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Swapped EX & IN Camshaft Sprockets


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Just finished rebuilding my carbs Esprit S2 and back in the car, initially car went ok but after filling up with BP Ultinate it started misfiring and was only running on 3 cylinders. 
First thoughts were stale fuel, but after a 2nd carb strip and rebuild the problem was still there. 
worked my way through all the potential culprits.

Turned out to be the NGK BPR6ES spark plugs, swapped these out with a brand new set of Champion N12YC and problem solved. 
 

Anyway that’s the background to the next issue, as when I was checking all the other stuff when I came to check the engine timing I noticed some Rocket PO has managed to mix up the exhaust and inlet camshaft sprockets. They are clearly stamped EX & IN, the mind boggles!

The workshop manual states not to get these mixed up but doesn’t say why.

Engine is running ok at the moment and I plan to do some engine work over the winter months and was thinking of addressing this then. 

Does this drastically affect engine performance and should it be done sooner rather than later?

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I’m looking at the sprockets from the rear of the engine and can see the ‘IN’ on the LH camshaft (exhaust) and ‘EX’ on the RH camshaft (inlet). wish I took a picture. 

I will check tonight when I get home and will also take some pictures. 

Thanks Barry! Makes perfect sense, so I can rest easy as looking at mine I can now see they are indeed fitted the correct way round.  Will do more digging and investigation before taking a PO i

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You are looking at the sprockets from the  FRONT of the engine, correct? They are marked EX an IN on each side.

 

The timing is different depending on orientation.

Atwell Haines

'88 Esprit

Succasunna, NJ USA

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I’m looking at the sprockets from the rear of the engine and can see the ‘IN’ on the LH camshaft (exhaust) and ‘EX’ on the RH camshaft (inlet).
wish I took a picture. 

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To expand on Barry's remark, there is more to the sprocket positions than one might expect. If your car is a Federal S2 then it may have been intelligently reconfigured by the PO, as Lotus set the intake cam in an inferior timing position owing to the smog regulations. Can't say why a UK spec car would have had things put amiss by that method.

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Thanks for the replies!

I'm confused, going by Barry’s picture it looks like it’s the same casting used for both sprockets (makes sense reducing manf. costs) so if the same part why would the workshop manual say not to get these mixed up?

Are they referring to which way round they go on the camshaft?

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  • Gold FFM

Pretty sure the dot is in a different place on the other side. You fit them one way round to EX - the other way round for IN. That picture is of the later pulleys though.

Only here once

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There are coloured dimples.

Standard for the 910S -

Red - 110 deg MOP exhaust.

Blue 100 deg MOP inlet.

Green 104 deg MOP, for the 920, but can be used on the 910.

Margate Exotics.

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4 hours ago, drdoom said:

David, are there coloured dots ( dimples ) on the pulleys?

Here is what you are looking for (circled).  You can see the dots on the engine side, too.

Cam Wheel dots.jpg

Atwell Haines

'88 Esprit

Succasunna, NJ USA

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Ok took some pictures and both sprockets have EX & IN on them as in Barry’s picture. 
 

I can’t see any colour in the dimples, see pics below ...

 

8F5903FD-37BB-4DA7-9114-7BA33CD7B597.jpeg

B4F20B15-3CB4-47FB-873F-A8B1D1BAAB19.jpeg

FAFDD5B3-8729-4676-945E-DDAE87D2CA35.jpeg

44E95DCA-C29D-4F92-8652-552C0DE89EAD.jpeg

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  • Gold FFM

Colour dots usually fall out leaving just the dimple. Oh and the belts rarely run in the centre - your picture is certainly not unusual - more typical 

Only here once

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  • Gold FFM

Hang fire - I’ll go and look at the one I have lying around 

B76D4770-0C27-427B-A1FA-BE522DC24362.jpeg.b2583df5be335a812234fb268082fd85.jpegD4D70881-7FAC-40E6-8F60-FCE934461A52.jpeg.4b11d04786a5f757365f521d4a02fc7e.jpeg

please note this is the same pulley - I’ve no idea of the dot colour - that’s largely irrelevant. You fit them one way round for exhaust - the opposite way round for inlet.

hope that makes sense 

Only here once

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Thanks Barry!

Makes perfect sense, so I can rest easy as looking at mine I can now see they are indeed fitted the correct way round. 
Will do more digging and investigation before taking a PO in vain. Trouble is there are so many bodges I have already had to put right It’s hard not to be sceptical.

Thanks to all the replies guys, as always valuable support.

 

 

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Hopefully you won't need to remove them with the engine in - if it's anything like the SE. I had a nightmare of a time trying to remove one for getting access to a bolt for the water pump. It was very much stuck on.

tdc_11.jpg.d6541c90a444c73d375435db8c49e409.jpg

tdc_12.jpg.5b7ab8301afbb910000098ae34c4525b.jpg

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  • Gold FFM
46 minutes ago, DavyJ said:

. Trouble is there are so many bodges I have already had to put right It’s hard not to be sceptical.

 

Oh I know that feeling all too well. Always from “specialist” garages as well 😱

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  • 2 weeks later...
On 17/08/2020 at 07:07, Barrykearley said:

Pretty sure the dot is in a different place on the other side.

The dot is in the same place on both sides of the green dot pulley, i.e. it is on the same tooth. The 'IN' and 'EX' are cast in different positions on each side of the pulley.

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Cheers, Derek.

 

Correction to my earlier post, which should have read:-

There are coloured dimples.

Standard for the 910S -

Red - 110 deg MOP inlet.

Blue 100 deg MOP exhaust.

Green 104 deg MOP, for the 920, but can be used on the 910 inlet and exhaust.

Margate Exotics.

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  • Gold FFM
1 hour ago, sailorbob said:

The dot is in the same place on both sides of the green dot pulley, i.e. it is on the same tooth. The 'IN' and 'EX' are cast in different positions on each side of the pulley.

Yup - you are absolutely correct - my original posting is incorrect. The dots in the same place.

ive got a sneaking suspicion it’s a blue dot pulley.

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Thanks for the info on the green dot sprockets. I actually asked this question but didnt get a real answer on my post. I indeed have green dot sprockets.

 

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Just out of interest, why do you think the Champion Spark Plugs are better? or in other words what do you think is wrong with the NGK ones?

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1 hour ago, Big Vern said:

Just out of interest, why do you think the Champion Spark Plugs are better? or in other words what do you think is wrong with the NGK ones?

Don’t think they are better just had a brand new set of Champion’s at hand.  
Also the N12YC are a hotter plug and didn’t soot up as much, but this could also have been down to the poor sparking. 

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