Building Chevy 4.3 liter V6 - 1994 with balance shaft

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[[Category:Engine|B]]
  
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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'll use this article to describe, report and evolve on this project to have one single place where to reference to in the various forums I'm a member.
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Please refrain from simply editing, instead leave your comments and ideas in the discussion section so I can correct my text and integrate your input (with reference to your contribution) to keep the text neat and clean and "in one casting". I'm editing the text in a file I have on my computer and usually replace all the text in the wiki with the latest version i wrote. Thanks
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== LIABILITY WAVER ==
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A bit of a warning and a statement about liability. I am not a trained mechanic. All advice given is to the best of my knowledge and I will normally point out where I'm not sure of my actions or cannot back it up with experience or advice from others. I will not be liable for anything be it information given herein nor advice or procedures I describe or use. It will be ALL AT YOUR OWN RISK.
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'''MY HISTORY - NICE TO KNOW'''
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Having said this you may want to know why you may continue reading the stuff a guy writes up which is not even a mechanic. Have a look at my profile.
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== PROJECT GOAL ==
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This shall become a daily driver able to tow and remain emissions legal. That means no fancy exterior bolt-ons, no crazy camshaft, no crazy horsepower, needs to remain within emissions with catalytic converter.
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'''WHAT IS PLANNED'''
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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.
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== TECH STUFF ABOUT THE 1994 4.3l V6 ==
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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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'''HEADS'''
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Nothing particular there. Stamped rockers, pinched nuts on pressed studs. This will most probably be one of the mods.
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At the moment I'm trying to figure if the heads correspond to L05 heads of the V8. They already feature the "ski-ramp" swirl ports (vortec) but not yet the kidney shaped combustion chamber.
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'''BLOCK'''
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Nothing particular there. A couple of threaded holes are not used according to the car. It seems that this is an engine still based on the GEN I smallblock-block.
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'''OIL PAN'''
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The 4x4 has a very deep oil pan. In order to clear the front axle the deep portion of the pan is shorter but taller.
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'''CAMSHAFT'''
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It has a hydraulic roller camshaft with the stepped nose and the retainer. This is a benefit for the build as "cam-walk" is no issue.
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'''LIFTERS'''
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This has come to a surprise. It employs a plastic retainer along the full side of the lifter valley. One left, one right which two bolts each fixed into the block. We'll see what to do of it. Seems a nice and easy way to keep the lifters where they belong. It has some oil holes and a lot of small fins I guess are for oil flow.
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I'll add more stuff as I go and discover what is particular or what differs largely from a standard pre 1988 small block.
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== 2016-JAN-21 TEARDOWN ==
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Teardown has started. The major challenge was to get the engine from where it was sitting at a friends warehouse to the garage where I work part-time for the teardown into handy pieces. All the work which can be done by myself will be done at my place where I have a room for such work.
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As it lays in a basement it is a bit of a hassle to get the engine there. For the further work I will always handle the disassembled engine (handy size and weight of parts). The final assembly will again be done in the garage which is outfitted for engine assembly. A properly drained engine will be worth gold once you start to tear it down. There is no mess, else an engine stand is mandatory with a large pan underneath.
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No surprises once I had it on the bench. The first thing I did was spray all bolts that I saw with a penetration oil, then went for lunch. Removed all stuff from the TBI, sensors, ignition coil TPI, EGR and other stuff. Removed all the small vacuum lines, the large ones, the supports for the various stuff on top, unplug all sensors and then remove the complete wiring from the top of the engine.
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I have some 100 re-sealable plastic bags handy, tags that can be tied to pieces and an indelible EDDING pencil. I store the stuff as I go and I clean up the worst of dirt and oil before bagging and labeling things. It may seem silly but I also add special observations on the bags such as location of specific fasteners or pieces, clips and such. What seems obvious now ("Ahh - You know where you have removed that support from") may not be so obvious in 6 months when it is assembly time.
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The next step is storing in cardboard boxes for transport. At my place in due time I will pick a couple of bags and start rebuilding stuff or make a list of what to order. During the process I have kinda three piles of stuff: Fine to be re-used / Rebuild or order / Trash. Once nearing completion I want an inventory of only Fine to be re-used and Trash as that means I have all parts ready for final assembly.
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'''TBI'''
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Next is the TBI, carefully remove all plugs and sensors. It's easier to remove them as long as the TBI is still attached to the intake manifold. Then remove the 3 bolts of which 2 are special ones and detach the TBI body from the manifold.
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'''MANIFOLD'''
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Loosen all bolts from the intake manifold and detach the remaining supports for various stuff, pre-clean and label. Then remove all the intake manifold bolts. A couple of light taps at the corners were enough to crack it loose despite the block having rusted quite a bit. All sheet-metal supports have rusted, some even rusted away completely. Remove the manifold, pre-clean and store. (Will be checked, cleaned, ported and finally painted in the process.)
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'''STUFF ON THE BLOCK'''
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Then I got rid of the engine mounts, lateral sensors of the block on the accessible side. Depending on how you disassemble you may also remove the other sides stuff such as the other mount, oil level dipstick and such.
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'''HEADS'''
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The 1994 engine has solid plastic covers with three retainer bolts. These are very special bolts, apart from that no surprises. As they have a rubber seal they crack loose when hit with the flat hand on one side. Now we have access to all the rockers. To just pull the heads (I will tear them down later at my place - for now it is just to get handy pieces) No need to remove all the stuff such as rockers, retainers, valves...
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I have switched to an air tool (as I have access to it) but it would be possible by hand as well. Loosen all the retainer nuts on the rocker arms. Leave them tightened a couple of threads on the studs so the rockers stay with their respective valves. I would recommend this as well for repairs. No need to take them all off, because when reusing them you have to keep them in the exact location from where they came. They break in to their respective pushrod and valvestem. Once loos you can simple lift them a bit and turn a couple degrees to free the pushrods.
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I took a 10 x 30 cm piece of cardboard and folded it in half. Then punched 6 holes x 2 into it where to stick the pushrods. Marked it accordingly (cylinder head left or right from front to rear and up and down, where down is in the lifter valley. (Oh - the 10 x 30 cm makes about 4 x 12 inches.)
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Still with the air tool (you will need a decent 1/2" wrench at least 40 cm (18") long to crack them open, and following the tightening order (I know, not necessary for disassembly - but still...) loosen them. As I had the engine on the bench and laying to one side I left the two outer (exhaust side) bolts in by a couple of threads to keep the heads on the block should they come off while removing all the bolts. No need to have them nick my bench, feet or floor.
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Then tapped them with a plastic hammer (a bigger size now) on the four corners a little bit with one hand on them and I felt them separate quite nicely. Once you are positive that they still sit on the centering pins, remove the two remaining bolts and lift them off.
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And now the other side - same, same.
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'''FLEXPLATE'''
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Six bolts (air tool again), then wiggle it off or use an appropriate puller. Just make sure, the engine is supported in a way, that the flex plate is not bearing any load of the block.
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'''OIL PAN'''
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The oil pan has four larger bolts in the corners, three special studs(bolts) on one side and a couple normal bolts for the rest. Two metal inlays serve as washers on the full length of the oil pan. In order to remove them I had to unbolt and remove the attachment for the remote oil filter hose from the oil pump outlet outside of the block. (This is a 4x4 version VIN Z engine). Tap it with your flat hand it should break loose quite easily. When removing pull it up slowly and gently. It will get stuck on the oil pump pick up which is nested through the slush guards inside the oil pan. It will need a bit of gentle movement fore and aft to clear the pick-up screen. And now we're at the crankcase.
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'''CRANK AND CRANKCASE STUFF'''
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The first thing to note is that the 1994 VIN Z engine has two bold mains. That means the main caps have only two bolts a piece. The next oddity I noted is with the numbering of mains and the rods. The mains have an arrow pointing forward and all different casting numbers but no specific locator or identification. So I will see where to add one with my machine shop. The next thing was the rods as I found the letters F-F, J-J, G-G stamped on them. Seems they are paired. Will see tomorrow what the logic is. As I want to keep them exactly in location I will number them as well to keep the sets properly together.
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== 2016-JAN-22 - TEARDOWN, THE REST ==
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After all the stuff has gone from the block I'm left with the rotating assemblies. Crank, rods, pistons, camshaft and balance shaft. I had to take the engine apart for transportation reasons. Needs to go up and down a steep ramp (next to a stair) so I'm not going to pull a 300 lbs engine into my place.
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To have it even more handy I'll now take the rods, pistons and the crank out of the block.
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'''OIL PUMP'''
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Now I removed the oil pump to get it out of the way. one center bolt is connecting it to the block. Carefully pull it out straight as the shaft is some 20 cm long (8 inches). Place it in a pan or your old oil drain as it may still contain some engine oil.
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'''MARKING'''
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Got 6 nice sized clear plastic boxes and some more boxes with separators and a lid from IKEA to store all the stuff which will come out and not mix it up.
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Marking will be done with the EDDING water resistant pencil on a cleaned and degreased surface (brake cleaner on a rag).
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As the block is upside down I first figured correct location of the cylinders. Left is odd, right is even. Number one is in front left also where the cam drive sits. Then wrote the cylinder numbers down on the freeze plugs which were the only places without rust or oil.
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I've used the harmonics damper loosely put on the crank snout to turn the engine over. If it does not turn easily by hand you're in for a heavy rebuild anyway. Mine turned just fine with a bit of resistance but could be turned with one hand. Place the rod you want to split into a convenient location where you can set the wrench and break the nuts loose without hitting your hands on the sharp edges of the crank. I normally write a little legend on the workbench (aluminium sheetmetal cover) for the nuts position and the rest. As I do not know at this point what I will do to the engine and don't go into the hassle of remembering all the stuff that has to be marked with position and direction of assembly I simply mark everything.
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A rag with cleaner I search for a convenient spot to mark the rods, wipe the oil and dirt off and mark it with the cylinder number. I also mark the forward position with an arrow and a 1 and 2 for the bolts and nuts. Mark the cap and the rod with matching cylinder numbers. Ever had your cat stray into the garage and push a box with stuff over.? Then try to match parts. In general the rods and crank and stuff are marked by the factory but they tend to use funny ways. My rods are marked F-F or J-J but then I found that three where marked F-F. So I'm not going to take chances on that.
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'''ROD AND PISTON REMOVAL'''
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Loosen the rod bolts but leave them on at least a couple of threads. Gently tap one of the two bolts with a plastic hammer. The rod should split right away. Because the bolts are still in place it will not fall into the depths of the crankcase, cylinder bores. Now remove the nuts carefully. Hold the rod part with one hand and with the other wiggle a bit on the rod's cap. They should come out easily with a slight pull. Sometimes residual oil will cause a bit of suction/adhesion on the bearing surface. Try to pull it straight or it may bend between the two bolts. Original bolts are kind of forced into the rod and will not fall out. Aftermarket may fall out, one of the reasons I at least hold the upper (long) portion of the rod where I can get my hand in to avoid it slide down or the bolts to fall out. If they do - use a magnetic pole or flex handle to pick it up. Do this anytime something falls down. Search as long as it takes to find and remove it. If you turn the engine for the next cylinder you can nick the cam or crank or a bearing surface with the bolt somewhere in the depths of the engine. Lay the parts aside on the legend of the workbench. The lower part of the rod bearing can stay attached to the crank. Leave it there as it is nearly impossible to get it out. It will stick to the crank due to residual oil. Once the piston is out you can easily pick it from the crank.
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The piston rings should have enough resistance that the piston will not fall out. Normally it should take a little push to move it up in the bore. Actually moving down, as the block is upside down now. Push the piston down by pushing on one of the bolts with your thumb, so you can leverage with the remaining fingers on the edge of the block. It will most of the time move down until the compression ring (aka the first ring on the piston from the crown) hits the cylinder wall where the rings do not run. This is in most cases an area some 3 - 4 mm (a little less than 1/4") on top of the cylinder bores. There is no abrasive force so it creates kind of a step a few thousands less in diameter than the cylinder bore where the pistons run.
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Think of how you can center the rod in the bore, tap it with an adequate tool to move down and once it slides out (actually falls out) catch it! Have somebody help you or as was my case with the block upside down on a flat space the piston will just fall 5 cm (2 inches) and lay on the table. Put some cardboard underneath to soften the fall and catch residual oil dripping from the piston and bore.
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To get it out the trick is to suspend the rod with one finger from the bolt and position it in the center of the cylinder bore in order for the rod not to touch the lower skirt of the bore and get stuck. The upper portion of the rod bearing is normally still in place in the rod. It is cramped in the bore despite the 4" bore. I use the plastic hammers handle (wood) after making sure that the end is round and has no protrusions from stuff embedded in the wood. Then try to tap slightly on the piston pin bossed or if that is not possible on the rod. Another possibility would be to remove the upper rod bearing and tap it in the rods bearing location.
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Put all together in the correct location and stored the pistons with rings, pin and rod with cap, bolts and nuts assembled loosely in the boxes I had prepared.
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'''WARNING!'''
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Light tapping should be well enough to have the piston slide out. If you hit resistance re-check your rod alignment with the bore. When dealing with really old engines with many many miles check the ridge on top of the bore. Check the bores for rust. If all fails it may be necessary to carefully lower the rods and pistons as much as possible and remove the crank first to pull the pistons out of the bores below. You may have to loosen all the bolts, remove the outer ones in order to be able to access all the inner ones with the crank in a horizontal position, then remove all the mains and pull the crank.
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Or maybe the best advice is to ask your machine shop or take the block to the shop right away.
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'''CRANK REMOVAL'''
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By removing the crank and the main bearing caps I can put the block back upside and it will rest on the base nicely for transport. To remove the crank crack all the bolts on the caps and remove them. I again kept them in the order I have removed them from. Clean and check the bearing surface. The crank has no discolorations which is a good sign. Seems that it never overheated somewhere. The bearings show normal wear for a 120'000 miles engine. Once all the caps were off I found one with a scratch through about 100 degrees of the lower half of the bearing. The small debris embedded itself into the soft bearing surface and did not scratch the crank as it is supposed to do. This is one of the reasons for a soft surface. Packed all neatly into the boxes and two large cardboard boxes and transported it home.
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== 2016-FEB-12 - DISASSEMBLY, HEADS AND BLOCK, CLEANING ==
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Taking the heads apart was easy with the appropriate tools. Valve spring compressor and a magnetic pick and valves are out of the heads within 30 minutes. Took the block and heads to my shop where they pulled the plugs. Some of the freeze-plugs had already started to leak from corrosion which hat eaten through from inside. Then had block and heads hot tanked. I gave them a thorough wash with the pressure washer. Then cleaned all with brushes and parts cleaner at the shop. All color is removed from the block as well as all the sooth from where it could be accessed. Brushed out the runners with a compressed air tool and a fine metal brush. Then took a grinding stone and got rid of all the casting ridges and brows. Chamfered all sharp edges taking care not to damage any seal areas.
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== 2016-FEB-27 - MEASURING FOR BLUEPRINTING ==
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''' CAMSHAFT '''
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The camshaft has terrible oddities. I'm a  metric guy and have measured up to .52 mm (0.02 in) differences in lobe lift vs. base circle from one lobe to the next. Also the base circles differed by 0.4 mm (0.015 in). I hope that CompCams or Crane deliver the precision they advertise. (BTW measured not only where the roller of the lifter runs but also at the edges of the cam.
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== TIPS AND TRICKS ==
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Drain the engine oil with engine hot. Or maybe place the engine close to a heat source or at the sun to heat up while draining. Maybe even a couple of days. Especially the water will still pool. By placing the engine at different angles you may drain most of it. Once the heads are off Some coolant may drain when turning the engine over from the passages in the back between block and heads and from the two located between the first and last and the middle cylinders. It is so much easier without the mess of oil and water.
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Spray all bolts with penetration oil and let it soak. Re-spray after 30 minutes and best is to go for lunch.
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Spray the gasket edges e.g. TBI, Thermostat, sensors, head-gasket as well.
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I nearly always wear surgical gloves when working on dirty stuff. At the same time these gloves save you from fine metal filings which can sting through the skin. Use the "nitrile" ones as latex will dissolve in most of the fluids we have around engines.
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Marking parts is easiest using an engraver such as one from DREMEL or others. Just got one a couple days ago for 40$ and works like a charm. Try to etch your marks in locations where they do not add a stress raiser. Where original factory markings is could be a good spot or check on the internet or books. All machined parts which touch another part is no-no. All surfaces where a bearing is being set are no-no unless treated accordingly. Try finding spots where there is no gasket. On the heads for example is a lot of room on the intake side surface where there is no gasket.
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Engravers stamp little craters into the metal. By sanding over it with a fine grit paper or a stone can relief the sharp craters rims.
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== ENGINE STAND ==
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Engine stands for U.S. engines are not readily available in Europe and very expensive to have them shipped. I opted for a build based on two 400 kg (some 850 lbs) dollies with four free steering wheels and brakes on two. A couple of scaffolding tubing and joints for some 180 $ make a nice and rather solid stand. I'll have a friend cut a steel plate to match the holes on the engine transmission side. Then I may be able to turn the engine on two axis. Could be handy to store the block on the stand.
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The block has been disassembled completely now, the lifters are out, everything except the crankshaft looks reasonably well in shape and could be reused right away. No surprises so far. The block is clean and dry now, the heads as well, all the stuff is out and shows reasonable wear. Above the lifter valley things look good. No scratchings as in the lower side. Camshaft looks good as well.
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Hot tanked and washed I ground all the casting ridges down and smoothed some of the sharp edges and corners on the block and heads. No more cuts from the heads and block. Talk to your machine shop where this is safe to be done and where not to touch the surface. In general all machined "surfaces" are no-go with the grinder. All external casting ribs and sharp machined edges are o.k. to get a slight chamfer or being deburred. Easy on thin surfaces that should seal such as the timing covers or the valve covers ribs on the block and heads.
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== NEXT STEPS ==
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I'll have to get my block and heads then I'll put the first and last cam bearing back into place to measure all the stuff from OEM and determine machining specs. Valvetrain geometry will be next to see if 1.6:1 rockers will fit. I'll retain the original valve diameters of 1.94 and 1.50 inches. I have to check with an engine builder close by which has just built a Ford 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. 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.
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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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== SEARCHING FOR PARTS ==
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One of the downsides of this engine is the fact that nobody ever took care of serious builds on this base. Although this engine has seen a myriad of applications and has been produced in millions it has never been seriously considered for racing or builds. It shares a great deal of common parts with the SBC V8 so a lot of parts can be sourced from there. The hot-rod magazine has probably built the ultimate 4.3l V6 showing the potential.
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'''CRANKSHAFT'''
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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 are external balance cranks.
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Most suppliers would supply a billet crank for this engine from 3'000 to 5'000 $.
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The problem is: Then you have a monster crank able to withstand 1'200 hp in a two bolt cap block able to put out 500 at max.
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So I'll have to go with the factory crank properly balanced (internal balance) which should easily withstand 300 hp. As the goal is below that number I should be fine with that.
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'''CYLINDER HEADS'''
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The 1994 V6 "Vortec" heads are '''NOT''' the same as the OEM LS31 heads for the 350ci V8's. They are "Vortec" heads but do not yet feature the heart shaped combustion chamber. Apart from the chamber design they already feature the "Vortec" ski-jump ramp.
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It would be cool if somebody with access to a flow bench could flow a pair of these heads.
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The 1.94 Intake and 1.50 Exhaust valves should have acceptable flow at low lifts which would be a nice thing for a daily drive and low to mid rpm power band modifications. At the same time this will keep the cost way down. Modifications for screw in studs and decent roller rockers should deliver more power and a sturdy valvetrain.
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=== MACHINING AND PORTING ===
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'''BLOCK'''
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Have to check if the block needs machining at all. The deck surfaces are nice. As we have a lot of compression gain to take advantage from I can equalize the decks to match the main crank bore. The cam bore is a bit of a question mark as we can measure that only after having the engine on the mill. If possible with oversize bearings I'll adjust that one as well.
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The big question now is if to use aftermarket billet main caps and drill the engine block now for a 4 bolt cap pattern or save that money for the next build.
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'''HEADS - PORTING'''
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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 stems will be blended to a blunt round shape inside the runner. Avoiding sharp edges there will help keep the flow.
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'''HEADS - MACHINE'''
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I have to remove all the studs and prepare the geometry for screw in studs. I'll go with whatever the cam company recommends either 3/8 or 7/16 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.
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Machine the valve pockets and the valve guide bosses for clearance to accomodate the new lift.

Revision as of 12:45, 27 March 2016

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