Don Terrill’s Speed-Talk

Where is the crack?
Is the crack in the red circle?

Many good questions, I'll try to answer later.

You still there?
I don't know if I answered you question or just made more questions.
Sime feedback would be nice

The rules shift depending on what recipe you choose, there are multiple ways to go. A "longtube even fire tri-y"...... may have no need for any final collector length beyond a few inches, but still benefits from the secondaries being merged, because at high RPMS once outflow becomes contin...

ok, now clearer so 20" primary and 12 secondary. Assuming port length not included so primary may be 21 or 22" Not far from my recipe of....... secondary half primary length, and 50% area increase after each junction. IMO would work well 4500-7000 even paired. (pairing 1/4 and 2/3) If you ...

I think I misunderstood all your measurements now that I re-read it
When you use the @ symbol does that mean length of section?

What is with that huge rpm window..... three on the tree?
Tho your very short length tri-y would have a broad range of rpm, tho it would not boost performance much, at least just basic educated guess.

If you want .005" over possibly knerl std pistons an have them coated.
Of all the engines that could benefit from a .005, .008" or .010" over this would not be high on my list.
They often have more wear than that in the end cylinders from injectors going bad or excessive idling.

I agree. Usually about .020" give or take, depending on how thick the wafer is to begin with.
Never seen an official spec, but I have seen several times they can fracture in service if you grind them too thin.

I did expect smaller stems to be more popular, but smaller stems can't handle as much side load from the rockers.
That may be why it has not become common.
Rockers are still a mystery to many.

I'm not aware of anybody who would intentionally run plain SS stem valves in an iron guide.
I would expect it to try to seize.

I'm assuming you mean iron powdered metal.

powder is not a material.

Yeah, but that depends what you are working on.

Maybe you should check the seat runout relative to the guide bore before you put the new guide in.
If it was way off do you think you could make a guide to match? I bet I could. But it better be a high paying job

Ring lands aren't supposed to hit the cylinder.

The normal thrust force from rod angle should center the piston in the bore front to back, so there should be no wear in the front or rear direction (above ends of pin).
It would be a very strange problem. Check rod alignment, and side play.

OK, I think I get it now. What if the seat rides EXACTLY up to the edge of the valve, ok, that might work for awhile, but nothing is exact or stays exact. Guides have clearance, seats wear. If the sharp corner of the valve edge is hitting the seat, then either it will round off the sharp edge of the...

Also just say distance from the edge of valve. In mm or inches. I have no idea what you were talking about with the terms you were using. The centerline of the valve face? That doesen't matter. If the valve face is a mile wide, then what? Just back cut the valve and narrow that down. If your boss wa...