Water leak

[Austin Nippy]

Good evening everyone,
Just to let you know that the water leak is now cured thanks to the excellent advice on here. It then fired up instantly and appears to be running nicely once more ready for the next set of adventures!...
Best wishes,
Nick

[dickie65]

Your Block might just be a 9E block but without the Chromidium Diamond.
I have two 9E Blocks one Has the Chromidium Diamond cast in.

The other one is stamped 9E and has 9E cast into it in the valve chest the one without the Chromidium Diamond came on a Nippy engine with no engine number stamped on the crankcase.

The block still had the sports Tulip valves with square holes for valve grinding installed.

[Austin Nippy]

Hello again everyone,
The good news is that the water leak fix has held and the engine also doesn't seem to be leaking any oil which is a first. However, whilst the engine sounded good in the garage where it fired up instantly and settled into a steady tick over and good pick up on the throttle, it really doesn't want to drive on the road.
There is absolutely no power whatsoever. It will struggle its way up to about 40ish on the flat but any slight incline causes rapid downward gear changes to get up them. I'm talking about short gentle rises as opposed to proper hills.
I've now fitted new plugs, points, condenser one at a time with no improvement from any of these. I've also advanced the distributor a bit more with no beneficial effect either. The throttle is fully opening when the pedal is on the floor, there's good fuel flow and no sign of air leaks when I've sprayed some light oil round the manifolds. This is becoming puzzling as the engine sounds fine when driving along - it's just painfully (almost dangerously) slow.
To add further to the issues, on my brief forays totalling about 40 miles, the recently rebuilt gearbox complete with a new set of Super Accessories gears is incredibly noisy in all gears except top - it kind of whines when driving in the other gears which it didn't do prior to having it rebuilt with the new gear set. It's slightly quieter on the over run and the noise disappears altogether when I press the clutch pedal down with the gear still selected.
Unfortunately, I suspect that we'll not be on the road any time soon now as I'm back to full time work next week and the Nippy will have to take a back seat until I can either find a quick simple fix for it or, more likely now, find someone who can sort it out properly.
Hopefully, we'll be back on the road at some point this year...
Best wishes,
Nick

[Austin Nippy]

Hello again,
Thanks Stuart for the phone call. Since then, I've managed to pinch 5 minutes and investigate a little further. The downdraft SU carburettor 
(the dashpot lies horizontally with the "top" being near the bulkhead) had no oil in the dash pot so I've now put some in. My initial thought that, perhaps there was no piston was incorrect. Having removed the dash pot cover, there is a largeish casting inside (a piston)  which slides in and out of the main body of the carburettor which has a needle attached to it that goes into a small hole. There is also a spring in there too. My only thought is, should there be another piece in the "top" of the piston? I've some vague recollection of there being another part between the brass cap and the main piston on a Morris Minor I owned 25 years ago but I may be mistaken.
I've not tried to start the car since due to it being late but will try to see if this has made any difference tomorrow if I get chance as "somebody else" wants to go out for the day instead.
I guess that if this hasn't worked, I could try to put the downdraft Zenith from the other (broken) engine on and see if this works better than the SU - I doubt it can be any worse.
I'll try to keep you all posted as and when I get chance.

And then there's the whining gearbox to contend with but that's for another day...
Best wishes,
Nick

[stuartu]

Nick, I now understand what you were saying last night. I believe that the d/d SU has no damper. If it is the original dash pot there is a small oil cap on the neck which permits one to add a little oil to lubricate the movement of the piston in the dash pot.

As I understand it, that engine ran tolerably on the same SU in the past rather better than it does now. If that’s the case the search for the snag continues, I fear.

Regards,

Stuart

[John Cornforth]

Hello Nick

As I am sure you know, the SU is designed so that the piston rises to accommodate increased airflow, whilst simultaneously withdrawing the tapered needle from the jet to give increased fuel flow. The needle taper is chosen to give a more or less constant Air/Fuel ratio over the whiole range.

With a downdraught SU (Horizontal Dashpot) there has to be a light spring for the piston to work against, unlike the more commonplace sidedraught SU (Vertical Dashpot) which can use gravity or combined gravity and spring. The horizontal piston would seem to me to be more at the mercy of slight wear which might cause it to stick somewhere in its travel, restricting the airflow to the engine and thus its top end power. The clearance between the upper part of the piston and its dashpot is very small, and the two are a matched assembly which cannot easily be swapped with others

I suggest you check the opening with your fingers and make sure it is genuinely moving freely over the whole travel.  Burlen have quite a lot of technical info and drawings on their website, but I have attached SU's 1958 Manual which may be useful.