Stuck tappet - how do I get it out?

[Lincoln62]

You really need to take the head off. There is so little clearance between the valves and piston a stuck valve could now be a bent valve. Need to check the piston is still OK too.

Peter
66S2

[lotusanglia1965]

I have successfully removed a stuck tappet from a jaguar xk engine(similar design) by bonding a large nut to the tappet with loctite 648,then turning it back and forth with a spanner.clean the tappet and nut first with brake/carb cleaner.still probably need to get the head off,esp as it stuck after a rebuild,could be some blasting grit that was left in the head which caused this problem.
Martin

[denicholls2]

I'm about to start taking the head off. Then I shall push hard on the troublesome tappet, wedge the valve open with a piece of wood between valve head and seat, then pull the no-longer-binding tappet out with a valve suction tool. Then out with all the valves, give everything a decoke as required, replace all the springs, put it all back together and drive off into the sunset. That's the rose-tinted version. We'll see soon if it matches reality.

John

While I agree with others that your end result will likely entail head removal, a simple test should get the tappet back up and confirm how bad things are in the combustion chamber.

Compressed air, high volume at 100+ PSI, may push the valve closed and bring up the tappet. It will also tell you if the valve still seals. If not, bent valve or worse is in your future -- head off.

If the tappet pops back up and the valve seals, remove tappet and assess the situation. If everything can be made to work properly without head off, you've saved the effort.

My guess, however, is that you've experienced the joys of the interference valvetrain.

[johnsimister]

Head off. Piston unharmed. I tried the superglue trick, sticking an Imp tappet (like an Elan one only smaller) to the troublesome one after pushing down on the weak spring pressure to open the valve fully and jam it there with a piece of rubber flex, thus allowing the tappet to rotate. The tappet still resisted full upward movement but I was eventually able to wind it out. There are marks inside it where the presumably broken valve spring was rubbing on it.

The valve rotates easily, and doing this reveals it not to be bent. I shall replace all the valve springs, all the tappets and regrind the valves, but first there's a little welding to do to the head face which has corroded around some waterways.

All told, it could have been a great deal worse. And isn't superglue amazing?

John

[tdafforn]

glad to hear it sounds like a happy ending!
Tim

[GrUmPyBoDgEr]

Nice to hear your good news.
A round of applause to Alan for a top tip

Cheers
John

[johnsimister]

Much progress. The corroded waterways in the head have been very neatly welded, and the lightest of skims (6 thou) made the head face perfect. The exhaust valve seats were in a terrible state, even though the engine has covered only a few thousand miles - under 5000 I think - since its rebuild. This may or may not suggest that Elan exhaust valve seats can't cope with unleaded fuel. It seems the original seats are cast into the head so the new hardened seats have been inserted into appropriately-machined recesses in the old ones. As for the broken valve spring, it had fractured into four pieces.

My friend Dennis Allt, who builds the best racing Imp engines, did the work and reassembled the head with new steel tappets from QED. Twink and Imp shims are the same diameter, incidentally. The valve guides were in very good shape, and Dennis has incorporated a mod he uses on the Imp engines. This is a rubber O-ring on each valve stem, initially positioned to abut the guide. Once the valve has opened the O-ring finds its own position and thereafter acts as an oil seal when the valve is fully open. My engine's smoke output has dropped considerably.

It also has more punch at low revs thanks to the improved compression, and is altogether smoother and sharper. I finished putting it back together late yesterday afternoon and it's a total joy. I have also carried out a mod so brilliant that every Elan should have something similar: a gear-reduction starter from Cambridge Motorsport. The old Lucas inertia starter's pinion was typically chewed and it had always sounded as if the battery was going flat, even though it wasn't - a mistake that had me buying a new battery unnecessarily. Now the engine spins over with a brisk ker-chunk, ker-chunk and bursts into life. Marvellous. Fitting it wasn't entirely straightforward, though, because the Spyder chassis tube got in the way. So Dennis re-drilled the mounting plate so the starter could be rotated into a different position, and now there's about 1/4in clearance by the chassis tube and the handbrake cable just misses the bottom of the starter when the handbrake is on.

Going further off-topic, I've replaced the small Momo steering wheel with a Chapman-signed original, contributing to eBay steering-wheel price inflation in the process. It feels much nicer; more sensitive and delicate, as an Elan should be. I think the new rear gas Spax dampers are too firm, though, even in their softest setting. Does anyone have views on ride quality with the Spax? I've driven two friends' Elans recently (the ?12,100 red eBay S4 dhc and a 1967 S3 dhc which was also on eBay with a full history and a whole new meaning of 'patina') and both 'breathe' better over bumps at speed. That's how I want mine to be.

John

[CBUEB1771]

It seems the original seats are cast into the head so the new hardened seats have been inserted into appropriately-machined recesses in the old ones.

The valve seats are not cast in place. Section E.13 of the Workshop Manual (at least for the +2) covers removal and replacement of the valve seats. I would be very concerned about installing one valve seat into a pocket machined into another. Done this way you will have an additional physical interface between the cylinder head and the final seat. This will interfere with cooling of the valve seat.

[johnsimister]

Hmm, yes, I've just read that in the manual too including the bit about a deft blow with a chisel. More of an immediate worry is that number three inlet valve has now stuck open and I don't know why. This time the tappet rotates freely so something has happened to the valve or seat, neither of which have had anything done to them other than being ground in. I seem to be fated with this engine... so much for driving it to Donington. Will report back on the carnage once I've lifted the head. Again.

John

[elansprint]

John sounds like the valve seat has dropped out holding the valve open head needs heating & valve seat inserts cooling & they should drop in the same as the imp i believe. As for the Spax i am not a fan i have had them on a couple of ginetta's & about click 3/4 they go from no damping to rock hard so haviving 22 clicks is a waste of time
Ian

[johnsimister]

Head off. Number three inlet valve bent and guide cracked. Seat fine. But why has it happened? The knocking started just after I'd changed up to third, not many revs, engine cold. Did the valve momentarily seize in the guide? Why should it when it was fine before the head rebuild, and hasn't been changed in any way? Unless something happened with the O-ring mod, but I can't see how that could be. It's only a tiny piece of rubber and there's still plenty of lubrication.

There are little depressions on the piston at the edges of the valve cut-out but they'll clean up. So I need a new valve, and I think I'll get all four inlet guides replaced and have the seats cut a bit further into the head. I've been wondering if the tiny head skim of six thou could have been enough to cause contact, but it drove fine yesterday. Also, the skim would retard the cam timing fractionally - I worked out by 0.2 degrees - so that works in my favour, clearance-wise.

Pic attached. Am fed up, but it will live again.

John

[dusty]

Is it possible that the valve seat dropped slightly causing the valve to jam and get bent whilst also forcing the seat back into position?

Unlikely but......

[GrUmPyBoDgEr]

Hi John,

this is a tale of wo indeed. The first problem should not have occurred so soon after a major rebuild.
I think I'd be talking to the P.O. about that rebuild.
Russ is so right with his comments on fitting new seats into old seats. The old seats should have come out & it is always "good practice" to fit new guides at the same time.
I don't recall any mention of what was done to the scored bucket bore or in fact if we are talking about the same valve failing again.
It's always a bit of a problem when something goes wrong & a friend was involved with the repair. Not a nice place to be in.
Is it possible that the mentioned O-Ring did cause a jam; have you taken a good look at it?
An analysis of damaged parts can be very difficult when "on site", via a forum just pure speculation.
The piston damage, according to your description, appears to be minor but if you have a record it would be worth while measuring the piston to deck height at TDC, to check that the con-rod is OK.
Seems like you're going to have to dig deep into your pocket again.

Good luck
John

[johnsimister]

John - the problem is that the rebuild occurred way back in the 80s, and the car went into hibernation shortly afterwards. So there's no comeback with the rebuilder (the Lotus Servicentre in Essex) after so long. And the engine had been running OK after that build.

The problem this time is number three inlet, whereas the original stuck tappet/broken valve spring problem was number four inlet. The tappet bore was OK, it was just the broken spring jamming the tappet.

Dennis and I have just taken all the inlet valves out again - the bent one took a bit of effort - and the cause of the problem is that the bent valve had seized in the guide. There's roughness on both stem and guide. All the other inlet valve guides have perfect shiny inner surfaces. Maybe the tolerance was too tight on that valve, but why it should suddenly manifest itself now I don't know. There seems to have been plenty of oil in the vicinity, and the O-ring tweak doesn't block the oil splash as far as I can see.

So, new valve and new guide. Maybe all new bronze guides to make sure, and get the inlet seats cut a tiny bit further into the head. As for the seat-within-a-seat idea for the exhaust valves, the chap who did that part of the work has used this technique many times, mainly with motorbikes, and there has never been a problem although I appreciate it's not 'proper'. I'll have to think carefully about this.

Thanks for the tip about checking piston heights. I did wonder if the upper big-end shell might have got squashed. The engine ran for mere seconds after the noise started so I hope I've got away without bottom-end damage.

John

[CBUEB1771]

Thanks for the tip about checking piston heights. I did wonder if the upper big-end shell might have got squashed. The engine ran for mere seconds after the noise started so I hope I've got away without bottom-end damage.

It is always a good idea to do a trial assembly with valves in one cylinder only and using very light springs. After getting the cam timing correct rotate the full engine assembly by hand through the compression and firing strokes. Check to see how far the valves can be moved away from the cam every few degrees of crankshaft rotation from about 30 degrees BTDC to 30 after. On a road specification engine you should be able to move each valve at least 50 or 60 thousandths before touching the piston or the other valve.