Carbon build up on the valves

[Paul G]

How can the carbon build up on the back side of the valves be removed?

[randy73]

depends, are you planning to take the valves out of the head, then if so you can clean it off with a mild abraisive like scotchbrite.

If you keeping the valves in, then hot tank the heads.

Else get a valve clamp and open the valves and clean them that way.

[Paul G]

Dont plan on doing any more work to this engine. It is a good running little small block. Is there any type of additive that will clean them up?

[74Rallye]

Seafoam spray added through the carb. Old school method used ATF.

Get the engine hot.
Spray a can in with the engine running, then turn it off and let it cool down at least 2 hours. You may need someone on the throttle to keep it running while adding the Seafoam.
Run the snot out of it. Don't be concerned with the smoke.

The Seafoam soaks into the carbon. The thermal shock when you restart the engine should eject most of the carbon deposits. It also has solvent properties. It's a good thing to do every 100K miles.

A lot of people use regular Seafoam drawn in by a vacuum line. If you use the PCV vacuum, adapt a smaller vacuum line to it so it's not enough to hydro lock the engine. Just make sure it's getting down each of the intake runners.   

[randy73]

How do you know there is carbon build up, if you cant see the buildup?

Did you scope the engine?

My best advice for a engine that is running and in the car is Chevron (Techron) and high speed runs and drive the car without stopping (long trip) to reduce sludge and carbon build up.


I feel Seafoam is another Slick50, Engine Honey, etc..., might not hurt, but will not help an engine.

[Paul G]

How do you know there is carbon build up, if you cant see the buildup?

The intake has been off. You can see the crud on the back side of the valve in this pic. Looks like barnacles sort of. They are all about the same.

[1BAD68]

I'm not sure seafoam will do anything to the backside of the valves.
Besides, unless your trying to get every available HP out of the engine, that carbon won't really bother anything.