norton connecting rods

Several years ago I researched Arrow titanium rods, but it seemed strange the big-ends were not through-bolted. I always thought big-ends would be highly stressed, when they stopped the pistons from going upwards.

jay*mac said:

that was my thoughts on the map rods as well
allthough at least

the head of the bolts hit the casing on both sides turning the crank anti clockwise

Click to expand...

Do the rods you're talking about look like the picture I included? It's clear in the picture that the bolt heads cannot hit anything.

From what I understand those rods are made in China and there seems to be a disconnect in what fits and what doesn't fit.

marshg246 said:

Do the rods you're talking about look like the picture I included? It's clear in the picture that the bolt heads cannot hit anything.

Click to expand...

yes thats the rods and i,m telling you the bolt heads hit the casings on my mk3

jay*mac said:

yes thats the rods and i,m telling you the bolt heads hit the casings on my mk3

Click to expand...

I'm guessing you mean the bolt nuts not the bolt heads?

johnm said:

I'm guessing you mean the bolt nuts not the bolt heads?

Click to expand...

there is no nuts the bolts screw into the rod body from the bottom leaving the head of the bolt protruding from big end

jay*mac said:

there is no nuts the bolts screw into the rod body from the bottom leaving the head of the bolt protruding from big end

Click to expand...

OK, that makes sense. Next question: Are you being sure the small ends remain centered over the crank while testing?

johnm said:

I'm guessing you mean the bolt nuts not the bolt heads?

Click to expand...

Here's a picture that shows the bolt heads interference with the crankcase. As jay*mac said, there is interference at both the front and the rear of the cases. Please note that this is not a standard Commando engine, but a longer stroke 1007 cc engine, with Maney 93 mm stroke crankshaft, Maney crankcases, and Don Pender rods. So it's an extreme case, with more interference than you would see in a standard 750 or 850 crankcase. But it does show where the interference occurs. The Hepolite, MAP, and Pender rods all look a lot like the Carrillo rods, except, as Jim has pointed out, the Pender rods use 3/8" bolts, where Carrillo uses 5/16" bolts. And on close inspection, there are other small design differences between them. From the pictures, it looks like the MAP and Hepolite rods could also have the smaller 5/16" bolts, but I can't tell for sure.



This is a picture of the crankshaft and rods after grinding the heads of the rod bolts for clearance.



The only other engine I've used Don Pender's rods in was an ultra short stroke 750 with Maney 75 mm stroke crankshaft and Maney cases, and there was no problem with rod bolt clearance.

I've encountered similar interference problems with a couple of other Commando builds using stock Commando cases, one with a longer (91 mm) stroke crank, and one with Crower titanium rods, both of which required grinding the fasteners for clearance. I haven't had any interference problems with Carrillo rods in either standard or short stroke 750 Commando builds.

That's all I can recall that might be relevant.

Ken

marshg246 said:

If the Hepolite rods do not work without modification, I'm happy to have Wassell update the fitment guide - I just need to know what hits and where.

Click to expand...

Greg, this picture shows the two areas, between the black marks, where there is interference. The area at the rear is clearly shown, but the one at the front is not as clear, but the two black lines are still partially visible. These are Maney cases, but the interference in stock cases should be in the same locations.



Ken

lcrken said:

Here's a picture that shows the bolt heads interference with the crankcase. As jay*mac said, there is interference at both the front and the rear of the cases. Please note that this is not a standard Commando engine, but a longer stroke 1007 cc engine, with Maney 93 mm stroke crankshaft, Maney crankcases, and Don Pender rods. So it's an extreme case, with more interference than you would see in a standard 750 or 850 crankcase. But it does show where the interference occurs. The Hepolite, MAP, and Pender rods all look a lot like the Carrillo rods, except, as Jim has pointed out, the Pender rods use 3/8" bolts, where Carrillo uses 5/16" bolts. And on close inspection, there are other small design differences between them. From the pictures, it looks like the MAP and Hepolite rods could also have the smaller 5/16" bolts, but I can't tell for sure.

View attachment 117792

This is a picture of the crankshaft and rods after grinding the heads of the rod bolts for clearance.

View attachment 117793

The only other engine I've used Don Pender's rods in was an ultra short stroke 750 with Maney 75 mm stroke crankshaft and Maney cases, and there was no problem with rod bolt clearance.

I've encountered similar interference problems with a couple of other Commando builds using stock Commando cases, one with a longer (91 mm) stroke crank, and one with Crower titanium rods, both of which required grinding the fasteners for clearance. I haven't had any interference problems with Carrillo rods in either standard or short stroke 750 Commando builds.

That's all I can recall that might be relevant.

Ken

Click to expand...

that is the exact same as mine
so it is fine to chamfer the bolts i am concerned

acadian said:

I encountered the same problem with steel rods from Don Pender, I did not relieve the cases, but cut a 30 degree relief on the bolt heads once they were installed and torqued

Click to expand...

Did you cut them hot or cold ? I bet that that torque was not the same if hot, maybe,I think. Cheers Ian

marshg246 said:

OK, that makes sense. Next question: Are you being sure the small ends remain centered over the crank while testing?

Click to expand...

yes

jay*mac said:

yes

Click to expand...

does this mean that Mk3 cases are different internally to earlier 850, enough to create clearance problems, even with standard crank??

jan nelder said:

does this mean that Mk3 cases are different internally to earlier 850, enough to create clearance problems, even with standard crank??

Click to expand...

it is looking that way