Lotus Elan

New cam followers bed in procedure.

PostPost by: englishmaninwales » Thu Feb 09, 2017 2:13 pm

I'm fitting new exhaust cam followers (QED). Original cast iron cam shafts. I have 2 questions, please:

I'm using camlube, I read the correct procedure is to start up and run at 2000 rpm for several minutes to bed the followers in, avoiding idle speed. How long should the engine be run that speed?

This is also a post oil/filter change startup; normally I crank with the plugs out to get oil pressure. Will cranking speed damage the followers?

Thanks
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PostPost by: rgh0 » Fri Feb 10, 2017 10:23 am

There are 3 critical periods for bedding in the cams and followers.

1. Initial startup - use a good quality assembly lube - I use Redline - this will protect during initial cranking over and for the first couple of minutes of running
2. Initial 10 or 20 minutes of running while you check the engine for leaks timing idle speed setting etc. Try to vary the engine speed idle to a couple of thousand rpm. If you using a high zinc running in oil that helps protect in this phase.
3. The first couple of hours running in - run with varying speed 3000 to 5000 rpm for around 100 km. This will do the bedding in of the cams, high zinc running in oil helps in this phase

After this change to a good quality synthetic oil and change the filter and your done. Once bedded in oil Zinc levels don't make much different but a high zinc synthetic oil does not hurt to continue with

If your using steel followers it can also help to get them phosphated as this helps prevent galling during running in. I do it on racing engines with higher spring loads, its not so critical on a road engine with standard spring loads.

If reusing your existing cams on new followers make sure the cams have no significant damage or wear as this can rapidly destroy the new follower which will not have worn to match. if you don't have the tools or experience to measure them up for wear get you local cam grinder have a look at them and regrind them if they are worn.

If replacing the followers also check the sleeves in the head as they will probably be worn also and may need replacing. The followers wear into a barrel shape and the sleeves wear into a hourglass shape. You can still end up with follower noise if you put a new follower into an hour glass worn sleeve.

cheers
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PostPost by: shaun » Fri Feb 10, 2017 11:24 am

Hi Rohan just building a 1700 twincam wet sump would you not advise a quality 20/50 muligrade oil
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PostPost by: rgh0 » Fri Feb 10, 2017 11:42 am

A 20/50 synthetic oil is better than a conventional 20/50 mineral oil if that is what you are asking.

Synthetic oils dont require the same amount of additives to maintain their properties so they last better as the additives deteriorate faster than the oil base stock.. They also dont oxidise as badly so their properties do not deteriorate due to this. Their properties also are maintained over a high range of temperatures better than mineral oils.

IN general they are better and worth the price.

There are 3 levels of "synthetic oil" and you can tell them based on price.

1. Cheap synthetic oils - built on highly cracked (highly processed) mineral base stock, not a true synthetic but won the right to use synthetic name in a USA court case. - OK and much better than a conventional mineral oil but maybe 50% more expensive compared to good quality mineral oil and good for a road engine if price is a concern. I use this in my road cars and change it frequently.
2. Poly alpha olefin synthetic oil - true synthetic the next cost step up maybe a 20% cost premium on level 1 synthetics - Mobil One is a good example of this.
3. Polyol Ester synthetic oil - different synthesis chemistry and better heat resistance and high speed shear stability, basis for gas turbine oils in aircraft - great for race engines especially but twice the cost of the level 2 synthetics. Redline is a good example of this and I use this in my race engines

you make your choice and pay the price

cheers
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PostPost by: englishmaninwales » Fri Feb 10, 2017 2:47 pm

Rohan, thanks for your, as ever, helpful advice.
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