Building Chevy 4.3 liter V6 - 1994 with balance shaft
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'''ROCKER ARMS''' | '''ROCKER ARMS''' | ||
| − | COMPCams 1618-1 (CCA-1618-1) Ultra Pro Magnum Rocker Arm at 1.6:1 ratio. I have ordered just a single one to be able to check the valvetrain geometry for the machining of the studs and check rocker arm height with the OEM valves. At the same time I want to make sure they do not interfere with the OEM plastic covers. With the new camshaft I should already have about .100" more lift at the camshaft. I'll see during a test assembly if it fits | + | COMPCams 1618-1 (CCA-1618-1) Ultra Pro Magnum Rocker Arm at 1.6:1 ratio. I have ordered just a single one to be able to check the valvetrain geometry for the machining of the studs and check rocker arm height with the OEM valves. At the same time I want to make sure they do not interfere with the OEM plastic covers. With the new camshaft I should already have about .100" more lift at the camshaft. I'll see during a test assembly if it fits (The result is - it does not fit and will need taller valve covers.). Inadvertently I have ordered a self aligning rocker arm which is just perfect for the application. It eliminates the need for guide plates and helps keep the stud height down. |
'''VALVE SPRINGS''' | '''VALVE SPRINGS''' | ||
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=== MACHINE THE HEADS - PORTING === | === MACHINE THE HEADS - PORTING === | ||
| − | I will not port the heads as this would imply access to a flow-bench. What I | + | I will not port the heads as this would imply access to a flow-bench. What I did 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. 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. | 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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'''HEADS - MACHINE''' | '''HEADS - MACHINE''' | ||
| − | I have removed all the studs and prepared for screw in studs. I'll go with 3/8" studs. The choice of rockers will also be decisive. Aiming at a nice steel roller rocker such as CompCams Magnum Pro Roller Rocker 1,6:1. The geometry defined I'll have the bosses machined for proper height of the studs then the centers bored according to proper alignment from the lifter bores to the valve stems. | + | I have removed all the studs and prepared for screw in studs. I'll go with 3/8" studs. The choice of rockers will also be decisive. Aiming at a nice steel roller rocker such as CompCams Magnum Pro Roller Rocker 1,6:1. The geometry defined I'll have the bosses machined for proper height of the studs then the centers bored according to proper alignment from the lifter bores to the valve stems. The bosses will need cutting down by about 7/16 (8 mm) in total to put the rocker arm pivoting point into a correct geometry with some leeway up and down. Final measurement to be defined. |
'''CAUTION: ROCKER ARM STUDS''' | '''CAUTION: ROCKER ARM STUDS''' | ||
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The diameter of 9.4 mm is a perfect center bore for a 7/16"-14 thread. | The diameter of 9.4 mm is a perfect center bore for a 7/16"-14 thread. | ||
| − | 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 | + | 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 the 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 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. | 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. | ||
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'''CAUTION: VALVE COVERS''' | '''CAUTION: VALVE COVERS''' | ||
| − | Even when having machined the bosses I'll end up about 5 mm (1/4") above the height the original rockers had. This is | + | Even when having machined the bosses I'll end up about 5 mm (1/4") above the height the original rockers had. This is without the poly lock nuts which protrude an additional 5 - 8 mm. In order to clear the rocker arms I'm planning on machining a 20 - 25 mm (3/4 to 1") thick aluminium plate to act as a spacer. The next step is to check on the installation if it will fit under the hood and clear the air filter element. |
=== PISTONS - ZERO DECK === | === PISTONS - ZERO DECK === | ||
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Next will be a test assembly to figure the correct dimensions for valves, beehive springs, retainers (maybe titanium - decided against as the beehive retainers are already smaller in diameter and lighter.), locks and finally the pushrods once I have the geometry defined. | Next will be a test assembly to figure the correct dimensions for valves, beehive springs, retainers (maybe titanium - decided against as the beehive retainers are already smaller in diameter and lighter.), locks and finally the pushrods once I have the geometry defined. | ||
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== 2017-03-21 TEST ASSEMBLY == | == 2017-03-21 TEST ASSEMBLY == | ||
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