Question about camshaft removal and replacement

[2cams70]

Hi Guys, is it possible to remove and replace the camshafts on a Lotus Twin Cam for valve clearance adjustment without removing the camshaft sprockets? Endless type timing chain fitted.

The reason I ask is that I'm currently tossing up what style of front "D" plugs to fit. The OEM type are best sealed with a thin smear of RTV on the periphery where they fit into the head and therefore I'd prefer not to have to remove and reseal them in the process of in-service valve shim adjustment. Scraping and cleaning old RTV is a pain and it's easy for bits of it to fall into the engine during the process. Yes you may be able to remove and replace the sprockets without touching the "D" plugs if you use a ring spanner but I prefer to use a socket and torque wrench on the sprocket bolts.

Lotus Marques on the other hand offer an aftermarket rubber D plug with extended sides which I believe will be a good deflector of oil and so their plug will be more leak resistant than the OEM type if no sealant is used when the "D" plug is fitted. If you do have to remove the sprockets I'll fit the Lotus Marques D plugs.

See below photos of the Lotus Marques "D" plug and the OEM type side by side.

[nmauduit]

I don't see cleaning RTV as such a hazardous step : one can protect the underlying zone with rags and even clean up the alloy with acetone and sticky tape prior to scraping... then even if tiny bits of RTV would escape, they will end up in the filter, not in the oil passageways.

[2cams70]

The Threebond stuff I use sticks like crazy. Electrical grade contact cleaner will soften it but if there's an easier way such as being leak free without having to use any sealant at all then why not?

[billwill]

To answer your original question. I think it is usually possible to get the chain off the cam sprockets, but is depends on how much free play there is in the tension adjuster. I would try taking the whole adjuster pusher out, it has an outer threaded portion, spring and a plunger.

When the chain is fully loosened tie a bit of tape or electric wire to the centre of the upper portion of the chain (so that you don't drop the chain inside the timing case, where it will be a bit of a pig to get hold of it again) and try easing the chain off the sprockets. Do the inlet camshaft first as that will have the slack part of the chain.

Tie the wire/tape to something convenient such as the water-pump pulley and lower the chain inside. Then you should be easily able to get the camshafts off. Don't forget that each camshaft bearing cap MUST go back eventually to exactly the same position that it came from. They are usually numbered, but if that is not clear, mark them yourself.

[tvacc]

Yes, you can adjust the valves without taking the chain or sprockets off. I saw it demonstrated at one of my early LOGs. I am out of the house right now but I will log on later and try and document it.

[Chrispy]

I found some d plugs with the edges/flanges on them in my stash when my original ones were damaged which fit well. Off a Jag 4.2L straight 6, or a Nissan VG30. I reckon they would be pretty easy to find if you go poking around.

I've always used RTV on them, and the invonveinance of that is less than that of a oil leak to me!

[steve lyle]

Just got through my first cam removal experience.

The Workshop manual didn't work for me - not nearly enough slack in the chain, even with the tensioner bolt removed.

I had to remove the sprockets. Don't forget the big washer under the 5/8" bolt - you don't want that dropping in the cover. With the bolt out, the sprocket is still a tight fit. Grab it with two hands at 3 & 9, and wiggle/pull, and mine came off. Then lever the cam out of the head.