Rover v8 cd175 carbs

[Declan303]

Maybe some can help. I am cleaning up a set of carbs for the v8. I took them off the inlet manifold and didn't find the gaskets as I thought I would so am a bit confused as to which is correct way to fit or does it matter.
What I found from the manifold side out to the carb was
manifold --- Gasket --- Saw tooth deflector ---gasket ---- plastic spacer --- gasket ---- carb.

What I thought was right is
manifold --- Gasket --- Plastic spacer --- gasket ----- Saw tooth deflector ---- gasket ---- carb

Anyone know which is correct


Declan303

[RoverP6B]

Hello Declan,

The order that you thought was correct is correct.

manifold---gasket---plastic spacer---gasket---saw tooth deflector---gasket-carb.

Ron.

[Declan303]

Thanks Ron,
I have now also noticed that there is a small arrow head on one edge of the plastic spacer. Should that arrow point twards carb or manifold. It appears that the center apperture of the spacer has one edge tapered more so than the other side

Declan

[RoverP6B]

Hello Declan.

The arrows on each of the phenolic spacers point towards the manifold and away from each carburettor.

Ron.

[Declan303]

Cheers Ron thanks for info.

Declan

[Declan303]

I have the carbs all put back together, new gaskets, new diaphrams, float level checked. mounted on the manifold and the whole lot refitted to the engine with new valley (inlet manifold) gasket.

Now proplem is that Im at the stage of trying to set the idle and mixture on the carbs. After multiple attempts to get it to run right, I have it that when I start it (engine already hot), it will tick over at normal idle speed and sounds right. However, if I rev the engine on either carb (carbs are still split ) the engine will not return to the idle speed. If I look into the barrel of the carbs I can see that the air valve pistons in both are raised about 8-10mm. If I switch off the engine, the air valve pistons will drop no problem. If I restart the engine, again it will sit perfectly at idle speed until once again I rev it.

I have double checked that all vacuum pipes are connected as was, and yes air valve springs are back in place.
Anyone any ideas what might be causing it, or some ideas on how to prove which carb it is, thats causing the problem (assuming its down to one of them)

Declan303

[harvey]

Have the throttle butterflies got emission control poppet valves in them?

[Declan303]

Yes there are valves on the butterflys

[harvey]

In that case I would suggest the factory mod that was done to cure the same problem with the SU's, which was to melt the solder on the poppet valve, screw it up tight so the valve can't open, and then resolder.

Personally I'd junk those carbs and use the SD1 SU's, but that's only my opinion.

[RoverP6B]

Hello Declan,

I have never heard of the poppet valves in the butterflies being a problem before, as has been suggested.

I can't imagine that they will be alone responsible for the tuning problems that you are encountering.

I have never set up a pair of Strombergs, but here is a link that you might find very useful in doing just that. Be sure to rotate the adobe file once it opens, makes it easier to read.

http://p38arover.com/misc_files/Tuning% ... 0Carbs.pdf

Ron.

[Declan303]

Thanks guys for the help. I stripped the two carbs off yestreday to investigate what might be wrong and have a look at the valves on the butterflies.

When I took the first carb off the manifold, the gaskets, sawtooth plate, spacer all came with it. I operated the butterfly and immediatly noticed why the sequence of the components was as I had orriginally found them. The butterfly was grazing off the teeth of the plate. I came to the conclusion that this could definately be a problem when all was sweezed back together, that the butterfly may foul on the teeth and not return to closed position. So decided to revert back to Manifold-gasket-sawtooth_plate-gasket-spacer-gasket-carb.

Next on examination of the driver side carb I found uneven ware on the butterfly where it had been incorrectly seated and now had a gap on one side when in the clossed position. So I got a butterfly off an old carb and replaced the worn item.

I unsauldered, closed up and resauldered the valves on the butterflies.

Put it all back together today at lunch hour and its ticking over like a swiss watch.


Declan303

[Declan303]

Another funny thing is since doing that, I have now founf a document for SU carbs and it shows the sawtooth plate closest to the manifold withe the spacer in between it and the carb.

Declan303

[RoverP6B]

Hello Declan,

Glad to hear that she is up and running sweetly!

With my twin SU, the saw tooth spacer was never fitted at all.

Mine run....manifold - gasket - phenolic spacer - gasket - carb.

Ron.

[Quagmire]

I took what i imagine are the sawtooth deflectors out when i fitted the SU's on mine. Is this what everyone is talking about?



Kept the spacer, and mine went back the same as Ron says his are- manifold/gasket/spacer/gasket/carb.

Haven't noticed anything bad without them- are they supposed to help the mixture go down and into the manifold more efficiently instead of just hammering into the manifold wall?

[RoverP6B]

Hello Quagmire,

Hmmm, maybe we are indeed talking about different things.

The sawtooth spacer that I was thinking of is a type of gasket with a sawtooth outer edge,...nothing like the item that you have included with your post.

I have seen such an item before, and can only imagine that its purpose might be to induce a change in the air flow.

The physics of flow is quite involved, and although I understand some of the mathematics involved,...representing the flow as a three dimentional function in cylindrical co-ordinates, taking curl of said function,.....but that tongue throws a spanner into the works!

The SU carburettors do have a metal tube sometimes referred to as a "swirl' device, which fits into the phenolic spacer and is captured by the gasket and the carburettor. I assume that it acts as a channel for accelerating the air as it enters the manifold..

Ron.