Zenith alternatives

[the big fist]

Hi everyone,
I am getting a bit sick of the Zenith carb on my landy. I think it has warped again as it is running extremely rich at idle and the mixture screw doesnt seem to do anything. My poor garage and part of the house now stinks of fuel thanks to the fumes.
What are some alternatives to the Zenith. I read up on the Weber 34ich and that looks almost like a direct swap over. Are there kits to swap everything over, bolt off bolt on propositions ?

Would be great to hear what others are using.

Cheers,

Peter

[incisor]

the weber...

prone to fuel evaporation and blocked jets

and can run too lean on a 2.25l out of the box

the stromberg carby seems popular as well

as used on holdens etc. again prone to fuel evaporation but a good simple carb when fitted with an adustable main jet... you need to make sure you get one with a decent throat size

used one and had no major issues other than the fiel evaporation issues.

i have a 55 with a 2.25 in it and it has a stromberg carby but it is a lot squater than the holden 6 variant (maybe a sunbird or something) and seems to work very well what little i have used it.

there is the solex but you will have to gin around to fit one of them.

[vnx205]

Have you replaced that big O-ring?

I found out the hard way that using one that was almost exactly the same didn't solve the problem, but the correct one did.

[zedcars]

Well for what its worth

I have fitted that Strombie conversion from England on two recent rebuilds one a Series 3 and the other a Brewery/Distillery Dray 2a. (Came from NZ)
https://www.breckenridgedistillery.com/hooch/about-us/

Running up to 12,000ft from about Denver at 6000' both units showed they could handle to altitude change without excessive rich running.
So I would give the Stomberg two thumbs up!
Dennis
zedcars

[incisor]

Well for what its worth

I have fitted that Strombie conversion from England on two recent rebuilds one a Series 3

got a limk to the kits?

[the big fist]

Have you replaced that big O-ring?

I found out the hard way that using one that was almost exactly the same didn't solve the problem, but the correct one did.

I shouldn't have said "again". It's a new re manufactured Zenith, my old original was warping a lot. I've got a rebuild kit coming for this new one though.

I just want something to bolt on and go.

Cheers,

Peter

[Michael2]

The Zenith 36IV was the most reliable carby I ever had on the 2.5. The previous stromburgs were troublesome. I did end up with a double barrel weber in the end, in my search for performance, which worked well. But a cam regrind* did more that the carby upgrade ever did.




*have the cam ground so that it opens all valves 5 degrees sooner and closes them 5 degrees later. It's like curing asthma - it breathes, exhales and revs freely.

[the big fist]

Thanks for the info.
I wound the idle mixture screw in all the way tonight and it just kept running, no change, I guess that's a sign it's warped ?

Also I couldn't see any squirt of fuel when I jabbed the throtle so i think the accelerator jet is blocked or pump stuffed.

Can anyone confirm those thoughts ?

Cheers,

Peter

[JDNSW]

Thanks for the info.
I wound the idle mixture screw in all the way tonight and it just kept running, no change, I guess that's a sign it's warped ?

Could be, but not necessarily. It means that the slow speed mixture control is not working, but there are multiple possible reasons for this. As well as a warped top cover, it could be a blocked passage or even simply that the idling speed is too high - it should be around 500rpm, about half the speed commonly set on current vehicles.

Also I couldn't see any squirt of fuel when I jabbed the throtle so i think the accelerator jet is blocked or pump stuffed.

Or the linkage is incorrectly set, or excessively worn, or the valve on the pump is not working due to a bit of dirt. Or the fuel squirt is not very visible - I would not worry about it unless there is a definite flat spot on sudden acceleration.

Can anyone confirm those thoughts ?

Cheers,

Peter

The main symptom of a warped top cover is excessively rich mixture, especially when idling, with black smoke from the exhaust, coupled with high fuel consumption. There is also usually signs of leakage, both from the join at the top and from the throttle spindle.

One problem that needs to be noted, not related to the warping, is that with the widespread use of ethanol blends of petrol, the fuel tends to absorb water. If the vehicle is not used regularly, this can result in corrosion, usually in the carburetter bowl. The corrosion products have a horrible tendency to block or partly block the small passages and jets in the carburetter, and a filter does not help!

John

[the big fist]

The main symptom of a warped top cover is excessively rich mixture, especially when idling, with black smoke from the exhaust, coupled with high fuel consumption. There is also usually signs of leakage, both from the join at the top and from the throttle spindle.

One problem that needs to be noted, not related to the warping, is that with the widespread use of ethanol blends of petrol, the fuel tends to absorb water. If the vehicle is not used regularly, this can result in corrosion, usually in the carburetter bowl. The corrosion products have a horrible tendency to block or partly block the small passages and jets in the carburetter, and a filter does not help!

John

Thanks John,
You've always got great advice for me !
Car hasn't been driven in about 3 years so I am going to strip the carby.
Being a new re manufactured one it has barely any kms on it

[the big fist]

Quick update:
Pulled the carby and stripped it down. The bowl is full of orange crystals plus they all around the block under the top side of the carb. Looks like crystalised fuel from lack of use ? I recieved a kit today so will put that through it.
I also found that the floats look to have small cracks in it. What affect would this have if they werent cutting the fuel flow off ?

On another topic, I found that the mark I am using to set my timing is not where the 3 strips are with the number 6 at each end. So could my dizzy be out of phase or my timing light not connected to number 1 ? I am taking number one as the cylinder closest to the radiator.

Interesting....

[JDNSW]

Quick update:
Pulled the carby and stripped it down. The bowl is full of orange crystals plus they all around the block under the top side of the carb. Looks like crystalised fuel from lack of use ? I recieved a kit today so will put that through it.

Sounds as if you have found your carburetter problems! Make sure that all foreign material is removed everywhere in it.

I also found that the floats look to have small cracks in it. What affect would this have if they werent cutting the fuel flow off ?

Would cause rich running and probably hard starting. Try the traditional test for a leaky float - submerge the float in hot water - if there is a hole, the heat causes the air inside to expand and there will be a trail of bubbles from the leak. No bubbles, no leak, and it only "looks" to have small cracks.

On another topic, I found that the mark I am using to set my timing is not where the 3 strips are with the number 6 at each end. So could my dizzy be out of phase or my timing light not connected to number 1 ? I am taking number one as the cylinder closest to the radiator.

Interesting....

Timing may well be out. But if it runs at all, it is not all that far out. The factory setting for timing is done using static timing, with the points just opening at 4 degrees for unleaded. This will give correct timing, provided that the distibutor vacuum and centrifugal advance devices are working correctly. However, for best results, having set this, adjust carburetter idling speed and mixture for best idle, then make slight adjustments to the distributor timing while the engine is idling for highest idling speed. If there is a big increase in idling speed, readjust the carburetter and repeat.

Then take it for a drive, and check for preignition under load. If this is encountered, retard the ignition timing a couple of degrees at a time until you no longer have the problem. If there is a big change here (unlikely unless there is a problem with the vacuum advance), you may need to readjust the carburetter.

No. 1 is the front cylinder.

John

[the big fist]

The saga continues !

Very hard to start unless almost full choke. When it idles it chugs badly. Increase revs and it chugs and the whole motor shakes around.

Idle mixture screw all the way in, all the way out, no difference.
Looking down the throat there is fuel coming out from that main u shaped nozzle in the middle of the carb ?

I run electronic ignition (Petronix) and have their coil. It has a 12V supply. It gets quite hot as well. Off before running I have approx 3 Ohms across the terminals. After running about 4.1 Ohms.

Spark plugs are sooty but I don't want to replace until carb is sorted. They look to be sparking decently.

Sucking on vac tube moves the internals of the dizzy. Reconnected at idle and viewing timing I give a small rev but the timing doesnt move. ???

What do you guys think. Is the root of all this that the carby is still not 100% ? I reset the floats to 33mm. They are these foamy sort of things, not brass ones.

Help !

Cheers,

Peter

p.s
the O-ring in mine is in the bottom half of the carby around the throat. In the drawings I've seen it looks to be sitting in the neck on the emulsion block !?

[JDNSW]

If the plugs are sooty, then the mixture is too rich - problem is carburetter. From your description, I would say there is a leak somewhere in the carburetter. The most likely is the O-ring. This may be damaged, or incorrect. It seals between the emulsion block and the venturi, and may have been dispaced aaand pinched during assembly. Alternatively, it may not be being clamped. This is normally due to a warped top cover, but can be due to the screws holding the emulsion block stopping the cover from going fully home (because they are the wrong screws, burred, or wrong washers. Fit the top without the O-ring - it should sit flat all round. Then fit the O-ring aand refit - should sit up about a millimetre, but pull down easily with the two screws each side of the throat.

The other possible cause for the rich mixture is the float and needle valve are not cutting off fuel -this may be due to either faulty valve or floats sinking - check that they do float in petrol.

John

[the big fist]

Thanks John.
I checked while running and there is a fair bit of petrol droplets coming from that emulsion tube. I couldnt see any coming from around the join in the venturi. I put a new O ring in and it sat a tad high which pulled down with the screws. Before it was flat with the old O ring.
I put the float in water and it floated. It's like a solid foam float. I left it for ages and it still floated. If I put it in hot water and submerged it bubbles would come out. With the landy off if I prime the pump manually it gets to a point where it wont prime anymore, I thought that might mean the needle and seat are ok ?
I am really lost now. How could excess fuel get into that tube ?

Any help greatly appreciated. I took a video if that helps !

Cheers,

Peter

[JDNSW]

Thanks John.
I checked while running and there is a fair bit of petrol droplets coming from that emulsion tube. I couldnt see any coming from around the join in the venturi. I put a new O ring in and it sat a tad high which pulled down with the screws. Before it was flat with the old O ring.
I put the float in water and it floated. It's like a solid foam float. I left it for ages and it still floated. If I put it in hot water and submerged it bubbles would come out. With the landy off if I prime the pump manually it gets to a point where it wont prime anymore, I thought that might mean the needle and seat are ok ?
I am really lost now. How could excess fuel get into that tube ?

Any help greatly appreciated. I took a video if that helps !

Cheers,

Peter


If bubbles come from the float when submerged in hot water, this indicates that it has petrol in it. You said it was a foam float, but if it is absorbing petrol, this mean that while it may not be sinking, it is probably floating lower than it should. This will set the actual level of fuel higher than it should be (despite being set correctly), giving rich mixture, especially when idling.

Your action priming the fuel means the needle and seat are working at least to some extent, but does not necessarily mean that they are not leaking sufficiently to upset idling mixture.

John

[the big fist]

If bubbles come from the float when submerged in hot water, this indicates that it has petrol in it. You said it was a foam float, but if it is absorbing petrol, this mean that while it may not be sinking, it is probably floating lower than it should. This will set the actual level of fuel higher than it should be (despite being set correctly), giving rich mixture, especially when idling.

Your action priming the fuel means the needle and seat are working at least to some extent, but does not necessarily mean that they are not leaking sufficiently to upset idling mixture.

John

Thanks John,
That would make sense. After I rebuilt it I reset the float level as it was at roughly 5mm out of where it should be. I have the original Zenith but it has plastic floats. I may test them. I also noticed under the seat fitting there was 2 quite thick washers shimming it up.

Hopefully I wont sound like too much of an idiot but why would the fuel be coming out from the main jet / emulsion tube at idle ?

Thanks greatly,

Peter


Also,
I found this on the net which was the fix to my problem on someone elses LR.


It turned out to be a plugged jet in the idle system. Since the idle system wasn't providing any fuel, I had the idle rpm screw turned in to make it run and it was activating the main jet circuit and dumping loads of fuel in. This idle jet has a ball valve, so you can't see thru it.
The only way I found out it was plugged was to poke a thin copper wire thru it.


On mine the idle rpm stop is also all the way in otherwise it just doesnt run.
Strange thing is that the carb was like this from new. Damn Indian copy. I wonder if I should check this valve as well !

[the big fist]

Far out, this is driving me nuts. Last night Iplayed with the float level. Filled the bowl first from normal idle running then pulled the top of the carb off. Fuel was about level with the O Ring. I lowered the float height by about 5 mm, reinstalled and ran at idle again. Ran the same. Took the top off and fuel level was about lower than the O ring aroudn the base of the casting. So I guess the float works ?

Played around a fair bit and found that my "idle" is infact very very light throttle. Found the dlow idle jet has a ball valve in it which was clogged. I also found that in my wisdom many moons ago I must have plugged the port that runs to the idle mixture port with O ring as per one of the dodgey zenith fixes.
So took it to work today and stripped it again. Lapped it again, new gaskets, new jets, reset floats and reassembled. Only issue is being a copy, the economy device diaphragm wouldn't fit so had to use the old one.

Refit this afternoon and the car starts easier and idles at half choke.

HOWEVER. It is still chugging roughly, all through the rev range, only on deceleration does the engine sound smooth. I checked the leads, all have low resistance. My last guess is the plugs ? Could the old fouled plugs be causing this chugging. It's really driving me nuts !

Any help appreciated.

Thanks.

*edit*
Great, just found this video and that is exactly how it sounds:
Land Rover Series IIA driving - YouTube

[JDNSW]

That sounds as if it is missing regularly, in other words, one cylinder is not working. This could be either a spark plug, or a high tension lead, or lost compression on that cylinder, probably due to a stuck valve or a piece of carbon on the valve seat. This last is the easiest to check - just turn it over by hand using the crank - all four compressions should feel about the same.

To confirm that it is a regular miss on one cylinder, with the engine idling, remove plug leads one at a time - if this is the problem, you should find one makes no difference.

When you find the one, try swapping the plug to another cylinder and see if it makes a difference. If it does not, try removing the complete plug lead and swapping it for another cylinder. Obviously, if it is a plug, change them all, and if it is a lead change them all.

There are two other, less likely possibilities for the sound. The first should be easy to find - an exhaust manifold leak - look for loose nuts on the studs holding it to the head, and a leak between it and the head, or a crack in the manifold casting, probably on the leg to either 1 or 4. The other one is that one cylinder is firing, but less well than the others. This will be due to low compression, either because of stuck rings or a burnt valve, and may not show up on the crank test - needs a proper compression check with a gauge.

Hope this helps. My best guess is the high tension leads (been there!).

John

[russellrovers]

Thanks for the info.
I wound the idle mixture screw in all the way tonight and it just kept running, no change, I guess that's a sign it's warped ?

Also I couldn't see any squirt of fuel when I jabbed the throtle so i think the accelerator jet is blocked or pump stuffed.

Can anyone confirm those thoughts ?

Cheers,

Peter
hi peter i have a solex b40-----ha105 date stamped lg 59 take from my s2 now gone to land rover heaven jim

[the big fist]

Thanks Russell but it's all sorted now.

I finally got time to have a fiddle on the land rover. After being dumb founded why it would not start at all I realised it had been running so rich that it had drained all 20L of fuel in just idling ! New fuel in and fired her up with her chugg chugg chugg idle. Pulled number 2 plug lead and straight way no change. Weird I thought and flukey that it was the first I pulled. Tried the others and they all stalled the engine. Pulled the plug and the electrode bit where the lead plugs on had undone ! So I put a new plug in, fired her up and she idles silky smooth. Idles at 550, set the timing to 6deg with vac connected and everything seems great. Revs up smooth. There's an occasional miss on cylinder 1 which actually caused my timing light to not show the timing marks. Bit strange, like it fired at the wrong time or something ?

New problem now though so I'll start a new thread.

Big thanks to JDNSW who is always replying to my problem threads !

Cheers,

Peter