Lotus Elan

Some questions on the rebuild

PostPost by: dlb123 » Sun Feb 04, 2018 8:34 pm

Hello again

The engine is slowly taking shape. Ive fitted the sump using my own half-moons made from O-ring rubber which fitted well. Hopefully no leaks!

I have a couple of questions for the wise among us.

1. Setting Cam chain tension. I understand you're looking for a half inch up/down movement between the cam chain sprockets. However, lets say I turn the engine over using a wrench on the crank end. As expected, this pulls the section of chain between the two cam sprockets tight because of the effort required to actuate the valves. At this point, adjusting the cam chain tensioner appears to have no effect on the up/down play between the two cam sprockets. Rather, it takes up more or less slack between the crankshaft spocket and the intake cam sprocket. Hope that makes sense?

I suppose what Im trying to say is that winding the tensioner in and out isn't giving me a change in deflection betweem the cam sprockets .... I'm sure im being a doofus but help always welcome.

2. As stated I'm a doofus. I didn't mark the Flywheel relative the crankshaft when I removed it. There are two witness marks on the flywheel (see below) caused by the hole in the crank end boss, which means it could have been bolted in one of two positions? How important is it that the flywheel goes back on exactly as before?

20180204_192630.jpg and


20180204_192340.jpg and


Also what dya reckon to the clutch surface? Should I have it refaced? The clutch plate is very low mileage, I tried to replace it but it's an 8" borg&beck item which I've been unable to get hold of so I'm tempted to just put it all back together. It worked fine before.

20180204_192354.jpg and


3. Finally, as per photo below I need to undo one of the cylinder head bolts because I didn't positon the washer correctly relative to the camsaft runner. So what do I do? Slacken just the one, undo all of them and retighten or do I need to start with a new gasket?

20180204_193129.jpg and


The learning is painful and the mistakes are irritating but I'm getting there!!

Thanks for the continued input

Dave
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PostPost by: 512BB » Sun Feb 04, 2018 11:28 pm

I will pass on your first Q Dave, its getting late.

No 2. If your flywheel was previously balanced to the crank as a unit, and it does not go back together as before, then you could be in trouble. Have a look around the outside circumference and see if there are any drill holes. In fact, have a look anywhere on the flywheel and see if it has been drilled for balance. I will post a picture tomorrow, of a flywheel that I have just had balanced, to show you what I mean.

However, I think it highly unlikely that your engine has previously been balanced as a unit, as so few people in the past bothered, and therefore, if that is the case, I do not think it much matters where you bolt it up.

No 3. Your flywheel face appears to have some surface rust on it, so it must have been apart from the clutch plate for a while. Why not take the opportunity to get it lightly refaced and balanced at the same time. Then you can be confident that it will run nice and true, be flat, and in balance.

No 4. Just undo the head bolt, turn the washer and do it back up. It will be fine.

Something seems to have gone amiss with my numbering system, or yours. Oh well

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PostPost by: Craven » Mon Feb 05, 2018 12:50 am

Method I use for chain adjustment is to move the slack to between the cam sprockets by a firm blow with the thick part of the palm of the hand to the chain at midpoint.
Adjustment too loose chain rattles, too tight the chain whines, this is the one to avoid !!!!!
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PostPost by: 512BB » Mon Feb 05, 2018 7:00 pm

Pictures to show where a flywheel is balanced.

Note where some twat has taken a hacksaw to the old ring gear in the past, and cut straight into the flywheel, twice!
Attachments
p101000628.jpg and
p101000531.jpg and
p101000730.jpg and
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PostPost by: Craven » Mon Feb 05, 2018 8:07 pm

In the picture the yellow mark shows the position at which the CLUTCH COVER was balanced on the complete assembly, marked in order it is positioned back when centre plate is fitted.
It does not show where the flywheel is relative to crank.
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PostPost by: billwill » Mon Feb 05, 2018 9:13 pm

I think that all you have done so far is take up the slack in the chain. You need to screw the adjuster in further to rotate the inlet cam. If you had put thin cardboard on the cam bearings to stop the cams rotating while the sprockets were off, remove the cardboard.

However check that the inner edge of the chain around the adjustment cog is not touching the moulded bump around the water pump. If it is touching your chain is too long; either has an extra link or has stretched.
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PostPost by: nmauduit » Mon Feb 05, 2018 10:02 pm

dlb123 wrote:There are two witness marks on the flywheel (see below) caused by the hole in the crank end boss, which means it could have been bolted in one of two positions?


yes, the hole would be for a dowel, that is not present in your setup.
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PostPost by: 2cams70 » Mon Feb 05, 2018 10:42 pm

I'd recommend you bite the bullet and have the whole engine including pressure plate dynamically balanced. The cost isn't that great and the benefits well worth it even for a road going engine. You'll have to strip it again though. My previous experience of Ford's standard level of engine balancing back then is that it was pretty ordinary and I don't think they cared much whether it was a Lotus engine or a run of the mill pushrod engine that was being balanced!

For my engine I just rotated it in the normal direction of rotation and then pulled on the chain between the two sprockets to maximise the slack then measured the chain deflection from there. I wouldn't get too fussed though as it's easily adjusted more accurately once the engine is up and running.
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PostPost by: 512BB » Tue Feb 06, 2018 10:08 am

Craven wrote 'It does not show where the flywheel is relative to crank.'

Nobody suggested that it did. What do you think I am, made of photos :lol:
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p101000237.jpg and
p101000142.jpg and
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PostPost by: 512BB » Tue Feb 06, 2018 10:39 am

2Cams wrote 'My previous experience of Ford's standard level of engine balancing back then is that it was pretty ordinary'

I have to say that that is not my experience. Every engine that I have built and had balanced, very little extra metal removal was needed, over how they came from Ford, to bring the crankshafts into a more accurate balance. See picture of the central webs, where fresh metal has been drilled.

What was it that Sir Dave Brailsford used to say, 'Add up all the incremental increases in performance'. You remember, the Performance Director of the England gold medalists, World Champions and Record Holders in cycling at many Olympics and other competitions.

And the same can be said for balancing an engine. A little bit of improvement here and there will make a difference. I don't suppose the OP is going to strip down his engine again, now that he has gotten as far as he has, but if he just had the flywheel balanced and skimmed, it wont make any difference where it is bolted to the crank.

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PostPost by: rgh0 » Tue Feb 06, 2018 11:02 am

In general I try to avoid balancing the whole assembly of crank , flywheel / pressure plate and front pulley. I prefer to balance these items individually as I dont want to strip out a crank everytime I replace a pressure plate or have to machine a flywheel.

Assembly balancing is good if your building a top line professional race engine for F1 and can fully assembly balance it every time you do a bit of work but I cant really afford the time.

If you take care to ensure the flywheel is truly centered and balanced on spigot that fits the crank and the crank hub is truly central on the crank journals then individual balancing of these items is fine. The flywheel does need to be balanced first individually and then rebalanced with the pressure plate in place and the pressure plate drilled to restore any imbalance that occured when it was mounted.

The front pulley is a lot less critical given its smaller mass and diameter especially if using a small lightwieght steel racing pulley but the same process applies.

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PostPost by: Craven » Tue Feb 06, 2018 11:19 am

I was referring to the original post,
? As stated I'm a doofus. I didn't mark the Flywheel relative the crankshaft when I removed it. There are two witness marks on the flywheel (see below) caused by the hole in the crank end boss, which means it could have been bolted in one of two positions? How important is it that the flywheel goes back on exactly as before? ?
Why, if you limit your pictures, post an irrelevant and possibly misleading one.
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PostPost by: 2cams70 » Tue Feb 06, 2018 11:55 am

rgh0 wrote:In general I try to avoid balancing the whole assembly of crank , flywheel / pressure plate and front pulley. I prefer to balance these items individually as I dont want to strip out a crank everytime I replace a pressure plate or have to machine a flywheel.

cheers
Rohan


I don't believe that they ever balance the whole assembly in one hit. First the crank gets balanced. Then the flywheel is bolted onto the crank and the crank + flywheel is spun up and metal removed from the flywheel only to get the assembly balanced again, then the crank + flywheel + pressure plate is spun up and metal removed from the pressure plate only to get the assembly balanced again and so on. In effect each component is individually balanced
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PostPost by: rgh0 » Tue Feb 06, 2018 1:17 pm

2cams70 wrote:
rgh0 wrote:In general I try to avoid balancing the whole assembly of crank , flywheel / pressure plate and front pulley. I prefer to balance these items individually as I dont want to strip out a crank everytime I replace a pressure plate or have to machine a flywheel.

cheers
Rohan


I don't believe that they ever balance the whole assembly in one hit. First the crank gets balanced. Then the flywheel is bolted onto the crank and the crank + flywheel is spun up and metal removed from the flywheel only to get the assembly balanced again, then the crank + flywheel + pressure plate is spun up and metal removed from the pressure plate only to get the assembly balanced again and so on. In effect each component is individually balanced


Yes that is the process but then if the whole assembly is not in balance when assembled from the balanced individual components you have to decide what you take metal off to bring it into balance as an assembly and this means one component goes out of balance again. if you do it right when assembled its fully in balance. If its not some component is not central and that problem needs to be corrected and not to do this by balancing the whole assembly. thus I believe balancing individual components is all you need to do if you do it properly

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PostPost by: rgh0 » Tue Feb 06, 2018 1:21 pm

One further comment

All 4 cylinder engines are inherently unbalanced in the secondary harmonic so getting the primary harmonic of the rotating assembly perfect to the nth degree is not necessary. It is better to work on a light weight set of rods and pistons to reduce the secondary harmonic unbalance that is caused by these components movements.

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