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Guest mkelite

Cambelt Replacement Help Please?

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Guest mkelite

hi guys. hope ive put this in the right place? i know ive only got a 5% chance of NOT having cambelt failure damage on our ' 87 Excel but can someone advise please? have replaced cambelt and lined up all markings on sprockets etc as per Lotus workshop manual. however, when crankshaft is turned the markings do not line up again. have been told this should happen after two revolutions. have i missed something? any advice gratefully recieved as i still hoping i can save her! doubt it tho! and im all alone here in Milton Keynes.........boo, hoo! best regards all. DC.

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Hiya. Wild guess, but I get the feeling you're looking to line up belt markings? If so, don't worry - it's the sprockets markings you need to be concerned with. Or have I guessed wrong? :thumbsup:


British Ambassador to Florida, New York, Denmark and Newfoundland.  And Sweden.

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Hi David,

If all the dots were aligned correctly then the everything should match up again after two rotations of the crank.

Best of luck.

Gavin.


Cheers, Gavin

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Yeah, what they said; the markings on the sprockets should all align after two rotations of the crankshaft; remember that two crankshaft rotations equal one camshaft rotation. But if you put markings on the belt, they won't align with the ones on the sprockets any more, because the belt has an odd (and greater) number of teeth.

When you install the new belt, with sprockets aligned, the belt should be tight (tight like the tensioner were already set) along the span from crankshaft to exhaust cam sprocket. It's easy to allow an extra tooth of slack there, which then shows itself when you rotate the engine manually; for this reason, people paint the old belt when they remove it from the car and duplicate the marks on the old belt to the new one before installing.

- T


Tony K. :)

 

Esprit S1s #355H & 454H

Esprit S2.2  #324J

1991 Esprit SE

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Guest mkelite

thanks for those quick answers guys. the markings i used were the sprocket markings which i highlighted. the belt was tensioned and i checked and rechecked everything. so unless theres any other mechanical reason why - i can only suspect the belt was a gnats whisker loose at some point. so the next question is please; should i loosen the belt with the camshaft at the 'safe' postion n try again or am i chasing my tail? as ive said before, i DO suspect damage as the old belt lost some teeth. its just im hoping folks....................regards . DC.

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I think the question I have to ask at this point is, how far out of line are your marks after you've gone your two revolutions on the crankshaft? I don't think you'll be too bad off if you only missed one tooth while rotating by hand. I would suggest getting everything back into "safe", realign all your marks, make sure you pull as much tension as possible to the tensioner side and take up that slack by setting proper tension and trying it again. Sometimes it helps if you counter-rotate the crankshaft just a couple of degrees to align on the next tooth up to pull more tension on the "long" side of the belt to eliminate the possibility of an extra tooth between your exhaust camshaft and crankshaft belt-run.

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David, I don't suppose you have a small camera that can go down the spark plug hole.

Assuming that you don't, and you want to know about possible valve damage, here's a check that will tell you if you have significant damage.

Remove the plugs and remove the inlet manifold. Shine a good light source down the plug hole when the inlet valves should be closed. can you see light making its way up the inlet port towards where the manifold would bolt to? Yes = damage, don't bother putting the belt on.

You only need to find one that's in that state and you can stop what you are doing and strip the head. If you find none, you could repeat for the exhaust ones but it's a fair bit of work.

Good news is MK to Marton is a nice little evening jaunt (Lotusbits), so relacement bits will not be too expensive.

Andy

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Ummmm, if you've started with all the dots lined up, done 2 revs, and the dots DON'T line up, then something is very very wrong! Either wrong belt or it's slipping on the way round. So, what's the belt spec, where you turning it in the normal direction of rotation, and how was the tensioner?

To be frank, if the old one stripped teeth then it's odd-on you have damage...


British Ambassador to Florida, New York, Denmark and Newfoundland.  And Sweden.

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Guest mkelite

thanks again guys. yep belt was Lotus spec belt from dealer. no prob there. i do suspect damage im jus trying a last hope attempt. other wise its £2.5 to £5k to rebuild engine cos i cant take head off myself etc etc. thats y im always looking for local Lotus nuts to at least give me moral support. any other ideas appreciated. i think im just gonna try one more set up from the 'safe' postion. regards .DC.

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Eeeek! I wonder where you'd find a bunch of local Lotus nuts...


British Ambassador to Florida, New York, Denmark and Newfoundland.  And Sweden.

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David.

Transport company to CV23, around £80, Mike and the guys could inspect engine and refurbish or fit good second hand engine for a lot less than £2.5k, or the engine guy who does Mike's rally engines is on site with him.

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Guest mkelite

..................already spoke to Mike Taylor at Lotusbits, guys....................... just trying last chance before i have to find the dosh or decide just to buy another Excel.................rather rebuild original engine than buy unknown quanity ........................................then i wanted to restore our Elite S2.2 this year..........................then get an Esprit V8 later this year.....................then..................money...............................errrm. DC.

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Whip the top off and have a look - won't take long!


British Ambassador to Florida, New York, Denmark and Newfoundland.  And Sweden.

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Guest mkelite

hi me again..................shouldnt speak too soon but ive manage to realign the new cambelt and got healthyish compression on all cylinders and she fires up n runs. albeit not smoothly yet. i did a static timing set up then checked with my timing gun but not quite there yet. so if any of u VERY nice Lotus fellows are passing my way - could anyone check my cambelt tension and give any advice to get her running smoothly. she has been in the garage for sometime now and i am still hoping i can save her. regards guys. DC.

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Nicely done David :thumbsup:

What were your compression readings?

Never thought a snapped/toothless belt on one of these would result in zero damage but your the second person in a short period of time to have acheived it :)

Can't help on your tensioning issue as i'm too far away but if its far too loose it will feel obviously loose, and if its far too tight you'll most probably hear a squeeling from somewhere! Think just about half twist in the belt on its longest span is a VERY rough and ready guide though and you should be safe in the short term, hopefully soomeone on here with a guage will be not too far away from you.


Chunky Lover

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Guest mkelite

hi. thanks for that. yep know about the twist approximation - but now that just makes me nervous, so if i get her running properly - shes not going anywhere till the tension has been correctly tested. compression readings were all 170lbs. and that was with slightly warm engine..............but still bit nervous untill she runs like she used to..................regards. DC.

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Guest mkelite

so u guys thinks that approx. 170lbs compression is healthy then? the workhop manual says 170 - 190lbs but someone told me should be 200lbs ! ? regards DC.

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Hi Dave - 170 is pretty good, and especially good if it's consistent across cylinders, so no worries there!

I'd love to come up and meet you and check your tension, but I'm up to my ears in it.


British Ambassador to Florida, New York, Denmark and Newfoundland.  And Sweden.

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It's called 'working for BA'. :)


British Ambassador to Florida, New York, Denmark and Newfoundland.  And Sweden.

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