Been reading up on these things and it seems like most high end performance and race cars use flat-plane crank shafts. Ferrari, TVR, Lotus, Formula 1 and I've heard Nascar could possibly be using flat cranks too. So this got me to thinking.. Why arn't there more (or any) of these flat-plane engines running around? I've been wanting to build a flat crank v8 for a while now, but there just seems to be a lack of info on them..

 

the advantages of a flat crank would be:
crank weighs less
some fuel system issues are simplified
crank counterweights need less radius, so engine
is not as tall (when using external oil tank)
probably cheaper crank
...
IMO. not worth all that much,
if your redline is 18,000 rpm, worth a look.

 

They don't run as smooth and the exhaust note doen't sound much like how you expect a V8 to sound. Basically two 4 cylinder engines sharing one crank. One of the big advantages is that it gives you "even" exhaust pulses on the 2 banks of cylinders. This helps a lot with efficient exhaust scavenging. A typical SBC V8 has uneven exhaust pulses on each bank as it goes down the firing order.

Like Patch says, if you're going to be road racing and spinning a lot of RPMs, probably worth the cost/effort. Otherwise, forget it.

 

what i don't really get though is if flat-planes arn't as smooth as cross-plane cranks how can they send them to 18k rpm? by smooth you mean the engine just runs a little rougher or it shakes more?

i'd still like to try and build a motor with one, sounds like kinda a fun project if nothing else

 

F1 cars are V10s, it wouldn't work for a V10. Just multiples of four. for an even fire V10 you would want 720(=2 rotations for 4-stroke)/10(=number cylinders) = 72 degree bank angle and rod journal displacement angles.

What they mean by rougher is that it is like four-cylinder compared to V-8 rough, not damaging off-rough.

not any more or less complicated than any other setup. carb is no prob, programmable ECU otherwise to replace stock ECU.


also no, the counterweights couldn't be closer to the axis unless they had heavy metal balancing. They don't have to go around as much arc like a split-plane crank necessitates. Even if the counterweights were shorter for the same stroke, the con rod side would still be the radius from the axis, plus the rods' additional width on the bearing.

for a factory car, sure. but for SBCs they are custom billet or forged.

it doesn't matter. An F1 quality 4-banger could rev to 18 the same way superbikes can do 16-17K. A beefier V-8 crank could handle it.

your peak revs for a given longevity come down to how high quality your pistons, rods, and valvetrain are.

it is against the rules. the firing order and header style, combined with the high revs make them sound much like flat plane cranks.

to run a flat plane crank, you would need a new ECU if you're EFI, a new ignition system ( for the different firing order ), and totally different cam to match the new firing order. it isn't that simple and there a little gains.

despite all that, I would still like to build one myself just because they sound so awesome.

 

The statment that they "aren't as smooth" is reffering to the power pulses. THere are two at a time, so it runs and sounds just like a 4 cylinder.

The point made about the superior exhaust scavaging with a flat plane crank is correct.

 

that is for an SBC. custom crower billet. more on this web site:

http://www.ferraris-online.com/cars/.../Lola332a.html

 

Or maybe it sounds like 4 V-Twins

 

i'm assuming you couldn't just swap around the plug wires and make it work right? (sounds way to easy)

any idea as to how you'd get the ignition system to work? or have any websites that may explaine it some?

 

With a carb, the fuel/air aspect would be solved.
After that, the spark could be done with either an optical or magnetic trigger with it's triggers custom mounted in their correct locations.
It wouldn't be that tough. Get the rotating assy and cam, and if you get to the point where you've got it all together and still haven't figured out the ign sequence, ask around and someone ought to be able to help out.

I hope someone trys it

Edit:
One more thing. Last yr I was trying to figure out some of the details of using LS1 heads on a gen1 sbc (it isn't impossible) one complication was that a custom cam would have to be ground cause the valve locations are different for the LS.
I called Comp for an estimate on a custom billet cam. It was $1000.
I just couldn't see it...

All things considered, ign timing is a small issue

 

to fire evenly, like a normal V8, it would have a power stroke every 90 degrees. every even V8 has 2 pistons at TDC every 90 degrees of crank rotation, one finishing exhaust stroke/beginning intake, the other finishing compression stroke/beginning power stroke.

on a 90 degree crank, those two cylinders are on opposite banks. with a flat plane crank, they are on the same bank. meaning the only possible firing orders jump bank-to-bank even-to-odd every time. that is why they are rough running like a four-cylinder. visualize it: flat plane, on the odd bank, when #1 is TDC so is #7; the even bank has all 4 cylinders at "middle dead center." (even though, it's a fact, when a crank is 90 degrees from TDC, it is further down than halfway stroke (because of the rod ratio relationship)).

I'm not sure what the optimal firing order would be, whether you want the next piston firing to be as far away as possible for balancing purposes or some compromise where the cylinders scavenge and breathe most efficiently.

actually you could just swap plug wires to the appropriate bank and piston, because the 90 degree interval is still the same, just in a different place; the computer and distributor don't care. if you had TBI or bank-to-bank batch fire, it wouldn't matter much. sequential EFI would be different, so you would have to swap the injectors' wires' around with respect to the spark plug swaps.

now that I've thought about it, you wouldn't need a new ECU or ignition necessarily. a new cam however, is required for it to work.

 

false. flat plane crank V8 still fires ONE cylinder every 90 degrees of crank rotation.

if it fired two it would shake itself to dust. that means it would be firing 2 cylinders, on the same bank, simultaneously if it worked like you said.

 

here's an audio clip of a flat plane crank V8 motorcycle:

http://home.mira.net/~iwd/av/sound.html

this website has some visuals, but has a few inaccuracies that I debunked in my first post:

http://autozine.kyul.net/technical_s...ne/smooth4.htm



so look up the Ferrari firing order and save up a lot of money.

 

You guys pointed out the exhaust advantage but forgot all about the intake design. It's a LOT easier designing a crazy cool hi-tech dual resonance intake manifold for a flat crank v8 as apposed to the current design.
For me it's all about the intake, big advantage.
I had no idea that a chevy flat crank was ever even made! Now that I know SOMEBODY else has done it I want to do it.

 

If you do, make it an LS1!

 

not me. if you were going all out naturally aspirated, it comes down to individual throttle bodies per cylinder, with badarse velocity stack trumpets:

 

Why? LS1s are great stock engines and respond well to mods but if you were to go from scratch there is no reason to use one other than to say it is an LS1.

The LS1 block is unnecessarily heavy, too weak a deck and cylinder liner.

iron motorsport-style small block, 18 degree or so heads with titanium valves, individual throttle bodies, tuned stepped headers, flat plane crank.

turn 8500 revs with a 3.625 stroke and a 4.125 bore, 388 cid/6.35L that could make ~650ish and be kinda streetable.

I figure if Sherman from the Engine Masters challenge could make a little over 600 from 366 cubes at less than 6500 revs with off the shelf parts and awesome porting, then ITBs, race heads, and higher revs could make a little more power, crazy high RPM power, without too extreme a cam that it wouldn't be streetable.

 

if i can find all the info i need, i'm building one. 350 block with 4 dual barrel webber carbs. thats my dream right now :hail:

i e-mailed Carobu about any info they could give me about the engine, hope to hear back soon with good news.

Ferrari's firing order is like looking for the fountain of youth, searching for over 3 hours and no luck yet, but still looking

 

Actually any v8 can use that intake so it isn't anything special. What IS special is a dual resonance intake (like a carb dual plane) and have a valve that opens up to resonate like a single plane It's a rather unique design.

 

Why iron when you could go with aluminum, and then get a killer set of 15 degree heads that come along with the package?

Not arguing... Just curious.

 

LS1s are 15 degree heads? I heard they were good...

although the LS1 is aluminum, it is heavier than an aluminum traditional small block with it's deep skirted block and pushrod boxes. does anyone know the weight of an LS1 bare block? the LS1's main cross bolts are pretty small, so the 6-bolt isn't significantly stronger (if at all) than billet splayed 4-bolt caps. I'd rather have iron for the strength. If I wanted aluminum I would save for a Dart aluminum block, or if I hit the lottery I would use this one:

http://www.cnblocks.com/detail.htm solid billet.

there's no reason you can't use some 15 degree bowties, or even better, SB2.2s. It's neat how the LS1 already has symmetrical port 15 degrees, but they would need more work anyway, or get AFRs.

you can't get a good enough intake for an LS1, unless you want Kinsler individual throttle bodies like the C5Rs use, or make your own. LS6, even LSX intakes are a compromise because they are essentially the same design; any plenum setup like that causes cylinders' breathing pulses to interfere with each other. that is why individual throttle bodies are the ultimate intake for high-RPM power, being as straight a shot to the cylinder as possible; no runner length differences; no breathing interference; the throttle body to valve distance is the same for every cylinder.

the small block parts are more developed, so you can make more power per cubic inch per dollar.

 

I'm not sure what you are describing...so I'm going to try to explain what I think it is and you tell me if I'm right.

Like a dual plane, but instead of having each plane go to both banks, have each plane for one bank with the 180 crank, to almost literally run like a pair of four-cylinders, then open the dividing valve to run like a single plane at high revs?

I think velocity stacks are pretty special!

 

They are... I'll give you that, but with a plenum it allows the use of a single throttle body.
With 8 individual runners, each having it's own throttle valve it wouldn't be very user friendly with an EFI setup cause keeping them sync'd would be a never ending task. Unless someone's come up with some miracle that I haven't heard about yet, which is entirely possible.

As far as the LS1 heads or, better yet the LS6 heads. I don't think there's a better head out there for a pushrod 2 valve/cyl V8.
Check the data on the AFR site
http://www.airflowresearch.com/
I haven't made any comparisons between the LSx heads and the 18 deg SBC gen1 heads, but I have a feeling they're very close. With either set of heads a custom intake would probably be in order.

I like the concept of the Dart alum block myself, especially the tall deck design. And for a long time I aspired to do a build using one of those, but of the flow specs of those gen3 heads is swaying me toward the LS1.

http://www.smokemup.com/tech/ls1.php
http://www.idavette.net/hib/ls1c.html

To me, it's all just a bunch of data on paper at this point. I don't have the personal experience with any of those products to present a good arguement. But I've done a bit of bookwork and if what they're saying is true, then an LSx series engine is an awfully good bet just cause it's the block that those heads bolt on to.

 

Keeping the throttle blades at the same angle isn't a big deal, they just have a more complicated linkage, but I think you mean the inconsistency of the vacuum signal with the short, direct, individual runners.

What some people do to get a better vacuum signal is tap each runner, run a small rubber pipe from each to a single box where they put the MAP sensor.

Here's TWM Induction's linkage:
http://www.twminduction.com/v8_kits/...e_capstan.html

And their vacuum accumulator:
http://www.twminduction.com/v8_kits/vacuum_acc.html

 

The opposite is true.

 

Just like I said... Unless someone's come up with a miracle that I haven't heard of yet.

I guess it isn't really a miracle, just technology.

 

It says in this article that the gen III bare block weighs 107 pounds, I just read:

http://www.idavette.net/hib/ls1c.html

Aluminum standard deck Bowtie blocks weigh 90 pounds.

http://www.sdpc2000.com/cart.asp?act...d=734&pid=1161

Until you post pics of weighing the blocks on a scale, I will assume that is correct!

As for the main bearings, for ultimate strength cross bolting is the way to go, but the LSx engines have little cross bolts with powder metal caps. There is an uprgade available, billet C5R style caps. I would think (unless an engineer proves me wrong in normal language) that billet steel beats powder steel with a little aluminum on the side.

Please don't just assert a rebuttal with no reasoning or facts to support it. It's rude.

So if I actually am wrong, I demand a reason.

 

I won't take sides on the block weight issue. To me the 17lb difference isn't enough to sway me, considering that it's more than offset by the (apparent) superior performance of the gen3 heads.
As a devotee of the gen1 sbc design, I'd love to hear of a set of heads that can match the performance of the gen3 heads.
Not just in flow #s, but in drivability and fuel efficiency.
If such a piece exists, I'd lean toward replacing my present engine with a Dart alum block, regardless of the added cost of the block and the accompanying intake mods to fit the heads.

 

I think he disagrees more with the strength difference.

I am almost positive that the SB2.2 heads can outperform anything but a splayed valve race style head, which GM also sells in varying degrees of readiness.

There are a couple more splayed/canted valve small block head options:

Dart:

http://www.dartheads.com/csbhlittle.htm

Brodix:

http://www.brodix.com/Head%20index.html

I don't know if any of them offer a port size small enough for any kind of smaller displacement range though.

The fuel efficiency and drivability of the GenIII engines isn't just because of the heads though. A small, efficient chamber will work well for any purpose.

I don't see any reason why an equivalent cammed, equivalent quality fuel injected small block would be any less drivable or efficient than an LS1 built to the same level. Almost all the upgraded LS1s use that same style intake with the broad breathing range. A lot of small blocks get changed to a single plane intake, almost none tapped for fuel injection, even more rarely do any use a sophisticated sequential ECU like the LS1. Most stay carb.

Because many don't go with 18 degree or better heads, their breathing is indeed inferior to the LS1, so they have to run a more extreme cam with more overlap to compensate some, which affects drivability and fuel efficiency.

My hypothesis is that for the same port quality, port-to-cylinder size, cam, fuel inj quality, and breathing system, there is no reason for one to be more drivable/fuel efficient than the other.

 

Here is the GM splayed valve, symmetrical port head:

http://www.gmpartsdepot.com/store/pr...Category_ID=57

 

so that head is for a normal chevy motor? (non-ls1)

 

I'll go along with that.
If you were able to find a set of heads that had the same port and chamber design, and then match that up to an intake and a fuel/air/spark management system, then put it on a gen1 block, the performance would be the same.
The point is, where you gonna find em, without going to a gen3 block?
Some 18deg 190cc-200cc gen1 heads would be a great find, but they aren't out there to be found.

A good point that you mentioned, is that guys cam up to compensate for the relative lack of flow that the 23deg heads offer, thus compromising the efficiency at the bottom end.
An illustration of that point is that the stock cam in the LS1 - 204*@.050 permits a much higher rpm range than the same cam in an engine using 23deg heads.

Something that I'm personally looking forward to is seeing a test of the 4bbl carb intake for the LS1. A test like that would place the comparison between the gen1 and gen3 on a more level playing field. Enabling us to make a more accurate evaluation of to what extent the gen3 heads are responsible for the engine's performance.

So... The 18deg heads are angle milled and in addition to that the ports are raised to smooth out the short side radius. It makes me wonder if an angle milled set of LT4 heads might be the answer.

Rage13... Those splayed valve heads are for the gen1 sbc.
I'd imagine that anyone running those on the street in an engine less than 400ci would be shooting themselves in the foot tho.
But then, I've never tried it.

 

The parts will never be exactly the same, but even across brands to Ford and Mopar, similar intention cylinder heads on similar displacements make about the same power as a Chevy equivalent.

You can get new 18 degree or 15 degree (really GM's own 18 degree milled 3) heads from GM Performance Parts, some even with porting, hot isostatic pressure treatment, etc...

Muscle Motorsports sells used Nascar everything, especially heads and engine parts that get outdated or thrown out from testing. If you got a set of short-track ported heads for their 358cid motors and put them on a 390-410 cid engine to make the ports usable, decent cam, and very cheap compared to what it would cost to build with all new parts:

http://www.musclemotorsports.com/eng...--intakes.html


If those LT1 or LT4 heads are 23 degree that's a lot of milling and redrilling (bolt holes, etc) to get ~18 degrees, and a weak-decked head.

 

what do you guys would think the best firing order would be?
still havn't found out what ferrari's is, mite beable to find out monday, found a ferrari shop like 3 blocks away from my work :hail: time to see if they need any part time help

 

1-6-3-2-7-4-5-8
i think this firing order should work
had to make a few drawing and my brain feels burnt, but it wouldn't be any fun if there was no challenge.

what do you guys think about this order?

 

we can't really evaluate it. I can't at least.

it's not so much the firing order that is important for whatever balance, it is the intake and exhausting order it dictates that affects power the most.

if there is an optimal breathing/exhausting order relationship, whether you want pulses closer or farther apart or which cylinder after which I don't know it or how to determine it yet.

I'd run the Ferrari or Lotus order or something, you won't go wrong.

Before you commit money to this call Crower and ask if they still make that crank or will make it w/o some absurd custom cost.

Other crank places could make it too, or might already make it but I don't know.

Plus you need to look at some numbers: that crank in the pic is a lightweight billet (see the holes in the rod journals and counterweights, not the oil holes) aerodynamic-style crank, at least $2000 by itself.

custom cam; heads, intake, headers & exhaust, valvetrain and rods/pistons all need to be high quality for high revs, which is massive money.

 

we can't really evaluate it. I can't at least.

it's not so much the firing order that is important for whatever balance, it is the intake and exhausting order it dictates that affects power the most.

if there is an optimal breathing/exhausting order relationship, whether you want pulses closer or farther apart or which cylinder after which I don't know it or how to determine it yet.

I'd run the Ferrari or Lotus order or something, you won't go wrong.

Before you commit money to this call Crower and ask if they still make that crank or will make it w/o some absurd custom cost.

Other crank places could make it too, or might already make it but I don't know.

Plus you need to look at some numbers: that crank in the pic is a lightweight billet (see the holes in the rod journals and counterweights, not the oil holes; where the flywheel bolts up at the end of the crank, it is kinda spoked instead of being a full circle) aerodynamic-style crank, at least $2000 by itself.

custom cam; heads, intake, headers & exhaust, valvetrain and rods/pistons all need to be high quality for high revs, which is massive money.

 

Both the flat plane and cross plane have power pulses
every 90 degrees. The diff is that the cross plane
balances the second harmonic of mechanical balance,
the flat plane does not. The flat plane is
just two inline four bangers, at 90 deg. An inline four has a
second-harmonic problem, that is only partly fixed
with the flat8. Flat8s have simpler looking cranks, without the
huge counterweights of the cross8.
(inline4, not the same as a VW Beetle 4)

 

Thanks for those links Rembrandt.
Looks like some high end stuff. Maybe I'll have a high end motor sometime and get some fancy heads like those.

 

anyone ever get a price?

 

havn't gotten a price yet, want to figure out the firing order first (witch i think i have)
went by the Ferrari shop today and found the order is 1-5-3-7-4-8-2-6 (motor turns clockwise) and the cylinders are numbered different
(4) (5)
(3) (6)
(2) (7)
(1) (8)

so, firing order on a sbc would end up being 1-4-5-2-7-6-3-8
Woohoo! one problem down

e-mailed Carobu and they asked what my interest in the motor was, but havn't heard back sence then..
think i'm going to put this into an LS1 when i get it all figured out (planing on doing an LS1/T56 swap on the Z anyway, so it kinda makes sence to do it that way)

EDIT: motor turns clockwise not counter-clockwise.

 

doesn't an LSx crank have to have one of those reluctor or whatever wheels on the crank for the crank position signal?

when I first read that firing order I thought "have I taught you nothing?!"

then I saw that Ferrari numbers the cylinders different.

so in the Ferrari case it alternates from a cylinder # less than four to a cyl# greater than 4.

 

yes LS engines use a crank triger instead of a distributor, but it shouldn't be a problem. the engine is going to fire every 90° weather its got a flat or cross plane crank so i'm just going to have to rewire the coil packs to fire on the right cylinder, as well as the fuel injectors.

the ferrari engines are setup like 2 inline 4s facing the opposite direction
(4) (1)
(3) (2)
(2) (3)
(1) (4)
and fire the same as an I4
also found out that they have 1 distributor for each bank and each distributor has 2 breaker points, 1 for advanced ignition and the other for retarded ignition. the points are controlled by a microswitch on the throttle.

not sure if its something that could be used on one of our cars, but i found it pretty interesting

 

I know this is reaaaaally old, but this is really interesting and I'd love the option of getting a flat plane crank for my sbc. Has anyone done any more research on this? Rage13? You still around? ™

 

What I don't get is where the real advantage is? To be different?

The HP/TQ numbers of that engine from Ferraris Online isn't very different than achieving the same with a cross plane crank like every other SBC uses.



Yea, it can go to 9,500 RPM, notice the HP falls off after ~7,200 RPM, so why rev it that high? It isn't like the cross plane can't rev that high.

Obviously they have their uses, but why use a flat plane crank if you don't need to?

 

From what I understand, they give a different engine note. I think they sound nice. Just wanted to know if I would be able to find an sbc flat plane crank if I wanted to go this route.

 

I think you could call up the big name custom crank companies and ask if they'll produce one (or some).
The picture of the old F1 car earlier in this thread has one. So if you pockets are deep enough it shouldn't be much trouble.
As for the advantage of flat-cranks... well everything except the vibration control. "Better" power. Why else would Ferrari invest in it if the clocked cranks were "just as good."
I'll go back again and repeat what I said about the dual resonance. There are certain RPM's at which having the engine run as dual i4's will make more power than combining the intake into a single v8. At higher RPM, believe me, a dual plane carb intake CAN make more power than a single plane! The problem is that this RPM is typically over 8000rpm so you would need to build the engine to rev well beyond that just to make up for the power lost in the “mid range” (4000-8000rpm) . Then there is the windage issue. A flat-crank v8 has the benefit of being able to move the air displaced under the piston with the cylinder next to it (one going down, other going up). This means it doesn't have to pump that same volume of air across the crank. Keep in mind this windage benefit only works if the engine case is windowed correctly. Too look at windage passages look at motorcycle engines, specifically 4 cylinder water cooled and even the later LS1/LS6/LS2/LS7 blocks (not the early production runs). Ever wonder why those later LS1 f-body/vette's were noticeably faster than their earlier models... 50% of it can be credited to the windage. To drown ON about the windage, a flat-crank can be balanced with less metal resulting in less displaced air again freeing up the hp lost to pumping the air around at those high RPM.
To summarize; you would be really REALLY stupid to turn down a flat-crank in an all out horsepower war (comforts excluded).

 

Thanks for the nice summary. I'd hate to wonder how much one of these would cost to be made. Any one know estimates on cost? How about some big displacement flat crank v8 sound clips? This sounds promising as long as costs are within reason... ™

 

Sounds like they are catching wind of crazy ideas... 2-3 years ago (whenever it was I asked about it), they quoted me like $600. Was still too much.

EDIT: Sorry, 2/15/01, $787
Ahhh, inflation.

 

For a cam to run with the FP crank?? Crank cost must be stupid high.