Engine Rebuilding: Cylinder Heads

Most engine rebuilds for restoration projects fall short when it comes to cylinder head preparation. That's okay if you don't plan to put on many miles and peak engine performance is not important. Show cars or cars that will sit in a collection are perfect examples. A simple "quick and dirty" rebuilder special will do just fine.


On the other hand, if you're going to drive your vehicle a lot or compete in club driving events, then you need to do it right. Cylinder head prep can run the gamut from a precision rebuild to a full-race port-and-polish job. We will break the possible levels of head preparation into three stages so that you can select the one that's right for you and your engine.

Stage I
Any cylinder head work should begin with a thorough inspection of the heads to determine if they are in fact rebuildable. The worst scenario would be to spend a bunch of money on your heads only to find that the head castings are cracked or have already been surfaced too much. Any reputable shop will Magnaflux or pressure check the castings for cracks and measure the combustion chamber volume to determine if and how much the head surface has been cut.


After inspection, the cylinder head-to-block surface should be resurfaced the minimum amount to ensure a flat sealing surface. Next hardened valve seats to combat erosion from the effects of unleaded gas should be installed. This is a fairly expensive operation but essential if you plan on getting 50,000-100,000 miles out of your rebuild. Next the valve guides and valves should be inspected for wear and replaced if necessary. A precision valve job to factory specs is next. Then the heads should be assembled with new valve stem seals with valve springs shimmed to the correct seat pressure. Expect to pay in the neighborhood of $500-$600 for a set of V-8 heads depending upon how many valves and springs need replacing.

Stage II
Stage II includes the inspection, resurfacing and hardened valve seats used in the Stage I prep but also includes the following additional modifications. The heads are surfaced to the minimum factory combustion chamber specification so that your engine will have the true advertised factory compression ratio. The original valves are replaced with lighter and stronger stainless steel valves that have a smaller stem diameter and are lighter and stronger. They are installed with a three-angle valve job that greatly increases the flow capabilities of the cylinder heads. These valves will require new retainers and valve locks, and you should install a new set of valve springs to realize the full potential of this work. A Stage II head prep will usually run in the $800 range, depending on the popularity of your engine and the number of cylinders it has.