Lotus Elan

Rusted Cams & Valves

PostPost by: sennafan61 » Mon Dec 06, 2004 10:40 am

I have two twin cam weber motors, one from my '69 S4 and one from a '66 S3 S/E that I used to own. About six months ago I decided to remove the head from the S4 and replace it with the S3 head, which was in better condition. A few days after I had removed both heads, I broke my leg and was forced to temporarily halt my project. I put each head in a Hefty bag and placed it in a plastic storage container along with the respective cams, sprockets and bearings. I put the crates in the corner of my garage where I store all my other Lotus parts. A couple of days ago I opened the containers and saw that they were each filled with about four inches of water. Apparently a water pipe in the garage ceiling had sprung a leak and slowly dripped water on all of my parts containers. I don't know how long the containers had been wet since I hadn't been in that part of my garage for 3-4 months, but it must have been awhile. The two containers with the heads got the worst of it because they were on top of the other crates. Anyway, here's what I'm faced with:

The cam bearings and sprockets were in plastic bags and were not directly exposed to water. There is some slight surface rust caused by the condensation in the bags, but it's not bad. Unfortunately, I had wrapped the camshafts in newspaper to prevent scratching, so they got soaked. There is moderate to heavy rust on several of the polished surfaces on each cam. I won't know the full extent of the damage to the valves, guides, etc. until I pull the valves, but I'm expecting the worst. The heads themselves have no rust but are completely coated with that white moldy looking stuff that forms on alloys (mineral deposits from the water?) As if this wasn't bad enough, a lot of my other parts got rusted (brake rotors, calipers, carb intake stacks, interior trim pieces, etc.)

Can anyone out there help me? I imagine there are some good rust removal products out there but I don't know what to use. Also, can I use wet/dry sandpaper or something else on the more heavily rusted surfaces? Thanks for any help you can provide.

Charles
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PostPost by: type26owner » Mon Dec 06, 2004 2:27 pm

Welcome Charles,
The valves are cheap. The cams are more costly but still easily replaced or repaired. The head is the really expensive item to replace. The white coating is aluminum oxide and it could be trouble depending on the severity. Start by measuring the thickness of the head to determine if it's worthwhile trying to save it. This is the first thing to do to determine if the head can be saved or not. Small Valve = 4.638/4.643" with another .045" allowed to be removed. Big Valve = 4.598/4.603" with only another .010" allowed to be removed. The most important surface to have intact is the head gasket surface. Post some pictures so we can guage the extent of damage.

Bummer! Don't give up or despair it's worth the effort to recover the engines. Don't have it cleaned up by bead blasting it with GLASS BEADS. The beads will embed in the soft aluminum and work their way loose later on and circulate through the engine in the oil and grind it to destruction.
-Keith
p.s. I miss Senna too!
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PostPost by: type26owner » Mon Dec 06, 2004 3:56 pm

On the rusted parts just use a Scotchbrite pad or if it is really bad get one of the rotary disc type Scotchbrite that goes in a drill motor. Don't try and chemically remove the rust cause it's rather messy for a small benefit. You can't passivate iron or steel so the best thing to do is coat it with a protective film of oil or better yet cosmoline. There are some metal conditioners that will provide some measure of rust protection by forming a film of iron phosphate. A phosphate coating is very soft and easily damaged that's why it's only really used for surfaces which are going to be painted. Phosphating paint primers are also available. Rusted bearing surfaces or close tolerances fit surfaces are the places to be most concerned about real damage. All the other surfaces are cosmetic only so don't sweat thoses places.

If you need metal brushes of all shapes and sizes then go to the nearest welding supply vendor because they carry all that sort of stuff.

If you need to get parts unstuck due to rust then use a penetrating fluid like Kroil oil or TC-11.

The red paint coating on the inside surfaces of the head is called Glyptal. It's actually a varnish and is tough stuff. It was applied to seal in the sand from the casting process.
-Keith
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PostPost by: nebogipfel » Mon Dec 06, 2004 7:12 pm

Charles, Hopefully you will find that much of the rusting is staining rather than deep corrosion and it can probably be removed quite easily with fine scotchbrite as Keith says or with fine perhaps P1200 paper (wet or dry, not sandpaper) in both cases luricated with oil.

It is surprising how often shortish term rusting looks worse beacause of heavy staining.

The important bits are obviously things like bearing surfaces and the cam lobes and these will probably clean quite well. Replace the shells anyway, they are not worth trying to save.

The ally "fur" will probably wash off quite easily. In my experience it takes quite a while for it to seriously damage castings, by its nature it tends to stabilise the surface once a layer has formed.

As Keith says, certainly urgently I would put copious amounts of oil and penetrant over everything to aid the clean-up and to prevent any further corrosion

Good luck
John
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PostPost by: sennafan61 » Tue Dec 07, 2004 5:31 am

Thanks to those who responded so quickly. I've already coated everything in oil and will start using the ScotchBrite tomorrow. I suspect that a lot of it is indeed staining and will come off easily, but there are definitely some trouble spots. My primary concern was the heads, which I know are rare and expensive. I hope they are okay. Well, at least I have a garage project this winter while my leg heals.

P.S. I guess I've learned a lesson about storing metal parts: make sure the containers are completely sealed.
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PostPost by: rgh0 » Tue Dec 07, 2004 10:24 am

If you have a lot of corrsion on the head bottom face that needs machining to clean up its not a great drama and dont be afraid to take off the minimum metal required to get a good clean flat face.

Dont worry about the nominal Lotus head thickness limits. They were set by Lotus to sell more new heads 30 years ago. These days given the cost of a replacement new head or a good second hand head I would ignore them.

The only reason to junk a head these days is really extreme softness which can develop in a head overtime with a lot of overheating and makes it hard to keep a head gasket seal as the head just creeps over time and you loose head bolt tension and compression on the head gasket fire rings. Anything else is recoverable.

You can take a Lotus head at least 40 thou below the Lotus limits with no real problems at all and I have seen heads with probably twice that taken off that can be setup to work perfectly well. On these heads all the casting numbers on the bottom surface had dissapeared so much had been machined off !

The issues that have to be managed in a thin head are combustion volume and valve location and if you have had to move the valves up in the head then how you setup the springs and shims and buckets and valve stem lengths to get a workable solution.

Combuston volume is best managed by a combination of opening up the hemi chamber and using a thicker head gasket.

Recessed valves are best managed by using the thinner steel bucket followers and if necessary a smaller cam base circle. Shims under the valves springs may be required to get the right installed height also thoughthis is less critical.

Trying to use a high lift racing cam in a thin head can become more of a challenge as you can start to run out of room but in the end you can weld new layer on the bottom face of the head and remachine it a lot cheaper than a new head especially if you have put a lot of work into porting a head for racing.

Having said all the above I still avoid machining the bottom gasket face of a head at all costs and only do it when absolutely necessary and to the minimum extent possible. Heads are just to rare and expensive to waste their life by unnecessarily taking off metal especially here in Australia.

regards
Rohan
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PostPost by: sennafan61 » Wed Dec 08, 2004 7:43 am

A quick update on my rust problem:

After soaking my cams, bearing caps, sprockets, etc. in oil for 24 hours, a lot of the surface rust came off rather easily. There is still rust on some of the cam lobes, but most of it looks like it will come off with a good scrubbing, or at least I hope so. As for the heads, I sprayed them with copious amounts of WD-40 and left them to "marinate" overnight. After 24 hours, the difference is amazing. Most of the "moldy" stuff has disappeared. The polished surfaces do not seem to have sustained any damage. After I remove the valves, etc., I'll do a more complete cleaning and see where I stand. (No, I won't do any bead blasting.)

Everything looks good so far. Will let you guys know how things turn out. Thanks again for the quick help.

Charles
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