[Grady Clay]

Reconditioning the cylinder heads is the single most important operation affecting performance. Done correctly, the heads will perform properly for a very long time.
If done haphazardly, they don’t work well and will have issues relatively soon.
This is not ‘back-yard’ stuff.



There are three critical issues:

The new valve guide must have the proper press-fit into the head. This means the new guide must be straight, properly finished and undamaged (no nicks, dents, etc.) The bore in the head must be properly finished and straight. The combination of guide and head must have the proper interference fit. Too tight and you break the head. Too loose and there is poor heat transfer to keep the valve cool and the guide can come loose. Of course the guide must be the proper material.

The bore of the guide must have the proper clearance for the valve stem. The bore must be straight and smooth. This is not possible with a drill or reamer. Only honing can get the bore straight. You must be able to measure the bore at individual spots, not just a ‘shaft clearance’.

Finally, the valve and seat must be properly cut, ground and lapped together. A ‘3-angle’ (or more) cut is necessary. The seat must be close or at the perimeter of the valve. The seat must not be low in the valve seat. Everything must be symmetrical.


The heads should be media cleaned. Of course the head cannot be cracked or damaged. The valves must be in excellent condition or new. The springs need to be measured and inspected. The spring ‘installed height’ needs to be set. The proper valve stem seals need to be installed. The sparkplug threads need to be inspected and repaired as necessary.

With the heads in your hand, now is the time to replace all the exhaust studs (and intake occasionally). Repairing broken exhaust studs is a pita in the car. It is easy at this stage.

If you intend to twin-plug your engine, now is the time.


All this takes the correct tools and very high skill and experience level.
There are quite a number of good vendors who can do this work.


Yes, you can ‘back yard’ this but you probably won’t be happy with the results.
There are some Pelicans who take exception to my concerns.
Let them argue their point.

Best,
Grady