new GM 4.3L V-6

Status
Not open for further replies.
Joined
Jun 3, 2003
Messages
4,410
Location
BC, Canada
The old 4.3 V6 was basically a 350 sbc with 2 cylinders missing.

There is 2 crankshafts available, one has a journal for every connecting rod
called the even fire crank.
The other crankshaft looks like a sbc crank with two connecting rods per
journal, called the odd-fire crank.

The even fire crank had a habit of breaking in marine or performance applications.
When I heard of someone using that engine in an ultra lite aircraft,
I said; "What!!!??".

If that crank breaks during a full power take-off he's toast.

The odd fire crank is many times less prone to breakage and used in motor sport
applications.

I've looked, but I can't find information on the engine design of the
new 4.3L.
 
The new one is based on the same design as the new Gen V v-8's like the new 5.3L and 6.2L engines.

Same 92 mm stroke as the 5.3L V8 but the bore is larger than the 5.3L at 99.6 mm vs. 96.01 mm.
 
A GM engine that doesn't hold up? Can it be? While Chevrolet is GMs "cheap",mass market brand it only makes sense that its engines be cheap to build too.I rarely see an old small block application that still has its original engine.Whereas Chrysler and Fords seem to retain theirs...
 
Pretty baseless comment if you look at the numbers. Far more SBC's made and still on the road.

Nothing wrong with GM's V8's, and the older ones may be even better. These aren't Northstars...
 
Originally Posted By: NHGUY
A GM engine that doesn't hold up? Can it be? While Chevrolet is GMs "cheap",mass market brand it only makes sense that its engines be cheap to build too.I rarely see an old small block application that still has its original engine.Whereas Chrysler and Fords seem to retain theirs...


lol you serious?
 
I was thinking more on the lines of connecting rod length,
crank journal size, block deck height and not the 60s all over again.
 
Originally Posted By: NHGUY
A GM engine that doesn't hold up? Can it be? While Chevrolet is GMs "cheap",mass market brand it only makes sense that its engines be cheap to build too.I rarely see an old small block application that still has its original engine.Whereas Chrysler and Fords seem to retain theirs...


GM uses the same engines between GM brands. 4.3 is used in both the Chevy and GMC pickup, 3.6 is used in multiple applications, etc. Your post doesn't make any sense.
 
Looks like the 200 and 229 were odd fire, while the 4.3 was always even. Wikipedia Link

I forget, do 60 degree V6's need balance shafts?

*

This new V6 is quite a step ahead, but it seems still a step behind. 285hp? Seems like everyone else is running 300+hp, and in the end, hp gets the work done.

Now if it had a proper transmission you could lug the motor a bit and let its torque run free...
 
Last edited:
There are no Buick, or Cadillac, or Chevrolet, or GMC engines anymore. They are all GM engines developed by GM Powertrain Division.
 
Originally Posted By: used_0il
I was thinking more on the lines of connecting rod length,
crank journal size, block deck height and not the 60s all over again.


How so? The main bearing size is larger, the connecting rod length is longer, and the block deck height is taller than the old small block Chevy. Furthermore, the deep skirt block design with 4 vertical bolts and two crossbolts in each maincap makes the engine much more rigid than the old SBC.
 
Originally Posted By: used_0il
There is 2 crankshafts available, one has a journal for every connecting rod
called the even fire crank.
The other crankshaft looks like a sbc crank with two connecting rods per
journal, called the odd-fire crank.

The even fire crank had a habit of breaking in marine or performance applications.
When I heard of someone using that engine in an ultra lite aircraft,
I said; "What!!!??".

If that crank breaks during a full power take-off he's toast.

The odd fire crank is many times less prone to breakage and used in motor sport
applications.

I've looked, but I can't find information on the engine design of the
new 4.3L.


Split pin crankshafts are prone to breakage? Thats news to me.

On the 90 degree V6 side, all production 4.3L had a split pin crank. Never seen one break. Most of the Buick V6 and all of the later 3800 had split pin cranks. Never heard of a breakage problem, even in high HP supercharged 3800 applications. The turbo 3.8L in the Grand National and 4.3L in the Syclone/Typhoon both have spint pin cranks. Again, there are no widespread instances of crankshaft breakage, even in modified applications. Last I checked, there are lots of Grand Nationals in "motorsports applications". IIRC, until you're in the 1300 HP range and running 7's, a split pin crank design will service in a Grand National.

All modern 60 degree V6 have a split pin crank. 1000+ HP Nissan GT-Rs use a split pin crank. Every V6 ever made by Honda and Toyota has a split pin crank. Never hear much about breaking crankshafts.

In short: A split pin is not a significant factor in crankshaft durability. The only widespread use of common pin crankshafts were early Chevrolet and Buick 90-degree V6 and extreme performance applications: Old NASCAR Busch Grand National series and 1200+ HP Buicks. A split pin crank will live just fine in your new pickup or even in an ultralight.
 
Originally Posted By: A_Harman
Originally Posted By: used_0il
I was thinking more on the lines of connecting rod length,
crank journal size, block deck height and not the 60s all over again.


How so? The main bearing size is larger, the connecting rod length is longer, and the block deck height is taller than the old small block Chevy. Furthermore, the deep skirt block design with 4 vertical bolts and two crossbolts in each maincap makes the engine much more rigid than the old SBC.


A_Harman, not directed at, or for you, but when you've got a rigid bottom end, you can tighten up clearances before things get close. At that point you can take true advantage of reduced film thicknesses, and aim for friction reduction.

When (take for example, a 1960s straight six, with a flat machined sump/bearing cap plane) the oil wedge is required to keep the crank and block in their variously distorted "hoochicoochi"...better bottom end stability is always worth striving for (V-6 helps that, deep skirt and crossbolt moreso).
 
Originally Posted By: supton
Looks like the 200 and 229 were odd fire, while the 4.3 was always even. Wikipedia Link

I forget, do 60 degree V6's need balance shafts?

*

This new V6 is quite a step ahead, but it seems still a step behind. 285hp? Seems like everyone else is running 300+hp, and in the end, hp gets the work done.

Now if it had a proper transmission you could lug the motor a bit and let its torque run free...


The 200 and 229 V6's were odd fire, but they did have split crankpins. On those engines, the pins were split 18 degrees instead of the 30 degrees required to make a 90 degree V6 even-firing.

Yes, 60 degree V6's need balance shafts to eliminate free moments caused by piston accelerations. Any V-type engine with an odd number of cylinders on a bank will have free moments.

The new 4.3 V6 basically replaces the 4.8L V8. Comparing the power and torque figures:
4.3 V6 makes 285 HP @ 5300 rpm, and 305 ft*lbs @ 3900 rpm
4.8 V8 makes 285 HP @ 5400 rpm, and 295 ft*lbs @ 4300 rpm

And comparing to the 3.6 V6:
288 HP @ 6300 rpm, 270 ft*lbs @ 3400 rpm in the Traverse, which is the heaviest vehicle that GM puts the 3.6 in. Yes, it makes more power in cars and small SUV's. But 278 ft*lbs of torque is as much as it makes in any vehicle, and that's at 4800 rpm in the Camaro.
 
So what is the consensus on the new 4.3L in my new GMC? I'm not as versed in engine tech as a lot of you are. I'll admit that I was a little hesitant when purchasing our new truck because of all the issues surrounding the earlier models and the cylinder deactivation issues. But I asked a lot of questions to a lot of people who told me those issues had been resolved. Since I only have 3200 miles on it so far, with one 900 mile round trip run on it, it seems to perform fine so far. While I have read of some oil usage issues on newer models (heck, what brand of vehicle doesn't have this issue, valid or not), ours hasn't appeared to use a drop so far.
 
Originally Posted By: supton
Looks like the 200 and 229 were odd fire, while the 4.3 was always even. Wikipedia Link

I forget, do 60 degree V6's need balance shafts?

*

This new V6 is quite a step ahead, but it seems still a step behind. 285hp? Seems like everyone else is running 300+hp, and in the end, hp gets the work done.

Now if it had a proper transmission you could lug the motor a bit and let its torque run free...
"the People" need midrange torque more than peak HP. 285 hp is tons for a street 4.6lthats over 142 hp per 2.3 L which is a good street tune. Leave the 300 HP for the "sporty cars" with mt or dual clutch manumatics
smile.gif
I don't think resource conserving ILSAC emissions oil will save a high density HP engine over the long run.
 
Originally Posted By: Sierra048
So what is the consensus on the new 4.3L in my new GMC? I'm not as versed in engine tech as a lot of you are. I'll admit that I was a little hesitant when purchasing our new truck because of all the issues surrounding the earlier models and the cylinder deactivation issues. But I asked a lot of questions to a lot of people who told me those issues had been resolved. Since I only have 3200 miles on it so far, with one 900 mile round trip run on it, it seems to perform fine so far. While I have read of some oil usage issues on newer models (heck, what brand of vehicle doesn't have this issue, valid or not), ours hasn't appeared to use a drop so far.


The 4.3 V-6 never had cylinder deactivation. I'm really glad I got the six in my pickup, as I don't need the extra HP because it's flat here and my boat only weighs about 3,000#. I get about 19 mpg average just running around, and 20-22 on a trip. What does your new truck get for gas mileage? It would be interesting to know as the EPA gives it 24 on the highway. My 2012's EPA estimated highway mileage is 20 mpg.
 
The current 4.3 is LS based and shares it arcitecture with the current LT1. Which has only gotten better since the introduction of the LS1 in 1997.
 
It looks like the old Buick Grand Nationals will be losing sleep
with this new engine around.

If things get serious, and they will, we might see odd fire cranks
and/or 1,000 plus HP from these engines.

What is the displacement limit for the new 4.3 with room for
an overbore or two?

For a pickup truck, the power of a V8 comes in handy from time to time.

But if your needs are more economy mined, perhaps a full time V6 is better
than a cylinder dropping V8.

Now I got me thinking.

A turbo'd 4.3 with a shot of nitrous oxide to get the exhaust flow happening.....

Yea, why start with an obsolete engine design?
 
But the new 4.3 has cylinder deactivation. It deactivates two cylinders, leading to a V4 mode with uneven firing intervals:
bang-bang-skip-bang-bang-skip

With the cast-in iron liners, don't expect to bore more than about .020". Of course there will probably be people out there that throw caution to the winds and bore out the liner completely, then install their own interlocking liners. The engine has the same bore spacing as the V8, so a 4.125 bore could be done. I wouldn't be the first to try it.

When I first heard there was going to be a V6 version of the LS, I thought they were going to make it with the same bore and stroke as the 6.2 V8. That would have been a 4.6 V6 and would have easily topped 300 HP.
 
All the driving I had done up until my 900 mile plus trip was short, around town, type driving and my computer said my average mpg was 19.1. After my trip, it's telling me it's 20.2 mpg. I don't have a clue as to how the mpg calculation is derived over what period of time. I got the V6 for what I hope is better fuel economy than the V8 and that the most I'll be pulling is around 2200 to 2500 lbs (that being a nice pop up camper or small utility trailer). 285 hp is more than enough for what I'll ever need. I'll also save on oil changes: V6's = 6 quarts, V8's = 8 plus quarts.
 
Status
Not open for further replies.
Back
Top