SU float chamber valves.

[Wagger]

Tried to do a run yesterday, but Vitesse went gutless after 400 metres. Engine is a 2500TC with SU's. Front carb needle valve is sticking, not quite shut. I removed the float and top of carbs and blasted it several times and it appeared to be clear operated by hand  with electric fuel pump running. However, it keep sticking again after 400 yards each time.The floats do not have shims. I guess it is obtain a refurb kit and fit new needle valves. All was well three weeks ago and I only use 98 ron fuel.

No crud visible and there are two filters in line. Flow rate and pressure are good and rear carb is doing well.

Are there any quick fixes until new parts arrive?

[Pete Lewis]

whilst i have sort of hate of SU's  my 2000 has two HS4   Grrr  

after initial purchase it did as yours contantly over filling   it took a while of much cleaning and messing around when under a big magnifier you could detect very small wear ridges in the 

floats plastic platform worn by the needle    tried some   gentle fettling but it took a pair of new floats and its since been trouble free for 4 years 

if that helps   

do not go into Grose jets they are quite hopeless these days 

Pete

 

[Wagger]

3 minutes ago, Pete Lewis said:

whilst i have sort of hate of SU's  my 2000 has two HS4   Grrr  

after initial purchase it did as yours contantly over filling   it took a while of much cleaning and messing around when under a big magnifier you could detect very small wear ridges in the 

floats plastic platform worn by the needle    tried some   gentle fettling but it took a pair of new floats and its since been trouble free for 4 years 

if that helps   

do not go into Grose jets they are quite hopeless these days 

Pete

 

Thanks Pete. This one shuts off, but does not open more than a hypo needle trickle. If I remove the float and operate the needle by hand, it will not fall without pressure. It could be notches in the float causing it to 'Latch' and/or wear in the bore causing jamming and latching. I will check today before the half term 'Dump and run'

Blocking the feed to the other carb causes enough pressure to open it.

Thanks for the tip on what to avoid.

 

[Wagger]

Nothing wrong with the float valves. It is debri in the fuel. The result of more enthusiastic use washing the inside of the tank. Two mesh inline filters are allowing fine sticky crud through fouling the needle valves and the carb jets. I can get a good run in for about a mile, then it all starts again.

Will now remove the tank and clean the whole system. B-I-L  fitted a modern inline filter to his Wolseley and that blocked within 50 miles. So, I need to clean the tank and line it. I'll search the forum as I know that many of you have done this. Neighbour of mine has a pal who fabricates tanks in aluminium and stainless. I wonder how much?

 

[DanMi]

What electric fuel pump and or do you have a pressure reducer as many electric pumps are simply to high pressure for the SU valves, actually as apparently are many of the repro mechanical pumps.

[Stratton Jimmer]

I dislike SU carbs with a vengence yet both my cars have them. The Sixfire has HS6 while the GT6 has HS4. The GT6 runs better than the Sixfire! Once I have the right manifold, one of the cars is going to inherit the pair of CD150s I have and the sooner the better. (It will probably be the Sixfire.)

[johny]

 Its just that this one seems low on pressure rather than high as the float valve doesnt open!

[dannyb]

I would put a pressure gauge on the pipe that enters the carbs and see what pressure your getting. I cleaned my I line filter and there was no rust or rubber particles but a bit of sticky crud. This also stuck the one of the float needles shut and needed a good clean.

Danny

[NonMember]

It may be as simple as a dodgy valve. I had that (Wagger's symptoms of sometimes sticking shut) on my Toledo and it nearly defeated us on the 2008 RBRR - until Dale diagnosed it and I re-fitted the old valve.

[Wagger]

I only run the electric pump when draining the tank. It is fitted so that I can use it in series or parallel with the mechanical one. There is a fine residue in the carbs every couple of days, so the answer is quite simple. When I drive off all is well for up to five minutes, then is runs on three cylinders. If I back off on the throttle, all six fire up until I want power again. So, it is pressure related, as you point out.

Removing the floats, draining the bowls and flushing through improves matters, but Crud is being stirred up by my more enthusiastic driving of late. I am not running on reserve, That caused problems last time that I did.

There is plenty of fuel pressure, but this drops with high demand. Therefore, the line is restricted and muck is blocking and sticking the needles.

I have no choice now but to drain the tank and clean it (again!), renew the pipe from front to back and put filters both ends. The filter before he electric pump is invisible, but is blocking. The mechanical one has the glass bowl and I can see debri in that too.

I really need a new tank or a reliable method of coating the inside. It stood empty for seven years. I have done this on a motor bike but that was easier to handle. I used a slow setting epoxy resin rotating the tank for an hour. Left it to cure for a month in a warm garage.

Filters arrive tomorrow but the half term 'Dump and run' with grand-kids will delay progress for a few days.

[DanMi]

It is more likely crud blocking the pipes and tank outlets, rather than the valves. Frost do a tank sealing kit, which has a heavy duty cleaner phosphoric acid and sealer, which I used on my spitfire 12 years ago and is still good, but has to be done carefully, I added gravel with the cleaner and shook it a lot and left each stage for a few days turning the tank regularly. Others have found it comes off though and it is not cheap at over£60, but then a new tank from Rimmers is £360

[Wagger]

4 hours ago, DanMi said:

It is more likely crud blocking the pipes and tank outlets, rather than the valves. Frost do a tank sealing kit, which has a heavy duty cleaner phosphoric acid and sealer, which I used on my spitfire 12 years ago and is still good, but has to be done carefully, I added gravel with the cleaner and shook it a lot and left each stage for a few days turning the tank regularly. Others have found it comes off though and it is not cheap at over£60, but then a new tank from Rimmers is £360

I agree. I have a length of 5mm bore copper pipe to replace the existing steel one. Filters have arrived, so I will clean the tank first and fit a filter in the boot and another between pumps and carbs. They are transparent, so I can observe their state after a week or so. I can't face shaking a tank with gravel in it again after some twenty years since the last time. There are some quite good kit car tanks around so I may obtain one for use whilst I fix the original. Pity I cannot insert a large neoprene 'Balloon' inside it and use it as a double skin.

I'll check the flow rate when I drain the tank next weekend using the electric pump. A month back, it was 5 litres per minute. That will be quite revealing.

[Pete Lewis]

and have 2.5psi as a maximum pressure or there abouts 

Pete

[Peter Truman]

On 14/02/2022 at 03:59, Wagger said:

I agree. I have a length of 5mm bore copper pipe to replace the existing steel one. Filters have arrived, so I will clean the tank first and fit a filter in the boot and another between pumps and carbs. They are transparent, so I can observe their state after a week or so. I can't face shaking a tank with gravel in it again after some twenty years since the last time. There are some quite good kit car tanks around so I may obtain one for use whilst I fix the original. Pity I cannot insert a large neoprene 'Balloon' inside it and use it as a double skin.

I'll check the flow rate when I drain the tank next weekend using the electric pump. A month back, it was 5 litres per minute. That will be quite revealing.

Ed China used a concrete mixer to shake/agitate to clean/derust a Range Rovers fuel tank with stones in worked well, who do you know?

[Wagger]

1 hour ago, Peter Truman said:

Ed China used a concrete mixer to shake/agitate to clean/derust a Range Rovers fuel tank with stones in worked well, who do you know?

Now there is an idea.

[trigolf]

Slight thread drift, but people seem to stand in one corner or the other,  in the SU versus Stromberg argument. I'm keeping quiet! 

I'll get my coat now.....😜

[Pete Lewis]

su or stroms   both will and can do a decent job all i add is strip them down to component parts and lay it out on a clean sheet 

one is engineered   and one is a lot of bits and pieces   

Ill leave you all to decide which is which  Ha !

Pete

[Iain T]

I think the CDS Stromberg is a superb carburetor especially as you can easily adjust the mixture! 

Iain 

[Pete Lewis]

yes CDS a good carb without the emission and anti twiddle add on's

it was emission and tamper proofing of the late 70s 80s that messed things up

not that tamper proofing remained tamper proof for long but was in place as the cars left the factory 

Pete

[Peter Truman]

I'm the odd ball out in our local car club here I prefer Strom's, for all Pete's reasons, where as the other 's are olden's "not really" and swear by SU's.

I've just rebuilt the Sprints HS6's SU's a PITA not helped by poor engineered butterfly shafts where the flats were out of line with the butterfly slot so the butterfly wouldn't close fully, the rebuild kits were sourced locally who get from a major UK SU supplier! To their credit the local suppliers Tech Dept acknowledged the fault and sourced from their stock a pair of correctly aligned shafts! One member who restored a 68 E type with new triple SU's and correct E Type manifold had major issues of adjusting the UK supplied parts to fit and that's after they cost over $4k to buy and ship in a beautiful plastic container!

The only issue I've had with Stroms other than my USA supplied Grose needle valves (my fault for believing the blurb), has been aftermarket poor quality ebay Diaphragms as Pete L appropriately said made from Rhino Condoms!

[Pete Lewis]

i have no idea what on earth has gone wrong with Grose float jets they used to be ok and the concept is good but the past few years of 

trialing odd ones when flooding arrives and they are just hopeless +  found by many others too

and a tip i keep repeating with proper gossamer diaphragms  if its all wrinkled and swollen by oil and fumes  a wash in petrol will return it to size

if its made form rhino or elephant by products they are so stiff you will be overcome with running problems 

flimsy and floppy is the name of the day ( no they are not pet rabbits ) 

but nice flimsy and flexible diaphragms not the  thick crap sold on some sites and even proprietary  companies 

that you expect to know better  !!!!

Pete    well the suns out 

 

[Wagger]

Resurrecting the original thread, there were many problems.

One obstructed filter.

Removed the puny filter, flushed the system through with the electric pump and fitted a large filter where the fuel line enters the engine compartment so that I can see if crud collects in it. I pumped 2 gallons o fuel out until it required reserve, then used the reserve setting on the tank and pumped fuel into an open bowl until it ran clear. I then turned it back to normal in order to work under the bonnet.

Dirty float bowls and delaminating gaskets.

Cleaned it all out. Gaskets ordered but will not fit until levels are set. They delaminate every time the bowls are removed. I may do away with gaskets if I can achieve a seal by lapping the joint or using a petrol proof sealer.

Mechanical fuel pump arm wrong side of camshaft. (Sorted, thanks to PeteL)

Watch this one, the pump had never been fitted properly and was in the spares box. All of the wear was on the inside of the operating arm, so I assumed the fitment incorrectly. It was still pumping at 200 mls per min. It now does at least 400!

Incorrect float levels.

Where the gap should be 1/8th to 3/16th inch, it is 7/32nds. The floats are non adjustable at the pivots and the valves have no washers, so this can only be resolved by fitting floats that have adjustment, or grinding away the float top face where the needle sits. I will puncture a float if I attempt this, so will not do it until new ones arrive, and only if they prove problematic.

Lowering the jets by using the choke does improve matters, so all should be well once this is sorted. If not, there is no more hair to pull out!

At present, up to half throttle is ok. Above that it is all popping and banging.

The bowl

[NonMember]

42 minutes ago, Wagger said:

Where the gap should be 1/8th to 3/16th inch, it is 7/32nds. The floats are non adjustable at the pivots and the valves have no washers, so this can only be resolved by fitting floats that have adjustment

You may have dud valves. I had that problem on my Toledo because a new valve that I'd fitted was just simply the wrong length.

[Wagger]

OK, I bought a low pressure fuel and vacuum gauge. Pressure was not sustaining and only 0.5lb. There was a split on the rear carb hose under the clip. No fuel coming out because of air in the fuel. The fuel pipe in the tank appears to have a hole as bubbles appear when the fuel is below 3 gallons.

With all new hoses, more fuel and new floats set correctly, it is much better, but the pressure is only 1.5lb, right on the lower limit. If I use the prime lever, it rises to 2lb and holds up.

Next move is a road test when the weather dries up. My electric pump now cleaned with a new filter will deliver 4psi. I will need a regulator if I have to use that.

I will need to get the pipe out of the tank next. Might be ready for Easter then.

[Pete Lewis]

On 23/02/2022 at 16:22, Wagger said:

Above that it is all popping and banging.

have you richened the mixture whilst using choke can disguise other problems  it does seem the basic setting is too lean 

along with duff condensers ...any back fires ???

Pete