Build Your First Performance Engine - Part 3: Cylinder Head Prep

Blueprinting and assembling a set of high-performance heads is not difficult and can be worth some power when done correctly.

Blueprinting and assembling a set of high-performance heads is not difficult and can be wo

So far, we only have about 1,600 bucks into our 406 short-block, including assembly and a bit of farmed-out labor (see July and Aug. '06). To complete the job, we started looking around for cylinder heads, and the idea struck us to look for used racing stuff online. The result was a well-beaten Gen I LT-1 engine with a set of 210 AFR heads and a monster cam for about $1,500. We dropped it in a car and buzzed around for a while, then started breaking pushrods, so we pulled it apart with the plan of dropping the heads on the 406.

But first, we are going to rebuild them. We have done the research for you, including all the little details that make for a professional rebuild. It's much more than just buying a bigger set of valves or cranking in a good valve job.

We'll go through all the details and steps a quality machine shop will perform to rebuild a set of heads, not so you can do it yourself, but so you know what's involved in the process and why it costs so much. You just might discover that rebuilding your stock heads will cost more than buying a brand-new set that will flow more air, make more power, and make your life easier all at the same time. The more you know, the smarter decision you will make about your next set of heads. And that's as good as getting a raise at work without the IRS knowing anything about it.

A Dose of Diagnosis
Whether you're rebuilding an existing set of heads or a used set of unknown origin, the drill is always the same: Look for the worst and hope for the best. Start by making sure there is no obvious damage. When disassembling heads, look for bent pushrods or stud wear that could indicate damage or misapplication. Are the valveguide seals damaged or mashed against the guides? Are the retainers the right size for the springs? By removing a spring, you can quickly check for loose clearance by wiggling the valve in the guide. Become familiar with what good guide clearance feels like-usually more than 0.0015 inch of clearance is too much. If several guides are damaged, look closely at pushrod length or poor rocker geometry as a potential cause.

Valves and Guides
It's damned near impossible to make valveguides sound exotic, but it is also tough to create an accurate seal between the valve and the seat if the valveguides are junk. Too much clearance allows the valve to move around and pound out the seat. So, before we can dive into the details of a high-performance valve job, valveguide clearance has to be right. Most production iron heads use iron guides or guide liners for durability, and they do a great job. For aftermarket aluminum heads, most companies use a version of a bronze guide.

Another variable in this mix is valve-stem wear. After cleaning the 2.08/1.60-inch valves in our used AFR 210 heads, the valves turned out to be in excellent shape. Ryan Peart (his friends call him RPM) at JGM measured for stem wear then bead-blasted the valve heads and lightly honed the stems to ensure good oil retention and to remove any scratches or burrs.

By Jeff Smith

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