Stromberg carburator oil

[Claudio]

Dear Jag Enthusiasts,
Again my holler of HELP.
My recently arrived from the USA, a 73 2+2 is currently at the workshop for a complete mechanical check-up. Since the engine has many many issues to be solved, we started with the carburator disassembly. Stromberg carburator pistons need new oil, so please gents: what is the correct amount of oil (cm3 in volume) and the correct oil grade (and brand, if applicable)? is the volume variable with the adjustment of the carburator?
Thanks, all best !
claudio

[christopher storey]

The quantity essentially does not vary in volume measurably with carburetter setting, and you do not need to measure it beforehand. Just remove the piston damper and fill the damper to about two-thirds of the way up the rod. I use engine oil, not too heavy, 10w40 grade is fine

[vee12eman]

Hi Claudio.

I agree with Christopher about using engine oil, I personally use 20/50 which is the recommendation of Jaguar themselves. (That doesn't always mean it's the best choice though.)

Another point though, is why you need it. Lots of cars do need the dash pots topped up but Stromberg carbs are prone to leakage. Top them up until the oil is just below the top of the cylinder within the removable cap (not to the top as the excess just leaks back into the throttle and then into the engine). The cap/piston assembly should meet a little resistance to going back in - this is the damping effect you want. Check again in a few days or after a drive. Any carbs with low oil again need new seals, which unfortunately requires removal of the needle from the piston and a retune, although if the leak isn't too bad you can just keep topping up for now.

Regards,

Simon.

[AussieEtype]

I fill mine up as far as it goes so that it just does not overflow when the piston is gently pushed back in.

On my series 3 I use auto transmission oil and have always done and in my landrover with the same carbs I use Castrol Sewing machine oil as it is in a small container and easy to pour in.

Garry

[Claudio]

Hello, just to give you feedback, I put Singer sewing machine oil (low viscosity) and the carbs are performing very well. It seems that the piston moves freely. Quick acceleration responses. Nice regards, Claudio

[PeterCrespin]

Any special reason why you asked for advice and then did something different to what most people and the workshop manual suggest?

Saying the car performs well isn't really a good answer because you put the oil in before you knew that and these cars perform very well anyhow when the carbs are serviced.

Do you or the mechanic have the workshop manual or owners handbook? Those contain the info and a lot more besides.

Happy driving.

Pete

[Claudio]

Hello Pete, my mechanic insisted using a low viscisity oil due to his prior background with same type of carbs used on other british cars we had produced in the country (Hillman, taken over by Chrysler and the car was named Dodge Polara). I also had a post replied in this forum recommending sewing machine oil, so this was a start. Good engine acceleration response may be explained by the low friction of the low viscosity oil, that will probably perform well at low temperatures in the winter. Your are right about the workshop manual, i have already bought it and is on the way over to me. Thank you for the response. Nice regards. Claudio

[PeterCrespin]

Thinner oil means less acceleration enrichment/weaker acceleration (usually). If it doesn't spit back then it's OK-ish, but the 'tuning' mod is usually to go up from 20W, not down. Still, a V12 is not short of pick-up :-)

[vee12eman]

Hi Claudio,

As I stated, the oil I use is 20/50 and as Peter says, the thicker oil provides more resistance to the pistons rising under acceleration, leading to a richer mix and, in theory at least, greater acceleration. How noticeable is debatable, but easily tested by substitution of the oil. Regardless of the experiences of your mechanic on a different engine entirely, I suggest you compare the performance you have now with thin oil (youe sewing machine oil), with that you get using the factory recommended thicker viscosity.

Easy to remove the oil with a syringe and short rubber tube (which is also the easiest way to top up). Remember, under bonnet temperatures of a V12 E Type are likely to be much higher than those of smaller engine cars, therefore the oil will become much thinner in use due to temperature. Also, as I stated, in an earlier post, the seals in the piston are less than perfect, especially with age; thin oil will only escape faster...

Regards,

Simon.

[Claudio]

Thank you Gents,
I will do this experience, replacing the oil by the thicker one.
Hey...I have to admit: I am already VERY IMPRESSED with the performance (wonderful torque!!!) of this engine... I just can't imagine it can perform even better...
As I meant before, everything related to this car is very new for me, perhaps more good surprises are still on the way.
Besides that - what wonders me a lot - I get thumbs up all over whilst driving...is this a rule for E-types????
Regards.
Claudio

[Herzeg]

Hi all

Just checked the oil in my carbs today and they were quite low. The car is a S2 OTS with twin strombergs.

Front one was ok but the rear one has a milky substance in the oil. Could this be fuel ? Engine runs ok but worried about this.

John

[vee12eman]

Hi John.
Milky deposit in oil tends to indicate water. It won't harm the engine in itself but might cause the two carbs to react differently, not good for performance or the engine generally. I doubt much harm will occur, if any but I suggest you remove the oil from both dashpots and replace with the correct level of oil and correct grade. Monitor in future and if the milkiness comes back then look for a source of water ingress, which may just be condensation.
Regards,
Simon