Building Chevy 4.3 liter V6 - 1994 with balance shaft
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| − | + | Valvetrain geometry will be next I will have to see if 1.6:1 rockers will fit with a cam at some 0.48 to 0.50" lift at the cam. With the flat top I need enough clearance. I'll retain the original valve diameters of 1.94 and 1.50 inches for good vacuum in the manifold and high speeds in the runners for torque. | |
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| + | I have checked with an engine builder close by which has just built a CHEVY big block using CompCams stuff on the heads. I'm on the right path. He used comps magnum pro steel roller rockers. Nice and neat for a 6'000 rpm redline engine. The next thing will be the geometry. There is a slight splay of angles between the centers of the pushrod holes, the studs and the valves. The splay may require guide plates which should be no issue with the screw in studs. | ||
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| + | Have to measure these next. Also the guide bosses have to be machined down. To achieve proper valvetrain geometry I may have to buy the rockers first and then machine for screw in studs. So I can do minor changes to the centers and heights and align the studs properly. | ||
Looks like the heads will have the pressed studs removed and replaced with screw in studs and the valvespring pockets will be machined as well as the stud bosses to get good seating for springs and studs. The seat height at the moment is nice. The difference measured over the valves tips is less than 0.01" (0,1 mm). Exhaust valves protrude a lot more into the combustion chamber due to thicker material which adds to compression. The decisions about the seat cutting can be done only after I have the proper geometry figured out. To get some basic figures I have to put a head onto the block and use clay to see what valve clearance is based on the OEM camshaft. | Looks like the heads will have the pressed studs removed and replaced with screw in studs and the valvespring pockets will be machined as well as the stud bosses to get good seating for springs and studs. The seat height at the moment is nice. The difference measured over the valves tips is less than 0.01" (0,1 mm). Exhaust valves protrude a lot more into the combustion chamber due to thicker material which adds to compression. The decisions about the seat cutting can be done only after I have the proper geometry figured out. To get some basic figures I have to put a head onto the block and use clay to see what valve clearance is based on the OEM camshaft. | ||
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