Zenith Carb, new. (any good?)

[ashhhhh]

Hey all

Has anyone purchased a new Zenith Carb?
Ive heard some of the new ones are poorly made.

Im looking at getting one from CLR - Land Rover Series 3 Zenith Carby - Brand New - eBay Engine Parts, Engines, Components, Car Parts, Accessories, Cars, Bikes, Boats. (end time 01-Jul-10 06:47:36 AEST) (http://cgi.ebay.com.au/Land-Rover-Series-3-Zenith-Carby-Brand-New-/220614936060?cmd=ViewItem&pt=AU_Car_Parts_Accessories&hash=item335dacc5fc#ht_500wt_928)

The price is reasonable I reckon.

Cheers
Ash

[JDNSW]

I have heard that some of the new ones are more prone to having the top warp, but I have yet to hear of a specific person who has had this happen.

That price is about what you would expect to pay for one.

John

[peterg1001]

It might be worth your while to look at ERC2886 CARBURETTOR ZENITH TYPE | shop | www.lrseries.com | L. R. Series (http://www.lrseries.com/shop/product/listing/4971/ERC2886-CARBURETTOR-ZENITH-TYPE.html), which works out to $A105 plus shipping.

The Zenith 36IV is also available from other overseas sellers, but these are the cheapest, and the carbs all seem to be the Indian made models.

There's nothing kicking around on ebay other than Gary's offering - I've got a permanent search set up.

Peter

[ashhhhh]

Yeah right thats a fair bit cheaper!

Ive gone with Gary's though - it will get here faster and if its rubbish I can go back to him. :cool:

Ill post the results when I get it.

[ashhhhh]

So I got the carb today, fitted this arvo - looks good so far. :cool:
I haven't driven it yet but the idle is much more steady and throttle response is a lot better.

Just a question about the mixture on these carbs though...
How do you tell when the mix is set right?
The manual basically says "turn until best idle speed"
What I always find is that there is a massive range (many turns) between the poor running "in" and poor running "out" positions... :confused:

Any advice?

[JDNSW]

So I got the carb today, fitted this arvo - looks good so far. :cool:
I haven't driven it yet but the idle is much more steady and throttle response is a lot better.

Just a question about the mixture on these carbs though...
How do you tell when the mix is set right?
The manual basically says "turn until best idle speed"
What I always find is that there is a massive range (many turns) between the poor running "in" and poor running "out" positions... :confused:

Any advice?

If this is the case, the most likely problem is that the idle speed is set too high. This should be 500rpm, about half the idling speed on modern engines. As you get closer to the correct idling mixture, reduce the idling speed to keep it close to that figure. If you have no easy way of determining the actual speed, reduce the idling speed to as low as it will keep running to adjust the mixture, and keep reducing it when it goes up as the mixture gets closer. (If the idling speed is too high, only a small part of the mixture going into the engine comes from the idling system, so of course, changing the mixture on this makes little difference)

Ensure that the throttle linkage is not limiting the idle speed, in particular the spring on the bell crank should push the linkage against the idle stop.

John

[dfendr]

Bought Carby from the above link in U.K.
Arrived yesterday ........genuine Britpart
Fitted today and engine now Purrs :):):)

[ashhhhh]

Just wondering, which way do you go on the mix screw to make it richer?
In or out?

[JDNSW]

Just wondering, which way do you go on the mix screw to make it richer?
In or out?

In, from memory - it adjusts an air bleed.

John

[ashhhhh]

OK thanks.
I may still be having some rich running issues with the new carb....im still confused by the idle adjustment.. :(

If wound in too far it stalls quite quickly but when wound out it seems to be 4 or 5 full turns before anything happens....

Im used to having a narrower band (motorbikes) so such number of turns make me think something is not right.

Idle speed it as low as it can be so im sure it is slow enough to be accurate with the mix.

[ashhhhh]

Well ive just been reading the Zenith manual and it states that clockwise (in) on the mixture screw weakens it?

[Timj]

Hi Ash,

It is usually helpful to have a tacho but it can be done by ear. If you screw it in until it is just starting to die then back off about 1/2 to 1 turn it should run smoothly. If you have a tacho you back it off until the revs are at their highest then usually put it back in about 1/4 of a turn from there. Timing has a very critical effect on idle speed and the perfect mixture so it is really a matter of adjusting everything then checking and resetting the timing, then adjusting everything again, then checking and resetting timing ..........., until you get it perfect. also though John is right about the idle speed for early motors the later ones with pollution control recommend an idle speed of 800 rpm. If the pollution control has been removed or blocked, which is very common, then you can lower it down again. I still tend to only go to about 600. Later motors also have a different timing setting to the earlier ones. I found though that if I used the timing and idle speed settings according to the later motor specs that i could not get the carbie to work properly so I advanced the timing and then I could get the carbie set right. Basically, play with it, drive it. and get it to where you are happy with the set up (play around anywhere from 500 - 800 rpm and timing anywhere from 6 before to 6 after but probably as far towards the required after as you can). Test drive to make sure it is not knocking under load if you have it fairly far advanced.

Hope that helps :).

TimJ.

[Timj]

and yes, turning the mixture screw in makes it leaner.

[ashhhhh]

Thanks a lot Tim, great info.

Just on the timing. If I set 6 BTDC I feel it is very down on power, it gets even worse if you retard it any further than that.

The best running I have found is pretty far advanced, it must be like 12 degrees at least!
I set using a strobe.

I'm pretty sure this is doing bad things to the mixture but cant see any way around it.

Whats your take on this?

[101RRS]

The best running I have found is pretty far advanced, it must be like 12 degrees at least!
I set using a strobe.



I assume you have disconnected the vacuum advance and blocked the pipe to the inlet manifold and are testing at about 600-800 rpm?

[ashhhhh]

Yep, sure have.

[Timj]

Hi Ash,

Mine is a 78 and has a plate in the engine bay that specifies timing and idle speed as 6 deg ATDC and idle speed as 800 rpm. I am assuming that mine is an 8:1 compression engine but haven't been able to verify that completely. There are a number of timing marks and if you are looking from the front of the engine ATDC will be to the right and BTDC to the left. When you rev the engine it will advance and that means further before top dead centre. Aplogies if I sound like I am repeating things but it sounded like you had it the wrong way round from your post above. I have mine set pretty much on TDC as that seems to work. If I put it on the 6 after that it is supposed to be and the revs at 800 it will not even continue to idle, it just dies, but all the pollution control was taken off before I owned it. I think if you put it too far advanced then it will knock under heavy acceleration. Also make sure that your points are set properly before you set timing. Use a dwell gauge while running or feeler gauges while not.

TimJ.

[Timj]

Also I looked at the plate before and it said to set with the vacuum line connected but that differs from what I have always done. That is for full pollution control though.

Timj.

[ashhhhh]

No thats fine, probably my description was just bad.
I also have the setup with a jagged set of timing pointers. As you say ATDC on the right and BTDC on the left when looking down on it from the front.

If I set to 6 BTDC (left most marker) its not good.
I have to go FURTHER left than that marker, maybe about 20mm further!
It doesn't run on, it doesn't detonate.
Im starting to think my timing chain is stretched or something??

It generally runs well expect that the mixture doesn't seem to adjust quite as I think it should. (exhaust is a bit "puffy")

Has anyone got an audio clip so I can hear what it SHOULD sound like?
I dont know anyone else who owns one locally so I have no comparison.

[ashhhhh]

By the way my plate gives the same info, it runs like crap at those settings... :confused:

Are you using a strobe for TDC or static?

[ashhhhh]

Well....I gave it a full tune today and found a couple of issues.

First and worst, the vacuum advance was not working....
One of the PO's had replaced the bolt which hold the points assembly in place with one that was too long, the breaker plate was jammed as a result and did not rotate at all! :eek:
Lubed it all up, filed the bolt down - vac advance NOW works. :cool:
Set the points while I was there.

Second, choke plate was not fully closing which explains why its so hard to start on a freezing cold morning.
Fixed.

Third, valve clearances were fairly off.
Strange because I only did them about a month ago.
Anyway....fixed.

Fourth, the dissy cap had cracked through where one of the clips goes on.
Cheap crap from a certain 4x4 shop....its only a month old. :mad:
Filled and shaped it back together with Devcon. (until I can order another)
Fixed.

After all that I redid the timing, I just advanced it until it sounded nice.
Im assuming the timing marks are no longer accurate for whatever reason (chain stretch?)
If they were it would be set about 12 degrees BTDC??
Does not pink on hills or at full throttle, doesn't run on.

Set the carby.

It runs like a dreeeeam now!
Much smoother, much more pull at low revs, really happy. :D