anyone know about valve lapping?

Funanin

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#1

• Aug 8, 2005

• #1

some kid that i know that just started mechanic school is going off telling me that I need to take my brand new X303 heads apart and lap the valves so they seat right. Something about taking the retainers and springs out and putting some compound or something on the valves while they are lose, then spinning them... i dunno and I kinda think its BS so if anyone knows about this it would help

 

stang22

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#2

• Aug 8, 2005

• #2

I would imagine that if your heads are new (complete), that was already done.

Tim

 

jrichker

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#3

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• #3

It is an old school method of insuring that the valves seat & seal all the way around their diameter.

I have done it when I was trying to get away cheap, or wanted to freshen up a valve job that had been run for a while.

 

RacEoHolic330

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#4

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On new heads, the valve should already be seated. If you really want to find out for yourself, take the heads into a dark room and use a high powered flashlight and probe around the edges of the valves in the combustion chamber. Look through the ports. You should not see any light. You could also fill the combustion chambers with water and see if any trickles out within a few hours. Those are the easiest ways to check the valves without needing special tools.

 

BlackGT89

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#5

• Aug 8, 2005

• #5

I thought most of the really good heads already came with a 3-angle valve job, and I don't think one would want to disturb that...

 

Funanin

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#6

• Aug 8, 2005

• #6

thats what i was thinking... im going to just leave them be, and maybe try the light-in-dark-room idea. thanks guys.

 

HISSIN50

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#7

• Aug 8, 2005

• #7

JR is spot on. If searching old articles, Car Craft (IIRC) did an article on it about 5-10 years ago.
It seemed to fit into the category of, "I need to make a 3000 dollar drag car from J/Y parts."
Hence no machining done, etc. In that case, using lapping compound was better than nada.

 

jrichker

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#8

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It works good on my lawn mower...

 

T

Ted87GT

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#9

• Aug 8, 2005

• #9

i work in a race engine shop and we usually lap the valves on new sets of heads because most heads "out of the box" don't have a good valve job. Some companies like AFR and a few others are good. A good valve cut will have an even appearance all around the valve seat. Bad cuts are "shadowy" looking which means the cut is uneven and the seal is not that good. I mean in your situation, i wouldnt do it because the heads are already on the car and its not worth disassembling the engine just to lap the valves. They are probably ok already especially on a street car. If you ever take the engine apart again though, its probably worth the effort. It's really easy to do and the tools arent that expensive either if you have the heads disassembled already.

 

Funanin

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#10

• Aug 8, 2005

• #10

ok thats what i figured, i put them on today and built it all back up... I still need to hook up my exhaust at the headers and put my accessories back on, then i can crank it up tomorrow and break in my new cam. wish me luck.

 

thumper460

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#11

• Aug 9, 2005

• #11

Lapping the valve is a way to insure the valve job is good!! New heads mostly use the carbide cutters to cut the seat, and they are pretty much right on.. the reason to Lap the valves to day is to see there the seat is hitting on the valve and then allow for the correct back cut or flow cut on the valve!! YES.. the aftermarket heads today all have a 3 angle cut on the seats.. IF you are installing a valve in a head.. with out the bennifit of the machine.. laping the valve will allow a better seal than not.. but it is pretty much a thing of the pass.. or a training tool for beginners.. cool??

Just me...........................

Thumper