27). Here's a picture of Cylinder 1 with the piston at TDC. The #6 mark its just an identifier. I measured all pistons and assigned them to a cylinder to keep the piston to cylinder gap within spec.

Just noticed that the mark on each piston would allow the intake valve to travel further, so the longer travel I measured on the intake valves makes sense.

[digger]

It's probably just a measurement error due to the technique not being that accurate