Engine reassembly

[jboy964]

A question. Does it matter which way the little end bolts face when reassembling a Mag engine? The bolt heads were facing away from the valves on disassembly. What are your thoughts please?

John

[AustinWood]

There is a convention about which way round they go. If reassembling the original big ends they should go back the way they came out. Also of course the thrust face of the piston must be to the correct side.

[Ruairidh Dunford]

I have always fitted them the same side as the piston split, however, this is not possible on two rods when building a 3 bearing engine!

[jboy964]

There is a convention about which way round they go. If reassembling the original big ends they should go back the way they came out. Also of course the thrust face of the piston must be to the correct side.

Big ends have been re metalled and crank re ground in this particular instance, so flip a coin, or eny miny mo to choose?

[Ian Williams]

In this case I would suggest following Ruairidh's advice.

[Robert Foreman]

On a two bearing engine I have always fitted the little end bolt heads opposite the split of the skirt.

[jboy964]

On a two bearing engine I have always fitted the little end bolt heads opposite the split of the skirt.

Many thanks Robert, this is the way that it was assembled and it would be wise I guess to put it back as it was. My engine still has its original crank, rods etc. and although I am not obsessive regarding keeping its originality it would be nice to put it back together properly!

The question regarding which way was because I have another 2 bearing engine, in which the little end bolt heads face the valve chest side, but then who knows how many times these engines have been apart in the past?

[Ruairidh Dunford]

The reason I developed a habit of installing them on the split side is that when I started building engines it was not always possible to get little end bolts of the correct length making it a very tight installation when using standard sized pistons, the split allowed for these over-length bolts to (just) go in.

If there is an engineering reason why they should go the other way around it would be interesting to know and, if so, how the three bearing engine differs.