Overhauling Stromberg carbs - difficult ?

franksm

Hi folks

Took my Stag to be tuned at Westward Engineering in Enfield last week - unfortunately it's running rich and they couldn't get it any leaner. Time for new carbs or time to recondition the existing ones !

The car has a pair of Zenith Stromberg 175 CD-2's under the bonnet.

At least all the parts are still available, overhaul kits plus floats plus jets are about £100 STG for the pair. Exchange carbs are about £250 for a pair.

Has anyone reconditioned carbs before ? It looks straightforward from the diagrams/workshop manual - just a matter of taking them apart and replacing all the perishable bits. My worry is that I do that, put them back on the car, and then am stranded with a car that won't start up.

Ta

Frank

Dades

franksm wrote:

My worry is that I do that, put them back on the car, and then am stranded with a car that won't start up.

Isn't that the question you have to ask yourself before any job?

Do you have any experience with this type of stuff? I've a pair of carbs that need tuning/reconditioning too - but am probably going to have to leave them with McNamaras or someone to do the job.

I have the manuals - I just wouldn't trust myself not to turn a running car into a stationary one. :eek:

G'luck with them anyways.

franksm

The Atheist wrote:

Do you have any experience with this type of stuff? I've a pair of carbs that need tuning/reconditioning too - but am probably going to have to leave them with McNamaras or someone to do the job.

With engines in general, yeah. I'm quite happy with fuel-injection/turbo type stuff, easy enough to tear all of that down and put it back together. I bought a cheapie carb off Ebay (a Stromberg 175 CD1) for playing about with, and it does look like a breeze to work on.

Difference between a car with an ECU & injectors and something ancient with carbs is that you're more likely to get the ECU car to start up first time, whereas the carb-car can be rich/lean/flooded/dry plus they need to be balanced... and then how to get the car moved to someone that can repair it ? ;-)

BTW how much do McNamaras charge for reconditioning/exchange ? And do they do all carbs or just Weber ?

ds20prefecture

franksm wrote:

Has anyone reconditioned carbs before ? It looks straightforward from the diagrams/workshop manual - just a matter of taking them apart and replacing all the perishable bits. My worry is that I do that, put them back on the car, and then am stranded with a car that won't start up.

From my own experience (1 carb - a Weber DDE2), the only adjustment within the carb is the float level, and that should be in your Haynes/shop manual.
Ensuring that the correct sized jet is used is the only other parameter to worry about.
You'll want to check the body internally for damage, and also that the butterflies are operating correctly (i.e. not sticking)

But your carbs could be _completely_ different. You have vacuum advance, right?

Regarding running rich - I assume your air filters are OK?

Sorry - I realise this is a useless post.

franksm

S'okay

The float level - yeah, I reckon that's my problem. The car is difficult to start when hot and sometimes smells gassy at those times too - could be floodnig due to a burst float. However to get at the floats, I need gaskets and all the other gubbins hence my idea that I may as well change everything that ought to be changed/overhauled. Especially since the carbs look original (1973) although will have been off at some stage as the car got new unleaded heads, and I see receipts from the previous owner for inlet manifiold gaskets.

ds20prefecture

franksm wrote:

S'okay

The float level - yeah, I reckon that's my problem. The car is difficult to start when hot and sometimes smells gassy at those times too - could be floodnig due to a burst float. However to get at the floats, I need gaskets and all the other gubbins hence my idea that I may as well change everything that ought to be changed/overhauled. Especially since the carbs look original (1973) although will have been off at some stage as the car got new unleaded heads, and I see receipts from the previous owner for inlet manifiold gaskets.

If you're reasonably careful when removing, the existing gaskets should work fine. Still, if you have rebuild kits...

There's a big difference between checking the float (standard service item) and overhauling the carb. I reckon you should start with what you can do yourself. Check the float, the gaskets, the butterfly operation, the air filter, and even replace the jets. If it's still screwed up, then you could look at getting it overhauled. A common problem with my type of carb is that the base warps, which screws up the venturi. To fix this, you need to get the base machined flat, or you can cheat and make yourself a thicker, spongier gasket by sandwitching two paper gaskets between some silicone.

If you get to the point where you can't get the car started again, just whip the carbs off and bring them to McNamaras or whoever. You won't need to bring the whole car.

franksm

Thanks for all the ideas. I didn't realise the plastic piece on the side was a temperature compensator, but searching out that nugget of info pointed me to a good article on http://www.vtr.org/maintain/temp-compensators.shtml

I have a spare 175CD that I bought cheap for practising with - took just an hour to completely dismantle and another 30 mins putting it back together - there's not much to it (although it doesn't have the temp compensator).

I'll order up some rebuild kits and make a go of it.

Blitzkrieger

ds20prefecture wrote:

the only adjustment within the carb is the float level, and that should be in your Haynes/shop manual.

There's so much more you can adjust than that. I'd go playing around with the air screws and the idle before striping the carbs, but stripping carbs isn't that difficult. If you go slowly and watch how everything is set up you should be okay. The amount of turns for the air flow, the size of jets and the settings for the (can't think of the name) thingies should all be in the haynes manual.

ds20prefecture

Blitzkrieger wrote:

There's so much more you can adjust than that. I'd go playing around with the air screws and the idle before striping the carbs, but stripping carbs isn't that difficult. If you go slowly and watch how everything is set up you should be okay. The amount of turns for the air flow, the size of jets and the settings for the (can't think of the name) thingies should all be in the haynes manual.

I agree completely - however the only adjustment within the carb is the float (well, my Weber carb anyway). Assuming the jets are fixed, the mixture and idle screws are "normal" external adjustments.