Little Mouse - The 1994 - 4.3l TBI engine blueprint and tuning
 

Blueprinting that oddball 4.3l V6 TBI with balance shaft.

THE RULES:
1st - I have to stick to this exact engine or my 1994 4x4 S10 Blazer will never get a license plate again! That means NO V8 swaps!

2nd - No way that rule #1 can be achieved by something visual from the outside of the engine - so NO TURBO, NO SUPERCHARGER, NO CARBURETTOR or fancy EFI.

3rd - It has to keep emissions within the OEM limits of the 1994 engine. Keep stock exhaust with catalytic converter, EGR and mufflers. BTW during the research I found out that the primary part of that exhaust for the 1994 blazer (Y-pipe and catalytic converter) is the same as the V8. So anything between the headers and Y-pipe is pretty much useless as it flows the volume of a V8.

GOALS
1st DURABILITY under load (towing). I'm not into repairs every 5'000 miles. Servicing every 5'000 miles is just fine with me.
2nd TORQUE, TORQUE and more TORQUE (hp is related to torque at a given rpm - if you get a high torque output you have high hp at that rpm)
3rd FLAT TORQUE CURVE for towing
4th LOW SERVICING REQUIREMENTS - means realistic valve seat cuttings, not always the lightest in materials (valves and such), quality steel parts for the valvetrain no aluminium rockers. Most probably retain the hydraulic lifters, eventually change to mechanical roller lifters. Valve leash adjustment on a rocker arm engine is easy enough - well once you get by all the stuff and reach your valve covers.
5th HP GOAL is around 200 - 225 shp with modified OEM TBI. For this hp target it will probably require ECU reflash.


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THE DISCUSSION POINTS

BLOCK MACHINING
This engine will, at this time not get 4 bolt main caps, simply because of the cast crankshaft. The rpm target will be a redline of 6'000 rpm but with the applied tuning a realistic max hp rpm is between 4'250 - 4'750 rpm. So I have some reserves built in.

OIL PUMP
Still open. The OEM pump will be enough to supply this engine.

DRY SUMP
That's a big temptation as this Blazer comes with the larger radiator with remote oil filter location and heat exchanger to the cooling system. That means plumbing is already half done. Enough room in the engine compartment is there for the tank location (left front). We'll see what happens when it starts coming together.

Without forced induction your only real options would me a lot of machine work, head porting, gasket matching, getting heads milled, thinner head gaskets, etc... The last 2 things may require custom length push rods.

Thanks for the thoughts. That is exactly the plan:

Machine for screw in studs, machine the valve pockets to use beehive springs.
Porting the bowls to the seats, round the sharp edges of the valve guide and port match to gasket and manifold. I can do this work myself so the cost will be reasonable. A little head work in the combustion chambers to equalize the volume, then machine the heads for compression.

At the bottom end I will use new rods and new pistons most probably flat deck and calculate the height to be flush with the block deck. The CR goal is around 10:1, maybe 10.5:1. With the lighter rotating mass (rods and pistons) balancing the crankshaft for internal balance should be possible. To complete I will use a new internal balance damper and remove the weight from the flexplate and balance that with the crank.

At the top end most probably compcams magnum pro steel roller rockers and new custom rods to achieve proper valvetrain geometry.

I have the time and the connections to get it done at a reasonable price. I work with and for a garage and a machine shop. So the machining is covered.

The next step will be re-assembly for measuring. So far I have the data for the material for the build. Now we'll have to determine the deck height to order rods and pistons.

Planning on some SRP 350 flat heads with 2 valve reliefs (adding only 5 cc) - and ended up with a set of custom JE forged pistons at 4.004" to fit an OEM bore which will be honed 0.05 over to fit the pistons. The rods will be either from Carrillo or Eagle. Turned out to be Eagle H-beams. Nice rods. Within 2 grams.

Basically everything that you have mentioned is classified as tampering with the emission control system, which is against US Federal law. The engine will no longer be "emission legal" for 1994 OBD 1. Just so you are aware of that, before starting the project ;)

I don't believe that he is in the US.

Yup, I was on my phone and the mobile app doesn't show where members are. I have a hard enough time remembering what year vehicle everybody has, much less where they live ;)

CaptainHook + Tajohns

you are right.

Usually we have a lot of trouble with modifications you can do easily in the US. But on the emissions side we have an advantage.

We need a dealer inspection every two years with pre OBDII vehicles with a printout of the test to be carried with the vehicle papers. Then during inspection they will measure exhaust gasses again and they have to be within the limits given in the vehicle booklet. We are actually allowed an hp increase as long as exhaust gasses remain within limits of the originally certified engine and it retains all emissions control measures.

The increase in compression, matching components, injection, ignition will most probably lead to lower emissions, not higher. Blueprinting will do it's own keeping emissions within legal limits. As it is not my intention to delete any of the emissions control measures this will pass inspection as long as emissions are within the given percentiles of HC, CO, and CO2.

What will be done now that I know the block's good:

Get either a new crankshaft or grind the one I have to first undersize.
Check main bore alignment, deck alignment and machine for that.
I will have to test assemble beginning of next week.

New rods 5.700" which makes a little more room for the deck alignment OEM is 5.703".
Best guess at this time is SRP 350 flat deck pistons with dual valve reliefs and 5cc addition to combustion chamber.
A 0.045 gasket (standard) thickness is perfect with a flat top for the squish and will raise CR to 10.2 : 1.

Balance for this rot assembly and as it will be several grams lighter than stock the crank will get completely internally balanced.
Fluidamper in front.

Keep the heads machine combustion chambers for volume adjustment (they range from 64 - 66 cc) then grind the bowls lightly just to match and get rid of ridges. Put a radius similar to the valve stem's on the valve guide. Then recut the valve seats for a 3 angle valve job and fit Milodon stainless steel valves. (nothing too fancy).
On top machine the guide boss to accomodate the new spring and shorten it a bit to get the required clearance for the new valve lift.
Machine the spring cups for the larger springs and the stud bosses for same height (depending on valvetrain geometry) and 3/8" screw in studs.

Beehive springs will get steel retainers and paired with CompCams Magnum Pro steel roller rockers at 1.6:1 ratio should be good for a 6'000 rpm redline with reserve to 6'500 rpm.
And of course new lifters and pushrods will be fitted, the latter custom lenght, again for proper geometry.

At this point I think that next weeks test assembly will have me ready to start ordering parts. Once I know if the block is square or how much to grind down I can derive compression height and order stuff.

I think I got my stuff together...

Major order at SUMMIT done yesterday night.

- Some gaskets
- ARP screw in 3/8" rocker arm studs
- 1 (one) COMP magnum pro rocker roller at 1.6:1 (for geometry checking)
- camshaft
- timing gear
- EAGLE rods H-Beam rods at 5.7" length

and last week finally got my test assembly and got deck heights and stuff. The block is nice and straight may need some 1/1000 angle decking to get it straight to the main bore. The cylinders are round and just need a couple 1/1000 of honing.

Pistons orderd
- Custom forged JE pistons with flat top and two reliefs to get a target 10:1 compression
- Ring set in file fit. All at 4.004" exactly. The hone will provide the necessary clearance for the forged pistons without the need to overbore.

We pay a lot for machine and labor hours here in Europe therefore replacing pistons with forged ones is actually a saver. I have access to a machine shop and can do a lot of work myself. This helps in expanding what can be done to the engine.

Instead of cutting the decks by nearly .025 inches to achieve a zero deck with shelf stuff we'll order custom pistons. Less hassle, less valve pockets.
Had to get them at 1.600" CD therefore the custom order. Hopefully not too much higher in price than the shelf stuff.

The compression of the stock engine is between 8.8:1 and 9.0:1 (sucks).
Gee this engine has no squish on the heads at all! The distance to the bottom of the piston dish including how much below deck it is and the gasket is nearly a 1/4" (5 mm).
Will be interesting to see the improvement once this engine runs.

It's time to deliver - there comes the images for the 4.3 V6 mild build.

Starting with the teardown of the engine itself. Had the engine sit on a palette nice to move around using a fork lift. Lifted up onto a table and taken apart.

TBI off, then the accessories from the intake manifold, the manifold itself, sensors and stuff from the heads and finally the heads.

This engine has 105'000 miles on it and looks pristine. Despite the car being fully rusted it shows that the truck had been serviced as per manufacturer instructions. The valvetrain and all internals are witness of this. Little, to nearly no wear. Even the hone on the cylinders is still there. Something to be expected from a low power low rpm installation which has been serviced well.

Taking more apart
 

Had it put upright on the back side (flexplate side) for an easy access to the front cover and assemblies.
At that time I had no access to an engine stand. But for a tear-down it is not required in my opinion.

Heads are off, all stuff around is off and the oil pan is gone. Next step will be rotating assembly and pistons.

Rotating assembly
 

Taken the rotating assembly apart and finally removed all the mains to pull the crankshaft.
All was looking o.k. could have been used again without hesitation. The crankshaft shows abrasion from particles. Under the microscope we found out that they were mainly from casting sand.

The bearings show wear on the thrust side something that is witness to poor lubrication at times. The truck had very long periods where it had not been run. (1 - 2 years at times).
At the same time many particle traces on the crank could be traced to particles now embedded in the bearing shells. (This is what the soft surface is supposed to do.)

Barely acceptable for an OEM and it could have been put back together to run an additional 100'000 miles using the same bearings in the exact same location. Not something to do when doing a build. The crank needs re-surfacing (grinding) one size under and new bearings. But I got a better crank which fits and is nicer.

The pics show:
- Rod bearing and crank thrust with scratch.
- My rod and piston packing
- A rod bearing showing surface abrasion and contact patches
- timing chain assembly
- a main bearing with a deep scratch through a part of the bearing. At the end of the scratch was found the particle that caused it.
- the crank with all the scratches
- a piston with the carbon buildup. Nice ring wear and just minor scuffing on the skirt.

Heads disassembly
 

Taking all the stuff from the heads apart. Again all looking like what you would expect from this engine. Will decide on the valve size later on in the build once I've got my pistons and can measure clearances to the pockets.

At the same time on the outside of the heads I ground all casting ridges and flesh away. Chamfered all sharp edges, more on the outside just a little on passages or where gaskets will be employed. I hate cutting my fingers on that stuff and these heads will be handled a lot before they go back onto the engine.

Pictures show:
- valves of one head - the liquid is from the parts cleaner.
- Combustion chamber, again the liquid is not oil but from the parts cleaner
- Head with ground casting ribs and sharp edges chamfered.
- various exhaust valves in different states of cleaning. Brushed them but no polishing as I will get new ones most probably.
- the camshaft and part of the valvetrain including one of the valve covers after a bath in the parts cleaner.
- the lifters (could be reused without hesitating)

Starting to build - JE Pistons and test assembly
 

The project is in no hurry which has suited me well. In the meantime I found a couple friends with the capabilities and interest to share their knowledge on fuel injection systems, ECU tuning and such to bring the build forward. The camshaft from COMP Cams is according to their advertising compatible with stock computer but I can even accept a tune now. Something that I will do anyways now that I can. A proper tune on the ECU will help with efficiency and fuel economy.

After 3 months the JE custom pistons finally arrived. Beautiful stuff! Measured and done a mix and match to adjust masses with the pins. Now I have to adjust a maximum of 1.5 grams on one piston while the others will be in the 0.8 gram range. I was wondering that the pistons had up to 3 grams of difference between them and the pins 1 gram of range. For once it has suited me well, so I have been able to reduce the difference to less than 2 grams without machining.

Taking the OEM pistons apart needed a press. CC'ing the heads had me wonder because the final compression this engine had was around 8.9:1, far from the advertised 9,3:1. It has no squish area that can be called such because of the pistons resting more than 0.050 below deck. With the gasket it ended up being 0.100 inches. No squish whatsoever. The dish and 4 pockets added even more volume (22 cc's BTW) to lower compression. No wonder the OEM 4.3l V6 is a pathetic engine.

Would be nice one day to just put a set of zero deck flat top pistons into an OEM engine without any other changes and see what the outcome is. (3 - 5 % more hp/torque?).

Some random pics of the front cover with paint removed, valves polished to be used for the cc'ing a rod on the scale and preparing the JE stuff. The last step as two days ago is that I have the pistons matched to their respective pins. Pins marked (electric arc tool) Pistons marked for their respective cylinders getting ready to be machined for weight.

Pictures show:
- pressing the OEM piston bolts
- cc'ing the combustion chambers
- the timing gear cover after paint and rust removal - waiting for powder coating
- a set of valves polished - will be using these for the cc'ing and valvetrain geometry.
- weighing the OEM rods - just out of curiosity. They came out very close to each other within 1.7 grams.
- unpacking the JE pistons forged pistons
- the respective ring set - all ordered for file fit - this way we can play with the hone to adjust for correct clearance and file fit the rings to match
- weighing the new pistons and compiling the master weight (mass) chart.
- pistons mixed and matched. Because of the 6 cylinder you need a set of 4 lefts and 2 rights. Just marked with paint, before marking them definitively

Loving the attention to detail; glad you have access to a machine shop! Do you think 10:1 CR will be achievable, even with all that clearance still?

Thanks - I try to be a good engine builder ;)

Attention when building engines is the difference in taking apart an engine and wondering if the mains and rod bearings have ever been used or finding them full of debris and scratches.

Clean workspace - e.g. new pistons will never be placed barely on the table where they pick up filings and other debris. After machining cleaner, brushes and hot tank them every time.

The pistons are 146 grams lighter than stock which may enable us to change the crankshaft to an internally balanced one.

Building with custom JE Pistons. They are sitting 0.011 inches below deck now. After straighting the decks and minimal machining the pistons will sit 0.008 inches below deck and I'll use a COMETIC 0.027 or 0.030 MLS gasket. This would end in a 11.1:1 compression as the JE pistons have only 4 cc reliefs.

Machining the combustion chambers to same sizes on all pistons and rounding out the bosses will put compression to a range of 10.4:1 to 10.8:1.

More pics coming. I'll also supply the specs once I have all measured.

Next headache is where to machine the beautiful JE Pistons for these 1.5 grams ;)

Found out that I don't need to work on the pistons. Could mix and match them with the differences in pin and small end weight of the rods. I'm below 1 gram now on the rotating assembly. Next will be the heads valvetrain and the crank.

Nice work man!

The heads
 

After having disassembled both heads I just had them deburred and chamfered on the outsides. I hate cutting my hands on sharp stuff, especially with a build where I will have to handle the heads dozen's of times.

Some pics, from what they looked when coming off the engine, after hot tanking and deburring. CC'ing the chambers had the surprise that they were within 0.3 cc's of each other. The highest number was 65.2 cc's which will most probably go up to 66 cc's because of the work on smoothing out the chambers. Cutting the heads will most probably remove 1 cc so my calculations are based on a 66 cc chamber. Even with a pessimistic assumption it will put compression to 10,8:1 as the lowest value.

The OEM style rocker studs were pressed in ones. Pulled them with a sliding hammer, then machined the bosses for equal height, chamfered and cut 3/8" threads through. For the next step once the clearance of the valves to pistons is defined with the new camshaft we will have to cut the bosses further down by about 1/8" for proper geometry with the rocker arms. There is plenty of thread with these bosses (about 1"). Within the inlet channels I will just round the edges but not go the hassle to epoxy the holes. It's a street engine not a race engine.

The valvetrain with the COMP Magnum roller rockers will no longer clear the plastic valve covers. I cannot get proper covers for this engine which would clear the air filter element. The plastic covers have a nice geometry and I will most probably just make an aluminium spacer about 7/8" thick with an o-ring groove on the lower side to rest on the heads rim as the OEM valve cover did and the top flat as for the OEM style gasket to have a seat. Will need some longer bolts but will most probably do them myself with a T on the top end for appearance and easy removal.

The pics show:
- cc'ing the combustion chamber a second time
- pulling the OEM pressed in studs
- the 4.3 V6 in good company. A 350 1970's corvette engine that had been f****ed up by the engine builder because they sanded the intake manifold. 2 quarts of oil on 120 miles.
- milling the stud bossed
- cutting threads into the bosses
- test assembly of the valves and rocker arm (just bought one 1.6:1 rocker arm for testing)
- side view of the rocker arm
- witness mark for valvetrain geometry. (This is still no good as this is the mark left on the extreme position. Rocker arm needs to go lower.)
- clearance issue with the valve cover. There is about 7/8" now but with lowering the rocker arm for correct geometry will add the clearance needed with a 7/8" spacer.

I love dry ice blasting
 

I have access to a company who does dry ice blasting and I can use the left over pellets sometimes to clean my stuff. I do their website and PR stuff. We had used my parts for demonstration purposes and to take pics.

Some pics from the cleaning of the valve covers. The covers had been in the parts cleaner and brushed two times to no avail. The brown gunk sticking to them in every crevice. 5 minutes with the dry ice and they looked pristine. Plastic surface had not even a scratch.

Same for the pistons. Especially the ring grooves came out mint! Whenever doing a rebuild and reusing pistons I will definitively go for this method. Has removed all the soot and more important the residues from the grooves without scratching. Passed a Kleenex through them and came out white.

Left piston is as it came out of the engine and just cleaned with a rag. Middle piston is after a thorough wash in the parts cleaner and wiping clean with a rag. Right is piston like the left one after 3 - 4 minutes.

Some parts restored
 

I'm a nerd when it comes to do things correctly. So a lot of time goes into details even some details that will never be seen once assembled.

I have several parts which needed restoring such as the timing chain cover or the aluminium support for the HVAC compressor. Some of this stuff will be put together in a different manner such as using studs instead of bolts. E.g. the stupid bolts on the climate compressor where you have to take the pulley off to get them out. I'll try a similar approach as for a racing engine with ease of access and servicing in mind.

Pictures of some of the repairs and changes. Timing cover has been in paint remover, straightened in two places where it was dented, sanded a scratch (not from me) and had it galvanized.

Also had both my TBI's rebuilt with a complete gasket kit and one put into my running Blazer. Had some issues and changed all the sensors on the engine and got a complete set of new ones for the build. Now I start to hope that the engine is not running too good or develop too many HP, else I have to switch injectors on the TBI and retune the whole thing. We'll see once it runs and hangs on the dyno.

The pics show:
- timing gear cover rust-free and repaired
- timing gear cover and the oil pan rails after black galvanizing.
- A/C compressor support disassembled
- TBI 220 disassembly
- TBI taken apart and laid out
- TBI re-assembly
- A/C compressor support after grinding the casting parting lines
- The support wile priming
- The support getting it's final aluminium silver color. A special paint we use in restoration of cars to paint the aluminium blocks of old italian sportscars. They did that in the 50 - end of 70's on the cast aluminium blocks to prevent the bare aluminium from corroding.

Working the heads
 

I do not plan on porting the heads. The flow up to 4'500 rpm should be enough and the engine being built for low end torque will hardly ever see above 4'500 rpm. Nevertheless I will do a "clean up" in all the runners and especially the bowls. The OEM casting and the cutting leaves a lot of irregular protrusions in the bowl area. Also the valve guides are sitting on a boss in the runners. All the cut edges will be smoothed out and the surface smoothed. Still working on the geometry to put on the straight edge towards the heads flat surface but a minimal radius might be best there to avoid hot spots.

Have to search for the good pictures. These are from the beginning of the work. Put about 2 hours into each head, doing runners and bowls so far.
Once I have another day to spend with them I have to cc the runners, make gauges from sheet metal to insert into the runners and cut them as close as possible to even out differences. The EGR port in the heads is still a problem and I'll see what happens there but again it is a street build and of minor concern.

Have put a nice smooth radius onto the intakes from begin of the bowl to about 1/8" to the seat. The rest will be done after cutting the seats for the final valve set. The exhaust ports have been smoothed and quite a bit of casting stuff, flesh and irregular ridges removed. The short bend radius has been left untouched except for smoothing it. The next step will be to match the ports to the gauges i'll make and then match them to the OEM headers.

Some pics of the progress and a series of what I do to the intake bowl. Valve guide bosses will just get a radius on the edge, nothing fancy here except of basic aerodynamics. I'll not cut them back as the bowl opens quite quickly on these castings and also retain the "ski-jump-ramp" for swirl. Have yet to find evidence that cleaning out helps low end torque. A race engine would be a different story but then I'd probably go with a set of aluminium BRODIX heads.

Many think that removing as much material as they can will yield benefits but not so in a low end torque engine. One of the reasons I do not cut back on the valve guide bosses is the opening of the bowl in this area. A volume flow will keep it's speed as long as the area in any place is the same. As soon as I open the area (which would be the result of cutting back the guide) it slows down. From what I have found out talking to race engine builders all suggested for my particular build (truck engine in a truck) to leave the area small as long as possible towards the valve. All agreed that the low rpm will not be an issue with the rather generous short radius but the higher airflow will leave more inertia in the intake charge. Also they agreed on leaving the ski jump for swirl and see what the results are. Some even think that it could handle a more aggressive camshaft without problems as the downward spiral vortex has a lot of energy that will keep it from changing direction towards an open exhaust valve and keep a better filling in the cylinder without too much of the mixture being drawn out the exhaust during overlap.

The pictures show:
- Heads innards on the top side. Two rocker arm stud threads and the head bolt location with chamfered edges. Removed the casting lines on the oil return holes and deburred the edges of the pushrod holes.
- Intake before working on it.
- Same intake (upside down) with initial grinding in the depths of the bowl.
- Same intake when working on the step that had been left from cutting the valveseats into the casting.
- Same intake working from the bowl up to that parting
- And still the same intake with smoothed changes from the bowl to the seat. Final porting to be done after cutting the seats into the throat. (backcut at about 70 degrees)

Finished cc'ing all my combustion chambers. To my surprise found them to match within 0.3 ccm!

All within a range of 64.8 to 65.2 ccm. How nice!

With the flat tops and a .027 MLS gasket this ups my compression to 11.5:1. So I can grind them by a lot without falling below 10.5:1 compression. Should make for a nice combustion chamber once I'm finished with them.

Enjoying the details of the engine rebuild. Please keep it coming. It would be great if you would give some tips and suggestions on how to do a less intense rebuild, but get some good results at a cheaper price. That would be appreciated after you have completed this project and reflect on the steps.

Thanks for the comment.

For the thoughts:

IMHO could be built for less than 3'000$ with the following limitations. Max rpm 4'500 (OEM redline) Max hp about 200.

Comp cams mild camshaft for some
200$

Timing chain set (aftermarket)
100$

Set of 8 flat top's from JE or SP depending on the actual CD of the pistons even the high ones from the 350
200 - 400$

Heads
maybe from a 96' from the junkyard
100$

Valves
120$

Machine work assuming the block is in good condition and crank is re-usable
Checking, cleaning, bore and hone, new bearings, decking, heads decking
1200$

Plus some 100 - 200 hours of your time building it. Head work etc.

What the outcome would be? I can't even assume. Guesstimating I would opt for some 15 - 25 hp more. Eventually when doing a proper mapping to the ignition and injection 20 - 30 hp more. Is it worth it?

You decide

The crankshaft
 

The crank I had in the engine was just barely within limits. It was scratched and gouged by particles in the bearings. To fit new bearings it would need grinding one under to use the first oversize bearings.

Shipping cranks around the world is expensive, the shipping costs more than the cast iron crank. But I lucked out with a marine shop nearby. The guy had a crank sitting for 20 years in his stock in decent condition. A couple of nicks but nothing serious so I have a crank to build upon. Should that crap... oh crank ever fail on me and I'll still be a Blazer aficionado I'll buy an expensive Arrow Precision billet one good for 700 hp and modify the block for 4 bolt mains and do a dry sump all out racing bottom. (Hopefully not within the next 10 years)

Crank inspected and measured. Within 1/10'000 of what it should be.

Again ground all sharp edges on the counterweights and the throws using a pair of old bearings to protect the surfaces against inadvertent slips with the file or Dremel grinder. Then worked the oil holes. The oil holes have a sharp edge on nearly all OEM cranks. The idea is to slightly chamfer them to get a thicker edge and then to polish it. The holes are huge so one tries to keep them as small as possible. This is required as we will have the crank nitrided for a harder bearing surface.

Pics show:
- the rod throws on the "split-pin" of the crankshaft. This is the offset of the V6 crank to make it even-fire. See the sharp edges...
- The throws with the left one polished and the right one showing the traces of the stone to egalize the small dents. (actually to make sure there are no protrusions/burrs.)
- The same throws after polishing both. You can also see the edges are no longer razor sharp. This also alleviates brittle material to brake off after nitriding.
- The counter weight before working on it. The edges are razor sharp
- And the counter weight after working on it.

The balance of the crank will not be affected by this as the removal of material is about 5 grams on the whole crankshaft. Now it is ready to be brought for nitriding.

For the inclined reader: https://en.wikipedia.org/wiki/Nitriding



Cleaned, polished for surface inspection. With a fine stone removed eventual burrs from all the nicks and dents. Then polished the crank again on a lathe. Now it's ready to go for nitriding. Next week I'll go for a ride (50 miles) to have it done and to advance this project. At the same time I'll get some more knowledge about nitriding.

Nice! Good score on the crank.

Oh, true, looks gross.

One of the pics actually (the one with the counterweight with the step and balancing hole) shows it during chamfering the edges. In order not to touch the throw surface I took a pair of old bearing shells and a piece of electrical wire to hold them in place.

Got a few very fine scratches, and a dent from the previous owner. polished away, with a fine stone made sure there are no protrusions.

Yesterday got the crank back from nitriding. Already straightened out now waiting for balancing.

Crank is back from nitriding. Had to clean it and polish all the radii and the throws as well as the mains. Then we had it on the blocks for straightening.

The master weights are readied and I hope to get it balanced this coming week.

This is so cool to watch your build. Thanks for sharing!

Here is a Super Chevy article on a 4.3 L V6 rebuild. They got 301 HP and shared the similarities and differences with the same era Chevy SB V8. I thought that you and the followers of this rebuild would be interested. I have been trying to find an old article on the 4.3L V6 rebuild I thought was in Popular Hot Rodding, but haven't been able to find it. If anyone knows of this Pop. Hot Rodding article , please let me know.

Chevy 4.3L 262ci V-6 - Engine Build

Thanks for the link. Nice build they did!

The heads are exactly the same ones that I work on.
I have not yet decided on the valves. It will depend on what a friend of mine tells me about the stock ECU. If we can do a proper mapping I will change the valves as well.
Just a little bit bigger at 2.02 and 1.60 (In / Ex) will allow to keep a venturi just before the seat and with tulipped valves and sleek stems I should have all the flow I could hope for without sacrificing low end power.

Or I will see if I can get a set of additional heads for cheap, so I can keep a set with OEM sized valves vs. bigger valves.
With the pistons at just 0.005 below deck I can change compression with the head gasket from 10.7:1 down to 9:1.

I'll just have to twist the arm of the guys with the engine dyno in order to have it for a week or so at the price for 3 days.

Not much going on. Waiting to balance the crank.

A little step further. Fixed the bobweights which are required to balance an asymmetrical crankshaft. Nearly all the V engines need those.
And finally got all my micrometers into one box. Before I had two different boxes. These are normed plastic containers with a lid which stack solidly on top of each or can be fitted by two's on top of the next size box.

Balancing - pre-balance
 

We wanted to know if it would work out to balance the crankshaft "internally" with the lighter pistons.

The reciprocating masses do factor in only for 50 % but at over 75 grams less per piston it makes a difference.

Turns out we have an imbalance of 277 grams on the rear end and 70 grams on the nose of the crank. Cool!
The front should be in balance by welding back two slugs of steel into the factory balancing holes they made.
The rear will be filled in by some 180 grams or more when filling the stock balancing bores. So we will balance it internally.

A set of pictures showing:

The master weights (bobweights) being prepared "exactly" to within 0.2 grams in total mass. Then I could balance them myself after an introduction to the balancing machine. Nice - I've learnt a new skill and the boss in the machine shop said that I did very well and that I had the machine and the balancing figured out properly.

Had to service my daily ride my SAAB 9-5. Oil and filter change, and change rear brake discs and pads this time. Just a couple pics to show how we work in the place I work for about 10 % of my working time. I have an 80 % fixed employment at the airport and work on my own account (sending invoices) for some 10 - 15 % time to fill up to a 100 % job.

Saab on the lift, and yes, we are "nerds" for sure at that garage. Nothing ever goes back in without cleaning, fixing, proper treatment and proper lubrication!

The balancing pics show :

The bobweights in their holder.
One of the weights (actually "masses") on a straight shaft being balanced themselves.
The CEMB balancing machines display after the first run showing 0.62 grams inbalance. (Corrected to less than 0.22 grams on all masses)
The Blazers crankshaft on the balancing machine.

The masses still have to be added in this pic but it was midnight and I forgot to take pics of the crank with the masses attached and the first spin we gave it.

The further pictures:


The "background"
Left rear brakes before putting on the new discs and pads
Right rear brakes already done.
Wheel bolts in the cleaner.
Saab on the lift for service and a view of the garage.

As I said, clean it, grease it.
That's how I work and how I got a reputation for being a conscientious and precise mechanic. Working on old cars also makes you learn a thing or two every day. And working on new cars gets me the routine to be fast but thorough.

Crankshaft preparation for changing from external to internal balance.

Measured the OEM balancing holes and made 4 slugs to weld into place to fill up as much as we can.
The mass at the flexplate removed we'll balance the shaft afterwards to "INTERNAL BALANCE". The less mass on the new pistons should take us there with just about 1 slug of tungsten at the rear. If lucky we are already heavy enough at the front end of the crankshaft.

Pictures now show:

Crank with the master masses after the first spin.
Doing the slugs on the lathe
The slugs which will go into the holes
Welding the slugs (my machine shop guy is a genius with a welding machine)
Crank with tape to grind away the welding beads and contour (for protection of the bearing surfaces)

I love seeing quality machine work being done! :)

Me too.
I lucked out on that guy. Know him since about 30 years and since 2 years I'm kinda his apprentice. I can do my stuff in their shop and I help them out whenever I can.

He shows me and instructs me on how things are done. Trying to keep records but the sheer amount of stuff you can learn from that guy is amazing.

Yesterday night we ran the balance once more with the slugs in place to determine the tungsten to be added.

Lucky us, two slugs at 7/8" diameter and a tiny bit in the front is all it takes. Another machine I got trained on: UMA horizontal drill. He showed me on one hole how to do it and I did the other two. Now ready to turn the slugs on the lathe.

On a reasonably sized lathe (some 1 ton heavy Oerlikon from the late 50's) I turned the three slugs for the inserts to 0.05 mm (.002") clearance so they slide in and out.
Once balancing is finished we will fix them in place.

The pics show:
The flexplate with the external balancing mass
Horizontal bore fixture pre-drilling
Horizontal bore cutting the 22 mm hole (about 7/8")
Horizontal bore with a reamer to get a nice bore.
The small one we had to use an adjustable reamer and reamed it by hand.
And the reasonably sized lathe... ;)

The final blance run showed:
rear end of crankshaft 0.18 g residual imbalance
front end of crankshaft 0.08 g residual imbalance

The specs:
The 4.3 V6 with balance shaft seems to be a bit of a mistery when it comes to balancing.
We looked up the tables and they all gave 50% of the reciprocating mass to be accounted for. It seems that some race engine builders do less than 50 % while only very few do a little more than 50 %.
The balance shaft has initially nothing to do with the balancing of the crankshaft as it takes care of different moments in the engine (vertical motion).
We will see what happens once the engine is running, because the pistons are lighter than the OEM it may require the balance shaft to be ground as well. I'll tackle that problem once it appears.

Now I have an internally balanced crankshaft. The next tasks will be measuring the block, crank and cam to order bearings, machine for deck height and squareness, then test assemble the full rotating assembly and measure piston to deck heights.

End of 2017

Latest update in 2017. The next steps may have to wait quite a bit as I have some training to do at my workplace until the end of January.

Got one more step ahead by balancing the flexplate and the balancer.
Mounted the flexplate onto the already balanced crankshaft and did a static balance on the flex-plate.
Then removed the flex-plate and did a static balance on the balancer alone.
Once completed to within 1/10 of a gram mounted both and did a final spin.

Balancing is now down to 0.02 grams static and less than 0.12 grams dynamic imbalance.
Normally an engine revving up to 5'500 rpm such as this V6 would be well within balancing limits at less than 1.5 grams.

So i now have an internally balanced assembly apt for a 10'000 rpm race engine.

As my friend said: "L'art pour l'art"

https://en.wikipedia.org/wiki/Art_for_art%27s_sake

That reminds me of the MGM iconic Leo the Lion and the Latin motto used since 1916: "Ars Gratia Artis" which translates as : Art for Art's Sake.

https://en.wikipedia.org/wiki/Metro-...ogo_and_mottos

Finally my courses are over. Looking forward to March when I have some vacation.

The only thing that has been done is grind the block and free all passages from casting ribs. Oil holes in the valley. All sharp edges chamfered and block ready to be measured.

Maybe today I'm able to measure the crankshaft and the block to get the correct heights and prepare the machine work. Then we'll sift through the shops main and rod bearing stock to see if we find the correct size or if I have to order some.