Author Topic: New crankshaft/connecting rod design for 2021 V7/V9  (Read 4231 times)

Offline kirby1923

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #30 on: February 02, 2021, 08:07:31 AM »
Because of tooling. They have forging dies $$$$ and most likely a lot of raw forging blanks. Cheaper to use up what you have.

:-)
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Offline acguzzi

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #31 on: February 02, 2021, 09:13:49 AM »
I've replaced big end bearings several times, it's easy to do and relatively cheap if you don't have to disassemble the crank, maybe I'm hard on them, or particularly picky, but you can't even check if it is a pressed crank. I had a pressed crank on my first motorcycle and learned that is an expensive repair option.

Offline twowheeladdict

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #32 on: February 02, 2021, 09:42:38 AM »
Um, no. Just another example of how the cheapest solution is the way Guzzi is run now. If the pressed together crank is a better solution, why are they still using the forged crank on the V85?

Were you lining up to buy a new V7 or V9, and now this news is going to stop you? 

There is something in the industry about building to a price point. 

You can build the most amazing motorcycle out there, but if you can't build it to a price point where it is competitive, then you have to price it with enough profit to justify the low volume sales. 

Every bike in your signature was built to a price point and compromises were made. 

I'm just thankful Moto Guzzi hasn't gone to overhead cams. 
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Offline Tusayan

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #33 on: February 02, 2021, 10:41:22 AM »
There was a time when the big block Guzzis were what serious admirers of quality bought, and small block Guzzis were mainly for European commuters who didnít care if the thing was by comparison a cheaply made throw away bike.  Ducati once did the same thing with bevel drive bikes and belt drive engines, but stopped the bevel drive engines around 1986.  Nowadays Piaggio has followed Ducatiís 1980s model and down-selected to the less expensive to produce engine family.   It then follows that theyíll build higher spec versions and lower spec versions of that engine to span the market, as Ducati did in the 90s with everything from 600 cc 2V engines to the 996 race spec engine, all based on their less expensive basic engine design. 

Yes, if I were buying a new Guzzi the built up crankshaft would stop me, but Iím not in the market for a low budget commuter bike - I use my four cam, one piece crank SV650 for that job if needed.  However, I might well be buying a V85TT in the future and if that model were by then to transition to the built up scooter crank with one piece rod/bearing assemblies Iíd buy something else. If I wanted a Vespa Iíd buy one.

« Last Edit: February 02, 2021, 10:55:13 AM by Tusayan »

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #33 on: February 02, 2021, 10:41:22 AM »

Online bad Chad

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #34 on: February 02, 2021, 10:55:03 AM »
I'm riding with Chuck on this one.  I have been riding motorcycle continuously for the vast majority of my life, and I have yet to wear a single motor out.
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Offline Tusayan

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #35 on: February 02, 2021, 10:59:50 AM »
Iíve worn out and replaced the rod bearings on a Honda VF750 that developed a rod knock after 30K hard miles, a big block Guzzi (part of a dumb maintenance error when I was young) and a high mileage bevel drive Ducati twin.  The bevel drive twin with built-up crankshaft was a big project, the Guzzi was a half day job at most, the Honda was somewhere in between.  This was one of several experiences that made me appreciate and buy Guzzis.
« Last Edit: February 02, 2021, 01:43:06 PM by Tusayan »

Offline Kev m

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #36 on: February 02, 2021, 11:08:26 AM »
I'm riding with Chuck on this one.  I have been riding motorcycle continuously for the vast majority of my life, and I have yet to wear a single motor out.

This

I have seen a friend "wear out" a pressed Harley crankshaft motor, well sorta, he was above 200k miles on his rubbermount Sporty when he made a critical error during an oil change and managed to (unknowingly) drop the seal into the bottle and pour it into the oil tank. Sadly he discovered this after he started hearing a bearing knock and only after tearing the bike down to find the foil blocking the oil feed from the tank.

But much ado - we have no evidence that this means the cranks won't last and if I'm not mistaken the previous cranks couldn't be ground and there were no oversize bearing inserts for them anyway right? So no effective change in ability to rebuild.
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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #37 on: February 02, 2021, 12:25:16 PM »
Still confused.  I can't see why a pressed crank is cheaper than a solid one. 

Also is the Guzzi crank forged or cast?  I don't think my Corvette has a forged crank (the rods are powdered metal, forged and cracked)
« Last Edit: February 02, 2021, 12:35:03 PM by LowRyter »
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Offline acguzzi

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #38 on: February 02, 2021, 01:15:30 PM »
I believe the forged and cracked conrods is the latest and greatest tech for strong rods

Offline lucky phil

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #39 on: February 02, 2021, 04:23:32 PM »
Still confused.  I can't see why a pressed crank is cheaper than a solid one

Also is the Guzzi crank forged or cast?  I don't think my Corvette has a forged crank (the rods are powdered metal, forged and cracked)

Because it sometimes depends on what the factory is already set up to produce. On top of that the real saving is in the rods. Much simpler to produce a 1 piece rod with around 3 machining processes (grind the big end bore ID, the gudgeon ID press in and ream the gudgeon bush, press in the big end bearing) and done. It would need to be deflashed after forging of course as well but it's a hell of a lot simpler to make than a two piece rod. 

Ciao
« Last Edit: February 02, 2021, 04:26:48 PM by lucky phil »
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Offline lucky phil

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #40 on: February 02, 2021, 04:26:18 PM »
I believe the forged and cracked conrods is the latest and greatest tech for strong rods

Not really, they are the latest tech for mass produced rods because they save machining processes. No upgraded performance rod I know of use fractured rod technology or sintered material for that matter. It's about manufacturing ease. Doesn't mean they aren't fit for purpose but you dont find them in race engines generally.

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« Last Edit: February 03, 2021, 04:38:04 PM by lucky phil »
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Online elrealistico

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #41 on: February 02, 2021, 05:45:27 PM »
I wonder how many people out there think that this means Luigi from the Vespa factory will be putting together MG cranks and rods using vise-grips :grin:
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Offline kirby1923

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #42 on: February 02, 2021, 06:29:14 PM »
Wait, I always thought that pressed cranks were quite a bit more labor intensive and expensive to build.  This is the first time I've ever read the opposite.   I don't know why two piece rods could be revved at higher RPMs and more stress than one piece rods; if there is a difference, I'd think would be the other way around. 

OK, since I'm the least mechanically inclined person on the Board, someone please educate me.

Thanks.


John,
The modern HD engine (45deg) has two separate rods,(not two piece). They are called a fork and blade set up so one rod (the blade) fits into the other rod(fork) and when the holes for the crank pin are lined up roller bearings are pressed in and then assembled onto the crank pin and then the whole thing is pressed together using terrific pressure.

This is done so the cylinders are lined up on the crankcase in a straight fore and aft line, therefore no shaking moment. Your Guzzi cylinders are off set...shaking moment present.

That's the why.

With the 45 deg setup there is enough back and forth rocking that vibration is a problem so one thing the designers did was eliminate the shaking moment as much as possible.

The RR merlin engine used in the P-51 is a V12 and in order to minimize vibration they used the same method, as in blade and fork rods.

These rods are difficult to machine correctly thus labor intensive and $$$.
As for being cheaper to press together???, by using the roller bearings and having a flywheel on each side, the HD method of pressing them together makes some sense rather than the tapered shaft with nuts torqued on both ends. Unknown.

It works but I know folks that are designing and  have been testing a forged single piece crank with a master and an articulated rod (plain bearings) and have been riding test machines for about a year.

FWIW

:-)

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Online Moparnut72

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #43 on: February 02, 2021, 07:04:45 PM »
I'll add my 2 cents. All of the radial aircraft engines I worked on had two piece cranks. The two piecs were held together with a pinch bolt.It took a lot of force to tighten the bolt, it was checked for proper torque by the amount of stretch. It was a lot of work to set it up and make sure it was correct when finished. So I am not sure how much money it is going to save Piaggio by going this way. I would think that the crank pin could be hardened to extreme levels if desired. I know that the slave rod pins in a radial were hard as hell and couldn't be scratched no matter how hard you tried. I had to mark id #'s in the ends with an engraver and that was the end and not the bearing surface.

Harley has used pressed cranks for a very long time with a very minimal number of failures. Most of the Harley failures were from modified engines with mega hp. The cranks that failed were usually scissors, one of the press fits slipped putting the two halves out of phase. Easily prevented by welding the joints.

I wouldn't have a problem with a pressed crank bike, especially a MG as MG engines are not overly stressed. I once lunched a single cylinder Yamaha crank from hopping it up well beyond design limits. It was not terribly expensive to have it repaired. I would not be concerned with pressed cranks from Moto Guzzi. Luigi has to be careful when putting these together.

A closing thought, not all 2 strokes use pressed cranks. Mercury outboards in the 50's and 60s that I am familar with used one piece forged cranks for their twins, fours and sixes. The main failures were from rod journals with the needles starting to slide from pitting on the needles or the journal itself. Unbelievable destruction.
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Offline jacksonracingcomau

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #44 on: February 02, 2021, 09:30:19 PM »
Does this Cycleworld comment raise an eyebrow with anyone?

"An unexpected and fairly radical technical modification separating the V7/V9 V-twin engine from all previous editions, and from the V85 TT, is that the crankshaft here is of the press-fit type, with one-piece con-rods turning on plain bearings, rather than a forged one-piece unit. This follows the same engineering approach used on all Piaggio four-stroke scooter singles. Reducing production cost is the ultimate reason for the change. The more powerful, higher-revving V85 TT retains its solid forged crankshaft and cap-type rod."

Iím calling journo BS on this one, not the crank/rods, I totally believe a pressed crank/ plain bearing set up could be lighter and better than 2 piece rods, modern metals/ machinery etc.
But that itís cheap ? No press release Iíve ever read said that about new technology UNLESS the product itself was cheaper than before.

This article reinforces my thinking
2021 V7ís with flat tappets, steel valves, bolt up rods still on sale

https://www.webbikeworld.com/2021-moto-guzzi-motorcycle-lineup/

Thereís the cheap one, retail prices will confirm, no way will they sell roller tappet, titanium valve bike with or without this crank cheaper than getting rid of old flat tappet engines.

My bet
This crank set up will be in the new model to be announced
Marginally more power than the v85tt but as in 1970 the difference will be in weight, handling, braking and suspension.
Good name Tonti chose ó-V7 Sport , the true game changer, the Le Mans (which I bought and still ride) was first twin to make revs and be competitive with state of art but the v7 sport led to multitude of other models too.
A new lightweight chassis with v85 engine, even I might buy one, pressed up crank and all.

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #45 on: February 02, 2021, 09:48:27 PM »

John,
The modern HD engine (45deg) has two separate rods,(not two piece). They are called a fork and blade set up so one rod (the blade) fits into the other rod(fork) and when the holes for the crank pin are lined up roller bearings are pressed in and then assembled onto the crank pin and then the whole thing is pressed together using terrific pressure.

This is done so the cylinders are lined up on the crankcase in a straight fore and aft line, therefore no shaking moment. Your Guzzi cylinders are off set...shaking moment present.

That's the why.

With the 45 deg setup there is enough back and forth rocking that vibration is a problem so one thing the designers did was eliminate the shaking moment as much as possible.

The RR merlin engine used in the P-51 is a V12 and in order to minimize vibration they used the same method, as in blade and fork rods.

These rods are difficult to machine correctly thus labor intensive and $$$.
As for being cheaper to press together???, by using the roller bearings and having a flywheel on each side, the HD method of pressing them together makes some sense rather than the tapered shaft with nuts torqued on both ends. Unknown.

It works but I know folks that are designing and  have been testing a forged single piece crank with a master and an articulated rod (plain bearings) and have been riding test machines for about a year.

FWIW

:-)

Thanks Mike, 

I knew HD had the "knife and fork" rods but I didn't know why.  In fact keeping the cylinders directly in line would keep the rear one totally out of air flow. 

I never considered that vibration from the 45 degree V, might be the reason.  I did think the Master Rod was the fork and the Articulated Rod was the blade.  Odd cylinder radial engines a have master rod and the the articulated rods are "pushers followers". 

« Last Edit: February 02, 2021, 09:58:36 PM by LowRyter »
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Offline acguzzi

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #46 on: February 03, 2021, 08:15:37 AM »
I thought it was strength because it was originally a one piece, but this link suggests it is precision:
https://www.ms-motorservice.com/en/technipedia/post/cracked-connecting-rods/

Online Dave Swanson

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #47 on: February 03, 2021, 08:22:07 AM »
Whatever it has I am sure I wont be able to wear it out if I knuckle under to Anniversary edition V7 bike lust. 

« Last Edit: February 03, 2021, 08:23:22 AM by Dave Swanson »
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Offline Kev m

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #48 on: February 03, 2021, 08:59:20 AM »
Whatever it has I am sure I wont be able to wear it out if I knuckle under to Anniversary edition V7 bike lust. 



I love that they copied my photoshopping on the side covers!  :cool:
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Offline kingoffleece

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #49 on: February 03, 2021, 09:45:10 AM »
+1 on kev
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Offline Bulldog9

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #50 on: February 03, 2021, 11:26:53 AM »
I love that they copied my photoshopping on the side covers!  :cool:

Kev is officially on the blame line........  :police:
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Online Dave Swanson

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #51 on: February 03, 2021, 11:30:20 AM »
Kev is officially on the blame line........  :police:

I am sure Kev is smiling all the way to the bank with those royalty payments he is receiving.   :wink:
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Offline kirby1923

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #52 on: February 03, 2021, 12:19:32 PM »
Thanks Mike, 

I knew HD had the "knife and fork" rods but I didn't know why.  In fact keeping the cylinders directly in line would keep the rear one totally out of air flow. 

I never considered that vibration from the 45 degree V, might be the reason.  I did think the Master Rod was the fork and the Articulated Rod was the blade.  Odd cylinder radial engines a have master rod and the the articulated rods are "pushers followers".

FWIW
All 4 cycle radial a/c engines have odd # of cylinders. And the rear cylinder on the HD loses very little air while in motion.   Flat aircraft engines have cylinders in line but they do use baffles to direct air 'cause they operate at high power (65% or more) when inflight at cruise/take off.

:-)
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Offline lucky phil

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #53 on: February 03, 2021, 03:24:36 PM »
Thanks Mike, 

I knew HD had the "knife and fork" rods but I didn't know why.  In fact keeping the cylinders directly in line would keep the rear one totally out of air flow. 

I never considered that vibration from the 45 degree V, might be the reason.  I did think the Master Rod was the fork and the Articulated Rod was the blade.  Odd cylinder radial engines a have master rod and the the articulated rods are "pushers followers".

With regards to the fork and blade rod design It's got virtually nothing to do with eliminating rocking couple, that's just a minor albeit nice to have by product of the fork and blade style rods in a V twin design and not really worthy of the effort alone as Ducati, Guzzi and many others that produce a very smooth running largish capacity V twins that also make high specific output and rev to 12,000 rpm safely without rocking couple or secondary vibration mitigation can testify to.
No the primary reason for it in Harleys case was simply expedience and a minimal design change to effect a twin cylinder engine and then like Chevrolet when they had to design a new V8 engine they stuck to pushrods primarily because that's what they had experience with and were too conservative to go the way of the rest of the world to OHC. Harley did the same with the fork and blade style rods.The advantages of fork and blade design are primarily reduced frontal area and engine width having the cylinders in line and reduced crankshaft length which is an advantage in a V12 aircraft engine but not so much in a V twin motorcycle engine. The elimination of a rocking couple is a minor by product. You cant really compare the aircraft rod designs directly to motorcycles as their specific output is quite low compared to Motorcycle engine. A Rolls Royce Griffon engine (the largest and most powerful V12 engine RR made during the war that powered the latest Mk's of Spitfires to speeds of nearly 500mph were 37 litres and 2400 HP for a specific output of 65hp/L and turned around 2800 rpm maximum) A Ducati 1198 for example makes around 190 hp from its 1.2 Litres and turns over 10,000 rpm for an output of 158 HP/L. I can tell you now Taglioni would never have even had the though of a blade and fork rod design even cross his mind when he sat down to draw up the first Ducati V twin.
This may interest some. I dont agree with Cameron on the aircraft engine logic. Not every design principle is transferable between every engine application. 

https://www.cycleworld.com/harley-davidson-roller-bearing-crankshaft-explained/


Ciao
« Last Edit: February 03, 2021, 03:33:37 PM by lucky phil »
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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #54 on: February 03, 2021, 04:34:31 PM »
 I agree with Phil for the most part..RR Merlin was built on the evolution of dozens of years of V12 aircraft engines.It's fork and blade rod may have been used out of tradition in a somewhat conservative industry...Allison being a very small manufacturer building their fist liquid cooled engine was likely going with the trend...
  Engineers call it a fractured rod, not cracked, LOL..
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Offline Tusayan

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #55 on: February 03, 2021, 05:33:17 PM »
No the primary reason for it in Harleys case was simply expedience and a minimal design change to effect a twin cylinder engine and then like Chevrolet when they had to design a new V8 engine they stuck to pushrods primarily because that's what they had experience with and were too conservative to go the way of the rest of the world to OHC.

I think Harley did it their way because it was 1908 at the time, and there wasnít a whole of prior experience one way or the other.  That which did exist was with early aircraft engines.

Re the V8 Chevrolet engine: the rest of the world (outside of the US industry) wasnít doing a whole lot with high volume production automotive V8s in 1955, or high volume OHC car engines in 1955 either.  However Chevrolet was planning on making a whole lot of them, for example 100,000,000 small block V8s were eventually built, and I think they had fundamentally the right idea.  It wasnít exactly the product of arbitrary decision, it was more like genius. The extremely low cost and completely effective valve gear and rocker arrangement was part of it. 
« Last Edit: February 03, 2021, 05:41:38 PM by Tusayan »

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #56 on: February 03, 2021, 05:39:04 PM »
There is no more room for discussion on this subject.   Settled business.  Whatever you thought going in, is still the case.
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Offline lucky phil

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #57 on: February 03, 2021, 06:36:24 PM »
I think Harley did it their way because it was 1908 at the time, and there wasnít a whole of prior experience one way or the other.  That which did exist was with early aircraft engines.

Re the V8 Chevrolet engine: the rest of the world (outside of the US industry) wasnít doing a whole lot with high volume production automotive V8s in 1955, or high volume OHC car engines in 1955 either.  However Chevrolet was planning on making a whole lot of them, for example 100,000,000 small block V8s were eventually built, and I think they had fundamentally the right idea.  It wasnít exactly the product of arbitrary decision, it was more like genius. The extremely low cost and completely effective valve gear and rocker arrangement was part of it.

If you read the history of the Gen111 engine the pushrod comfort factor/no OHC experience among its design team was a big component of the design decision to not go OHC. However in defence of Chevrolet the engine is very compact and used in everything from delivery trucks to Corvettes in various stages of tune. I've owned Gen111 engines in 2 cars and am actually a fan of them however Ford when faced with a similar decision did decide to go DOHC which I'd like to have in either a Cobra replica or GT40 replica one day. There's a long path from what the engineering team would like and what pops out the production line:)


Ciao
If you're not living on the edge you're taking up to much room.

Offline lucky phil

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #58 on: February 03, 2021, 06:39:22 PM »
I'm riding with Chuck on this one.  I have been riding motorcycle continuously for the vast majority of my life, and I have yet to wear a single motor out.

What about a multi cylinder engine? have you worn out any of them?   :grin:

Ciao
If you're not living on the edge you're taking up to much room.

Online LowRyter

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Re: New crankshaft/connecting rod design for 2021 V7/V9
« Reply #59 on: February 03, 2021, 07:14:06 PM »
If you read the history of the Gen111 engine the pushrod comfort factor/no OHC experience among its design team was a big component of the design decision to not go OHC. However in defence of Chevrolet the engine is very compact and used in everything from delivery trucks to Corvettes in various stages of tune. I've owned Gen111 engines in 2 cars and am actually a fan of them however Ford when faced with a similar decision did decide to go DOHC which I'd like to have in either a Cobra replica or GT40 replica one day. There's a long path from what the engineering team would like and what pops out the production line:)


Ciao

Phil, I don't remember if it was you or one of your fellow countrymen that trolled me about the Chevy V8 on the LeMans board.  But I'm pretty sure it was you.

HAHA.

Funny you didn't mention pushrod Guzzi engines.   :rolleyes:
John L 
When life gets you down remember it's one down and the rest are up.  (1-N-23456)


Harper's Moto Guzzi
Harper's Moto Guzzi. Where we still answer the phone, use the highest quality parts, and also do Transmission, rear drive, and carb rebuilds fast. Call us at 816.697.3411 and get your problems resolved.
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Harper's Moto Guzzi
Harper's Moto Guzzi. Where we still answer the phone, use the highest quality parts, and also do Transmission, rear drive, and carb rebuilds fast. Call us at 816.697.3411 and get your problems resolved.
http://www.harpermoto.com
Advertise Here