Understanding the Stromberg CD175 Carburettor

[mickeyw]

In the continuing effort to get my 110 V8 back together, I thought I'd give the carbs a check over.

This has opened up another collection of crimes committed by garages and previous owners. The engine was fitted with an unmatched pair of carbs, and came with four 'spares' (alarm bells anyone? )

Anyhow I am trying to select parts from all six to make up a matched pair, and I think two of the spares may be the originals, but I'm still finding different needles fitted to each one/

In choosing carb bodies to use I need to understand more about the various ports present. Now I know that carbs are a dying breed these days, but I am sure some folk on here will have spent long enough living and tinkering with them in the past, and have a wealth of knowledge tucked away.

In this exploded diagram, can you tell me the purpose of the two brass tubes I have arrowed? Some carbs have both, some just the top port, and some none. They feed very small drillings that meets the air inlet above and below the throttle butterfly.

Now to the float chamber. I've opened up two 'pairs' and found a brass tube that hangs down beside the needle orifice. It seems to be present on one hand and not the other. Any clues to it's purpose, and that one hand with, and the other hand without it is correct?

Now needles are easy enough to replace. These are the top adjust type of carb, although one of the ones fitted to the engine was a bottom adjust type. But can anyone tell me how the jet is fitted? It looked like it is pressed in but confirmation ould be good before I go breaking anything!

[Josh NZ]

Hi Mickey.

I used to have a Stage 1 V8 and it had huge problems with the carbs. I got sent this link. It may help you, I found it a great resource. Let me know if the link works.

Josh

http://forums.lr4x4.com/index.php?app=core&module=attach&section=attach&attach_id=48534

[mickeyw]

Thanks for your link Josh. I actually have an original copy of that booklet.

Unfortunately it only really covers the earlier adjustable jet variety of CD carb, and doesn't go into much detail of what port does what.

[tacr2man]

Forget about the strombergs , and fit a pair of HIf SU carbs . It makes more sense in the long run . You wont have the trouble with the diaphragms perishing . You also need a special tool to adjust the mixture on the stroms, it goes down thru the damper .

[pat_pending]

In the first picture the tubes you arrowed are the vacumn take offs for the distributor.

Some engines had a double acting advance/retard system, the upper tube goes to the advance side of the dizzy's vacumn capsule(the tube that points away from the dizzy) and the lower to the retard (points the other way).

Later engines only had advance, therefore only the upper tube is present. They are only on left hand (nearside) carbs.

The purpose of the advance/retard was to do with emissions IIRC.

[mickeyw]

Forget about the strombergs , and fit a pair of HIf SU carbs . It makes more sense in the long run . You wont have the trouble with the diaphragms perishing . You also need a special tool to adjust the mixture on the stroms, it goes down thru the damper .

Yes, I agree the SUs can be easier for maintenance, I changed to HIF 44s on my 90 when it was a 3.5. That said the Stromberg was considered to achieve marginally better emissions, and therefore economy.

I have all the adjusting tools from 15 years ago, I don't get rid of much, lol. TBH I never had much trouble with the diaphragms.

Seems it is hard to come by V8 carbs these days, unless you want to pay ££££ to RPI for new ones. This engine just needs to tide me over for a year or two while I overhaul a 3.9 serp lump, so I am trying to avoid unecessary expense.

[mickeyw]

In the first picture the tubes you arrowed are the vacumn take offs for the distributor.

Some engines had a double acting advance/retard system, the upper tube goes to the advance side of the dizzy's vacumn capsule(the tube that points away from the dizzy) and the lower to the retard (points the other way).

Later engines only had advance, therefore only the upper tube is present. They are only on left hand (nearside) carbs.

The purpose of the advance/retard was to do with emissions IIRC.

Thanks for that tip Pat, especially the ports being just one carb. Now you have said it, I can remember my 90 having these A & R pipes. The grey cells are ticking rather slowly these days

It seems so long ago I took this all apart. More photos should have been taken.

[mickeyw]

Well today I took my collection of needles and one pair of carb bodies to work, and had a close up look and measure of them with the shadowgraph projector.

I have five needles, two B1FP (which is what should be fitted to a Landrover V8), one B1FQ, one B1FK and one B1FT, and guess what - as far as I can tell, they are all the same!

I've no idea how much one version should differ from any other, Google doesn't seem to know. Anyone???

The other positive result is that the jets appear to be perfectly round and the same diameter.

Looks like it just a pair of diaphragms and damper springs to order.