Bore out connecting rod?

[seijirou]

I want to take the small end of a connecting rod from 0.912 to 0.975. Any reason why I can't do this? Stock 351C rods.

 

[poneypower89]

Im curious as to why one would want to do this?

 

[seijirou]

Because the pistons I'm looking to use have a .975 wrist pin.

I would get into it, but the tendancy there is for people to respond with "why in the world do that, it's dumb, just do yadda yadda" rather than answer the question

And I don't want to deviate into the details of my ideas just yet untill I get some opinions on opening up the rod.

 

[poneypower89]

fair enough. I won't be treading on ur grounds.

Good luck. At least I gave u a bump.

 

[seijirou]

PM sent.


So anybody have opinions/experience on boring out the little end of a rod?

 

[seijirou]

Bump

 

[dragnazz5.0]

im sure it can be done and im sure people have done it but im be kind of scared to do it on a motor that was gonna make lots of power. if you make the hole bigger, that means youre taking away from the metal that is holding the wrist pin. you might run into problems with that part flexing and the wrist pin becoming loose or even worse the wrist pin breaks through the thinner wall. granted we are only talking .063" here but it could still make a difference. are they full floating pins or press fit pins?

 

[seijirou]

im sure it can be done and im sure people have done it but im be kind of scared to do it on a motor that was gonna make lots of power. if you make the hole bigger, that means youre taking away from the metal that is holding the wrist pin. you might run into problems with that part flexing and the wrist pin becoming loose or even worse the wrist pin breaks through the thinner wall. granted we are only talking .063" here but it could still make a difference. are they full floating pins or press fit pins?

I'd imagine with this, i can have my choice. Factory is press fit I'm pretty sure.

I'm thinking, the main load goes down through the rod towards the big end, not towards the thin side, that end dosn't see force accept on decel. So it really should have little to no effect on the strength of the rod itself. But that's just bench racing

 

[dragnazz5.0]

well you would typically think there was no force on it but everytime that piston is going up on the exhaust stroke and than comes to an abrupt stop it wants to keep going right up through the cylinder head.

 

[seijirou]

True enough. How much force? Dunno. I guess I'll find out.

 

[txstang84]

You might wanna talk to a local machinist and see what they might have to say about it. taking 0.060" out of a stock rod is a little more than one might think. I once asked my machinist about boring out the ends for bushings so I could use floating pins...he told me that with the stock rods it wasn't the best idea, and it would be cheaper to find rods already setup for bushings...I'm guessing that 0.975" isn't readily available unless you call up Eagle for custom rods though...so, sorry if I haven't really helped you.

 

[txstang84]

...one more thing; as far as the forces go, with a 500g piston @ 6000rpms, I want to say it's somewhere in the 50ksi neighborhood...but I don't remember how to do the math off the top of my head, and I'm sure that someone who does will come along and correct my math

 

[seijirou]

Thanks for the input guys.

I did talk to my machinist. Who officially thinks I've lost my mind. But I think he's just the last one to find out

The cost involved in making the rods fit pins they weren't designed for is almost as much as buying a set of custom pistons. So I agreed that I might aswell just get some custom pistons that will bring the deck closer to 0 and bolt in without playing games.

I'm playing games everywhere else though