Zenith Carbs Wanted

[lord_rootes]

Hi,
Does anyone have a good set of Zenith 36 WIP 2 carbs they would like to sell?
I'm having trouble (and so is my mechanic) getting the WIA's that are on my Series II Alpine to run properly. I had the same problem with my Rapier and when I switched it to the WIP's it ran fine. Some folks have told me that the WIA's were jetted for a different type of air filter (oil bath) that the Rapiers used hence the reason they wouldn't run properly with the birds nest type of filters (which the previous owner had put on my Rapier as well).
Most of the literature I've read seems to indicate that only WIP's were used on the Series II Alpines but I know a few members of this forum have stated they have the WIA's and they work fine for them. I was however recently sent a Zenith catalogue listing which shows the WIA's were used on some Series II cars so I guess Zenith would know.
Anyhow I'm thinking if I can find a good set of WIP's I might give them a try.
Thanks,
Alan
BTW the problem I'm having is that they just won't idle well. The car is fine while accellerating and driving but as soon as you slow down to almost a stop it wants to stall so you have to heel and toe it on the brake and gas to keep it going. once you give the gas it will idle but not great.

 

[AlpineII]

Allan,
I am running a rebuilt set of WIA's after finding the threads for the fuel line to the front carb were stripped. I had several others sets of WIP's but they all needed rebuilding and the WIA's were in very good shape and needed less work.

I also had a problem with idle but found they were quite responsive to drive with. It turned out the needle valve was not seating properly on the rear carb and it was flooding out. Played around a lot with the seat and the float and finally got it all running ok. Haven't had a problem since.

I have oil bath set up but run the birds nest air filters and all has been fine since.

 

[lord_rootes]

Thanks Eddie,
Maybe I'll have to dig a little deeper and play around with them a bit more, look into the areas you have suggested. I'm no expert but I've found in the past that with these old Rootesmobiles I can be just as successful as my mechanic in diagnosing problems (with the help of folks like youself on forums like this).
Other than the fact that they won't idle well and will accept virtually no choke (makes it hard to warm up the car) the car goes like stink once you're moving. Much faster than my Rapier which has the same engine (obvious I guess but still surprised me how much pep it has).

 

[bernd_st]

Actually and according to all literature I have (incl. an original Zenith parts book) WIA´s were never used on SII´s. They came up with Alpine SIII GT´s and Rapier III´s. As far as shown in that documentation all were jetted to just accept oil bath or dry element air filter.

Would check the actual 4 digit code stamped on the float chamber cover at first. If the code is 1695 F/R or 1720 F/R they are WIA-2s and came from Rapier SIII. If you read 1763 F/R they come from a Rapier SIIIa. The main jets are either 115 or 117 which is too small to work with the "birdnest" airfilter. Generally would go for a bigger main jet from a WIP set for example 130.

However what puzzles me is the strange idle and choke behaviour. Does it die when you pull the choke ? Another quite common failure could be an air leak coming from either worn spindles or loose carb body screws.

Bernd

P.S. I´m rebuilding the early Zenith sets as a hobby but think shipping them over the pond to Germany is no meaning. For me they are the best carb setup ever used on the Alpine. If well rebuild or even slightly tuned they make the early engines fly...

 

[lgurley]

link

I am a novice to carb adjustment. My cars all have the Stromberg 150 carbs. What is he difference between these type of carbs.
I found this link that might help someone.
http://www.enfostuff.com/carbs/carburetor-zenith-wia-2-wip-2.html

 

[SIVAllan]

Actually and according to all literature I have (incl. an original Zenith parts book) WIA´s were never used on SII´s. They came up with Alpine SIII GT´s and Rapier III´s. As far as shown in that documentation all were jetted to just accept oil bath or dry element air filter.
.

Hi,

I have a Chilton's repair & tuneup guide Sunbeam-Hillman (1969) that lists the following for Alpine II:

36WIA2
36WIP2
36WIP3

There is no way for me to know if the Chilton's was correct, but the listing included 3 diff Zeniths.

Allan

 

[lord_rootes]

Thanks for the info, Bernd. I am going to go out to the garage and check that out.
It's interesting that you mention that the WIAs were not used on the Series II because that's what my literature says as well. I did however recieve a Zenith parts list from someone on this list and it listed WIAs as being fitted to Series II cars. I think it also mentioned WIPs as being fiitted as well.
As far as my set goes you can only pull out the choke very slightly or else it will stall.
Thanks,

Actually and according to all literature I have (incl. an original Zenith parts book) WIA´s were never used on SII´s. They came up with Alpine SIII GT´s and Rapier III´s. As far as shown in that documentation all were jetted to just accept oil bath or dry element air filter.

Would check the actual 4 digit code stamped on the float chamber cover at first. If the code is 1695 F/R or 1720 F/R they are WIA-2s and came from Rapier SIII. If you read 1763 F/R they come from a Rapier SIIIa. The main jets are either 115 or 117 which is too small to work with the "birdnest" airfilter. Generally would go for a bigger main jet from a WIP set for example 130.

However what puzzles me is the strange idle and choke behaviour. Does it die when you pull the choke ? Another quite common failure could be an air leak coming from either worn spindles or loose carb body screws.

Bernd

P.S. I´m rebuilding the early Zenith sets as a hobby but think shipping them over the pond to Germany is no meaning. For me they are the best carb setup ever used on the Alpine. If well rebuild or even slightly tuned they make the early engines fly...

 

[lord_rootes]

Thanks for the link, Larry.
The difference between the WIA and WIP carbs I believe is that the WIA has an accellerator pump on it. I could be wrong about that though as I'm a novice at this as well. I'm sure someone else will know.

I am a novice to carb adjustment. My cars all have the Stromberg 150 carbs. What is he difference between these type of carbs.
I found this link that might help someone.
http://www.enfostuff.com/carbs/carburetor-zenith-wia-2-wip-2.html

 

[lord_rootes]

That goes along with the Zenith parts list I recieved. I guess they did use all three at various times. Why I don't know. Maybe using up old stock before the switched to the Strombergs?

Hi,

I have a Chilton's repair & tuneup guide Sunbeam-Hillman (1969) that lists the following for Alpine II:

36WIA2
36WIP2
36WIP3

There is no way for me to know if the Chilton's was correct, but the listing included 3 diff Zeniths.

Allan

 

[lord_rootes]

I looked at my WIA carbs on my Alpine and the numbers on it are C 1732.

 

[bernd_st]

I looked at my WIA carbs on my Alpine and the numbers on it are C 1732.

Thanks will check what application 1732´s were originally build for.

To Igurley: Zenith has a completely different design compared to Stromberg 150´s. The latter ones are called "constant velocity" carbs which make a carb piston/needle assy rise depending on the actual suction level at the inlets. So the mixture is always depending on needle shape vs. airflow. They are quite similar to SU´s -only difference is Strombergs have an additional rubber diaphragm which is told to hold vacuum better. Spring and damper oil helps to achieve/keep even piston motion.

For the Zeniths we are talking about a "normal type" carb featuring a Venturi tube/fixed jet in the center. For that they directly compare with Webers (single tube) however with bit lower complexity. Also and that can be regarded the biggest advantage - they have an accelarator pump which enriches the mixture when it is badly needed, i.e. under hard acceleration. After all the fuel economy is told to be better while on the Stromberg the piston/needle always needs a bit time to find the optimum position.

Don´t get me wrong Stromberg DO WORK when they are in proper tune but on the other hand they do lack a certain lifelyness and ultimate power. So after all would recommend the Zeniths. Another proof is that Rootes won the Thermal efficiency reward at LeMans with that setup...

 

[lord_rootes]

Thanks, Bernd.

Alan

 

[puff4]

Zenith has a completely different design compared to Stromberg 150´s. The latter ones are called "constant velocity" carbs which make a carb piston/needle assy rise depending on the actual suction level at the inlets. So the mixture is always depending on needle shape vs. airflow. They are quite similar to SU´s -only difference is Strombergs have an additional rubber diaphragm which is told to hold vacuum better. Spring and damper oil helps to achieve/keep even piston motion.

Actually they are not "constant velocity" but "constant depression" (hence the name "150CD"). The constant depression refers to the vacuum over the orifice where the fuel needle comes up (the 'jet'). As the throttle plate is opened vacuum passes from a small hole up into the top of the bell chamber, lifting the air valve piston and raising the fuel needle out of the jet. Since the needle is tapered, the higher you raise it, the more fuel comes in, and the higher the air valve piston goes, the more air is allowed to pass. As the throttle plate is opened even wider, more vacuum is allowed to pass, raising the needle still higher and allowing more air and fuel to enter the engine. It is a highly accurate way of metering fuel/air to an engine, and when tuned properly offers years of trouble-free service. The tricky bit, of course, is getting them right in the first place. Also, they are very difficult to tune if the vacuum source (the intake manifold) is subject to problems, since any disturbance of the vacuum will directly affect the running of the carburettors, particularly on idle. So for example a vacuum leak is a nightmare with Zenith-Strombergs and S.U.'s - you'll never be able to tune them until it's tracked down and eliminated. Also, if you have a lumpy camshaft, that will induce intake pulsing and foul up any sort of CD carb.

The spring and damper do indeed regulate the piston, but the oil in the piston chamber serves to create what in other cars is an 'accelerator pump'... essentially, when the throttle is opened quickly the oil momentarily restricts upward movement of the air valve piston, increasing the vacuum over the jet and temporarily increasing the air/fuel ratio, which provides an extra shot of petrol for acceleration. So, if you need a higher amount of accelerator pump, go with a thicker oil. Most folks use a very light oil in the dashpots - I use "Marvel Mystery Oil" and it works great.

I've found that tuning is best accomplished by first ensuring that the carburettor float heights are exactly correct - this is a critical step and often overlooked. Once done, then fill the dashpots with the proper oil, set or check all the other adjustments (timing, dwell, plugs, etc.) and warm up the motor. Then carefully loosen the throttle connector between the carbs and adjust the idle screws to balance the air flow in each carb (best to use a manometer such as a UniSyn). Once they are exactly balanced, lock the throttle connector and recheck them. If that's all OK then next you install a pair of Gunson ColorTune plugs - one in #1 and one in #4 - and adjust the fuel metering nut (below the carbs in the centre of the fuel bowl) until you get both ColorTune plugs showing a nice blue flame. Finally, check and adjust the choke cam gap if needed. That's it... and you're good for many years of happy motoring.

 

[bernd_st]

Puff´s comprehensive explanation is even better than mine. Of course I meant "constant depression" rather than "velocity". However whatever you do to the 150 CD´s you´ll never achieve the performance / responsiveness of Zenith´s. At least that´s my actual experience.

Coming back to the original question . Checked my partsbook for 36 WIP2 1732 F/R´s and result is as follows:

Original application : 1600cc SII Export models w Air cleaner , Late 60-61

Choke tube: 28mm
Main: 112
Idle: 45
High Speed bleed: 60
Pump discharge: 70
Power jet 57

So you actually have WIP´s (if top cover has never been exchanged).
Just to make sure you should check that there is only one idle mixture adjustment screw.

Looking at the jetting and especially the small size main would recommend to go for 130 when using "birdnest" type air filters. For idle you should go for 50.

Think with that jetting you should be at least "in the ballpark". But make sure no other faults such as loose carb bottom or worn spindles inhibit proper function.

Cheers

 

[65beam]

150 carbs

puff 4,
i'm glad i don't have to go thru all that adjustment with the 150's on my 69 GT .

 

[lord_rootes]

Hi Bernd,
Thanks for looking that up.
I'm pretty sure these are WIAs not just because it says so on top but because the idle adjustment screw is on the right hand side (looking from front of car) as opposed to the WIPs I have on my Rapier which have the adjustment screws on the left side (hard to adjust).
Also didn't only the WIAs have the accellerator pump piston on them? I know the housing is there on both carbs (must be empty on the WIPs) and I haven't opened these up to look at them but that should verify it shouldn't it?
Either way I'm going to have to dig a little deeper and try to figure out why they're not idling well. It'll give me an excuse to learn more about them.

Thanks ,
Alan

Puff´s comprehensive explanation is even better than mine. Of course I meant "constant depression" rather than "velocity". However whatever you do to the 150 CD´s you´ll never achieve the performance / responsiveness of Zenith´s. At least that´s my actual experience.

Coming back to the original question . Checked my partsbook for 36 WIP2 1732 F/R´s and result is as follows:

Original application : 1600cc SII Export models w Air cleaner , Late 60-61

Choke tube: 28mm
Main: 112
Idle: 45
High Speed bleed: 60
Pump discharge: 70
Power jet 57

So you actually have WIP´s (if top cover has never been exchanged).
Just to make sure you should check that there is only one idle mixture adjustment screw.

Looking at the jetting and especially the small size main would recommend to go for 130 when using "birdnest" type air filters. For idle you should go for 50.

Think with that jetting you should be at least "in the ballpark". But make sure no other faults such as loose carb bottom or worn spindles inhibit proper function.

Cheers

 

[puff4]

puff 4,
i'm glad i don't have to go thru all that adjustment with the 150's on my 69 GT .

Hmm. Well, not sure how your 150's are any different than mine, but in actuality you only have to adjust them once - they pretty much stay set up for many years thereafter.

 

[65beam]

carbs

puff 4
when rootes switched to the fastback , they also started using the 150 emmision carbs that have no mixture adjustment like the earlier carbs . they do tend to run on the lean side .

 

[lord_rootes]

Here's something interesting I found on the Victoria British website, Sunbeam Alpine catalogue page 36.
"Series 1 and 2 cars that were fitted with a paper element air filter were fitted with 1 WIP carburetor and 1 WIA carburetor. Cars with the wire gauze cleaner had two WIP carburetors"
Anyone ever heard of that?
It's funny because a friend of mine had a set of Zeniths mounted on a manifold in his parts bin and I was looking at it one day and noticed that it had one WIA and one WIP. I just figured a previous owner had put the set together not realizing they were different. Perhaps not.
Anyhow I'm now thinking of putting a single downdraft Weber on the car. I have an old one that came with the extra parts included with my Alpine and another friend has a manifold that will work. There is also someone on Ebay selling a Weber conversion kit if I decide I'd rather go with a completely new unit (which for someone of limited mechanical knowledge might be the right decision).
Thanks,
Alan

 

[Gary T]

Zenith Carburetors WIA and WIP

According to the Work Shop Manual page 15, the following carbs and air cleaners were provided for Alpines.

S-I Gauze type air cleaner with 36WIP2
S-II Gauze type air cleaner with 36WIP2 or 36WIP3
S-II Dry Type air cleaner with 36WIP2 or 36WIP3
S-III Standard Gauze type air cleaner with 36WIP3
S-III GT Dry Type air cleaner with 36WIA3

Rapier III-IIIA 36WIA2 or 36WIA3

So this information indicates that only the Alpine III GT had WIA3 carburetors and with a Dry Type Air Cleaner.

Over the years carburetors and air cleaners could have been switched, but this is the current information from Rootes.

The difference is the bypass valve and jet assembly shown on page 31 for WIA carburetors only.