Don't know if this is the right place for it but didn't get any responce in the LT1 tech.

I am going to be settng up my brand new LT4 heads with brand new Manly Race Flow valves (2.00 and 1.56) and was wondering if I still need to lap the valves in?

This is all pretty much new stuff to me so can you explain valve lapping to me.

can this be done at home? how hard is it to do?

or does this have to be done professionally?

Thanks
John

 

it can't hurt, and it might help.

you can do it yourself. go to the local auto parts store. in the chemicals section they sell "lapping compound", and in the tools section, they sell valve lapping tools. easy stuff man.

have spring off valve, so you can move the valve around real easy like. take valve out and put a little lapping stuff all around the seat. stick it back in and twist the valve against the seat for a minute or so. do this to all valves. after your done, remove all the valves and WASH, WASH, WASH. to get rid of the lapping compound.

i do this even on heads fresh from a valve job. it can only help.

 

Valves should always be lapped in a new valve job, if for no other reason than to verify that the valve is concentric to the seat. After a few seconds of spinning the valve you should have a dull grey ring all the way around the valve, and a matching ring around the seat. If you have any voids in this ring, keep going!

 

Yeah.. what they said.. lap them, it's easy. You dont want them to be perfectly concentric, but you dont want to be able to SEE the runout either

 

Has anyone ever heard of indicating the seats and valves to check for runout B4 and after lapping? To use one of Phil's favorites, (not meant to be demeaning) LOL!

 

can you explain run out?

sorry still a rookie at this and I'm probably looking at it to hard

John

 

http://www.efunda.com/DesignStandard...ricalspecs.cfm might help a little to visualize

 

Along with Phil's 'graphics', we'll find out if I explain well enuf to understand.

When machining or grinding valves and valve seats, the ground/machined surfaces are intended to be concentric to the centerline of the valve stem (for the valve face), and concentric to the cenerline of the valve guide (for the valve seat. Runout is the amount, expressed in thousandths of a inch, (.00X") the surface (valve face or valve seat) deviates from true concentricity. A dial indicator is used to check for this concenricity.

The intent of my previous post was being critical of the lapping process. With the use of the dial indicator to verify the accuracy of the grinding process, we can determine whether or not any additional work is needed to achieve the desired tolerance (again expressed in thousandths) from a true concentric surface, or IOW, runout.

For instance, I achieve a maximum runout for the valve face, of .001". I also achieve a maximum runout of .001" on the mating valve seat, unless I am resurfacing gigantic BBC intake seats, of which then the tolerance is up to .002". With this machining accuracy, I find not only unnecessary, but detrimental, due to the need/time necessary to clean out any embedded grit from the two mating surfaces.

For those that can not hold 'tight' tolerances and attempt to use lapping as a crutch to true up the surfaces, (reduce runout) will find, upon rechecking runout with the indicator, that very little, if any progress has been made, in reducing the amount of runout.

If the person performing the valve job has the equipment, and the ability to use this checking equipment accurately, that person can check the progress as the surfaces are refinished, thus negating the need for lapping. I have no clue if such a device is available, that can perform 'power' lapping. LOL Why anyone would want to embed grit into a seat, is beyond me. I would have hoped that process died in the 60's. Call me meticulous if you like. Anyway, HTH

 

That's not quite why we lap .

And FWIW, you do_not_want the seat and guide (valve stem) to be concentric .

 

Hey Phil.....checking the relationship/location of the seat to the valve is easily done with a felt pen and a calipher, which the method I use. Like I alluded to, I prefer to avoid lapping at any cost. If you have some other reason for lapping, we can make that your secret.

Oh, I agree. I can satisfy the .001" runout with little difficulty. However, it's not like 'oops, I made this one perfect.' It's not that easy.

Don't really know what is considered ideal in terms of runout. Haven't tested or experimented with that. Probably, didn't feel an urgent need. I've had a BBC head that had some previous 'handiwork' put in a new seat without grinding to true the 45. Must have run out .020". Funny thing, didn't notice any discernible miss B4 disassembly. Those valve heads can be pretty flexible. Course, me, wouldn't bet the engine on how many cycles that valve would be able to take.

 

Whatchoo talkin bout willis?

Yea, it's to see where the valve is seating, but it's also to smooth out the seat by removing any chatter marks etc. I dunno what to tell ya.. dont do it if you dont want to... all the top head guys in the country do it... maybe theyre all wrong.

As far as runout, it depends on what youre machining with, but if you're using a Sunnen seat & guide machine, then it's got a tapered pilot, and you ARENT going to get it closer than the machine is capable of.

FWIW, we generally want .003" runout or so..

*shrug*

EDIT: d'oh, typo

 

Lapping is for lawnmower engins,todays cars use hardened seats,besides don"t valves get ground at around 45degrees and the seats at 44degrees(or visa versa)?,which would make lapping somewhat diffacult?.

 

LOL riiiiight

 

Phil,

Why is .003" runout desireable over a perfect valve guide to valve seat true position? Doesn't make sense to me.

Thanks

 

Of course there's no such thing as "perfect" but I do know for a fact that the closer to "0" TIR the better. Stands to reason that valve guide life would increase considerably, not to mention the reduction in valve stem loads in comparison to a valve that's constantly readjusting every time it hits the seat.

Seen quite a few valve failures from excessive runout too. Not to mention, I read an article some time ago which stated that many F1 engine builders and the like, go through great pains to achieve seat/guide concentricity of better than 0001. I'd recon their opinion is that less TIR is better too.

-Mindgame