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Could use some help checking timing


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Hello,

I'm the new owner of a 1975 Elite 503 - my first lotus and introduction into classic british vehicle ownership. The cosmetics suggest the car has spent its life well cared for, but it will need some "recommissioning" considering it was last on the road in 2006. 

My first and biggest concern is that something prevents the engine from rotating all the way by hand. My hope is that a pump or accessory is blocked, but I first want to make sure the cam timing is even set right. This is tricky since I only have a small range of motion and can't rotate the engine all the way to TDC. This attached video from the auction seller demonstrates the engine's limited range of motion. 

Here are some pictures I took. I hope there's enough information for someone experienced to tell if there's some top-end interference happening. Let me know if there's anything else I can supply

 

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Welcome to TLF. :welcome:

I am not fully aware of whatever accessories etc are attached that could effect the rotation. I would not attempt to turn the engine over until any accessories are removed and tested and even then I would highly suggest getting all the information you require and starting from the beginning to time the engine. I am not sure whether the engine in the Elite is an interference engine, but since it looks very similar to the one in my S4, I suggest it is. That makes me worry that a piston has quite possibly impacted a valve. Other guys that own Elites will get on here shortly, but I would hazard a guess that you could be looking at having to take the heads off. Do you have any information as to whether the previous owner has changed the timing belt?

Also, you may have an issue with the belt on the left in the photo of your crank pulley. It is siting very deep in the pulley. It should not sit that low in the groove. Could be just belt wear or could also be that the pulley groove is worn. Even the belt on the right of the pulley is sitting further in than it should.

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  • Gold FFM

Greetings!

The video implies mechanical interference.  Crank is close enough to TDC to allow verification of valve timing - either the cam sprocket marks are very close to each other, or on the opposite side, but I can't see for sure from the pics.  Aux shaft has been timed by someone not accustomed to this engine, I'd suggest.  Camshaft pics imply they might be a bit out.

As I said, the video implies mechanical contact, but remove the aux belts from the equation (just cut them off; they're useless to you) and try again.  But I do suspect you'll be removing heads or, more likely, the whole engine.   A wonderful start to Lotus ownerhip!

British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

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A valve stuck open. Remove the valve covers and compare each one of a pair of valves. When an engine stops turning there are always one or more valves open and when sitting for so long corrosion can occur and cause a valve to remain open even when the camshaft position wold indicate that the valve(s) should be closed.

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Have you got the workshop manual that shows the timing marks.

eg 1 page from my old one.

 

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Thanks everybody! I found the google drive with the scanned workshop manual and saw the above page in there. The lack of white/red/blue dots on the pulleys threw me off a little so I wanted to check online. 

My first impression is that the intake cam looks to be +/- 6 teeth off. Might try to loosen the belt and rotate just that pulley, then see if it allows me to rotate the engine any further. 

 

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It's not a big job to remove the cam carriers. Just remember to hold the tappets with magnets so they don't fall out when you lift the carrier and mix up the shims.  With the cam carriers off you can check that there's nothing in the bottom end preventing the engine turning and it makes it easy to see if a valve is stuck open.

S4 Elan, Elan +2S, Federal-spec, World Championship Edition S2 Esprit #42, S1 Elise, Excel SE

 

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Update: timing was indeed off.

I slid a thin piece of plastic between the belt and pulley so I could spin the intake cam independently from the rest of the engine. I set the crank at TDC, got the cam pulleys lined up looking something like the workshop diagram (also thanks to the pics on this thread), then removed the plastic again. Now the engine hand-rotates all the way without binding. Turns out the Intake cam was off by 8 teeth 😬

Next step, gonna buy a compression tester to see if the damage has already been done. I'm not getting my hopes up but I suppose there's always a small chance. Do you think the starter motor would have enough torque to bend valves, or is that more an internal combustion type force?

 

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I'd be saying definitely enough torque to bend a valve. However, if you did have a bent valve, I expect you would see one or more of the cam followers and shims sets going quite loose as you rotate the engine. Easy to check each time a valve is in its closed position.

Compression test will yield better results though.

All we know is that when they stop making this, we will be properly, properly sad.Jeremy Clarkson on the Esprit.

Opinions are like armpits. Everyone has them, some just stink more than others.

For forum issues, please contact one of us Moderators.

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8 hours ago, abalslev said:

Do you think the starter motor would have enough torque to bend valves

Definitely, they're bent & will need replacing. Once you've got the head off check the valve guides haven't cracked as well. :thumbup:

Cheers,

John W

http://jonwatkins.co.uk

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On 25/08/2021 at 16:56, ramjet said:

if you did have a bent valve, I expect you would see one or more of the cam followers and shims sets going quite loose as you rotate the engine. Easy to check each time a valve is in its closed position.

Had to think about it for a sec but this makes total sense. I cycled it through and it didn't look like any valves were getting hung up in the cylinder head, everything was smooth and normal. I then checked the valve clearances and things were close to spec - if anything, the intake valves were erring on the side of being too tight! The manual says 0.005-0.007in, a couple of mine were closer to 0.004. Exhaust side had a few on the loose side, but again pretty close to spec. I'm not as worried about the exhaust since the timing wasn't off on that side. 

Welp, now I'm getting cautiously optimistic that maybe the valves/head aren't damaged! A compression tester is in the mail and should arrive next week. I'll post the numbers here once I've got them! Also looks like I'm gonna be ordering some valve shims now...

 

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From front to back I got 105, 120, 75, 135. Definitely not great, but I was expecting zero compression with bent valves. Anyway I guess the head is coming off. 

Right now I'm trying to decide how much of this I'm going to do myself. I removed the head & lapped valves on a 2006 tacoma last year. This went well with no issues 20k miles later, and took me about two weeks including waiting for parts & the machine shop. 

The lotus seems more straightforward than that toyota, the only thing giving me pause is gaining access to separate the exhaust manifold. Can head removal be done without removing the engine or body?

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The easiest way to approach it (other than removing the engine/gearbox, which is what I would do) is to unbolt the engine mounts, lift the engine a little and move it to the right as far as you can get it to go.  The manifold is indeed a tricky component to remove while it's in the car.

Is the spidery-looking hardware part of some smog-reducing arrangement?  That looks like it will be difficult to get off as well.

Pete

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That spidery bit is indeed part of the Federal smog kit, a manifold by which the ancillary air injection pump ( driven off the back end of the exhaust cam ) delivers air into each side of the exhaust ports. 

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Hi Steve.  I thought as much.  How big is one of these air pumps?  Are they attached directly to the end of the cam housing or are they belt driven?  Just wondering if one might be converted to a cam position sensor housing 🙂

Pete

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  • 2 weeks later...

Hi Pete,

Sorry, just spotted your reply, many distractions of late. I recall recently seeing a rare image of one of these things in native Federal Esprit habitat, not often possible as they were rapidly discarded over early years in service. Had a quick browse of various folders but no luck conjuring up a pic. Will pass one along if found, meanwhile you might peruse the Bring a Trailer website for Esprit sold lately, thinking that might be where I'd seen it. In a 300-odd page PDF of late Esprit S2 vintage Shop Manual, the system is depicted with pump looking to be on a scale comparable to the tiniest alternators now sold and is belt driven via pulley off the exhaust cam.

Cheers

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