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Measuring Correct Install Height - Pre-Check - CHP Step By StepMeasuring For Correct Install Height From the January, 2011 issue of Chevy High Performance By Sean Haggai Photography by Sean Haggai
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Piecing together high-performance components can take time and patience but correctly measuring for clearances is just as, if not more, important. When it comes to the technicalities of engine building, the more you know the better off and more capable you'll be when choosing the right components. A less-than-adequate valvetrain can make or break your build-potentially leaving you stranded. In an effort to clear the confusion on valvetrain assembly and we headed out to Quarter Mile Performance in Chatsworth, California, to see how the pros set up one properly. There we followed along in order to showcase for you, the reader, the correct methodology when assembling a set of cylinder heads for the street or strip. For this build, we've gotten hold of a set of iron GM big-block heads destined for the street. Fortunately, for us, the machining was all completed and they were ready for reassembly. Assuming you are either having your local speed shop do the assembly or you intend to assemble them yourself, having the know-how on what's going on can expedite the build. To prevent bent valves or broken valvesprings, properly checking and measuring will ensure your build is starting off correctly. Once the measuring is complete, it's only a matter of putting it all back together. Generally speaking, most install... Generally speaking, most install heights are checked after a set of cylinder heads has been restored. This would include checking the heads for cracks, resurfacing the deck, lapping the valves, and giving it a final cleaning. At this point, Michael Consolo began to assemble the cylinder heads by first applying some assembly lube to the stem of each valve. Note: assembly lube will stick to the stem longer than oil and will prevent galling of the valve once the engine is started. Michael Consolo headed up our reassembly of the cylinder heads and demonstrated the steps. We followed along as Consolo measured for the correct install height of the valvesprings, valve seal clearances, and tested for an accurate set of spring pressures. That's what is involved to turn the heads into a complete package. Now our big-block heads are ready for the street. Quick Notes
What We Did
Determined the correct install height Bottom Line
Some forethought can prevent valvetrain failure with these simple steps
| SEAT LOAD: |
146 lbs at 1.800-inch |
| OPEN: |
369 lbs at 1.222-inch |
| SPRING RATE: |
386 LB/IN |
| COIL-BIND: |
1.150-inch |
 For this assembly, we used...  For this assembly, we used a set of 2.19/1.88-inch intake/exhaust valves. Once fully lubed, Consolo slid them into each guide by spinning them in. Be aware of any sharp edge on the valve as it may gall the inside of the bronze guide.  Using an install height checker,...  Using an install height checker, Consolo slid the tool along with a 1.550-inch Comp steel valve retainer (PN 741-16) over the valve and locked it in with an 11/32-inch, 10-degree lock. For the intake valves, the install height measured in at 1.8005 inches.  Using the same method, Consolo...  Using the same method, Consolo measured the exhaust valve install height; each came in at 1.845 inches.  Next, the springs were checked...  Next, the springs were checked for strength and size. A set of Comp dual springs (PN 924-16) was placed into the spring-pressure checker with the retainer. As the spring is compressed a set of values is established. For this particular application, an install height of 1.800-inch was determined  With the steel retainer attached...  With the steel retainer attached to the valve using the 10-degree lock, a micrometer is used to measure the distance between the bottom of the retainer and the top of the seal. Our measurement showed a clearance of 0.550-inch. Knowing this distance will help you to prevent the retainer from bottoming out onto the valve seal, which could eventually tear and allow engine oil to leak down the stem of the valve. Note: our camshaft has 0.540-inch lift, allowing 0.010-inch of clearance.  Utilizing the intake (1.8005-inch)...  Utilizing the intake (1.8005-inch) and exhaust (1.845-inch) valve install height measurements, with a predetermined 1.800-inch install height, valve shims are used to gain the correct overall height. In our case, since the installed height was greater for our exhaust springs we used a 0.005-inch shim combined with a 0.040-inch shim to get a total of 1.845 inches of clearance for the exhaust. No shims were used for the intake valves. Note: some shims are directional.  After everything checks out,...  After everything checks out, 1.500-inch spring cups are added to each intake, while the exhaust receives the correct height shims and spring cups to those valve pockets. Each valve then receives an 11/32-inch valve seal. A combination of springs and retainer are then placed over each valve.  While a professional Sunnen...  While a professional Sunnen cylinder head machine was used for this application, a manual valvespring compressor will get the job done too. From here, it was only a matter of compressing each spring and dropping each 10-degree lock into place. Before the compressor is released we checked to assure each lock had seated into the valve stem's groove.  A properly checked cylinder...  A properly checked cylinder head should provide years of trouble-free service when it's measured and assembled correctly. In a matter of an hour, we had both cylinder heads ready for the engine.
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