Little Mouse - The 1994 - 4.3l TBI engine blueprint and tuning
#81
04-30-2020, 12:31 PM
I hope Plan B works out for you. . . .I'm sure even without all the engine work a good tune with the MS would yield a improvement in the 4.3. I was actually just looking at the EPROMs on Summit the other day and wondering if they're worth it. Not too expensive at ~$100, but would love to hear feedback from someone on those too!
Also, totally with you on the sports thing. Would much rather spend my time researching upgrades, shopping parts, or tinkering with a vehicle than watching a bunch of guys chase a ball and run into each other lol.
Also, totally with you on the sports thing. Would much rather spend my time researching upgrades, shopping parts, or tinkering with a vehicle than watching a bunch of guys chase a ball and run into each other lol.
#82
04-30-2020, 06:37 PM
Les,
Good idea, despite them being custom order to specific C.D. I may find a buyer.
It would need a stock bore which needs just a slight hone.
They are only 4.002" and C.D. (compression distance) is slightly higher than normal to bring them up to the deck. *
Plus they are 70 grams lighter than stock pistons. That means crank balancing for sure.
* I still wonder why they wanted to sell me a shelf flat top piston for a zero deck application.
With the advertised C.D. I would have had the pistons nearly 3 mm (0.100") below deck.
Good idea, despite them being custom order to specific C.D. I may find a buyer.
It would need a stock bore which needs just a slight hone.
They are only 4.002" and C.D. (compression distance) is slightly higher than normal to bring them up to the deck. *
Plus they are 70 grams lighter than stock pistons. That means crank balancing for sure.
* I still wonder why they wanted to sell me a shelf flat top piston for a zero deck application.
With the advertised C.D. I would have had the pistons nearly 3 mm (0.100") below deck.
#83
04-30-2020, 07:21 PM
Originally Posted by error_401
Les,
Good idea, despite them being custom order to specific C.D. I may find a buyer.
It would need a stock bore which needs just a slight hone.
They are only 4.002" and C.D. (compression distance) is slightly higher than normal to bring them up to the deck. *
Plus they are 70 grams lighter than stock pistons. That means crank balancing for sure.
* I still wonder why they wanted to sell me a shelf flat top piston for a zero deck application.
With the advertised C.D. I would have had the pistons nearly 3 mm (0.100") below deck.
Good idea, despite them being custom order to specific C.D. I may find a buyer.
It would need a stock bore which needs just a slight hone.
They are only 4.002" and C.D. (compression distance) is slightly higher than normal to bring them up to the deck. *
Plus they are 70 grams lighter than stock pistons. That means crank balancing for sure.
* I still wonder why they wanted to sell me a shelf flat top piston for a zero deck application.
With the advertised C.D. I would have had the pistons nearly 3 mm (0.100") below deck.
Just checked on the Skip White site and the Wiseco pistons in their 350 SBC rotating assembly (same as 4.3 but with 8 pistons) has a CH of 1.575. What is yours? But probably these are heavier and your crank is undoubtedly already re-balanced - so not a choice for you at this point - I'm just curious. Their pistons give CR of 10.3 with 0.041 gasket, zero deck, and 64cc chambers which is perfect for pump premium fuel.
I'm curious about the balance on your crankshaft, especially with the light pistons. 4.3 V-6's have a funky strange balance as they do not balance naturally (hence addition of the balance shaft in later years). Did you balance with harmonic balancer and flywheel included? A lot of different crankshaft and piston/rod weights plus specific balancers and flywheels over the years. I'm sure you may have seen this info? https://www.s10forum.com/threads/the...3-info.131868/
Last edited by LesMyer; 04-30-2020 at 07:47 PM.
#84
05-01-2020, 05:07 AM
Les,
You are right, as always. I was mistaken, we went 0.001 inches "less" CD for another reason. It's 2 years from the order and too many projects gone by in the meantime.
We had to put a custom order in, as we could not find flat top pistons, off the shelf, with only two valve reliefs at that time. All advertised shelf pistons were 1.55 CD which would have put them way too far down into the bore to come up with a decent compression. The final order is 1.574 CD which is 0.001 less than stock to allow for the machining of the block without getting crazy with the compression. The CD has been ordered in such a way, that after machining of the block we can retain maximum deck thickness. At the time we did not know that 1.575 would be zero-deck. 1.574 has been calculated based on measurings taken off the engine block.
The second reason being, that with this setup, should anything happen to the engine and require machining the deck, we can shave off some of the top of the pistons safely and rebuild the engine with the same gasket thickness, or even cut the deck more and use a 0.030" MLS gasket to compensate.
Machining for a perfectly square block and sealing surface was achieved by shaving off 0.15 mm (0.006") which puts the pistons down into the bore to 0.35 mm (0.018"). With a 0.68 mm (0.027") MLS it sums up to a perfect 1.00 mm (0.040") squish. The rocking of the pistons is fully accounted for within the bore and below deck. They would not touch the heads even without gasket. The slightly less CD on the order would have allowed us to shave off the piston should for one or another reason arise the need to lower compression, i.e. cutting more off the deck.
Very unfortunate that the bores turned out to have these humps, the pistons with the stock length rods turned out to be just perfect matches for what had been planned. So hopefully this time with the oversize pistons after boring the block and honing we'll have a perfect short block. The pistons mass difference should be negligible. Once I have the pistons we'll weigh them and take appropriate measures.
Finally, yes, they should fit into any V6 where the deck has not been cut down like crazy. Pretty much exactly what you proposed with the Skip White pistons.
Balancing (in this thread #32 until #37)
The machine shop guys are friends of mine, so we got a little crazy in this aspect. Somewhere up the thread we got to the point where we stopped going any further having a good laugh. The shop's owner just said... for art's sake. (Lit: l'art pour l'art - a French saying for going out any bounds just because we can.)
So for about 750$ I got myself a 3'000$ race balancing job on the rotating assembly. All the work around the balancing has been done by myself, so my friend only spent about 2 hours on the crank himself. My hours added up to about 12 hours, so we have a 14 hours work into balancing.
Final ISO balancing grade 6.3 which is about what you do for a race engine. (Final Mass imbalance 0.17 grams - about a knife tip of sugar, a pointed knife)
About 5 hours went into changing the balance from external (weights at the balancer and flexplate) to fully internal.
Pistons and pins matched to below 1 gram (0,30 grams), rods were so close, that by matching pistons, pins with rods we had the differences below 1 gramm (if I have converted it correctly this is 0.002 lbs). Once the crank was balanced we first balanced the flexplate (with the external balancing weight removed
of course) and the balancer (for internal balance), before putting everything together and back on the balancing machine for checking. Residual imbalance less than 0.30 grams of the whole rotating assembly.
Technicalities on balancing
Balancing the V6's seems to be a philosophic question as well. A bit less on the even fire engines. Talking to several engine builders and consulting a bit of literature on the subject we decided on the normal 50 %, that is the same you do for a V8 SBC. That is half of the rotating parts plus 100 % of the oscillating. 50 % rod big end with bearings and an oil allowance, plus all of rod small end, piston and pin and ring and locks.
Should have gone for a 4 bolt main install as well. The rotating assembly should be good for up to 9'000 - 10'000 rpm, with the 2 bolt mains 6'000 rpm should be just a fine redline limit with plenty of margin.
Balance shaft - or wobbling theory
The 90° V6 has some vibrations (better term: oscillations) in first and second order. They create a complex shifting of forces and moments which we have to take into account. While it is balanced internally (all inside the engine, not the type of balancing) the whole engine is now subject to changes in the forces acting from within. The internal engine balance takes care of the mechanically damaging forces and is an absolute "must" to make an engine run at all. All engines with odd number of cylinders (1 cylinder engines being a special case) and V6 and V8 engines have asymmetrical crankshafts. That means even if the system is statically in balance, over the length of an engine we'll have some forces acting in elliptical ways. They create a wobble on the whole engine. While a V8 can oppose all movements somehow (too complicated in detail, consider 4 x 90°), the V6 lacks a set of pistons acting as the countering force (3 x 120°).
Put simply: All engines create some kind of wobble. 90° angular engines are less "wobbly" than 120° or odd angle engines. The worst must have been that early Blazer engines with the 90° V6 "odd fire" crankshaft. Must have been a terrible shaker.
Our actual V6 engines "even fire" are less shaky but still wobble.
The wobbling which causes discomfort or the impression of a rough engine is more pronounced in the vertical than lateral. About the same thing as if you took a garden hose lying in a straight line on your lawn and then you give it a vertical jolt wich creates a wave running away from you. Now add a bit lateral movement and you have the shaking of the V6.
Balance shaft - countering the wobble
The balance shaft between the banks counteracts this wobbling. I've not been able to find literature where you could properly calculate the required masses. It probably comes down to testing and most probably the lighter rotating assembly I have will not be affected by the balance shaft. I'll see if I can get my hands onto a vibration measuring device (probably writing an app and strapping a smartphone to the engine LOL) to see the difference between stock and the lighter engine. I'm not too concerned at the moment about ride quality and smoothness of the engine.
A nice illustration video for the forces.
The article you pointed out is kind of the 90° V6 bible. Published in the engine builders magazine quite a while ago. Unfortunately it has never been updated and reflects the engines roughly until 1995.
That's it for the 1st of May 2020. Keep healthy and busy.
You are right, as always. I was mistaken, we went 0.001 inches "less" CD for another reason. It's 2 years from the order and too many projects gone by in the meantime.
We had to put a custom order in, as we could not find flat top pistons, off the shelf, with only two valve reliefs at that time. All advertised shelf pistons were 1.55 CD which would have put them way too far down into the bore to come up with a decent compression. The final order is 1.574 CD which is 0.001 less than stock to allow for the machining of the block without getting crazy with the compression. The CD has been ordered in such a way, that after machining of the block we can retain maximum deck thickness. At the time we did not know that 1.575 would be zero-deck. 1.574 has been calculated based on measurings taken off the engine block.
The second reason being, that with this setup, should anything happen to the engine and require machining the deck, we can shave off some of the top of the pistons safely and rebuild the engine with the same gasket thickness, or even cut the deck more and use a 0.030" MLS gasket to compensate.
Machining for a perfectly square block and sealing surface was achieved by shaving off 0.15 mm (0.006") which puts the pistons down into the bore to 0.35 mm (0.018"). With a 0.68 mm (0.027") MLS it sums up to a perfect 1.00 mm (0.040") squish. The rocking of the pistons is fully accounted for within the bore and below deck. They would not touch the heads even without gasket. The slightly less CD on the order would have allowed us to shave off the piston should for one or another reason arise the need to lower compression, i.e. cutting more off the deck.
Very unfortunate that the bores turned out to have these humps, the pistons with the stock length rods turned out to be just perfect matches for what had been planned. So hopefully this time with the oversize pistons after boring the block and honing we'll have a perfect short block. The pistons mass difference should be negligible. Once I have the pistons we'll weigh them and take appropriate measures.
Finally, yes, they should fit into any V6 where the deck has not been cut down like crazy. Pretty much exactly what you proposed with the Skip White pistons.
Balancing (in this thread #32 until #37)
The machine shop guys are friends of mine, so we got a little crazy in this aspect. Somewhere up the thread we got to the point where we stopped going any further having a good laugh. The shop's owner just said... for art's sake. (Lit: l'art pour l'art - a French saying for going out any bounds just because we can.)
So for about 750$ I got myself a 3'000$ race balancing job on the rotating assembly. All the work around the balancing has been done by myself, so my friend only spent about 2 hours on the crank himself. My hours added up to about 12 hours, so we have a 14 hours work into balancing.
Final ISO balancing grade 6.3 which is about what you do for a race engine. (Final Mass imbalance 0.17 grams - about a knife tip of sugar, a pointed knife)
About 5 hours went into changing the balance from external (weights at the balancer and flexplate) to fully internal.
Pistons and pins matched to below 1 gram (0,30 grams), rods were so close, that by matching pistons, pins with rods we had the differences below 1 gramm (if I have converted it correctly this is 0.002 lbs). Once the crank was balanced we first balanced the flexplate (with the external balancing weight removed
of course) and the balancer (for internal balance), before putting everything together and back on the balancing machine for checking. Residual imbalance less than 0.30 grams of the whole rotating assembly.Technicalities on balancing
Balancing the V6's seems to be a philosophic question as well. A bit less on the even fire engines. Talking to several engine builders and consulting a bit of literature on the subject we decided on the normal 50 %, that is the same you do for a V8 SBC. That is half of the rotating parts plus 100 % of the oscillating. 50 % rod big end with bearings and an oil allowance, plus all of rod small end, piston and pin and ring and locks.
Should have gone for a 4 bolt main install as well. The rotating assembly should be good for up to 9'000 - 10'000 rpm, with the 2 bolt mains 6'000 rpm should be just a fine redline limit with plenty of margin.
Balance shaft - or wobbling theory
The 90° V6 has some vibrations (better term: oscillations) in first and second order. They create a complex shifting of forces and moments which we have to take into account. While it is balanced internally (all inside the engine, not the type of balancing) the whole engine is now subject to changes in the forces acting from within. The internal engine balance takes care of the mechanically damaging forces and is an absolute "must" to make an engine run at all. All engines with odd number of cylinders (1 cylinder engines being a special case) and V6 and V8 engines have asymmetrical crankshafts. That means even if the system is statically in balance, over the length of an engine we'll have some forces acting in elliptical ways. They create a wobble on the whole engine. While a V8 can oppose all movements somehow (too complicated in detail, consider 4 x 90°), the V6 lacks a set of pistons acting as the countering force (3 x 120°).
Put simply: All engines create some kind of wobble. 90° angular engines are less "wobbly" than 120° or odd angle engines. The worst must have been that early Blazer engines with the 90° V6 "odd fire" crankshaft. Must have been a terrible shaker.
Our actual V6 engines "even fire" are less shaky but still wobble.
The wobbling which causes discomfort or the impression of a rough engine is more pronounced in the vertical than lateral. About the same thing as if you took a garden hose lying in a straight line on your lawn and then you give it a vertical jolt wich creates a wave running away from you. Now add a bit lateral movement and you have the shaking of the V6.
Balance shaft - countering the wobble
The balance shaft between the banks counteracts this wobbling. I've not been able to find literature where you could properly calculate the required masses. It probably comes down to testing and most probably the lighter rotating assembly I have will not be affected by the balance shaft. I'll see if I can get my hands onto a vibration measuring device (probably writing an app and strapping a smartphone to the engine LOL) to see the difference between stock and the lighter engine. I'm not too concerned at the moment about ride quality and smoothness of the engine.
A nice illustration video for the forces.
The article you pointed out is kind of the 90° V6 bible. Published in the engine builders magazine quite a while ago. Unfortunately it has never been updated and reflects the engines roughly until 1995.
That's it for the 1st of May 2020. Keep healthy and busy.
Last edited by error_401; 05-01-2020 at 06:36 AM.
#85
05-01-2020, 06:36 AM
- Glad to hear you got the balancing sorted out. I think the 50:50 bob weights are right for the non balance shaft engine. Balance shaft engines are 48:52 IIRC for some reason. Internal balance is the best! I would like to see this with the Brodix heads
#86
05-01-2020, 06:39 AM
Correct, that's the philosophical question. I got all numbers from 45 to 55 on balancing. More extreme for the odd-fire crankshafts. Race engine builders like to overcompensate, one said going a bit less with the balance shaft "may" make the assembly a bit lighter over all but he also agreed that 50% would be in the middle of the field.
Brodix Heads ... had a look at them, but because building a daily driver out of question. Way too large ports for decent low end torque.
Well - once the engine is in the Blazer - I do have a spare engine again, do I!?
Brodix Heads
... had a look at them, but because building a daily driver out of question. Way too large ports for decent low end torque.Well - once the engine is in the Blazer - I do have a spare engine again, do I!?
Last edited by error_401; 05-01-2020 at 06:43 AM.
#87
05-01-2020, 09:06 PM
Originally Posted by error_401
Correct, that's the philosophical question. I got all numbers from 45 to 55 on balancing. More extreme for the odd-fire crankshafts. Race engine builders like to overcompensate, one said going a bit less with the balance shaft "may" make the assembly a bit lighter over all but he also agreed that 50% would be in the middle of the field.
Brodix Heads ... had a look at them, but because building a daily driver out of question. Way too large ports for decent low end torque.
Well - once the engine is in the Blazer - I do have a spare engine again, do I!?
Brodix Heads
... had a look at them, but because building a daily driver out of question. Way too large ports for decent low end torque.Well - once the engine is in the Blazer - I do have a spare engine again, do I!?
https://brodix.com/90-v6
Last edited by LesMyer; 05-01-2020 at 09:09 PM.
#89
05-17-2020, 03:33 AM
Block has been bored as well. Monday or Tuesday will be honing. Then taking care of the piston weight.
We can shave off about 5 grams by cutting down the remainder of the piston skirt left and right of the piston pin down to the piston pin bosses. Anyway funny that JE has left that circular section at the base of the piston. Not doing much for stability and useless in that direction as it will never touch the cylinder walls. We'll probably ask JE pistons if it hurts cutting that off. But for the low power build I'm not overly concerned by cutting it off.
Then calculate the difference to the actual balancing. A bit under-balanced should not hurt. Anyway we have been talking balancing rules for these V6's range from 40 - 60 % of the alternating masses. We may even do - nothing.
Looking forward to next week.
We can shave off about 5 grams by cutting down the remainder of the piston skirt left and right of the piston pin down to the piston pin bosses. Anyway funny that JE has left that circular section at the base of the piston. Not doing much for stability and useless in that direction as it will never touch the cylinder walls. We'll probably ask JE pistons if it hurts cutting that off. But for the low power build I'm not overly concerned by cutting it off.
Then calculate the difference to the actual balancing. A bit under-balanced should not hurt. Anyway we have been talking balancing rules for these V6's range from 40 - 60 % of the alternating masses. We may even do - nothing.
Looking forward to next week.
