My understanding is Type 4 valve clearance is 0.006" for all stock engines except stock 2.0 exhaust valves. This is for the greater expansion of the sodium filled valves the factory installed.

I've seen the same recommendation for rebuilt engines with stainless steel valves for exhaust and intake. If stainless steel valves are used on the exhaust, shouldn't lash be set to 0.006"? If the 0.008" is recommended to ensure valve closure, shouldn't the intake be set to 0.008" too?

I'm not sure this matters, but my setup has custom cut Al pushrods with 1.7 rockers/swivel foot tappets.

Thermal coefficient of expansion is very similar between steel and stainless steel. Sodium filled or not is just a distraction.

Exhaust valves run more clearance because they run hotter than intake and therefore expand more.


Simple as that.

Then I guess 1.8's run same clearance on both sides because they're just cooler cars overall? That's what I thought:)

Was trying to keep it simple.

Smaller valves less exposure in combustion chamber, less flow, less heat produced overall with 1.7 & 1.8 vs 2.0l that was a significant power bump. Solid stems vs hollow sodium stems = more stress on 2.0l sodium valve stems that would be more prone to stretch. Sodium valves did move more heat up into the valve stem. Therefore, more thermal expansion in the stem of a sodium valve.

Running a little extra clearance on exhaust gives some margin for error to avoid burning an exhaust valve, etc.

Run what your builder recommends.

I challenge your use of the word 'significant'! maybe if measured as a percentage change I could agree. But as an empirical figure, I dunno man, we're all living in toy car numbers lol...
Ok now I'm done trolling a perfectly legit thread.

You troll? all in good fun

1.7 - 79 hp
1.8 - 84 hp
2.0 - 99 hp

So you’re right about the relative percentages being significant.

Yes toy # in modern world but what everyone forgets is that bumping HP on air cooled motors is harder because it’s so hard to get rid of the extra heat. Ultimately that limitation (and emissions) of air cooling is what forced Porsche to water cooling.

Now I’m on my usual tangent - I really was trying to keep it simple

You adjust till you get frustrated trying to hold the feeler gauge, screwdriver, & box wrench. Then you call it good.

I agree with that.

Since you state Al aluminum push rods, the coefficient of expansion is the same for a stock engine so the same valve clearance.
If your swivel feet adjusters were actuated by custom cut chrome molly push rods than the lash would be zero as they would have the same coefficient of expansion as the stainless steel valves.