Crankshafts and rod combos?

[Jacques Lefriant]

All
I will soon commission a large run of cranks and rods with a proven supplier. Is there a desire for at least 5 sets of some non standard combination. cranks light or reg/stroke/journal size/rods to suit/lenght/pin dia etc.
j

[C J Murray]

Hi Jacques. There is a question mark in the title but I don't see a question in your post. Are you asking people to pre-order what they want?

[Jacques Lefriant]

Hi Kid
pre orders would be great but i am trying to get a feel for what would be considered optimum in a custom big "stupid" engine. Basically i don't think John Wilhoit would share his extensive development with me to compete against himself. but eventually someone will clone his efforts or a variation. if i get it right from the getgo the cost to the end users could be much more attractive. Besides that i need a big order to get my stuff done.
j

[C J Murray]

As you know I established the method for achieving the 82 mm stroke and shared that with John so that he could offer 2133cc(not 2132 actually) to his customers. He has the sort of business and customers to do a decent volume of large engines and he does a great job on his engines. I think that the price John charges precludes most owners taking the plunge. I think he quoted $35k on Jay Leno's Garage but my memory is not good. Anyway, I have a couple in process right now and it is quite easy to build one for much less than $35k. The result is very pleasant to drive on the street and worth the lower amount of money that I spent on mine. I have 21k miles on it now and it runs more like a modern car than any 356 I have driven. I caution people though that there are tricks to making the 2133 into a civilized engine. They need special attention to make them smooth and to create linear power without detonation or overheating.

All that said, have some 82 mm cranks and rods made with standard wrist pin diameter and location and then all the ready made piston and cylinder sets will work. That wouldn't be any more expensive than any good crank and rods and the builder could use 86 mm bore(no case modification) for 1905cc or 90 mm bore for 2087cc or 91mm(not necessary) for 2133cc. You can get away without other expensive modifications at the expense of a little high rpm power or go ahead and get fancy.

[Jacques Lefriant]

Hi CJ are we talking 53mm/2"/49mm?why use the standard CH piston measurement? i think i would rather than shorten the rod by 4mm go with a longer rod to keep the rod to stroke ratio closer? or even use the stock lenght and only change the piston and have rods available for a different journal size. pistons are easy to change rods aren't
j

[C J Murray]

82mm stroke with 4 mm shorter rod, don't worry about the rod ratio it's not that wacked out and you need a small pin to get only a little longer rod, 45mm Honda journal(be careful there is more than one version), small rod bolts to get good size cam base circle for wear

It would be a mistake to have the crank and rod combo require special pistons. KISS! Affordable!

Don't try to make it a race engine, it's a torque monster street engine that can even use Zeniths and will look totally stock if you want.

[Wil Mittelbach]

82mm stroke with 4 mm shorter rod.
It would be a mistake to have the crank and rod combo require special pistons.

CJ -
Perhaps a naive question; but couldn't one just shim the cyl/crankcase interface at 4mm rather than shortening the rod, and use standard short skirt 3-ring JE pistons??
- Wil

[C J Murray]

CJ -
Perhaps a naive question; but couldn't one just shim the cyl/crankcase interface at 4mm rather than shortening the rod, and use standard short skirt 3-ring JE pistons??
- Wil

That is a good question. In my motorcycle racing days we did just that, sometimes. We weren't allowed to change the stroke, just like in vintage car racing, but some engines benefitted from a longer connecting rod. Generally a short rod offers more low rpm performance while a long rod is best at high rpm. Short is around 1.5 x stroke and long is around 2.0 x stroke. Most engines designed for production cars have fairly short rods for easy packaging(shorter engine) and low rpm performance.

The problem with the 356 is that the engine tin and the body of the car means that a lot of work would be required to make the engine wider, even just 8 mm. I don't think most 356 owners would want to make those modifications. Motorcycles are easier because there is no tin but sometimes there is not enough room in the frame for a taller engine.

The original Porsche design of placing the oil ring below the piston pin has to do with engine width and rod ratio. It was not a good idea but they had a reason they did it that way.

[C J Murray]

Also...

OHC engines are difficult to make taller.

Maybe the serious SCCA racers have tried longer rods/cylinder shims? Vic?

[Vic Skirmants]

SCCA specced stock length rods. Period.

[C J Murray]

SCCA specced stock length rods. Period.

SCCA is no fun. Boring!

[Wil Mittelbach]

CJ -
Perhaps a naive question; but couldn't one just shim the cyl/crankcase interface at 4mm rather than shortening the rod, and use standard short skirt 3-ring JE pistons??
- Wil

That is a good question. In my motorcycle racing days we did just that, sometimes. We weren't allowed to change the stroke, just like in vintage car racing, but some engines benefitted from a longer connecting rod. Generally a short rod offers more low rpm performance while a long rod is best at high rpm. Short is around 1.5 x stroke and long is around 2.0 x stroke. Most engines designed for production cars have fairly short rods for easy packaging(shorter engine) and low rpm performance.
The problem with the 356 is that the engine tin and the body of the car means that a lot of work would be required to make the engine wider, even just 8 mm. I don't think most 356 owners would want to make those modifications. Motorcycles are easier because there is no tin but sometimes there is not enough room in the frame for a taller engine.
The original Porsche design of placing the oil ring below the piston pin has to do with engine width and rod ratio. It was not a good idea but they had a reason they did it that way.

CJ -
Agree that 356ers may be reluctant to trim engine tin to accommodate shimmed cyls as possible deterrent for shimming the cyls, as are stroke limitations (per cam interference).
Per your motorcycle days, I also recall early Harley cruising hot-rod bikers with stroked engines having about a 1/8+" aluminum plate under the "jacked-up" cyls, plus some also converting their "stroker" bikes to a foot operated shift and/or "suicide" clutch.
- Wil

[C J Murray]

There is a tank shift class for vintage road racing Harleys and Indians. They aren't allowed to stroke them but you should see those guys operate the hand shifters and foot clutches while sliding through corners with no rear suspension and almost no front suspension. You have to be a "real man" to race one of those!