OPS and Picco Rod lengths

[ids987]

Hi All, Long story. I’m trying to fix an MDS .61 engine, for a friend (actually more than one). These engines seem to have borrowed quite a lot (in design terms), from Italian engines of the time. Porting layout is like Mk1 Picco (four transfer / boost ports), with a drum induction setup like the old Rossi DS (more recently known as “Valvola” style).
Current need is to find a rod which fits. I have a OPS speed 60 rod, and a rod which I believe to be for a Picco 67 EXR. the Picco rod came fitted to one of the MDS engines. Both Picco and OPS rods, have the correct big / small end IDs. The Picco rod (~42.5mm between centres), is 1mm too long. The OPS rod (~40.5mm between centres), is 1mm too short. I’ve built an engine, with the Picco rod, and shimmed the liner up by 1mm. This puts the squish etc, back in the right place, and should run.
Does anyone happen to have any data for the OPS 67 rods please. Thinking if (by luck), these should fit, they are still available. Between a couple of friends, they have about 5 of these engines.
Any help gratefully received.

 

[Ricky Neal]

Hi Ian,

I have a few 10cc engines here and an un-run MDS .61 so thought I could do a bit of measuring to see if I could find something that would be suitable. Unfortunately, I do not have any CMB or OPS Rods to hand but maybe someone on here does and can add to the information below

See below rods and measurements taken.

The standard Picco Speed .60 Rod would be perfect but unfortunately is 1mm too long. The Novarossi rod is the correct length but the big end pin is smaller on the Novaroosi and the width at the big-end is 1mm narrower.

I would be tempted to use a modified Novarossi rod, the width should not be an issue at the piston will limit the movement as it does normally but you would need to machine out the bore and fit a new bush then hone it to the correct size.

 

[ids987]

Hi Ian,

I have a few 10cc engines here and an un-run MDS .61 so thought I could do a bit of measuring to see if I could find something that would be suitable. Unfortunately, I do not have any CMB or OPS Rods to hand but maybe someone on here does and can add to the information below

See below rods and measurements taken.

The standard Picco Speed .60 Rod would be perfect but unfortunately is 1mm too long. The Novarossi rod is the correct length but the big end pin is smaller on the Novaroosi and the width at the big-end is 1mm narrower.

I would be tempted to use a modified Novarossi rod, the width should not be an issue at the piston will limit the movement as it does normally but you would need to machine out the bore and fit a new bush then hone it to the correct size.

View attachment 286904

View attachment 286905

View attachment 286906

Thanks very much Ricky. Much appreciated. Looks like the Picco 60 rod you have, has the same dimensions as the “believed Picco 67 EXR rod” I have. I think some of the early Picco 60/65/67 rods (the ones with cast rotor discs), may be a good fit all round, but obviously very much out of production now. The Novarossi rod, however, does sound like an interesting possibility. Thanks again.

 

[Joe Wiebelhaus]

Ian,
OPS 67 rods c to c =1.6"
Picco exr 67 rods c to c =1.69"

 

[ids987]

Ian,
OPS 67 rods c to c =1.6"
Picco exr 67 rods c to c =1.457"

Thanks very much Joe.
Sorry to cast doubt, but could there be a typo in the Picco rod measurement, or could that length be for a Picco 45 EXR rod ?

 

[Joe Wiebelhaus]

Correct, 1.69 for the Picco 67 exr rod

 

[ids987]

Correct, 1.69 for the Picco 67 exr rod

Thanks Joe

 

[mike gelson]

Hi Ian,

I have a few 10cc engines here and an un-run MDS .61 so thought I could do a bit of measuring to see if I could find something that would be suitable. Unfortunately, I do not have any CMB or OPS Rods to hand but maybe someone on here does and can add to the information below

See below rods and measurements taken.

The standard Picco Speed .60 Rod would be perfect but unfortunately is 1mm too long. The Novarossi rod is the correct length but the big end pin is smaller on the Novaroosi and the width at the big-end is 1mm narrower.

I would be tempted to use a modified Novarossi rod, the width should not be an issue at the piston will limit the movement as it does normally but you would need to machine out the bore and fit a new bush then hone it to the correct size.

View attachment 286904

View attachment 286905

View attachment 286906

I'm interested to know what is the engine on the right hand side on this photo please ?. Looks very useful.

 

[Ricky Neal]

I'm interested to know what is the engine on the right hand side on this photo please ?. Looks very useful.

Ha, thats a Picco speed .60, in fact all 3 engines on the RHS are Picco speed .60 engines. These are the engines used on the 200+mph tether cars

Very powerful, i may convert one to run with a Carb and fit one to a RC hydro for a laugh, look at size of the Venturi

 

[Ricky Neal]

 

[mike gelson]

Thank you. Definitely looks nice. That carb bore looks larger than my CMB91 m line engine lol. But of course used for a different purpose compared to mine.
Very special engines you have. Very specialized.
Thanks for photos. Much appreciated.

 

[Anders_Martinelle]

Hi All, Long story. I’m trying to fix an MDS .61 engine, for a friend (actually more than one). These engines seem to have borrowed quite a lot (in design terms), from Italian engines of the time. Porting layout is like Mk1 Picco (four transfer / boost ports), with a drum induction setup like the old Rossi DS (more recently known as “Valvola” style).
Current need is to find a rod which fits. I have a OPS speed 60 rod, and a rod which I believe to be for a Picco 67 EXR. the Picco rod came fitted to one of the MDS engines. Both Picco and OPS rods, have the correct big / small end IDs. The Picco rod (~42.5mm between centres), is 1mm too long. The OPS rod (~40.5mm between centres), is 1mm too short. I’ve built an engine, with the Picco rod, and shimmed the liner up by 1mm. This puts the squish etc, back in the right place, and should run.
Does anyone happen to have any data for the OPS 67 rods please. Thinking if (by luck), these should fit, they are still available. Between a couple of friends, they have about 5 of these engines.
Any help gratefully received.

OPS use the same rod length in 60, 67 and 80 engines.

 

[ids987]

Thanks Anders.

 

[Timbo Whalen]

Ian,
OPS 67 rods c to c =1.6"
Picco exr 67 rods c to c =1.69"

Joe, are the Picco 67 EXR rods the same length as the 'P-67' rods?....

Thanks