Dashpot Dampers

[Darren Groves]

I noticed a while back that the dampers in my HS2's are different, in one it's a AUC8103 and the other AUC8114. Visually they look the same, same length etc. both vented, but is this an issue? Whish one is the correct one for the Carbs?

 

They were sold to me as from a 1300 MKIV Spitfire.

[Pete Lewis]

Darren  I find   on Burlen both seem HS2

 

auc 8103 is spitfire 111  67/68

 

and auc8114   spitfire mkIV  73>

 

if thats any clues

 

Pete

[Guest]

Darren.

 

The difference is that some are externally vented (hole in the top) and others are internally vented (angled hole in suction chamber).

 

I think your dampers are externally vented.

 

Both dampers MUST be the same for smooth running.

 

As you are running a 1968 vehicle and I presume the engine equates to that same period, then you should be running a set of AUC 8103. 

 

The later 1296cc engines ran with AUC 8114; as far as I am aware.

 

Cannot be 100% but I think that is correct.

 

Hope that helps.

 

Regards.

 

Richard.

[Darren Groves]

Thanks for the replies.

 

Both these dampers are vented through the cap, the difference seems to be the piston lengths on them, 8114 is a long piston, 8103 short. The shorter piston on 8103 allows an initial undamped amount of travel of the carb piston upon acceleration, whereas 8114 doesn't. I will have to have a closer look tomorrow as I'm sure visually they are the same, there's no saying that someone hasn't just changed the plastic cap with the wrong one.....

 

The carbs were advertised as MKIV when I bought them, so if that's the case I should have AUC8114, but who's to say that the PO was correct in his description.

 

The identification tags are long gone, do the part numbers on the carb bodies give any indication on their heritage?

[Pete Lewis]

not really as the base components can be very mix and match to build up the specification tats related to the  tag numbers.

 

the Burlen site gives a good breakdown of the specified parts but lists al the dampers  , give them a call  ??

 

(0)1722 412 500

 

http://sucarb.co.uk/cf/vehicle/list/?manufacturer=Triumph&vehicle=Spitfire

[Guest]

Darren.

 

As you highlighted on your 1st thread, that the carbs are alleged to be from a Mk4 Spitfire which of course ran with the later 1296cc engine; then if these are the carbs from that particular model then I agree you would require the AUC 8114 items.

 

Perhaps (unscientifically) as you have 1x of each - is it worth buying another odd set and seeing which seems to work the best - i.e. smoothest delivery when dampening ?? 

 

Out of interest, do you use 20/50 in your dashpots or ATF ?? If not those, what do you use ??

 

Regards.

 

Richard.

[Pete Lewis]

and later IV   would have had the big inlets and HS4     

 

would not have thought ATF has the required viscosity to damp.  the  SU spec is a straight   sae20

 

light damping gives a weak acceleration mixture ratio.

 

Pete

[Clive]

In the dashpots always 20/50.

 

The thicker the oil, the longer you get enrichment, which has to be a good thing. Thin oil lets the piston move too easily, and the mixture will go lean during acceleration.

[Darren Groves]

I always use engine oil for dampers.

 

I had 2 other dampers tucked away in a drawer, both AUC8103's, but one had a slightly different spindle length, but of the 4 I found 2 that had the same spindle and piston, so I have a matching pair albeit the wrong ones. I did speak to Burlen and they just said that as long as they were matching it should be fine. I'll order the correct pair at some point.

 

On something slightly different, whilst balancing the carbs I gave up on the Gunson Balancer and just used a length of tube. The rear carb was definitely sucking in more air and the idle was a little high, but I couldn't reduce the idle on that carb and the idle screw was fully up....any ideas?

[Pete Lewis]

Hi darren,  yes   check the throttle plate is the right way round , and its centred in the spindle slot

 

may need to slacken the two screws and get it to close , ie no daylight visible around the edges then re nip the screws

 

the plates have a chamfered edge to make a ight fit to the bore if they happen to be wrong way round 

you have a big gapnand a fast uncontrolled idle when the stops fully out.

 

ans a thought ..........make sure there's a small gap to the choke fast idle cam tappet screw

 

Pete

[Darren Groves]

Thanks Pete.

 

I would hope throttle disc is in there correctly as they were fitted by Carb Exchange up your way as I had them re-bushed, but will check again.

[Pete Lewis]

never had any issues with them over the years but  who knows ,  think I would whip one off and look through the barrel 

 

double check the choke cam is not interfering

 

 

pete

[Mike Lester]

I've always used Penrite Damper Oil, it's quite light but seems to give a good effect. You get good resistance when pushing the dampers back into their pots.

[Darren Groves]

Sorted the balancing of the carbs, throttle discs were closing correctly so slackened off all the linkage and backed the fast idle screws right off and set-up from scratch, all seems fine now.