valve lapping??

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jimandkathiekrise - 06 Oct 2006 00:31 GMT

I just had a valve job done on a v8.
I asked "were the valves lapped in?"

answer: no.

Is there a new school of thought on this process.

He did say that the valves were vacuum tested, and tested ok.

thoughts??

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midlant@earthlink.net - 06 Oct 2006 01:03 GMT

If the faces of the valve and the seat don't match exactly, you might
get a poor seal after they expand at different rates, leaving a small
sealing area. (Wish I could draw on this thing!)

Karl

> I just had a valve job done on a v8.
> I asked "were the valves lapped in?"
[quoted text clipped - 6 lines]
>
> thoughts??

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Nate Nagel - 06 Oct 2006 01:41 GMT

> I just had a valve job done on a v8.
> I asked "were the valves lapped in?"
[quoted text clipped - 6 lines]
>
> thoughts??

If they vacuum tested OK they should be fine. I think the theory is
that modern machining methods are precise enough that lapping really
doesn't accomplish anything.

nate

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Grumpy AuContraire - 06 Oct 2006 02:28 GMT

> > I just had a valve job done on a v8.
> > I asked "were the valves lapped in?"
[quoted text clipped - 12 lines]
>
> nate

I only lap valves in heads that do not really need valve grind work.
IE, if one is replacing the seals, might as well lap the valves/seats.

JT

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Freddy Badgett - 06 Oct 2006 02:38 GMT

If they passed the vacuum test,all will be fine. I'm a bit peculiar, I
hand lap lightly with fine compound to check for a perfect sealing surface.

Freddy

>>>I just had a valve job done on a v8.
>>>I asked "were the valves lapped in?"
[quoted text clipped - 17 lines]
>
> JT

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keith_kichefski@wed.dresser.com - 06 Oct 2006 14:02 GMT

Shops are getting away from hand lapping. Typically they use an
interference angle of ½° difference, which allows them to fully seat
within a few miles. If you still have the heads off the car, you can
wet-check the valves by pouring solvent in the intake and exhaust
ports. If the fluid runs out, you have an unseated valve. Some
dampness around the head of the valve after a couple of minutes is OK.

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Mike - 06 Oct 2006 17:12 GMT

Yea, the wet method is more accurate.

Using vacuum, "IF"...they actually did it is actually pulling the valve
toward the seat...plus if they don't have very accurate gages...they
won't see any leak. Using vacuum to seat the valve AND check for leaks
is cheating.
If they are listening...for a leak..use a new shop!

I normally don't bother checking the heads I have done. I'm not gonna
admit how I do it but the shop I use has never given me a bad valve
grind. I do my own assembly when I port heads, he just does the
grinding.

He uses (as noted above) a 45 degree head cut and a 46 degree valve cut
on his street stuff. On hot rod or race heads, it's 45 - 45.

Mike

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