Spindle fuel leak

[peteyg]

I have a leak around the spindle between the barrels of the rear carb. I'm guessing there's no seal there, only on the ends of the spindle so is it likely to be a worn spindle? Fuel only leaks when engine is revved.

Cheers,

Pete

[jonwat]

The nuts securing the carbs to the manifold have been overtightened, there needs to be a gap between the carb flanges & the spacers & the manifold faces. The size of the gap is specified in the manual 

[peteyg]

If anyone is interested I replaced the spindle which solved the leak.

Pete

[jonwat]

47 minutes ago, peteyg said:

If anyone is interested I replaced the spindle which solved the leak.

Good, did you replace the O rings & correctly set the gaps either side of the spacers? 

[peteyg]

@jonwat

Not entirely sure what you're referring to with the gaps. There is no adjustment on an S2 as far as I know, only getting the correct tightness of the the rubber washers.

Pete

[jonwat]

22 minutes ago, peteyg said:

Not entirely sure what you're referring to with the gaps

In your picture I can see the securing nuts have been overtightened & the spacer is hard up against the manifold & the carb faces. Check the manual, it will show what I mean & specify what the gap should be. The carbs must not be hard fixed to the manifold as this will cause frothing of the fuel in the float chambers at higher revs which will cause misfiring & also damage the carb faces. This is the reason for the O rings & spacers as opposed to the more usual, cheaper paper gaskets.  

Edited October 20, 2022 by jonwat

[jonwat]

Weber & Dellorto carbs, start reading at page at 67 

http://foxed.ca/rx7manual/manuals/carb_book.pdf

Edited October 20, 2022 by jonwat

[mike.griese]

Those o-rings are there to isolate the carbs from vibrations of the engine.  With the nuts cranked down hard like they are, the carb bodies are coupled to the intake manifold, which causes the carbs to vibrate.  This causes aeration of fuel in the float bowls, which causes erratic fuel delivery to the cylinders.  There is no torque spec on the nuts, however there are gap specs between the intake manifold and the spacer and between the spacer and the carb body.  Those o-rings will need to be replaced, as the overtightening will have damaged them.  You will also need to replace the rubber isolators next to the nuts.  Vibration isolation is why there isn't a brace between the intake plenum and the block like on injected cars.

[ekwan]

On 11/2/2022 at 5:12 AM, mike.griese said:

Those o-rings are there to isolate the carbs from vibrations of the engine.  With the nuts cranked down hard like they are, the carb bodies are coupled to the intake manifold, which causes the carbs to vibrate.  This causes aeration of fuel in the float bowls, which causes erratic fuel delivery to the cylinders.  There is no torque spec on the nuts, however there are gap specs between the intake manifold and the spacer and between the spacer and the carb body.  Those o-rings will need to be replaced, as the overtightening will have damaged them.  You will also need to replace the rubber isolators next to the nuts.  Vibration isolation is why there isn't a brace between the intake plenum and the block like on injected cars.

Having said that, the old Alfa engines have some form of support between carburettors and the engine block......I believe to relieve the stresses on the carb flanges.

 

[peteyg]

So, replaced O rings and tightened to specified gaps as per advice above and Des Hammill's book. I now have petrol pissing out of the bottom of the spacers. Tightened further to eliminate fuel leaks but still with gaps between spacers and carb/manifold but now have major air leak on front carb between spacer and carb. Tempted to crank everything up as per my original picture where I didn't notice any issues with poor running due to frothy fuel.

Thoughts?

Pete

 

[drdoom]

I've heard many accounts over the years of owners running carbs of this form with tight or solid mountings and none reporting the froth related concerns published. Not a scientifically derived conclusion, but consistently reported anecdotally. There can be be no tolerance of fuel leaks in this application as Esprit in numbers are no longer with us due to catastrophic fire loss. With such significant leakage I'd double back on floats condition and fuel pressure setting, just to be careful. Running DCOE's on my Elan for years over long distance journeys, urban jaunts and track day outings it was my experience that the Thackery's were better than the rubber bits, and that it was best to have things pulled up tighter than the printed dogma, as air leakage arose otherwise. FWIW

[LOTUSMAN33]

I prefer the thackery washers as well, many of the rubber grommets are so soft these days compared to years ago you have to overtighten to eliminate leaks.

I’ve used both carriers with O seals and the plate/seal arrangements, my preference is the carriers as per Pete’s car.

[drdoom]

Right, agree on Thackery's preferred over the cushions and we should ever be mindful that just because replacement bits are offered by our faithful suppliers does not ensure they are up to spec in all instances. No where will one see the Durometer figures for hardness of rubber components listed, something obviously altogether pertinent to effectiveness in a given application.

There now exist alternative cushioning elements in the form of stainless steel wire clumps, some of which may afford a solution for our classic cars, here or there. Link attached.

 https://www.knitwire.com/knitwire-products/anti-vibration-mounts/

https://www.meshfilterscreen.com/product/knitted-wire-mesh-discs/

Cheers

[jonwat]

21 hours ago, peteyg said:

I now have petrol pissing out of the bottom of the spacers.

You need to check that the spacers are flat & have not been distorted by over tightening the nuts as that could result in fuel dripping onto the distributor beneath. 

[peteyg]

I've just swapped the spacers around and the air leak is still there on the front carb unless I tighten the nuts right up though it's still there, just. Suspect carb face or manifold face. No fuel leaks though so a small but important win. 

[jonwat]

39 minutes ago, peteyg said:

No fuel leaks though so a small but important win. 

My first S3 had the nuts done up tight like yours when I bought it & there are drillings in the carb flanges which the maker fills with lead plugs to seal them. On mine the over tightening had forced the plugs back into the drillings so there was an indentation which the O ring couldn't seal. I filled the indentations with a small amount of filler & smoothed it flat, 

[peteyg]

@jonwatcool, I'll take a look.

Thanks.