Lotus Elan

Stromberg rebuild

PostPost by: redskatejbf » Wed Jul 14, 2010 9:47 pm

Hi......Advice needed please, What viscosity oil should be used in the Stromberg dashpots, I think I used `3 in 1 oil` but it might have been Duckhams 20/50.

What is the best spark plug to use in a new rebuilt engine.

Can anyone suggest a max advance at a given rev.

It will be a road car, standard comp. ratio but with VJ5 cams and big valve head.

Thanks for any help or info.
Regards John.
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PostPost by: 69S4 » Thu Jul 15, 2010 7:01 am

I just use 20/50 engine oil in mine. Anything thinner just vanishes faster :)
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PostPost by: Tonyw » Thu Jul 15, 2010 12:48 pm

John,

IIRC it should be ATF mind you it will disappear quite quickly from memory.

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PostPost by: Frank Howard » Thu Jul 15, 2010 3:04 pm

It will last longer if you replace the "O" ring at the bottom of the tube, available at any hardware store.
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PostPost by: 69S4 » Thu Jul 15, 2010 3:54 pm

Tonyw wrote:John,

IIRC it should be ATF mind you it will disappear quite quickly from memory.

Tonyw



Hi Tony. Are you sure about the ATF recommendation? It says engine oil in the Elan workshop manual, SAE20 oil in the Stromberg workshop manual, 20/50 engine oil in Miles Wilkins's twink engine book and SAE20 in Burlen's online technical info.

I know ATF is recommended for some Mercs using Strombergs but in the Elan world SAE20 seems to be king. It's been discussed here in more depth a couple of years ago - link http://www.lotuselan.net/forums/elan-f15/stromberg-needles-t17483.html
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PostPost by: Tonyw » Fri Jul 16, 2010 5:12 am

Stuart,

I am probably getting my cars mixed up..............I have been known to be wrong before :oops:

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PostPost by: rgh0 » Fri Jul 16, 2010 6:46 am

A straight SAE 20 engine oil and ATF have a simillalr viscosity at 100c of around 6-8 centiStokes (cSt). and at 40 C also similar viscosity around 30 to 40 cSt. So I believe you can use either successfully in the Stromberg Damper pot. A 20w-50 oil has different viscosity profile and may have to much viscosity at the typical 40C to 80C under bonnet temp that the carbs will run at.

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PostPost by: redskatejbf » Fri Jul 16, 2010 10:05 pm

Hi, Thanks everyone for your replies.........anyone care to comment on s/plugs and timing.
I have a new (spare)set of N G K -BP6ES plugs that worked really well in a Weber engine I am not sure if they would be suitable for the Stromberg.
Thanks John.
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PostPost by: rgh0 » Sat Jul 17, 2010 1:18 am

BP6ES certainly a good starting point. You may need to go a step colder depending on usage but they should be right

cheers
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PostPost by: 69S4 » Sat Jul 17, 2010 8:54 am

rgh0 wrote:A straight SAE 20 engine oil and ATF have a simillalr viscosity at 100c of around 6-8 centiStokes (cSt). and at 40 C also similar viscosity around 30 to 40 cSt. So I believe you can use either successfully in the Stromberg Damper pot. A 20w-50 oil has different viscosity profile and may have to much viscosity at the typical 40C to 80C under bonnet temp that the carbs will run at.

regards
Rohan


Now that does surprise me. I don't have any background in this area but my "eyeball" viscosity meter would have put ATF at somewhere around SAE 5 -10, based on using it in motorcycle front forks and feeling how they respond. There's obviously more to it (than meets my eye anyway).

I can see that using 20-50 in place of straight 20 might cause the piston response to alter as the carb (and therefore the oil) warmed up but how hot does the damper oil get in normal running? It's not something I've measured but the carbs are usually cool to the touch when I open the bonnet during a fuel stop on a run and the whole area round the jet and piston is actively cooled by fuel atomisation (to the point of icing up in cooler conditions). That's got to counter heat transfer from the surroundings to some extent.

No real arguement from me as to what to use in the dampers though. I have bigger problems to sort out on the car so I'll just chuck some 20-50 in for the time being as it's what I have to hand. Eventually though I should do some back to back testing and see if I can feel any difference.
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PostPost by: pauljones » Sat Jul 17, 2010 3:57 pm

john,

I got a bit fed up with my plugs fouling up on a webber headed twink.I used the advice on here for different hot/cold ratings but they all seemed to foul as quick as each other.Now I know I was running a bit rich, but not that bad.Anyway,I changed on to a set of bosche super 4's from local halfords.The transformation was brilliant, better starting,smother pickup ect ect ect.It is as ever your choice but im sticking to them.

Hope it helps.

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PostPost by: redskatejbf » Mon Jul 19, 2010 8:38 pm

Thank you all for the info. I will try the BP6ES and see how it runs.
Regards John.
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PostPost by: redskatejbf » Wed Jul 21, 2010 9:13 pm

I have been given a set of new NGK BP5ES. Can anyone tell me if they are cooler running than NGK BP6ES.
I would suspect with a Stromberg engine that if I need to change the grade of plug it would be to a cooler running set.
Thanks for any info. Regards John.
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PostPost by: 69S4 » Thu Jul 22, 2010 6:24 am

redskatejbf wrote: I have been given a set of new NGK BP5ES. Can anyone tell me if they are cooler running than NGK BP6ES.
I would suspect with a Stromberg engine that if I need to change the grade of plug it would be to a cooler running set.
Thanks for any info. Regards John.


Sadly they're not. From their website:

For NGK spark plugs there is a simple rule of thumb:
Low heat rating number (for inst. BP4ES) "Hot spark plug".
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PostPost by: redskatejbf » Thu Jul 22, 2010 4:19 pm

Thanks Stuart, I never thought to look at their website, suffering from brain fade perhaps is my excuse.
Thanks again, John.
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