SU HS6 carb damper.

[swedemash]

My PV544 had started to run a bit rough/hesitate on initial acceleration so i popped the bonnet up this morning to do some basic checks and found this:



The damper rod was ticking out the top of the cap like the end of a rivet! I pushed it back down, quite stiff to move, but after a 20 mile drive it was just the same. Easily solved, I'll have a rummage in my spares or maybe get a new one from Burlen Fuel Systems.

Is there anything I should be checking or is it just likely to be fatigue of the plastic cap?

Stuart

[Ron Kwas]

Stuart;

Welcome to this Forum!

I've seen this before...it's not a huge problem, but what you have experienced on your Damper is a result of either a backfire and/or possibly too thick a Damping oil...or a combination of the two...

As the Dashpot tried to quickly rise (against the CLOSED Damping valve), oil could not bypass the valve-assembly quick enough so the force transferred to Valve threaded top was too much for it to take, (SOMETHING HAD TO GIVE!) and it blew the rod right through the plastic cap...

See also: http://www.sw-em.com/su_carbs.htm#Da...lve%20Assembly

I recommend you check your Damping oil viscosity (should be 20W, not thicker)...also don't stomp on the accelerator pedal before engine is warmed up, resulting in a lean backfire. Also check your Choke is enriching as it should! You MIGHT be able to (super)clean the area, file some burs into the rod to give it some "tooth", push it back into its normal position, and epoxy it into place...otherwise, replacement is always an option, but check other things I mention or it might happen again with a replacement...!

Cheers from Connecticut!

[swedemash]

Thanks for that Ron.

I had suspected the oil may be too thick and was going to change it before I fitted the new damper.

You mention the choke function. Coincidentally the motor is twin carb but only has a choke cable going to the rear carb, starting as the weather has got colder has become more difficult (in the summer was fine). Not heard any backfires but certainly not smooth for the first minute or so then runs well. New twin carb choke cable on order

Only had the car a few months and I have some things to 'iron out'.

Cheers, Stuart

[Ron Kwas]

Stuart;

Just as long as it helps get started, choking only one carb may be enough...but obviously, that one had better be adjusted and work well or Starting success is unlikely when it's really cold.

I expect that your idle is rough during choked condition, because with a single choke, there is also only a single Fast-Idle linkage, so while choked, induction is also unbalanced. Again, I don't consider this a big problem...choke is a temporary condition only for a short while after Starting. Carbs should be adjusted and motor should run evenly for unchoked condition.

I request your permission to use your picture and include it in the linked article.

Cheers

[swedemash]

Your welcome to use the photo how you wish Ron. Thanks for the advise.