J-Body Automobiles Forum banner
1 - 1 of 1 Posts

11,294 Posts
How to Lap Your Valves

About This How-to
Author: scott0999
Added: 08.03.05
Updated: 08.03.05
Discuss (1)

What lapping does is makes the valves seat like new again. when the valve is closed and theres not a perfect seal you loose compression. Lapping the valves restores this. this is a great thing to do if your doing a hybrid since you will have the heads off anyways. on high mileage engines its recommended to take the valves in to be gound before lapping.


  • New valve stem seals
  • Valve lapping compound (course/fine)


  • Valve spring compressor
  • Magnet
  • Suction cup
  • Napkins

How To Do It

Step 1

With the heads off the car you first need to remove the valves. Do this only one at a time as its best for the valve to go back in its original location. Take your valve spring compressor and place it as far at the bottom of the spring as possible and compress the spring. Tthen you need to take a magnet and remove the keepers. There's 2 on each valve you do.

Gas Machine Metal Audio equipment Engineering

Step 2

Once the keepers are out put them somewhere you wont loose them! now you can lift the valve spring up and uncompress the spring. On the top of the spring is the retainer.

Now all you should see left is the valve stem seal. you need to get a gripping pliers and pull out the seal. You have to pull somewhat hard to get them out. once its out throw the old one away. If you see oil once the seal is off clean it up.

Step 3

You're now ready to get the valve lapping compound. You need to start with the coarse grit first. Put a little on your finger and go all the way around the valve as shown in the pic.

Cup Font Wood Drink Table

Musical instrument Wood Flooring Audio equipment Metal

Step 4

Take the valve with the lapping compound on it and put it back in the head. Now take a small suction cup and put it on the valve and turn it side to side. this is lapping the valve. You will hear a grinding noise at first which means its working! Keep doing this until the noise quiets down. Then take out the valve and clean the lapping compound off it and also in the head. Then take your fine lapping compound and do the same thing with it until its quiet. Clean off the valve and inside the heads again.

Finger Wood Nail Thumb Close-up

Step 5

When your all done lapping and everythings clean put the valve back in and set the head down flat. The valve stem seals you got should have came with a small piece of straw. Put this on the top of the valve stem as shown

Wood Eyewear Gas Font Glass

Step 6

Take the valve stem seal and push it down until it looks like this. The seal wont go down all the way. This is normal. When you put your springs back on it will push the seal down automatically so dont even worry about it.

With the seal pushed down take the straw out. then take your valve spring and place the retainer on the top of it.

Fluid Wood Gas Musical instrument Font

Wood Font Natural material Close-up Auto part

Step 7

Now compress the spring and place it on the valve stem seal. Get the 2 keepers and put them back in. You may want to get some white grease to put on the inside of the keepers to help them stick on. If your having trouble getting the keepers in place try compressing the spring more.

Once everythings in place take the spring compressor and lift it up until the retainer moves up to where the keepers are. Then uncompress the spring as shown.

Automotive fuel system Gas Motor vehicle Auto part Household hardware

Step 8

Your all done with this valve!!!! Repeat the same steps for the rest of the valves. Try to spend more time on the exhaust valves when your lapping because they need it more than the intake valves do.

Sink Gas Household hardware Auto part Engineering

How-to Home
1 - 1 of 1 Posts