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Author Topic: Aluminium Piston  (Read 491 times)

Martin

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Aluminium Piston
« on: July 08, 2021, 04:46:58 PM »
Hi Everyone,

I have a Listeroid CS8-1, built in India. It is Powerline brand and I bought it from Power Anand in 2012. It has served me well at my off grid house where it is used several times per week for battery charging and/or powering tools that are too big to run off the house batteries. I'm currently doing a few upgrades - I suspect that it has a cast iron piston, so I'm planning to change it to aluminium. It appears that two different aluminium pistons are available - one with 4 rings and one with 5 - the 5th ring being below the gudgeon pin, so it's an oil ring. The question is, which should I use?

Here is the 4 ring piston: https://www.stationaryengineparts.com/Lister-CS-8-1-Aluminium-Piston-Assembly.html

And here is the 5 ring piston: https://www.stationaryengineparts.com/Listeroid-CS-8-1-Aluminium-Piston-Assembly.html

My next question is...whatis the best way to do the job? Should I undo the big end and lift the piston/conrod assembly out of the top of the cylinder, or should I leave the big end alone and lift the cylinder off the piston?

By the way, last weekend I had the flywheels off for balancing and I managed to get the balance pretty good. I've already put a bronze bushing in the governor linkage where the fork (for want of a better description) slides vertically in what was a pretty rough hole. And I've just received an air dashpot to add to the governor linkage which will hopefully prevent overshoot when the generator is under heavy load.

Cheers,
Martin

mihit

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Re: Aluminium Piston
« Reply #1 on: July 09, 2021, 08:09:33 AM »
On the smaller CS, I've taken the barrel off to get at the piston. You need to put gaskets/shims under it to set the deck height anyway.

As to which piston, I'd guess the larger CS are still splash lubed, and I'd guess the bottom ring on the 4-groove is an oil control/wiper ring as well.
I would say either would do, but that's just a guess on my part.

What are you looking to achieve moving to a lighter piston?

38ac

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Re: Aluminium Piston
« Reply #2 on: July 09, 2021, 11:07:49 AM »
The 4 ring piston is a copy of the original Lister part while the 5 ring is an India modification. I have used both with equal success. There is less weight to lift if you first lift the cylinder block up off the piston. Then undo the big end and remove the piston and rod. Keep track of all shims between the block and crankcase and also between the rod and cap. Assembly differs in that you will insert the piston from the bottom of the cylinder block with rod attached. Then drop the assembly over the long studs. ALLWAYS check squish or bump when assembling.  The specs aren't handy to me as I type but per memory an 8/1 or non COV equipped 6/1 should be  .070". I will check and confirm later.
Collector and horder of about anything diesel

Martin

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Re: Aluminium Piston
« Reply #3 on: July 09, 2021, 11:22:53 PM »
Thanks for the info, both of you. If there's no clear advantage, then I'm tempted to stick with the original Lister spec and use the 4 ring piston. It's cheaper too, although that is not so important - I live in Grenada,  so by the time I paid shipping and import tax, the original cost price kind of becomes less significant.

Thanks for the tip on checking the head clearance.  I've just looked it up - for a 6-1 it should be 45-50 thou and for an 8-1 it's 75-80 thou. I must admit, I don't understand why the 8- runs at lower compression. Any ideas on that? My listeroid was sold as an 8-1, but interestingly it has the change over valve. I suspect they sell the same engine as a 6-1 or an 8-1, just changing the flywheels and governor spring.

I'm pretty good at general DIY mechanics, but I have to admit, I've never undone and reassembled a big end. Are there any obvious pitfalls for me to walk blindly into. Upon reassembly I guess just make sure it goes together as it came apart and tighten the bolts. Should I use a torque wrench or is f...ing tight good enough. I think the nuts are wired on.

Cheers,
Martin

Martin

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Re: Aluminium Piston
« Reply #4 on: July 10, 2021, 12:09:56 AM »
38ac, I'm just chewing over your recommended assembly method  - lowering the piston, con rod and cylinder onto the studs as an assembly. How do you stop the piston from falling out of the cylinder as you lower it. The lister book recommends lowering the cylinder onto the piston, while it rests on a couple of bars across the crank case. The Lister method sounds easier,  but maybe I'm missing something.

38ac

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Re: Aluminium Piston
« Reply #5 on: July 10, 2021, 02:48:40 AM »
It's one heck of a lot easier to get the rings started in the bore when the block is upside down on a bench and everything is right in front of you than looking sideways or up under the block while also fighting the weight of the block, but to each his own. The drag of the rings will keep the piston from falling out. As compared to a COV equipped engine and non COV will have more compression than when the COV is screwed out, but less than when it is screwed in.
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Martin

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Re: Aluminium Piston
« Reply #6 on: July 10, 2021, 01:03:32 PM »
Ok, assembling the piston/cylinder on the bench makes sense.

As my 8-1 has a COV, I guess I should set the head clearance at 45-50 thou rather than 75-80 thou for a true 8-1. What do you think?

38ac

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Re: Aluminium Piston
« Reply #7 on: July 10, 2021, 11:36:18 PM »
Exactly! The correct bump depends on if equipped with COV and has nothing to do with HP.  The endless India Modifications cause much confusion with specs.
Collector and horder of about anything diesel