8 replies to this topic

[RooBoonix]

Hello all,

 

I'm rebuilding my 1275 for various reasons and I have a (hopefully quick) question regarding con rods which have been previously heated to fit press-fit gudgeon pins.

 

I had the pistons fitted to the con rods by the machinist/engine builder who bored the block etc... and there were visible markings where the rods had been heated to fit the pins. Some say this is the way to do it, others say it's a big no no. I have no idea how much they were heated. I'm looking at changing to floating pins, would my con rods be suitable for machining and fitting a bush to? Or would I be best off not risking it. Do I need to fit a bush, or can I just hone out the small end and run the pin directly in the rod?

 

They are standard A+ 1275 rods.

 

Thanks in advance,

Cameron

[mini13]

tricky one, yeah the heating isnt ideal, and its hard to give an opinion without seeing the rods,

 

floating pin wise, Ive honed rods out to run floating pins with no bush before, when Ive done it I have added a hole at the top of the rod for pin lubrication, ive also run the pins with PTFE buttons rather than clips.

[Spider]

Here's what the factory said regarding the heating of these Rods;-

 

When I find them that have been heated, I bin them - not worth the risk.

[RooBoonix]

Thanks for the replies guys. I'm in no particular rush so I'll keep an eye out for a set of good A+ rods. 

 

Also planning on running buttons, I'm not a fan of clips either.

 

Cheers

[DeadSquare]

IMHO, this is a bit like replacing the rubber suspension doughnuts with springs;  a detraction rather than an improvement.

 

Unless you are building a short life, frequently overhauled competition engine, for a "cooking " engine, stick to the manufacturer's specification.

 

The special tool is:-  18G 1002.  BUT

 

With a large enough vice, a piece of soft wood to cushion the piston and a 1/2" blot to slide in the one end of the pin, by leaving the pins in the freezer overnight (turned as cold as it will go) and the little ends boiled with your breakfast egg, it is possible to fit the pins 'at home'.

[RooBoonix]

IMHO, this is a bit like replacing the rubber suspension doughnuts with springs;  a detraction rather than an improvement.

 

Unless you are building a short life, frequently overhauled competition engine, for a "cooking " engine, stick to the manufacturer's specification.

 

The special tool is:-  18G 1002.  BUT

 

With a large enough vice, a piece of soft wood to cushion the piston and a 1/2" blot to slide in the one end of the pin, by leaving the pins in the freezer overnight (turned as cold as it will go) and the little ends boiled with your breakfast egg, it is possible to fit the pins 'at home'.

 

The car won't be a mile muncher, I'm supercharging it and it will purely be a weekend/fun car. Not expecting it to last 80-90k like it did in standard guise.

 

Cheers

[DeadSquare]

"The Mini Man" in Faversham has a set of 'buy it now' rods on Ebay for £50-00

[Spider]

The special tool is:-  18G 1002.  BUT

 

When you look up the instructions for the factory tool, it uses a threaded puller and it's used with a torque wrench when fitting new pins so that the friction between the Pin and the Little End can be tested the whole way in. if it falls below their specified value, their advice is to replace the Rods.

I don't have this tool, I have a Rod cradle and I do them in the Press, however I check the pressure needed and if it's not up to the mark,,, in the bin they go.

 

And,,,,,

This also shines a light on another reason why the Rods shouldn't be heated to fit the Pins, you have no idea how much friction (or grip) the rods have on the Pins when fitted.

With some Rods, the manufacturer will say to heat the little ends to fit the Pins and they'll give specifications for doing that, but clearly, that's not the advice with these particular Rods.
 

[RooBoonix]

New rods it is. Especially for this engine as it's going to be under additional stress.

Thanks for the replies