Building Chevy 4.3 liter V6 - 1994 with balance shaft
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I will not port the heads as this would imply access to a flow-bench. What I will do is blend all sharp edges in the combustion chamber even if it will cost me a bit of CR (compression ratio) to avoid hot spots in the chamber. Then the blending will extend into the runners behind the valve-seats. Also the valve guide bosses will be blended to a blunt round shape inside the runner. Avoiding sharp edges there will help keep the flow laminar. | I will not port the heads as this would imply access to a flow-bench. What I will do is blend all sharp edges in the combustion chamber even if it will cost me a bit of CR (compression ratio) to avoid hot spots in the chamber. Then the blending will extend into the runners behind the valve-seats. Also the valve guide bosses will be blended to a blunt round shape inside the runner. Avoiding sharp edges there will help keep the flow laminar. | ||
| − | Then the bowl will be matched to the seats and finally I will have to touch them with the grinder to get smooth radii on the long and short side of the bend. | + | Then the bowl will be matched to the seats and finally I will have to touch them with the grinder to get smooth radii on the long and short side of the bend. This will be done before final cut on the seats. At the same time we'll see how to set the valves on the same altitude into the seats. Maybe the OEM valves will even do the job and just get a 3 angle job done. |
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| + | === MACHINE THE HEADS - VALVETRAIN === | ||
'''HEADS - MACHINE''' | '''HEADS - MACHINE''' | ||
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Last week (OCT 2016) I had the stud bosses machined by 1 mm (0.04") and 7/16-14 threads cut. Then we made a test assembly with some old TRW screw in studs and a new COMPCams 1.6 ratio rocker arm. | Last week (OCT 2016) I had the stud bosses machined by 1 mm (0.04") and 7/16-14 threads cut. Then we made a test assembly with some old TRW screw in studs and a new COMPCams 1.6 ratio rocker arm. | ||
| − | What we found was that the valve geometry is too far to the exhaust side and I need to lower the | + | What we found was that the valve geometry is too far to the exhaust side and I need to lower the pivot point of the rocker arm. We modified 1 of the studs (on a lathe cut a smaller radius onto the shoulder above the hex to lower the assy by some 3.5 mm total. This just put it about right and withouth the 3/8" rocker arm nut it just barely clears the valve covers. |
| − | With this information we'll most probably cut the bosses down an additional 4 mm (0.16") for a total of 5 mm (0.20") to get enough clearance to adjust the valvetrain geometry on all valves. Maybe even | + | With this information we'll most probably cut the bosses down an additional 4 mm (0.16") for a total of 5 mm (0.20") to get enough clearance to adjust the valvetrain geometry on all valves. Maybe even 1 mm more. |
I will order a set of 16 studs from Summit and go with the ARP 134-7101 7/16"-14 base thread and 3/8"-24 adjuster thread with a protruding lenght of 1.750". With the bosses cut this will end up nearly exactly where the OEM studs stood. | I will order a set of 16 studs from Summit and go with the ARP 134-7101 7/16"-14 base thread and 3/8"-24 adjuster thread with a protruding lenght of 1.750". With the bosses cut this will end up nearly exactly where the OEM studs stood. | ||
| − | Machine the valve spring pockets and the valve guide bosses for clearance to accomodate the new lift and oil seals. | + | Machine the valve spring pockets and the valve guide bosses for clearance to accomodate the new lift and oil seals as well as the new springs. |
=== PISTONS - ZERO DECK === | === PISTONS - ZERO DECK === | ||
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