Building Chevy 4.3 liter V6 - 1994 with balance shaft
From Crankshaft Coalition Wiki
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== LAST EDIT == | == LAST EDIT == | ||
| + | 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 | 26 MAR 2017 updated - test assembly | ||
27 OCT 2016 updated - valvetrain | 27 OCT 2016 updated - valvetrain | ||
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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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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. | 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. | ||
| + | |||
| + | === 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. | ||
| + | |||
| + | === 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. | ||
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| + | === 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. | ||
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| + | The final run with all bob-weights, flexplate and damper showed less than 0.3 g residual imbalance. | ||
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| + | Crankshaft = done! | ||
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