4 replies to this topic

[The_Doc]

Before anyone tells me 'search', I can confirm I've read about the blowtorch method of fitting new pistons to conrods, plenty of info and a couple of youtube videos to be found on that.

 

My question is firstly on removal...my conrods are standard A+ and I'd like to reuse them.  How do I remove the pistons without damaging the conrods?

 

Second part of my question is on refitting, if I could get access to a hydraulic press, is this preferable to the heating method (i.e. less risky), and if so what's the best way to go about it.  I've used a press for bushes but never for a critical engine component like a gudgeon pin, I feel brute force and ignorance might not be the best approach!

[ACDodd]

Brute force and ignorance is definitely not the best approach, you need correctly shaped tools to support the piston properly when doing this work. Coke press fitting is not recommended as it’s far too easy to damage the pistons. You also need to be able to check the interference fits before fitting to ensure that when assembled they will intact stay assembled.

I use the hot fitting method. All too easy to ruin the rods when heating. You see videos of people taking the rod to red heat which is far too hot and will actually soften the steel and reduce its strength as you are actually annealing it. Deep straw to just blue is the colour for most fits. However you need to check the sizes as the tighter fits need a little higher temp but no more than a bout 450celcius. The main point here is practice, as it’s very easy to get the pin stuck halfway in and then you have to move it with force, and things can quickly end up with damaged and broken pistons.

If you are only planning on doing 4 for one engine beat leave it to someone who has experience in doing it.

This is one of those subjects that you will likely get lots of different answers.

Ac

[The_Doc]

Brute force and ignorance is definitely not the best approach, you need correctly shaped tools to support the piston properly when doing this work. Coke press fitting is not recommended as it’s far too easy to damage the pistons. You also need to be able to check the interference fits before fitting to ensure that when assembled they will intact stay assembled.

I use the hot fitting method. All too easy to ruin the rods when heating. You see videos of people taking the rod to red heat which is far too hot and will actually soften the steel and reduce its strength as you are actually annealing it. Deep straw to just blue is the colour for most fits. However you need to check the sizes as the tighter fits need a little higher temp but no more than a bout 450celcius. The main point here is practice, as it’s very easy to get the pin stuck halfway in and then you have to move it with force, and things can quickly end up with damaged and broken pistons.

If you are only planning on doing 4 for one engine beat leave it to someone who has experience in doing it.

This is one of those subjects that you will likely get lots of different answers.

Ac

 

Thanks for this, I'll take your advice!  I have a bit of a background in metallurgy, hence my nerves around heating the steel up too hot and affecting the material properties.

[DeadSquare]

I have had chaps come and weep over the damage that, so called experienced engineers, have done to their pistons.

 

I have even seen damage on the piston, where an ill aimed hammer blow had struck off the gudgeon pin.

 

If Mr Dodd will accept the job, take or send the bits to him,   OR     to some one that he recommends.

[Spider]

Before anyone tells me 'search', I can confirm I've read about the blowtorch method of fitting new pistons to conrods, plenty of info and a couple of youtube videos to be found on that.

 

That is NOT the way to do the job. Here's what the factory have to say about that;-

 

 

Regardless how they are heated, there is no way of knowing how tight the pin will end up in the Rod.

One correct way;-

In particular, note their caution;-