Little Mouse - The 1994 - 4.3l TBI engine blueprint and tuning
#31
10-28-2017, 07:54 AM
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
Chevy 4.3L 262ci V-6 - Engine Build
#32
10-30-2017, 02:52 PM
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.
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.
Last edited by error_401; 11-03-2017 at 07:07 AM.
#33
11-19-2017, 04:58 AM
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.
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.
Last edited by error_401; 11-23-2017 at 04:44 AM.
#34
11-23-2017, 04:43 AM
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)
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)
#36
11-24-2017, 04:32 AM
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.
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.
#37
11-24-2017, 04:33 AM
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.
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.
Last edited by error_401; 11-26-2017 at 06:38 AM.
#38
01-04-2018, 01:01 AM
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
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
Last edited by error_401; 01-04-2018 at 01:03 AM.
#39
01-05-2018, 09:20 AM
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
https://en.wikipedia.org/wiki/Metro-...ogo_and_mottos
#40
01-30-2018, 03:30 AM
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.
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.