22 replies to this topic

[Ray Bell]

Over the years it has come to be 'received knowledge' that the flat plane crank will give more power in a conventional 90° V8 engine...

But this has always been, it's said, at the cost of vibration problems that are nearly impossible to solve.

Then there is the story, which appears on TNF somewhere, about Niel Allen using one at Bathurst when he set his liesurely 2:09.7 lap record that has stood ever since. According to that story, the vibrations were such that it was buzzing through his backbone and rivets were popping out of the M10B tub.

Kevin Bartlett subsequently told me that this was eased by changing the firing order, so a lot of F5000s subsequently ran flat plane cranks without these problems.

So if this is true, why would it be? Where is Marion Anderson when we need him?

[Joe Bosworth]

Ray

On subject of flat plane engine vibes I thought that

http://forums.autosp...showtopic=92055

said about all that needs to be said on the subject back in 06.

The reality is that a flat plane V8 is just like two inline fours bolted together. It has been well known forever that I4s vibrate too much once you get masses involving more than about 2.3 liters. This has been overcome by many by installing a counter rotating balance shaft. This can not be fit while adapting a standard V8 block.

Howe Racing on the US ARCA circuit developed an effective flat plane crank and firing order about 40 years ago. They sounded great!!!

On the issue of HP, there is no reason a flat plane V8 is going to make more HP other than being able to optimise the exhaust system. They also can end up with a slightly lighter crank that means that during acceleration that moore HP hits the road. Friction and heat losses are independent of crank configuration as is volumetric efficiency except as exhaust optimisation provides.

Regards

[Scotracer]

A flat-plane V8 generally produces more power because of the lower masses involved in the engines (i.e. lighter cranl), therefore allowing higher RPMs and more power under acceleration. But as Joe said, a balancing shaft is required to stop them from vibrating themself in to their constituent parts.

[mariner]

I suspect ome of the "problems" of single plane cranks is size ( capacity ) related - also the factor of gear driven vs chain driven camshafts is relevant.
Way back in 1962 the first Coventry Climax 1.5 litre V-8 ws a twin plane crank engine with a complex and heavy "nest of snakes" linked exhaust system. The engine started at 8,500 rpm and was part chain driven. Later it went to a flat plane crank and moved towards 10,000 rpm.

The switch was mainly to simplfy installation since with the flat plane each exhaust was on just one side and could be lower down. Also the length of the primaries to get the dual plane exhausts matched up and behind the engine would be marginal as revs rose and ideal primay length reduced.

The designer , Wally Hassan to told the SAE " our surprise the vibraion of the engine was not noticably diffferent to that fitted with a 90degree phased crankshaft. There was a small improvement in bearing loading , and a slight reduction in weight due to the simplified system of crankshaft balance weights".

So at 1.5 litres and chain drive no real problems in racing it seems . In contrast the 3.0 litre DFV flat plane crank was famous for vibrating and one of its most intransigent problems was gear train damage.

So maybe the daul/ flat plane differneces are only significant at bigger capacity ( = more rotating mass)

[Lee Nicolle]

While I know that flat plane cranks were a 70s 80s thing wether they really made more power is subjective. They do not seem to be around today. The packaging was always a problem ofcourse that probably outweghed any power advantages. But they sure sounded good!!
I believe McCormak used one with the Leyland, I have heard storys of it shaking rivets out of the tub regularly.
On a Chev I have never heard of one using the standard firing order. Though I have never had anything to do with one, just periphial knowledge from people that had.

[Magoo]

I don't think a flat crank conversion has ever proven to be worth it in an OHV stockblock V8. The cost and trouble are formidable while the benefits are debatable at best in the rpm range a stockblock (so called) is capable of running.

This has been mentioned before, but there is a pretty good ABBA comparison available on the question: the 2000 IRL 3.5L V8. The League was in the process of switching from 90 to 180 degree cranks that year, primarily for exhaust noise reasons, and allowed both styles to run straight up, side by side, while the changeover was accomplished. The two cranks reportedly made identical power at the 10,700 rpm limit while the 180 had vibration issues to iron out early on. For the Indy 500 Ganassi Racing opted to run the 90 degree crank (as it was the known quantity) and won the race comfortably. One key difference: the 90 degree crank used a bicycle(roller) timing chain, while the flat crank used a Morse Hy-Vo link belt setup. Naturally, the firing orders were also different. With the right bank numbered 1357 and the left bank 2468:

90: 12734568
180: 18547236

[Ray Bell]

Originally posted by Joe Bosworth
.....Howe Racing on the US ARCA circuit developed an effective flat plane crank and firing order about 40 years ago. They sounded great!

So the firing order does make a difference?

I mean the firing order for the flat plane, not the difference when changing from a 90° crank to a flat plane.

That is, after all, the question I'm asking.

[John Brundage]

I beleive Peter Molloy used a flat plane crank in some of his engines in the Formula 5000 cars.

[Ray Bell]

Well, that could well be so...

He did Niel Allen's car mentioned in my opening post.

[Lee Nicolle]

I beleive Peter Molloy used a flat plane crank in some of his engines in the Formula 5000 cars.

I read that too. I bet KB would know who was using what in those days.

[Ray Bell]

Yes, KB was mentioned in the opening post too...

And you're right, KB would have known. Anyone listening to the notes of the cars would have known whether or not they had a flat plane crank, those closer to the action would have known the finer detail.

[Villes Gilleneuve]

Wasn't the BRM H16 two flat-plane V8's?

[gruntguru]

Wasn't the BRM H16 two flat-plane V8's?

Two flat-eights with single-plane cranks and paired firing until they changed it. Then it became two flat-eights with eight-throw, four-plane cranks and sequential firing.

Edited by gruntguru, 27 January 2011 - 23:14.

[jrobson]

180 degree V8 engines have better exhaust tuning and therefore can produce more power than a similar size 90 degree crank V8 engine.

[venator]

Two General Motors engines of very similar layout (horizontal valves) from the late 1920s, the Oakland and the Viking V8, were different in particular in the crankshaft configuration. The Oakland, with a 180 degree crankshaft, produced 85 hp from 251 cubic inches displacement, while the Viking, with a 90 degree crankshaft, produced 81 hp from 259 cubic inch displacement. The Oakland had a patented balancing mechanism operated by an additional cam on the camshaft, with apparently excellent results.

[Magoo]

Two General Motors engines of very similar layout (horizontal valves) from the late 1920s, the Oakland and the Viking V8, were different in particular in the crankshaft configuration. The Oakland, with a 180 degree crankshaft, produced 85 hp from 251 cubic inches displacement, while the Viking, with a 90 degree crankshaft, produced 81 hp from 259 cubic inch displacement. The Oakland had a patented balancing mechanism operated by an additional cam on the camshaft, with apparently excellent results.

There was a great guy here named Marion Anderson who was fascinated by these two engines, particularly the Oakland. With the forum search function you can find some good stuff. We haven't heard from him in a while -- it's possible he's passed on.

[Bob Riebe]

While I know that flat plane cranks were a 70s 80s thing wether they really made more power is subjective. They do not seem to be around today. The packaging was always a problem ofcourse that probably outweghed any power advantages. But they sure sounded good!!
I believe McCormak used one with the Leyland, I have heard storys of it shaking rivets out of the tub regularly.
On a Chev I have never heard of one using the standard firing order. Though I have never had anything to do with one, just periphial knowledge from people that had.

Another item, in the U.S. anyway, some GT racers ran 180 degree exhausts. It was a semi-popular item through the seventies.

Did it actually gain much?

[Ray Bell]

Originally posted by Magoo
There was a great guy here named Marion Anderson who was fascinated by these two engines, particularly the Oakland. With the forum search function you can find some good stuff. We haven't heard from him in a while -- it's possible he's passed on.

It seemed to me that he started on his pursuit of information on these engines when I posted a pic of one...

He was fascinated, but he was quite intrigued by all V8s and the various possibilities of design variations. While I would love to see him posting again, I fear something has befallen him, I believe he would be over eighty now if he's still around.

[Magoo]

It seemed to me that he started on his pursuit of information on these engines when I posted a pic of one...

He was fascinated, but he was quite intrigued by all V8s and the various possibilities of design variations. While I would love to see him posting again, I fear something has befallen him, I believe he would be over eighty now if he's still around.

Good guy. I first encountered him over ten years ago on another message board when he sent me an old formula he had discovered regarding imbalance in V-type engines. He has (or had, honestly don't know if he is still with us) a wonderful curiosity about things.

[cheapracer]

I was at home one day when one of my Dad's friends rang looking for him about the possible firing order of a flat plane crank'ed V8 (didn't mention what) they had just installed in a F5000 and couldn't get it started - Dad (who has spannered on F5000's) wasn't home so I asked if they had taken the rocker covers off and watched the valve action .....

I don't know how some of these shops survive.

[WhizzMan]

One of the primary reasons why you might want a flat crank in your V8, is if you want to choose a non-90-degree angle for your V. Since a flat crank is inherently balanced by itself for 1st order resonances, you get away with quite some vibration if you choose to go 60-75 degrees for your angle. That way, you could narrow your engine considerably and have more space left for exhaust headers, suspension and all that sort of bits. Notably, the fast European "supercars" with V8, V10 and V10 engines use the smaller angles to build a more compact engine and still get good cylinder filling and high revs.

[Greg Locock]

1st order resonances

Que?

First order is an excitation, a resonance is a response. Any solid rotating machine with a stiff rotor can be balanced for first order.

[WhizzMan]

Que?

First order is an excitation, a resonance is a response. Any solid rotating machine with a stiff rotor can be balanced for first order.

That'd be second order. I need to work on my physics/math, obviously.