Building Chevy 4.3 liter V6 - 1994 with balance shaft
From Crankshaft Coalition Wiki
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[[Category:Engine|B]] | [[Category:Engine|B]] | ||
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| + | == LAST EDIT == | ||
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| + | 15 DEC 2017 update - rotating assembly is ready. | ||
| + | 15 SEP 2017 update - had the crank finished and readied for nitriding | ||
| + | 15 AUG 2017 update - finally the pistons from JE arrived. Test assembly | ||
| + | 12 JUN 2017 update - still waiting for the pistons nothing else done :( | ||
| + | 26 MAR 2017 updated - test assembly | ||
| + | 27 OCT 2016 updated - valvetrain | ||
| + | 27 FEB 2016 updated - measuring up | ||
| + | 16 FEB 2016 updated - heads disassembly | ||
| + | 21 JAN 2016 started - disassembly | ||
I had a 1994 Chevrolet 4.3 Liter V6 sitting at my place waiting for rebuild and tune. Actually it is in single pieces right now in the midst of the project. | I had a 1994 Chevrolet 4.3 Liter V6 sitting at my place waiting for rebuild and tune. Actually it is in single pieces right now in the midst of the project. | ||
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I can throw a bit of money at it and do all the stuff except for machining myself. The budget is 7'500 $ to start with with a bit of allowance for better parts. I can keep the machining in reasonable limits as I know the guys well and can help with the time consuming stuff. | I can throw a bit of money at it and do all the stuff except for machining myself. The budget is 7'500 $ to start with with a bit of allowance for better parts. I can keep the machining in reasonable limits as I know the guys well and can help with the time consuming stuff. | ||
| − | == TECH STUFF ABOUT THE 1994 4.3l V6 == | + | == TECH STUFF ABOUT THE 1994 4.3l V6 - VIN Z (TBI fuel injection) == |
Apart from having many similarities with the small block there is a couple of things that are not well documented in the forums about this engines more advanced, more modern features. | Apart from having many similarities with the small block there is a couple of things that are not well documented in the forums about this engines more advanced, more modern features. | ||
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'''CRANKSHAFT''' | '''CRANKSHAFT''' | ||
| − | Cranks are available as cast cranks for as little as 150 $. For a more serious build a forged crank would be nice. All the OEM cranks including those used on the marine engines producing 200+ hp are cast cranks. All the V6's are external balance cranks. | + | Cranks are available as cast cranks for as little as 150 $. For a more serious build a forged crank would be nice. All the OEM cranks including those used on the marine engines producing 200+ hp are cast cranks. All the V6's are external balance cranks. The cranks weighted in at 18.9 kg (41.7 lbs). |
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Most suppliers would supply a billet crank for this engine from 3'000 to 5'000 $. | Most suppliers would supply a billet crank for this engine from 3'000 to 5'000 $. | ||
| − | The problem is: Then you have a monster crank able to withstand 1'200 hp in a two bolt cap block able to | + | The problem is: Then you have a monster crank able to withstand 1'200 hp in a two bolt cap block able to withstand a mere 400 hp at max. |
'''MAIN BEARING CAPS''' | '''MAIN BEARING CAPS''' | ||
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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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The block turned out to be quite nice. Decks are very straight may need machining just a couple hundredth's or so - talking in mm that means just a couple thousandth's in inches. Turned out that the deck height was 9.025" at my reference point at #1 cyl. | The block turned out to be quite nice. Decks are very straight may need machining just a couple hundredth's or so - talking in mm that means just a couple thousandth's in inches. Turned out that the deck height was 9.025" at my reference point at #1 cyl. | ||
| − | The bores are the same. They just need honing 0.001" over which is about 0.02 mm. This with forged pistons at 4.000" will give just the right clearance and save me | + | The bores are the same. They just need honing 0.001" over which is about 0.02 mm. This with forged pistons at 4.000" will give just the right clearance and save me money. |
| − | + | One question was if to use aftermarket billet main caps and drill the engine block for a 4 bolt cap pattern or save that money for the next build. The answer to this is "NO", not at this time. The next build may include this modification but aiming at some 250 hp does not require such measures. | |
=== 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 === | ||
| − | It turns out to be the major problem of this build and to solve it I'll have to do a complete test-assembly including camshaft and rockers with valves. JE Pistons states that 1.585 CD (compression distance/height) pistons are a "zero deck" application | + | It turns out to be the major problem of this build and to solve it I'll have to do a complete test-assembly including camshaft and rockers with valves. JE Pistons states that 1.585 CD (compression distance/height) pistons are a "zero deck" application. As my block is 9.025" deck height and I do not intend to machine .050" off that block. As I'm getting really close to the head now and using just the gasket to form the squish distance of some 0.030" - 0.040" (0.85 - 0.95 mm) in order to get good results, I will assemble it with the heads and valves and at the same time determine clearances. The pistons will need valve pockets to accommodate the greater valve lift. |
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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. | ||
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| + | == 2017-03-21 TEST ASSEMBLY == | ||
| + | It took quite a while to get it together for a test assembly. Mid of March 2017 it was the opportunity to put the block together with the crank I wish to use, one of the new EAGLE H-Beam rods and an OEM piston in order to come up with the compression distance (compression height) of the piston we want to use to get zero deck clearance. | ||
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| + | The final result is a CD of 1.575" to reach zero deck. The pockets need not be very deep. Despite the higher lift of around 0.555" with a 1.6:1 ratio rocker arm with this lame camshaft it looks as not being a big issue. We'll see what comes from it once I have the new pistons where we end up. | ||
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| + | ''' ASSEMBLY ''' | ||
| + | The crankshaft is in good conditions and only needs polishing. I have used two old bearings in the first and last bearing as the forces of a test assembly of this kind of engine won't make any difference if all or just two mains are used. When assembling for final testing with the real valve springs I'll have all mains installed. All put together with a generous amount of engine oil. | ||
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| + | The piston and rod were easy. We had one piston pin polished by about 1/1000 and the OEM which are a press fit in the stock rods are a float in the new EAGLE rods. With no rings it was just cleaning out the bore add a bit of oil and slide the assembly in and center the rod on the crank pin. The quality of the rods is amazing. | ||
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| + | Make sure you have the correct orientation of the rods - they are offset. | ||
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| + | In order to assemble the block we put the first and last camshaft bearing (the old ones) back into place after having checked and deburred them. Make sure the new camshaft is not nicked or scratched by a bad bearing or when putting it into the block. | ||
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| + | Next was the new chain drive which installed easily. | ||
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| + | I found that when the camshaft marks are aligned and the engine is at TDC the valves are actually in overlap on the #1 piston and not on the compression stroke. Interesting that this is never explained in any literature I have. | ||
| + | After having looked at several cam diagrams there seem to be both versions. For the CHEVI most use -360 deg to 0 and up to +360 deg on the charts. My raw data chart does simply look different but has the same data. The datapoints measured are exactly where the advertised cam chart said they should be. | ||
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| + | === CAMSHAFT DEGREEING === | ||
| + | At the same time I had all the parts together I had the cam degreed. Turns out that the COMP CAMS grind is exactly on the advertised durations. The overlap is minimal, all in all a very mild cam which could work with the stock TBI without a new chip. Finally we'll see it on the dyno how it works out. | ||
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| + | The large COMPCAMS degree wheel was a perfect assistant. The only thing I have to change is insert two thin plastic washers between the nut and the wheel in order to tighten the nut without turning the wheel again. A small pointer was quickly fabricated with a 1/2" wide strip of stainless steel sheetmetal. Makes a nice pointer and I can put the heads on without touching the pointer. | ||
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| + | === PISTONS - FINALLY THERE - TEST ASSEMBLY WITH NEW STUFF === | ||
| + | 2017-SEPT | ||
| + | It took 3 months for our custom pistons to arrive but finally unpacked the JE forged pistons. Nice stuff, flat deck with 6 cc valve reliefs. We forgot to order the offset pin so they came centered. The slapping should not be audible and when warm it shouldn't really be an issue. | ||
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| + | At 4.004" diameter they fit the OEM 4.000" bore easily. Turns out they are just a couple 1/1000s below deck. When milling the deck to equalize and get the finish for the gasket they will sit at zero deck. The distance to the valves is also o.k. Pockets are nice and may just need some radiusing on the still rather sharp edge. | ||
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| + | Next thing will be the crankshaft. | ||
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| + | == 2017-12-01 CRANKSHAFT == | ||
| + | Over the summer and autumn some steps got done: | ||
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| + | === CRANKSHAFT - PREPARATION === | ||
| + | We have straigthened the cranksaft and in these mid September days I got a couple things done on it. Put it on the lathe and had all the oil holes chamfered. One side of these holes is normally paper thin and sharp. Just used a Dremel to radius them, then polished all the holes. | ||
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| + | Next step was to cut down on all the sharp edges on the counter-weights and throws. The removal will facilitate the work with the crank (no more cutting your hands) and the overall removal of 5 grams will not hurt balance. | ||
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| + | Then got a fine equalizing stone and checked that all the dents (the crank was handled carelessly before) not to protrude. Then using the lathe I polished all the bearing surfaces. The end of the crank needed a bit more polishing and a second pass with a 400 grit paper to get rid of the slight pitting where the one piece seal runs. I'll have to see that the new seal does not run in that area. | ||
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| + | The next step was to take the crank for nitriding which was done in a weeks time. After nitriding we straightened it again and i cleaned and washed it including polishing the bearing surfaces again. Nitriding leaves a powdery surface on the material. | ||
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| + | == BALANCING == | ||
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| + | It took the better part of the year to do other stuff and work on other projects like a 1963 Studebaker AVANTI. My friendly machine shop had me read the user manual on the balancing machine and showed me how it works. Then it took several evenings setting up the machine and get a first balancing run to figure out if we can modify the crankshaft from external to internal balance. | ||
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| + | === BOB WEIGHTS === | ||
| + | Setting up 6 bob-weights at 0.05 g was just the beginning. The next step was an introduction to the balancing machine and I could balance all the bob-weights in order for them to spin round to 0.1g as well. This was done on a rotor shaft. | ||
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| + | === CRANK - 1st RUN === | ||
| + | Then we sat up the balancing machine for the crankshaft, fixed the bob-weights and did a first spin to see what the imbalance was. | ||
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| + | Turns out there was a 170 g at the end of the crank and 70 g at the nose of the crank. Exactly where the factory had drilled the counterweights of the crankshaft. As the JE-Pistons are lighter we decided that it would be possible to balance the crankshaft as an "internally balanced" assembly. | ||
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| + | Taking all the weights off and the next steps would be to add material to where it had once be drilled away. | ||
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| + | === FILLING THE GAPS === | ||
| + | Factory drills big holes into the counterweight, most probably for an economic manufacturing. Adding mass to the flexplate and the damper means, they can drill away on the counterweights. We wanted it to become internal balance so the first step was to make stell inserts to be welded into the counterweights. Chamfering the holes, and the inserting the 7/8" steel slugs into the holes was easy but time consuming. Welded into place and ground flat to match the counterweights. | ||
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| + | === CRANK - 2nd RUN === | ||
| + | We needed a second run and I had to put all the bob-weights back on, spin it and determine the mass to be added. This time we were down to 70 g and 25 g. This would be achieved by two 7/8" slugs of about 1 1/4" length on the back and a single slug of 1/2" in the front. Determined the axis of the correction, then drilled the crank, reamed the holes, cleaned and washed the crankshaft and went on to turn the slugs of Tungsten to be inserted. | ||
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| + | === CRANK - 3rd RUN === | ||
| + | Once the slugs were set we were in for a new run to adjust the mass and finally after some more turning and drilling we had the crank balanced internally to less than 0.5 g. | ||
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| + | For comparison: This balancing has been done by myself so I could spare the time and in addition learn about the balancing and how it is done. This would be in no case economical. If you had to pay for this service even in the US you would probably end up with a 1'000 $ bill for the balancing. 0.5 g dynamical balance is a race engine balancing job able to spin in excess of 8'000 rpm. | ||
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| + | === CRANK - FINISH === | ||
| + | Once the slugs were solidly fixed in the crankshaft we could go on to work on the flexplate and the balancer. | ||
| + | |||
| + | === CRANK - 4th and 5th RUN === | ||
| + | The flexplate was relatively easy once the additional mass had been removed. We could now balance for a static balance but even the dynamic showed excellent results. Flexplate done it was time to remove it again and balance with the damper. This one had been advertised "factory balanced" but was off by several grams. Would have spun up to 6'000 rpm without causing too much problems the machine shop guy said but we brought the imbalance down to 0.7 g. | ||
| − | + | The final run with all bob-weights, flexplate and damper showed less than 0.3 g residual imbalance. | |
| − | + | Crankshaft = done! | |
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