Tappets

[madmezza]

I'm learning about the inticacies (sure that's not spelt right) of Lotus engines (or car engines in general), and have heard about tappets.

Now, I think that he cam rocks up and down, opening the inlet and exhaust valves at the approriate times. And the tappets do something here...

Can someone

(a) explain what the tappets do, and

(B) they're adjusted by shims on my engine (910S) - is it a big job to check them and do you guys advice having it done during my C"+" service

Sorry about the blast of questions, but my new S3 HC is potentially going in on Wednesday for MOT+C service+other obvious things and I want to make sure everything is done.

Cheers everyone, and have a nice day! (no, I'm not American, I'm just happy today for a change! B) )

[Guest teigan]

the tappets are cam followers. they shouldn't need adjusting unless you're driving the car at high rpms for extended periods. if you've got performance issues, then yes, have the cams and tappets refitted. have a nicer day. ta.

[madmezza]

Cheers Teigan.

Are the tappets exposed during a cam-belt change? If so, then it should be fairly easy to get then checked during the service.

I'm a little confused as there's a bloody great belt that runs over two cogs that appear to be on shafts that run the cams (through the cylinder head) - is that the cam belt? On other (normal) cars that I've had, the cam belt seems to be buried deep in the engined - I assumed it might be the same?

[Guest teigan]

i think we have the same car. on mine the tappets are stainless steel bucket shaped beauties. yes a cam belt change is a good time to check them, but it may be premature. what's the odometer read?

[Guest teigan]

i think you are describing the cam belt. it's the one you see looking at the furthermost part of the engine while seated in the boot.

[Paul C]

My SE needed the tappets/shims doing at the 'C' service, as stated this is the best

time to do it, and the most probable time it is going to get noticed/inspected in that

area anyhow. It's worth noting that this is over and above any quoted C Service

cost, so be aware of the possibilty of this needing doing if you are on a budget.

Also (and this was my case), i had the classic Esprit 'cam tower oil leak'.

This either leaks from the top and into the sparkplug holes, or (as in my

case) from the bottom and drips onto the manifold producing little plumes

of smoke.

IF, You are getting a C service and then need the cams out to do the Shims etc,

Then this IS the time to get the (now stripped) cam tower off and sort the oil

leak.

Ergo, my last 'Cambelt service' spawned two items of further work that would

have been much more expensive done at any other time.

[Evil_Dr_Fish]

OI!! I said not 'til *after* my car was done!!

[Guest teigan]

previous previous owner of my car was told he had the same oil leak paul describes. according to the service notes, he told the mechanic to stuff it. i have to agree as 10,000 miles later, the amount of oil leaking is normal for an english car. be careful, and take a greasy friend along to tut at everything.

[TimRdLotus]

Simply put, the tappets are the connection between the camshaft and the valve stem designed to ride along with the camshaft. Without the tappets, the small diameter of the valve stem would wear out the camshaft very quickly.

Tappets come in varioius designs from an american v-8 with lifters (also considered tappets) with pushrods and rockers to overhead camshafts with rockers or tappets or in the LOtus engine also called buckets.

The lotus engines use a tappets that fit into a sleeve that sits in a housing on top of the valve stem. The camshaft lobes ride on the tappets and as the lobe approaches pushes against the tappet which inturn pushes the valve open. As the camshaft lobe continues through the lift and begins on the backside of the lobe, the valve spring pushes against the tappet and follows it to close the valve.

To adjust the lotus engine you measure the gap between the camshaft and the lowest part of the lobe. Then remove the camshaft housing with the tappets and shim the difference between the gap and specifications.

[madmezza]

Fishy

Geoff reckons he might be able to fit me in on Wednesday. Will yours be done by then? Still want to see the lack of door handles, so I was hoping yours would still be there!

[Splashout]

Rich as described the tappits or cam followers are little buckets that fit over the end of your valves and are adjusted by a shim that fits between the two. As the cam turns it is these buckets that then push the valves down.

To check them the cam carrier lids need to be removed, and then the clearence between the rounded part of the cam and the tappet checked with feeler gagues.

If some are found to need adjusting then the cam carriers have to be removed and a bigger or smaller shim fitted to adjust the clearence.

Then when this is done they obviously all need to be checked again.

As you can imagine this is a time consuming job and i believe it is quoted as a 6hr job by dealers!

Hope that helps

Glyn

[madmezza]

Thanks everyone for the information - I'll chat with Geoff when I take the car in and see if it's worth doing now (car's done 58k miles).

It's great to have access to such a wealth of knowledge from you all!

[Evil_Dr_Fish]

Hi Rich...

Don't worry... mine WILL be there! It always is!

[Jussi]

Mine also leaks from the top and into the sparkplug holes and drips onto the manifold producing little plumes of smoke. Smoke is coming only some short time when oil evaporates from manifold.

It's quite a big job and I think it's better do when engine is out of the car. Or what kind of job is it with engine on the car?

[WayneB]

Checking the valve clearances is relitively easy (remove valve covers and check with feeler gauges , engine cold) However changing the clearances involves removing the belt (why it is best to do this as part of "C" service) and after measuring all the tappet clearances removing the whole cam tower and substituting different shims to alter the clearance between the camshaft and the followers. When I got my car it had the usual oil leak from the cam tower to the head , dripping oil on to the exhaust manifold. The previous owners had overtightened the tower bolts (trying to stop leak)stripping 2 threads out of the head and warping the cam tower! I did mine with the engine out (not a big deal) , but you could do the work in the car(more tedious) I used the Lotus recomended Loctite 504 to seal the tower to the head(expensive stuff) and after 3 yrs. it is still leak free.

[watership down]

I had the same problem so I got rid of the paper gasket that Lotus used and bought some cork gasketing sheet from Canadian tire, sat my cam cover on the sheeting after putting some grease on the mating surface, got my outline of the cover, and cut it out. Solved the leak, and if you want to use some instant gasket seal also, you can. I have the same rattle from the tappets until it gets warm then the engine is "quiet", for want of a better word.