Reducing the Cylinders on an engine

"Yowen - not necessarily not spaghetti and meatballs" (yowen)
08/27/2014 at 15:05 • Filed to: None

What are the considerations in taking for example a V8 and turning it into a V6? I imagine things could get out of balance. I remember the Northstar V8 having a Shortstar V6 friend. Does it happen often that manufacturers take this approach? To me it seems like they don't...

DISCUSSION (60)

KusabiSensei - Captain of the Toronto Maple Leafs > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:08

At the very least, you'd need a new crank (V8 to V6). Possibly might also need counterweights to smooth everything out.

BMW is turning their small engines into a modular system from an I3 to an I6. So it's possible, but there are drawbacks.

Logansteno: Bought a VW? > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:08

All I know is the GM 4.3 is basically a 5.7 with two cylinders chopped off.

HammerheadFistpunch > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:11

The vortec 4300 and the ecotec 4.3 are both 90 degree v6 engines that are essentially cylinder hacked V8's You just have to add balance shafts and realize that a 63 degree v (ideal for a v6) isn't THAT far off 90 degrees.

GhostZ > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:12

The biggest problem is balance, since if you're going to keep the same angle, your cylinders will be firing unevenly and you have higher-order vibrations. This requires a rebalanced crank, possibly the addition of balance shafts/counterweights, I believe, if you stay with a 90 degree V6 like the shortstar. In cheap cases, they don't add balance shafts they just use rubber dampeners and a low RPM camshaft (making less power).

Then there's also oil and cooling line locations, but that usually isn't a problem.

Other examples are the Jaguar I6 and V12, which I believe are pretty damn similar.

thebigbossyboss > KusabiSensei - Captain of the Toronto Maple Leafs
08/27/2014 at 15:14

Wrong. At the very least all you need is a sawzall.

RamblinRover Luxury-Yacht > Logansteno: Bought a VW?
08/27/2014 at 15:14

Just like how the Buick 3800 is developed from a Buick 300 with two cylinders chopped off.

BigBlock440 > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:14

The 90's V6's (3.9) in the Rams and Dakotas were basically the 5.2 V8's minus 2 cylinders.

Party-vi > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:17

The reason for building a larger engine from a smaller engine is to use existing architecture to increase power output and to decrease costs for manufacturing or development. GM needed a big ass engine with lots of lazy power, so they took two V6s and smooshed them together to make the Twin Six V12 (one-piece block and crank, V6 heads and everything else).

Also, the Short North V6 ("Shortstar") was based off the Aurora V8 (which was based off the Northstar V8) but used an entirely new block.

thebigbossyboss > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:17

Consideration: Get the metal blade for the sawzall. The stone blades won't work that well.

Alec Hall > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:19

The gts-r V10/8. It has two non-functioning cylinders and is worth looking up because it's pretty damn interesting and sounds incredible.

RazoE > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:20

balancing is what sucks. You can always "add" cylinders, but the angle of the bank(s) can have weird effects. That's why the Viper's V10 sounds weird, and why the VW Inline 5 sounds nothing (and makes nowhere near as much power) like half a Lambo V10. Aston Martin's V12 is essentially 2 Ford Taurus engines put together.

twochevrons > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:21

Fun fact: both Triumph and Pontiac also produced 'slant-fours' that were effectively a V8 with one bank lopped off.

In Triumph's case, the resulting engine was far better than the V8 it was based on, and went on to be the first mass-market 16-valve engine, and then to be the basis of the excellent Saab B and H engines. Pontiac's was ...not so great. It wasn't much lighter than the engine that it was based upon, and with a 3.2 litre displacement and no balance shafts, was terribly harsh.

CalzoneGolem > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:22

1. Take SBC.

2. Saw off 2 rear cylinders.

3. ????

4.3

Yowen - not necessarily not spaghetti and meatballs > KusabiSensei - Captain of the Toronto Maple Leafs
08/27/2014 at 15:26

Ah interesting. and then there is of course the cylinder deactivation some mfr's are using.

Yowen - not necessarily not spaghetti and meatballs > thebigbossyboss
08/27/2014 at 15:26

sawzall part of the crank off? lol I kind of want to try it.

Yowen - not necessarily not spaghetti and meatballs > HammerheadFistpunch
08/27/2014 at 15:31

ah ok, I figured there was more to it than just lobbing a cylinder off, I remember reading the V is different form engine to engine.

I wonder if anyone has ever tried this at home, in other words, someone that isn't a car manufacturer just taking an engine and attempting to turn it into a V6.

Yowen - not necessarily not spaghetti and meatballs > GhostZ
08/27/2014 at 15:33

Ah I think I remember remember GM creating a unnecessarily heavy I4 in this manner. (like Jaguar did).

I'm very curious if anyone has tried this that isn't a car manufacturer, just someone wanting to make a big engine smaller.

Textured Soy Protein > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:33

It's often simpler to chop a engine in half to make an inline engine, or double up two inline engines to make a V, than it is to take just a couple cylinders off an existing design.

The VW 2.5 liter I5 is "loosely based" on half of the Gallardo/Huracan/R8/S6/S8 V10.

The Porsche 928 V8 is doubled up VW/Porsche/Audi I4s from the 924/944/968 series.

The BMW M70 V12 is two M20 I6s joined together. At the time, BMW didn't have an ECU capable of running a V12 engine, so the M70 has two ECUs, one for each bank of cylinders.

The VW/Audi/Bentley W12 is two VR6es put together.

I'm sure there are other examples.

thebigbossyboss > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:34

It might not run very long or very well, but it might run.

Yowen - not necessarily not spaghetti and meatballs > Textured Soy Protein
08/27/2014 at 15:35

Yes, Cadillac's V16, haha, thats end-to-end though.

And I recall the story of the dual ECU BMW, that's a good one.

6cyl > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:36

Kinja'd!!!

Yowen - not necessarily not spaghetti and meatballs > Party-vi
08/27/2014 at 15:37

That Twin Six must be an oldie? Not sure I've heard of it before.

Meaning the Aurora V8 was a new block? But the V6 is still a shortened version of this block, or also a entirely new block?

GhostZ > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:37

The Iron Duke? I think it was heavily modified, but dimensions-wise was pretty close to a Pontiac V8.

KusabiSensei - Captain of the Toronto Maple Leafs > thebigbossyboss
08/27/2014 at 15:40

It would if you have a Ford 300 I6. One could get them to run even with an entire piston and connecting rod removed.

Not for very long, but it could be done.

KusabiSensei - Captain of the Toronto Maple Leafs > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:42

But they still have the mass of the piston and the con-rod in place, and that does a lot to smooth the operation out.

Example, you would find that on the GM V6 in the Silverado/Sierra, it only goes to V4 mode (shutting off two cylinders fuel supply) above 1500RPM, because otherwise it would be a bit too rough (even though it's a truck)

Klaus Schmoll > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:42

I've heard of air-cooled Tatra V8s that were cut to become a V6 by some Bavarian rednecks in an attempt to build some sort of mud racer.

Yowen - not necessarily not spaghetti and meatballs > thebigbossyboss
08/27/2014 at 15:42

I'd also want to shut off the fuel to whatever two I don't use anymore. And probably spark too, that'd be good. Come to think of it, block of the cylinders with a plate? haha.

Also, maybe repurpose the extra injectors as flame throwers :D

Yowen - not necessarily not spaghetti and meatballs > GhostZ
08/27/2014 at 15:43

Yeah, that might've been it.

Full of the sound of the Gran Fury, signifying nothing. > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:45

Didn't Ducati take a twin and convert it into a single a few years ago? As I recall, they used a dummy piston (or something similar) as a counterweight to keep things in balance.

Yowen - not necessarily not spaghetti and meatballs > KusabiSensei - Captain of the Toronto Maple Leafs
08/27/2014 at 15:46

Ah interesting. I imagine doing it about 1500 would also help longevity.

So they are still lubing the cylinders, just not fueling them?

Yowen - not necessarily not spaghetti and meatballs > Klaus Schmoll
08/27/2014 at 15:46

Haha very interesting.

Yowen - not necessarily not spaghetti and meatballs > Full of the sound of the Gran Fury, signifying nothing.
08/27/2014 at 15:47

Oh cool. So I need dummy Pistons to create my Franken-V6 :P

KusabiSensei - Captain of the Toronto Maple Leafs > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 15:48

Correct. The valves are still allowing air in and out of the combustion chamber (Because while you could design a system to disconnect the valves, it would only appeal to Germans because of the technical complexity), but there is no fuel and no spark (Almost all the cylinder de-activating engines have COP ignition)

(Except the Cadillac V8-6-4, but no one talks about that...)

KusabiSensei - Captain of the Toronto Maple Leafs > GhostZ
08/27/2014 at 15:57

Same thing with the BMW M20 and M70. So much so that the M70 had two M20 ECUs, one for each bank.

Texican > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 16:01

Considerations of turning a V8 into a V6 are many. When Chevy turned the small block into the 4.3L V6, they kept the basic design of everything the same, but it still needs a new block, heads, manifold, crank, cam, valve covers, etc. The crank is changed, not just shorter, but with the arms in different spots, 120* apart instead of 90.* It's not a home project.

You could theoretically convert a V8 into a 4, but that still needs a custom cam. The vast majority of V8's fire three cylinders on one bank each 360* of rotation. If you keep the V8 cam and only use four holes, it will shake itself to pieces. Using one of the two sets of even holes would be an engineering nightmare.

BTW, if the goal is to get a very heavy, low capacity, over-engineered slug of an engine, I have a variety of vintage Volvo powerplants available.

Full of the sound of the Gran Fury, signifying nothing. > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 16:04

Well, a few other changes would be needed, such as blocking off the intake and exhaust ports on the unused cylinders as well as modifying the firing order (probably through a distributor change). Modifying port fuel injection to not fire on those two cylinders would also be challenge, but not a problem if it was TBI. A carb would probably be better for this project.

Back in the '60s my dad had a V7 in his Chevy, although that really wasn't by his own choosing...

Mathias Rios > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 16:05

Mercedes Benz M112 and M113 are pretty much perfect examples of this. I own a M112 engine in my ML320.

You can tell a Finn but you can't tell him much > CalzoneGolem
08/27/2014 at 16:10

Apparently that was a little too subtle. Or people around here are too young to remember the 350/5.7/4.3.

CalzoneGolem > You can tell a Finn but you can't tell him much
08/27/2014 at 16:20

I thought it was pretty clever ... might be my breath.

Yowen - not necessarily not spaghetti and meatballs > Texican
08/27/2014 at 16:30

Awesome, thanks for this extensive reply, part of my reason for posting this was finding out what's stopping people from turning bigger engines into smaller/less cylinder engines.

Jordan and the Slowrunner, Boomer Intensifies > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 16:30

Early 60's in base model Pontiac's. They were half the 389, with no relation to the Iron Puke. They were replaced with a V6 IIRC, then an alloy V8.

Yowen - not necessarily not spaghetti and meatballs > Full of the sound of the Gran Fury, signifying nothing.
08/27/2014 at 16:31

Haha, even with all that, it sounds like the engine wouldn't run very long, but it would be a very fun project if you had access to some cheap/running engines.

Jordan and the Slowrunner, Boomer Intensifies > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 16:31

The Cummins 5.9 6BT and 3.9 4BT are so close, everything but the cam and crank are interchangeable IIRC.

Yowen - not necessarily not spaghetti and meatballs > Jordan and the Slowrunner, Boomer Intensifies
08/27/2014 at 16:33

Omg, I should have known this, I read about swaps utilizing these engines ALL the time.

I also read very often about parts swapping over between the two. So you are probably right.

Jordan and the Slowrunner, Boomer Intensifies > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 16:36

If it weren't for the added weight, the 4BT would be a candidate for my 4Runner. Not that it wouldn't work, it would just require extensive beefing up of everything else.

Yowen - not necessarily not spaghetti and meatballs > Jordan and the Slowrunner, Boomer Intensifies
08/27/2014 at 16:53

Hmm, perhaps at some point a 3.2 diesel out of transit van? I am curious how the longevity on that engine will turn out. I suppose I just need to look at Euro Rangers and other world market vehicles with that engine.

Jordan and the Slowrunner, Boomer Intensifies > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 16:59

For mine, if not something in the LS V8 family, I will probably go with a 1KZ-TE swap. Toyota diesel with about the same amount of power as my current V6, but a LOT more torque at a lot lower RPM. Also, it was available for them in other countries.

Texican > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 18:35

Basically because it's insanely difficult, lol. Changing the number and configuration of pistons has dramatic effects on the balance. Consider that a V8 has well over 100lbs spinning very fast in the bottom end. The "sharing" between muti-configuration motors is at the engineering level.

ranwhenparked > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 19:20

I think people did try this during the '73 and '79 oil crises, with varying results.

The Magic Rev Matching 4Runner > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 20:44

Just chop the heads too and throw all the injectors and spark plugs into the exhaust! Oiling might be a bit of an issue with half the oil pan and galleys gone, but oh well...

Yowen - not necessarily not spaghetti and meatballs > Jordan and the Slowrunner, Boomer Intensifies
08/27/2014 at 21:20

It would make sense to do something that has already been done from the factory, is it hard to source an engine?

Yowen - not necessarily not spaghetti and meatballs > Texican
08/27/2014 at 21:21

Haha ok, I will leave it to the engineers then :D

Yowen - not necessarily not spaghetti and meatballs > ranwhenparked
08/27/2014 at 21:22

Hmm, would love to hear some from people that did this successfully

Yowen - not necessarily not spaghetti and meatballs > The Magic Rev Matching 4Runner
08/27/2014 at 21:23

Hah, let's get a 1,000 miles out of it, a 1,000 miles of FUN!

Jordan and the Slowrunner, Boomer Intensifies > Yowen - not necessarily not spaghetti and meatballs
08/27/2014 at 21:40

Just overnight parts from Japan... On a serious note, it isn't really that bad, you just buy a half-cut to have a cheat sheet or just buy an engine and go from there. As long as you aren't importing whole vehicles, it isn't that difficult.

Party-vi > Yowen - not necessarily not spaghetti and meatballs
08/28/2014 at 08:24

The Twin Six is an oldie - think before 1970s. I don't think the Aurora was a new block, but the V6 was definitely built from scratch. The Aurora V8 had a smaller bore and different cam profiles than the Northstar. The V6 engine was a newly designed block that used the same DOHC 4v configuration as the Northstar engines. I think the bore spacing was different too.

Yowen - not necessarily not spaghetti and meatballs > Jordan and the Slowrunner, Boomer Intensifies
08/28/2014 at 09:20

Hmm, very interesting, what's the price range for something like that?

Jordan and the Slowrunner, Boomer Intensifies > Yowen - not necessarily not spaghetti and meatballs
08/28/2014 at 14:23

The engine itself is like 2500 and the half cut is like 3500.

Yowen - not necessarily not spaghetti and meatballs > Jordan and the Slowrunner, Boomer Intensifies
08/28/2014 at 15:40

Hmm, doesn't seem like a bad deal, does that include getting it shipped to your front door?

Jordan and the Slowrunner, Boomer Intensifies > Yowen - not necessarily not spaghetti and meatballs
08/28/2014 at 15:45

That I don't know, haven't researched that much yet.