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Discussion Starter #1
In preparation for honing the bores and fitting new rings to my 1500 sud engine I started removing the pistons today.

I'm building one motor out of two. The block I'm using is a low mileage 1500 originally fitted with a single carb and the heads and carbs are from a twin carb cloverleaf (which has dropped a big end shell).

As I've already stripped the cloverleaf and subsequently discoverd that it had suffered the failure, I have the pistons/rods already removed.

Just out of curiosity, the first thing I did was compare the pistons/rods from both engines.

To my surprise, there appears to be a significant difference in the dimensions. Specifically, the rod from the cloverleaf is approximately 4mm broader accross the shank at the small end and weighs-in at 7.5 grams heavier.

Obviously, that means an extra 30 grams of reciprocating weight on the four rods alone (over the smaller rods from the single carb motor).

I have the option of using either set as the critical dimensions will be the same (I'm assuming at this point). Which should I choose?

I favour the lighter ones but don't wan't to compromise the motor by fitting rods which are perhaps too light for the bit of extra grunt provided by the cloverleaf top end.

Any thoughts?

Thanks
 

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The rods from the 105 bhp engine are much stronger,we always used those in race engines but lightened,polished and shot peened,but if one has spun a shell it is no good anyway as it will have ovaled,so you may have no option but to use the 85 bhp ones.
You said you are building a motor out of two,take into account that the 85 pistons are lower compression to the 105 ones.
 

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Discussion Starter #3
The rods from the 105 bhp engine are much stronger,we always used those in race engines but lightened,polished and shot peened,but if one has spun a shell it is no good anyway as it will have ovaled,so you may have no option but to use the 85 bhp ones.
You said you are building a motor out of two,take into account that the 85 pistons are lower compression to the 105 ones.
Thanks for this information. There is also some blueing on the rod so, yeah, I guess the rod is truly shot.

I'm thinking that as this motor is not for race use and taking into account the lower compression ratio, that it may be safe to use the 85 hp ones?

Thanks again
 

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Yes they will be fine,we used to use those rods for the group 1 engines up to 150-160 hp before even the 105 came out in 82.
 
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