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What to get crack tested


Peter Carmichael

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Rightho. Everything is stripped from the big engine and ready to be crack tested. I have had every valve kiss the pistons and 3 valve heads fall off and get mangled in number 4.

 

Never done crack testing before, so don't really know what's involved but my current view on what gets crack tested is:

Crankcase

Crank bearing ladder

All through studs

The hi-tensile nuts that hold it all together

Steel baseplate

3 liners

Crank (check for straight as well)

All conrods

All gudgeon pins

3 pistons

Inlet cam (check for straight as well)

Exhaust cam (check for straight as well)

All followers (check for flatness)

All spring caps

 

My current view on what goes in the bin is:

Head

1 Piston

1 liner

All valves (in 19 bits)

All valve springs - cos they were getting on

All valve collets

All follower shims

 

I need to get:

1 piston, dished and balanced

A full set of piston rings

1 liner

A new head, ported and machined for the strengthened through bolts

All new main bearings

All new big end bearings

New conrod bolts

 

Does this seem about right 🤔

 

Edited by - Peter Carmichael on 25 Sep 2002 16:19:54

 

Edited by - Peter Carmichael on 25 Sep 2002 16:20:55

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I would also check that the followers are still flat faced as they may have taken a hammering when the valves were forced skywards ??

Also check that the cams are still straight , as these would have taken some force of impact too .

 

Good luck with the build Peter ,

 

See you soon

 

Dave

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Peter, Im a few years out of practice but your list of bits I would break down into three classes:

1. Bits that are too difficult to get reliable results on like bolts and nut which are simply replaced

2. magnetic parts that can be checked within an ultra-violet light tent using Magns-Flux techneque

3. Non-ferrous bits that you have to use dye-penetrant and developer on.

The skill in spotting cracks using either techneque is developed with practice just like medical X-rays you have to know how to do it and what are the false clues in castings and changes in section.

Fully machined items like pistons are easy on the skirts but ring lands need special skills.

You can buy the dye penetrant aerosols and do the aluminium castings yourself so long as you take real care in the preparation and are not too enthusastic with the dye.

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Ammo's contact is doing it all for me using a combination of Magna Flux and dye penetrant. A lot of stuff is just going to be replaced out of hand.

 

Can anybody here imagine how embarrassing it would be if I kept the followers and then one let go, having been given the above advice by RK.

 

Adrian's first squint at the damaged piston prompted comments like: "that's not at all bad", "seen a lot worse"

When he saw the fully counterweighted Doug Kiddie crank he said: "If it was my engine I would just give it a wipe and put it back in"

 

I think I am reaping the advantages of having built it strong in the first place.

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