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Engine Valvetrain UpgradesFreshen up your Cylinder Heads From the April, 2012 issue of Chevy High Performance By Henry De Los Santos Photography by Damon Rivetti, Henry De Los Santos
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It’s true, nothing lasts forever and all good things tend to have a cycle. In this instance, we’re talking about the lifespan of your cylinder head’s valvetrain. Obviously a lot of this is contingent on its environment; mild performance applications tend to last, whereas those pushed through strenuous conditions will undoubtedly require much more maintenance. If you recall our 525ci big-block build (“Big-Inch Punch”, Dec. ’11) where we installed a set of Brodix BP BB-3 Xtra 380 heads, we’ve been throttling that motor at full tilt with 39 pounds of boost. Unlike most of our test mules, we’ve actually dropped this thing in between the wheelwells of a 3,500-pound chassis with factory-style suspension; the results: 7.48 at 193 mph on 275 drag radials! As impressive (and scary) as that is, we also learned that big boost can really take a toll on valvesprings, in the form of spring fatigue. After a number of pulls on the engine dyno and 30-plus passes on the tarmac, we noticed the engine fluttering around 8,500 rpm; it felt as if the rpm limiter was kicking in. Once we pulled the valve covers and checked the valvesprings, we found that the spring pressures were down significantly. On the big end, the springs were allowing the valves to move erratically, which is also the reason it wouldn’t rev past 8,500 rpm. The fix was only a matter of swapping out the springs, a straightforward job. However, we decided it was best to do a complete rebuild and make sure all of the components were still in tiptop shape. To handle this job, we headed to A.R.E. Performance & Machine in Simi Valley, California, where Rocco Acerrio took us through the entire process. So whether you’re looking for a simple factory rebuild or a performance upgrade, the process is the same and this is how it’s done.
The Goods |
| PN |
Components |
| 26082-16 |
Valvesprings |
| 517-16 |
Valve seals |
| 4860-16 |
Spring seats |
| 4756 |
Spring shims |
 [01] First thing is to clean...  [01] First thing is to clean up the heads and prepare them for disassembly. Here Rocco Acerrio uses a valvespring compressor to remove the springs. After the springs are compressed, it’s just a matter of removing the two valve locks. With the locks out of the way, he slowly released the pressure to remove the valvesprings. Then the entire valvespring assembly can be removed, including the retainer, stem, and the spring seat.  [02] With the cylinder heads...  [02] With the cylinder heads completely disassembled, they were given a thorough cleaning. Next, the combustion chambers are glass bead-blasted to remove all carbon deposits and inspected for any cracks.  [03] Our cylinder heads checked...  [03] Our cylinder heads checked in healthy with no cracks, however using a straightedge on the surface of the heads, we learned they were slightly warped. Generally, high-mileage street motors, with the number of heat cycles they go through can cause this. Another scenario is caused by overheating. In our case, the high volume of boost caused the head to move around.  [04] Our heads only required...  [04] Our heads only required 0.004 inch to be cut from the surface. Most cylinder head rebuilds will require 0.002 to 0.004 inch to be removed. In a severely overheated head, it can take as much as 0.008 to 0.010 inch. This machine is also used to mill heads to reduce combustion chamber size.  [05] The next step is to move...  [05] The next step is to move the heads over to the seat and guide machine, where the valve seats are cut. This process uses a dedicated carbide cutter that has four specific angles built into it. For our heads, we left the factory seat angle at 45 degrees and only had to cut 0.005 inch off the seat to true them up. The same is applied to the exhaust seat.  [06] The process of machining...  [06] The process of machining the valves is similar; they’re first blasted clean and then placed on the valve grinder to reface the 45-degree angle on the sealing surface of the valve. This ensures they are true and will match the cut in the seat and seal cylinder pressures.  [07] With the machining complete,...  [07] With the machining complete, the heads are then put through a final wash prior to assembly. Here Acerrio measured the valvespring installed height, which is the distance between the spring seat and the valvespring retainer with the valve closed.  [08] To freshen up our heads,...  [08] To freshen up our heads, we went with a set of COMP Cams’ valvesprings, valve seals, spring seats, and shims. We also decided to try out their latest set of triple valvesprings, both for longevity and to hold 40 psi of boost.  [09] After verifying the valvespring...  [09] After verifying the valvespring pressure at the installed height, we used different shims to achieve the seat pressures we were looking for. The previous springs were 400 pounds on the seat and 950 pounds open, whereas the new springs are 460 pounds on the seat and 1,067 pounds open.  [10] Here are the valves installed...  [10] Here are the valves installed with the clean combustion chambers and freshly surfaced deck.  [11] For final assembly we...  [11] For final assembly we placed any shims necessary, along with the spring seat and valve stem seal. From there the springs went into place and again used the spring compressor, which squeezed the springs down and allowed the valve locks to be installed. CHP
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Brodix
301 Maple P.O. Box 1347
Mena
AR
71953
479-394-1075
www.brodix.com
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A.R.E. Performance & Machine
2243 Agate Court
Simi Valley
CA
93065
805-583-0602
areperformance.com
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Comp Cams
3406 Democrat Road
Memphis
TN
38118
800-999-0853
www.compcams.com
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