My twincam strip and rebuild/put together

[berni29]

Hi

Thank you for your post. Professional polishing would definitely be the best way forwards, but its not an option I usually go for unless I cannot do it myself to an acceptable (to me) standard. So I decided to do some research.

Having watched the wisdom of the youtube, I decided to use a strip of cloth with some metal polish to lightly polish the journals. The result was pretty good. I only spent a couple of minutes on each journal, but it was enough to clean up the vast majority of the staining.

I will take some pictures when I fit the crank.

A small update....

I disassembled the piston and rod assembly. The gudgeon pins are an interference fit in the pistons, and I gently heated the pistons around the pin area with a hot air gun so that they would release. An alternative would have been to dip them in boiling water for a short while.

The piston rings were stuck in two of the pistons, but with some degreaser and gentle persuasion they freed off. I then put all the parts in the ultrasonic cleaner. I left the rings on the pistons because `I do not want to damage them on removal, especially if it is unnecessary.

I weighed the individual components and then together as sets. I used a set of good quality digital kitchen scales that weigh to a resolution of 1g, which is not as good as I would have liked. Excluding the gudgeon pins, bolts and shells, but including the rings. The weights of all the QED pistons were 400g each . The conrods ranged between 530g-532g, so the final result was:

Piston assembly 1 931g
Piston assembly 2 931g
Piston assembly 3 932g
Piston assembly 4 930g

I'm not sure if this is normal for a twincam or not. I have not weighed the gudgeon pins yet. I can hope that there is some variation between them that will let me even up the assemblies, but I think that will be unlikely.

I have a bit more cleaning to do then I will take some pictures and maybe make a video of the build up.

All the best

Berni

[rgh0]

You could end weigh the rods and then even up the weights. The big end of the rod is probably the weight difference and a small amount carefully filed of the bottom cap on the flat boss between the bolts will even them all up.

cheers
Rohan

[2cams70]

Note this is the reason why it's best to have crankshaft linishing done professionally - particularly for nodular iron crankshafts such as the original Lotus one.

https://www.mahle-aftermarket.com/na/en ... ishing.jsp

What you done by hand may look ok by eye but how it appears at a micro level probably isn't optimum. It just means you bearing life may not be a good as it could have been.

[berni29]

Hi Guys

Thank you for your input again.

I had arranged to have the block and crank etc taken to an engine man for inspection, but managed to miss the pickup slot, so decided to take the crank out again, clean everything and reassemble with just engine oil as a lubricant.

Lo and behold, it now rotates (fully torqued up) as nature intended with no binding, and actually continues to rotate a bit after you stop turning it. I do not know what the problem was but very possibly there could have been some debris involved.

Anyways, I shall now continue the rebuild...... Video of easily spun crankshaft below.

https://wefm.co.uk/lotus/lotusengturn2.mp4

All the best

Berni