Rebuilt engine in and running - need help with the tuning

[Ozdunc]

Morning chaps,

Got the engine running over the weekend, it idles OK but its down on power under load. So much so that you really need to rev it to stop it stalling as you lift the clutch. It seems to drive along ok under steady revs but put your foot down to accelerate it seems to bog down, hesitate and then accelerate.

It's a 8:1 compression engine running new NGK BR5ES plugs set at 0.8mm, plugs look good, distributor is electronic set at 6BTDC. Leads are new - brand I think is FML, coil is old but was working fine (ECHLIN 80).
Fuel pump is new (and primed really quickly), as is the filter (fuel has been in the tank about 3months).
Carb is new and s a Zenith 361V, air filter is stock oil bath. Idle is probably higher than 500, maybe 6-700 hard to tell but it seems higher than the old idle.
I've adjusted the low volume screw to give what I think feels/sounds like the smoothest running, but it does seem to resonate though the car at times (although that could be due to the exhaust being hard up against the gearbox mount atm). The low volume screw doesn't seem to be that sensitive, I seem to have to turn it a fair bit (1-2 turns) to notice any difference, and if anything I'd think I'm more likely to be running rich than lean on idle.

Can someone give me an idea of where to be looking to sort this problem out.
I have the old carb, and everything else to swap in and out for trouble shooting but would appreciate a nudge in the right direction.

I think once I get this sorted its going to be awesome!!!:D

Cheers

[Ozdunc]

Just realised I should have put this in the Series forum.

Sorry.

[Tank]

You said the timing is set at 6 BTDC, how did you achieve this it would be hard to do if you can't get it to idle, also you need the dissy vac hose diconnected and blocked off at the source, regards Frank.

[Blknight.aus]

accelerator pump and linkage adjustment

[Ozdunc]

Frank: it idles fine. I set the timing with a timing light but the vac advance tube was connected.
Dave: how do I change the accelerator pump and linkage on a Zenith? It's brand new, will I need to strip the carb?

[Blknight.aus]

thats the sort of question that indicates that its something you probably dont want to mess with...

My Zenith is driving me to take up zymurgy (http://www.s2cforum.com/archives/index.php'topic=9157.0)

that link leads you jpegs of the docs for it

[vnx205]

Are you sure the timing isn't one tooth retarded?

In that situation, it tends to start easily and idle well, but have no power.

[Ozdunc]

Thanks Dave,

You're right I'd rather not have to take the carb apart if I don't have to. I have the green bible if necessary.
In that link they mention a fix with a o ring on a port but the link takes you to a Dutch website advertising Ukrainian ladies!
Any idea what the fix was, or which port was affected?

Cheers

[ian4002000]

Wheres the link ? I like Ukranian ladies ...

[Blknight.aus]

the linked page should have the pages from the green bible.

Land Rover FAQ - Repair & Maintenance - Series - Engine - Zenith Fix (http://www.lrfaq.org/Series/FAQ.S.carb.zenith.fix.html)

is the link that works to a good set of instructions on lapping the housings.

[Ozdunc]

Thanks gents, for punting me in the right direction.

I thought I'd go back to basics, so I warmed the engine up.
Set the timing, with my thumb blocking the vacuum advance tube, by ear.
Seems to be smoothest about 4-5deg BTDC. Its 8:1 on 98 RON.
I also changed the plug and coil leads to my old TopGun ones (cause the other FML ones just dont feel right when you plug them on)

I then dialed in the low speed volume screw until its started to putt occasionally out of the exhaust, then dialled it out 1/4-1/2 a turn.

After that I checked all the bolts on the inlet manifold, the carb adaptor, and holding the carb to the adaptor, some were fairly lightly tightened down so I nipped them up. On the carb itself I gave the screws holding the emulsion plate to the float body a 1/4 turn, (at prob 5Nm) and tightened the 3 little screw on the cover for the economy diaphragm (they were really only finger tight, I tightened them sequentially to about 3-4Nm as well).

I checked the accelerator pump and linkage by pulling the inlet hose off the top of the carby and opening the throttle, you could hear the fuel coming in when the throttle was snapped open. I couldn't see any fuel, are you meant to do this test with the engine running or stationary? But the revs rose instantly.
There's no play in linkage at all, but I did notice on both my Zeniths the linkage is connected in the long throw position, which is supposedly for colder climates. Would that make any difference to throttle response?

Put the air filter back on and took it for a drive, a big, big improvement.
Its still a little hesitant if you come up to a junction in 2nd at walking pace, then accelerate to say half throttle, but overall drivability is pretty good. Its certainly not threatening to stall on acceleration like it was yesterday.
I also put into 3rd at walking pace and turned into a street with a reasonable incline and pressed down on the throttle, whilst it lugged it showed no signs of stalling or fuel starvation.

I think the crankshaft timing is OK as it seems to be running fine at wider throttle openings, although I've probably only done a maximum of 2kms on the road since firing it up for the first time.

Maybe I just need to take it for a decent drive to settle things down and see if that hesitancy goes as things free up. What do you think?

[Tank]

Frank: it idles fine. I set the timing with a timing light but the vac advance tube was connected.
Dave: how do I change the accelerator pump and linkage on a Zenith? It's brand new, will I need to strip the carb?
Sorry, i misread the bit about Idling when you said it was stalling, anyway try removing and blocking the dissy vac. hose and see what your timing light says and see if it goes better without the oil bath air filter, good luck, Regards Frank.
I posted this without seeing your last post, would also check if any of the valve clearances are too tight. I seem to remember that valve/diagphram thingy on the side of the carb causing problems. Regards Frank.

[Ozdunc]

As I hate threads that don't have a conclusion...

Rather than keep trying to tinker, I thought I'd just fit the old carb on in place of the new one to either confirm or refute the new carb as the issue.

Popped the old one on, fired it up and hey presto, runs like a charm.

I'll strip the new one down and rebuild it at some point just for fun.

Does anyone know what the jet specs should be for a Zenith 361V, so I can check the carb is actually setup for the 2.25 engine?