Lotus Elan

My first engine rebuild

PostPost by: Concrete-crusher » Sun Nov 26, 2017 1:05 pm

Progress is a little slow , I'm trying to finish the head first as I'm running out of space for all the bits. New valves , seats , and guides as well as cam bearings. I need one of the long head studs on top that fix the rocker cover , somehow one got bent ,

I have bought the rounded type thrust bearing and a new carrier from Burton , to match the NOS clutch cover which does not have the thrust pad. my old mismatch explains why I had no more adjustment but the clutch plates not worn

I have noticed the 6 bolt crank does not have a locating dowel just the hole , the flywheel does not have a corresponding hole ? Does anybody know if this is normal and is the crank flywheel balanced to compensate or does it not make much difference ?

Or is this another factor as to why the engine felt a bit rough before

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PostPost by: 2cams70 » Sun Nov 26, 2017 11:13 pm

That's just normal. Have a dowel fitted if you are tuning the engine beyond a standard level. I'd recommend however having the engine rotating components and clutch balanced as a matter of course. The small additional cost is well worth it regardless of the level of tune.
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PostPost by: MarkDa » Mon Nov 27, 2017 5:09 pm

Steve
I'm not an expert but if this is the first rebuild (or are you a 'virgin') then the valve seats won't be hardened for unleaded fuel will they?
Is this as big a deal as was made out at the time?
Maybe that explains the wear pattern?

My comments are probably far too late anyway - but I think you were right to go for seats and guides.
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PostPost by: Foxie » Mon Nov 27, 2017 5:51 pm

MarkDa wrote:Steve
I'm not an expert but if this is the first rebuild (or are you a 'virgin') then the valve seats won't be hardened for unleaded fuel will they?
Is this as big a deal as was made out at the time?
Mark


The big problem with unleaded fuel was with cast iron heads where the seats were cut directly into the cast iron.

Lotus always used alloy steel seat inserts, and I have never heard of unleaded fuel causing any damage.

However, some sections of the performance industry did a lot of business unnecessarily replacing perfectly good valve seats. :shock:
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PostPost by: MarkDa » Mon Nov 27, 2017 6:22 pm

Thanks for the explanation - there were plenty of engines that had separate seats but still basically cast iron, such as BMC A Series like i had in a 60s Midget.
Further reading suggests that quite a lot of pre 84 Ford engines needed new seats as well.
Glad to hear that our engines were future proofed from the start.
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PostPost by: Concrete-crusher » Mon Nov 27, 2017 10:30 pm

I had one of the shims down to 59 thou and several at 60 which was the minimum. You could see the old seats were cut quite deep so I think they needed changing any way. The guides were carlsbro whatever that is , and the seats supplied at the same time , both by the very helpful Sue Miller

I had to get new collets as a few of the old ones were also worn , and the thought of a collet failure is horrendous.

The collets came from Burton engineering and look just right.

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PostPost by: Foxie » Tue Nov 28, 2017 12:54 am

=" The guides were carlsbro whatever that is ....

Steve
"Carlsbro". Maybe that was "colsibro", an alloy of copper, silicon, and bronze.

https://www.chriswitor.com/datasheets/colsibro.pdf

(Carlsbro: The best valve guide material. Probably. :) )
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PostPost by: 1owner69Elan » Tue Nov 28, 2017 8:01 am

COLSIBRO = COpper nickeL SIlicon BROnze
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PostPost by: Foxie » Wed Nov 29, 2017 2:11 pm

1owner69Elan wrote:COLSIBRO = COpper nickeL SIlicon BROnze


Yes there is nickel in there too, but COLSIBRO seems to be a bit of a mongrel trade name rather than a full metallurgical description.

Since bronze is not an element but an alloy of copper and tin, it would be more accurately described as 'Copper tin nickel silicon' or 'nickel silicone bronze' :D
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PostPost by: Concrete-crusher » Fri Dec 01, 2017 8:08 pm

So today I finally got everything off and dismantled.

The crank has 3020E cast into it so that matches what's stamped onto the block.

The rear thrust washer was quite worn , in fact it's about half the thickness of the forward thrust washer.
I put the pistons with con rods attached on a scale , numbers 2,3&4 are all the same weight but number 1 is 6 grams lighter.

The cylinder walls look smooth but you can feel a difference at the bottom of the stroke , I don't really know how to measure the bores but that's what the machine shop will do.

So now I'm soaking in a solvent to remove the paint before taking the block , pistons and crank / clutch to Saunders for machining and balancing.

Also I'm bracing myself for the cost.
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PostPost by: rgh0 » Fri Dec 01, 2017 8:14 pm

[quote="Concrete-crusher"]

The rear thrust washer was quite worn , in fact it's about half the thickness of the forward thrust washer.
.../quote]


The thrust washers come in different thicknesses so that the crank endfloat can be set. The washers may not be worn

cheers
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PostPost by: promotor » Fri Dec 01, 2017 8:22 pm

Concrete-crusher wrote:
The rear thrust washer was quite worn , in fact it's about half the thickness of the forward thrust washer.



Thrust washers can and will end up a different thickness if they've been installed the wrong way round - the crank gets machined down by wearing against a non-bearing material (ie the back side of the thrust washer) - check the crank thrust face over whenever you see/have a thinner thrust washer. This problem only ever exists on the rear most washer and corresponding crank face.

The "quite worn" is what you'll see on the the thrust washer if it's been in the wrong way.
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PostPost by: Concrete-crusher » Sat Dec 02, 2017 8:48 am

Thanks for the advice , which way round should the thrust washers be fitted. Should the two grooves face the crank surface or the block.?

Some web sites say they face the bearing surface which I call the crank , but page 115 of miles book has a picture showing the grooves facing the block.

The ones I took off , had the grooves facing the crank on the front and the grooves are worn off the rear.

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PostPost by: Craven » Sat Dec 02, 2017 11:17 am

Thrust washer have a ?soft? (white metal) face on the side with the grooves, this goes against the moving surface ie the crank.
Thrust washers are available in oversize thickness in order to set the crank end trust clearance, your well-worn washer if it has been fitted correctly, would I suspect be the nearest the clutch as this takes the pressure of the opening of the clutch. If it is a badly worn as you say then check the corresponding surface on the crankshaft for scoring and wear as the soft face of the thrust washer will have gone and the hard metal backing will have been in contact with the crank.
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PostPost by: alan.barker » Sat Dec 02, 2017 11:42 am

+1 page 115 in Mile's book the thrust is shown the wrong way round
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