A contention that I would agree with, as long as the runout is less than the guide/stem clearance, guide 'abuse' would not become a issue.

 

On the Spintron it's shown that having some runout as opposed to none is better.. it keeps the valve from bouncing off the seat by allowing it to effectively 'lay down' around it's circumference.

 

Sorta like using the bending spring rate of the valve stem as a deceleration means. I'll buy it, but man that way out there.

 

• .001" TIR....up to 7000 rpm.
• .002" TIR....up to 8000 rpm
• .003" TIR....up to 9000 rpm
• .004" TIR....9000 rpm and above

And just on what do I base this on? Nothing!
Just a guess. It's not even an educated guess.

 

Hate to be a horses (I) but I'm not buying that one. You run that much TIR and you're gonna end up with a broken valve.
The way I understand it... the valve transfers heat through the seat. The better it seats the better it dissipates heat. The hotter metal is, the weaker it is.
The only way I see to control the valve bounce is to run the right spring and use a cam with a good closing ramp profile. Just my opinion FWIW.

-Mindgame

 

*shrug* you dont hafta buy it if you dont wanna . It's what valvetrain development guys (one personal buddy who helps with heads runs a spintron for Evernham day in & day out, so i'm pretty lucky to have access to some killer info) have seen in their money is no object research on a spintron, and what they teach down at the school of automotive machinists. You want some runout.. and usually it doesnt matter.. b/c tolerances as tight as youre talkin arent within the ability of most seat & guide machines anyway.. so yay, it's likely taken care of w/o even trying... , so it's kinda a moot point methinks .

Way out there? nawww.. the stuff i cant repeat.. it's way the hell out there

Doesnt matter.. cut your valvejob how you want. The original question was whether or not to lap, and every pro-shop will tell you "do it every damned time."

 

Phil, don't say every. By definiton, pro means getting paid for a service. Doesn't mean they have all the answers. If they did, their methods and procedures would not change or be modified as time goes by. And yes, you made it clear, "cut your valvejob how you want", it's just to me, it defies logical common sense. But, as long as someone will pay for that service, also, like you stated, doesn't matter.

 

Well sorry bout that...

Howsabout.. every winston cup cylinder head shop I know ppl at(evernham, dei, hendrick etc,), Judson Massengill (SAM), Greg Good (jesus with a grinder), cyl head shop @ my old employers run by a gentleman who defected from Dart, & other shops i'd say were "professional" because theyve got competitive engines in circletrack/drag/road/etc. series.

*shrug* Doesnt matter, lap em, dont lap em.. it'll hammer itself out in short order anyway