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+--- Thread: 2 bearing crank in 3 bearing case (/showthread.php?tid=7385)
RE: 2 bearing crank in 3 bearing case - Ian Williams - 19-04-2022
The Mason Bee nest was only what Alistair told me he found when we were trying to diagnose the issue over the phone. Check the bore sizes of the oil feed take off union and the lines that go the the oil filter are adequate, also look at how the oil gallery's have been modified to feed the filter and then the jets, you obviously had inadequate oil to number one and two.
I raced my special for many years with Jet feed and a Phoenix crank and I never encountered any problems with lubrication of the bottom end, the oil pump and pick up was modified, jets were realigned, crank troughs modified, camshaft bushes O ringed and restricted etc all as I have posted about in the past. The Mike Forest 4 jet mod may be worth while for additional security if you have enough oil pressure and flow to cope with the two extra jets, but I have not found it necessary particularly with modern oils and filter. That last part is probably even more relevant in a road car that never runs at a sustained 6000 RPM+
RE: 2 bearing crank in 3 bearing case - Humps - 19-04-2022
Thanks Ian, It is now at Ryan MacDonalds and he is removing the crankshaft for me and at the same time, between us, we hope to finally suss the problem.
I don't want to go the four jet direction, as I certainly don't intend to race it. I've pumped liquid through all the pipes and passages and they all appear free.
We'll try to spin the crank with the oil pump immersed and see if it all works, but there is an oil filter in the line and an oil pressure take-off for which I don't currently have a fitting.
Cheers,
Keith
RE: 2 bearing crank in 3 bearing case - Ian Williams - 20-04-2022
If you are intending to keep the filter just make sure that you make all the necessary modifications, failure to do this will restrict the volume of oil reaching the BE bearings. You have taken your engine to a self proclaimed A7 expert who obviously knows all of this so there is no need for me to repeat anything.
RE: 2 bearing crank in 3 bearing case - Humps - 25-04-2022
We have extended the troughs to the 5.25" line and in consultation with the original owner, it does appear probable that there was a partial blockage of the jet.
I am now only waiting to learn if undersize Renault big end shells are available to be able to decide whether to get all the journals ground down, or to get the damaged journal built up and reground.
Also, as the shaft and conrod are discoloured from excessive heat, I will get them tested by heat treatment specialists, and rectified if necessary.
O rings will be fitted to the camshaft bearing as an additional precautionary measure.
It's all looking hopeful.
RE: 2 bearing crank in 3 bearing case - Bob Culver - 25-04-2022
The tempering temp is typically in the 600C range, a red heat, unlikley to have been reached. Full heat retreatment sure to cause distortion. If nitrided important the layer is not removed, at least from radii. Dunno about metal sprayting and prep for, but chrome accentuates fatigue.
RE: 2 bearing crank in 3 bearing case - Colin Reed - 25-04-2022
HI Keith,
which ever way you go with the crank after that is done speak with the heat treatment specialist about having it re nitrided
Sounds Like you have every thing under control
Best of Luck
Colin
NZ
RE: 2 bearing crank in 3 bearing case - Colin Reed - 26-04-2022
Hi Keith,
Have sent you A PM
Cheers
Colin
NZ
RE: 2 bearing crank in 3 bearing case - Humps - 27-05-2022
The crankshaft was tested by heat treatment specialists and found to have lost no strength.
Then, the damaged journal was built up using laser welding. This proved very successful, but cost NZ$660 rather than the NZ$210 quoted due to the crank being nitrided and consequently gas bubbling out as it was being welded.
It has now been reground back to standard as all the queries I made to various supplier indicated the undersize Renault big end shells were not available.
The regrinding of one big end journal cost NZ$253.
It's all looking good!
RE: 2 bearing crank in 3 bearing case - Bob Culver - 31-05-2022
The purists will wince but shells can be used as undersize with backing shims. A jig needs to be made to exactly reduce the circumference. I ran my Javelin with shimmed bearings for years.
I have dismantled engines whch were running merrily with paper behind the shells; not rcommended.