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Bottom end refresh


Wilf

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Engine on my 83 na will be coming out thus weekend due to excessive crank end float.

Plan to just strip the sump and cradle off check mains and big ends as it has got 84k on it. Engine has good oil pressure, compression and no unusual noises. 

What else is recommended? Will obviously dig further if I find anything unexpected, but are there any other known mileage based issues to address whilst I am in there?  Head was reconditioned in last 20k after po suffered cam belt failure.

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I'd suggest taking a look at the engine and gearbox mounts and checking the flywheel and clutch while its all out of the car and easy to get at.  There were little micro surface cracks on my flywheel which the guy doing my engine spotted when it came out recently. He's fitted a new flywheel and clutch for me so I've ended up with a spare new pressure plate from SJs. It's just sitting on a shelf in my garage so give me a shout if you find you could make use of it, 

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Normally Aspirated - and lovin' it!

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Thanks choppa, my flywheel looks to have similar issues, my end float is approx 3mm(!) And the input shaft comes out of the gearbox....

I shall be busy for a while by the look of it.

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3 mm  Is MASSIVE...!"!!!  When you put the engine on the stand and invert you may well hear the thrust bearing tinkle it way into the crank case... 

I have seen this a few times before and in most cases it damages the crank on the relevant thrust face.  After they are ground the thrust area can get a bit too thin , also the bearing replacements are not available in the extra large size required .. however you can always have a special thrust bearing made for that particular job... Don't short cut this it will come back a bite you.. 

To give you an idea , I have just finished a rebuild on an engine that on strip down inspection had 0.013'' end float , I thought that was excessive ...    

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Gave the outside a clean and removed sump. No remains in there so will remove the bearing cradle and see what horrors await. Is there a published figure for the big end clearance fore and aft on the crank as I am concerned all this movement will have damaged that too. Not found anything in the manual for this specific measurement.

Just been on lotusbits, second hand replacements of cranks etc not too extreme price wise so all is not yet lost.

Edited by Wilf
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Wilf,   What you need to do is check everything very carefully before ripping it to bits..  This will tell you a lot on the general condition and areas needing attention..   On the big end lateral movement, This should not be an issue . There is enough free play in the wrist pin to allow crank end float movement. Before this reaches its limits the counter balance weights on the crank will of hit the crank case (block)  but it takes a lot .. you may just get away with it.   By carefully looking you will be able to see if they have touched, by scuffs or grooves on offending areas.  A good indication on engine condition will be the main bearings.. The front top shell (#1 in the block half with a hole in )  will probably be fully worn..  and the others at the thrust point on the lower shells. This is not unusual .  If the thrust bearing face is ok or can be salvaged then a new set of bearings all round should be fitted regardless.. mains and bigs...  At this point be aware of the cheap two ply alloy backed bearings  that are available , you should only fit 3 ply metal backed bearings.. they cost more but will work out cheaper..  Always remember any work done on an engine is not cheap when done correct.. 

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Some progress, oil pump housing off, front and rear oil seals off. Did not have sufficient feeler guages to measure the movement but use of an Allen key and measuring that confirms my estimate of 3mm was actually correct.

Some concerning signs of contact where it should not on one side of one of the main bearings. See photo. That is no 4 cylinder looking towards the front. No witness marks anywhere else.

Will remove bearing cradle tomorrow once I have taken my brave pills!

IMG_20160705_211902.jpg

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3mm of end-float is a lot less than DaveFreeman had on his, the machined faces of the crank that re like washers, well they were no more. He had clutch issues in that you pressed the pedal and it wouldn't clear properly as it was pushing the crank into the engine. 

Hopefully that makes you feel better about what you expect/ fear to find.

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That's pretty impressive...I've just done mine as I had .012" (about.3mm) float, which the book states as the wear limit!

removing the main bearing panel was no real hassle' but I'd be interested to know if your engine has the chamfer mod, or is a later manufacture...mine had the mod, so I presume it was done after leaving the factory at some point, (no record of it) but has still worn to the limit by 75k.

Pics in This thread if any use

 

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My engine number is before the mod was done routinely at the factory so who knows! Using a torch to peer down through the holes in the bearing cradle I can see the thrust bearings still in place with bronze coloured bearing face still visible on the parts I can see.

The face on the crank however is stepped and not flat and it looks like this small step was originally he only part of the crank running against the thrust bearing. This has then worn to the point the rest of the crank is now actually against the thrust bearing which appears to have limited the movement beyond 3mm.

Crank looks scrap, block hopefully OK. Photos once I have it apart for discussion.

 

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This has been apart since the factory as the rear main bearing has a notch in it, but the bearing cradle is not modified. 

Damage evident to the cradle 180 round from the rear thrust bearing, and on the rear facing side of the bearing between 3 and 4 both can be seen in the picture.

IMG_20160706_193725.jpg

Thrust bearing is stepped to match the crank

 

IMG_20160706_192654.jpg

And the crank in all its glory

 

IMG_20160706_192526.jpg

So is this wear pattern typical of the lubrication issue, or have I got other as yet to be determined problems?

Will remove crank later this week.

The front thrust bearing is mint.

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This needs a complete rebuild, the bearing shells show some of the iron filings off the crank made it into the oil circulation. 

 

Will need to strip everything to get the oilways cleaned, and at that point it would be crazy not to do everything.

May be more than I really want to take on currently.

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Its more a time and cost vs benefit back. I only manage 500-750 miles a year for the last 4 years as its a two seater and I have young children who both want to come along. My fag packet maths suggests the value I sell for needing engine rebuild will probably be equal to the running value minus cost of full rebuild by someone else.

Slapping it back together and selling with a known problem is not something I would do.

One for me to ponder a while.

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I've been faced with a similar dilemma, minus the kids :-)....

I would suggest that you already have most of the skills, or if not, then help from forumites will likely provide the lacking bits, especially in your location. Cost of the full rebuild is not prohibitive, I'm sure, - it's the labour.

stick with it, and within 12 months, you'll be back behind the wheel..or in a much better state to sell a running legend!

atb whatever you decision

Dave

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I have no need for the money tied up in it and no need for it to actually work (as annual mileage proves), though it defeats the purpose of owning it to a degree! I may well just mothball it for a while until the time situation gets better.

I have one restoration under way already so need to finish that first as that is a 4 seater that will get used.

 

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