New seats, with new valves should require no lapping to get a good seal - my machinist refuses to lap in the first place, considering it to be a half-baked solution.

Do I have to lap my valves?

Although some seats may need two or three times of lapping, it is not necessary or good to over-lap the valves. It is unlikely, but possible, to remove too much, and doing so will ruin the valve seat. If you are unable to achieve a consistent grey ring, the seats are probably worn out and will require cutting.

Why is valve lapping done?

The disc and nozzle relief valve that has been checked if it looks scratched or the surface of the seat is not flat then the seat or nozzle must be turned first, to smooth the results of the lathe then we do lapping.

Do you need to lap new valves in a new head?

there is no NEED to lap a new set of valves in a new head.... the head will have the seats cut for the new valves....

How long should you lap a valve?

The lapping process for each valve should take less than a minute if the valve seat and face were ground correctly.

How-To: Lap Valves (by hand and drill method explained)

24 related questions found

Can you lap pitted valves?

Any time you change the seats, re-grind the valves or put new valves into an existing seat, it's a good idea to lap them in and make sure they are seated. ... Since valve lapping paste is a highly abrasive pumice, there is a right way, and a wrong way, to do it.

How do I know if my valves are seating?

So to test the seat, take a new valve–or one that you are certain is good–install it in the guide, give it a good push and see if it bounces back off the seat. A bad seat tends to damp the action, so the valve will feel like it sticks in the seat.

How do you know if you need a valve job?

A valve job is simply a re-cutting or "re-facing" of the valve seats, and sometimes the valves. Valve jobs are necessary when the seats are worn to the point that there is no longer a proper seal between the seat and the valve. By re-facing the seats and/or valves, the proper seal is re-established.

Why is valve grinding important?

A valve grind (commonly referred to as a valve job or valve lap) can be crucial for proper functioning valves/seals. It is the process of smoothing out the engine valves so that they are effectively able to seal in the valve seat in the cylinder head to completely seal the engine's combustion chamber.

How much does it cost to get valves lapped?

Therefore, a total valve job can cost upward of $1000. Know what price you should pay to get your vehicle fixed. The average cost for a valve adjustment is between $246 and $336. Labor costs are estimated between $220 and $278 while parts are priced between $26 and $58.

What can I use for lapping compound?

A diamond compound makes the best slurry because diamond is the strongest and hardest material on earth. As such, it can produce the desired close tolerances and precision finish. Lapping compound can also come from aluminum oxide and silicon carbide, but they are not as efficient as the diamond version.

Is valve grinding compound the same as lapping compound?

Those are just 2 different words for the same thing.

Are hardened valve seats necessary?

Original engines in cars built before the early 1970s generally don't have hardened exhaust seats that are resistant to unleaded gas. ... In other words, if you don't do a lot of towing, don't have really steep gears, and/or don't frequently run your car at the track, you should be good to go.

Can you grind valve seats?

Grinding valve seats with abrasive stones has been aound about as long as the internal combustion engine. ... The variety of materials also means new and different abrasives are required for proper machining. The first step in grinding seats is to know what you are grinding so you can select the proper abrasive.

How do I know if my valve seat is hardened?

A lot of times it is very difficult to see them once a head has been run. What you are seeing is probably just a machinig mark from when the valve seats were cut at the factory. I would look at the date code on the heads. If they are 1973 or newer, they should have hardened seats.

Can you grind valves?

Generally valves should be ground , or 'lapped', into their respective seats to ensure a gas-tight seal . Grind-in each valve (including new valves) by hand, using a valve-grinding tool and valve-grinding paste. ... Grind the valve in its seat by rotating the grinding tool back and forth between the palms.