Pointers On Driving A 30's Jowett

[george garside]

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I also have another question to ask, I seem to have a strange, vibrational clunking noise coming from the gearbox, I can feel it when I push the clutch towards the floor, and hear it a little bit when its relased. I thought it was the gearbox mounts not being tight enough, but after tightening all of that. Its still making the noise. Its continueous noise but not constant, i dont really know how to describe it but say if you have a circle and it rotates, and it gets to a few points and clunks and vibrates. Ive had the top cover off the gear box, checked levels and things. But still not sure what I would be looking for.[/quote]

have you checked the clutch thrust race. it should spin freely by hand and not make any noise when being spun. The thrust surface that presses on the clutch toggle leavers should not wobble about relative to the outer bearing housing. If it is noisy when spun try some engine oil via oilcan - a few drops of oil in/on 'joint' between bearing housing & thrust plate (that pushes toggle leavers) then spin bearing by hand to work oil in. Also check clearanc is correct and dead even on all three clutch toggle levers.

In theeory the gearbox should not be the culprit as when clutch pedal is pressed there is no drive to the box & therefore should be no noise! On the other hand noise & thumps as clutch is released & drive engaged may indicate gearbox ? bearing probs. similarly clutch 'judder' would only occur as clutch is being engaged i.e. pedal released.
george

My thinking behind this is that the noise occurs when clutch pressed which is when thrust bearing is in use - when clutch pedel not pressed thrust bearing is not working for its living so shouldn't make any noise.

[AlanBartlett]

Thanks George, it is the thrust bearing, its slightly catching on the toggle levers as the flywheel spins its just catching and slowly spinning the bearing. But other than that it spins freely making a lil noise, im sure a few drops of oil will cure that.

Another thing, What is the correct settings for the later carb, i know the mixture screw, how about the throttle screw? or anything else. I'm not sure its running as smooth as it could be I've already adjusted the dizzy a couple times to try and get it right. But with the carb something just doesnt seem right, if you put the throttle hard down sometimes it kinda pops back and makes a bubble in water type sound. I'll video it to give a better picture.

[ian Howell]

Alan: -

I have similar problems with my carb - although obviously this is not under 'road' conditions ! (Yet!).

I think we need to look at what - if anything - can be adjusted in the compensator jet arrangement and possibly the petrol level as set by the float needle valve, and here I have some ideas-

I have seen references to turning over the toggle levers on the float chamber cover if they are worn flat, and it is apparently OK to re-solder the little collar on the needle valve that the float arms work on, but I would hesitate to do this until I knew which way to go. So here are a couple of udooable ideas: -

First, float the float in petrol and note the level when upright.

Then, to raise the petrol level put a few lead shots in the hollow on the top of the float and refit the lid to the float chamber. These could be added to or subtracted from until things seem 'right'. Then see where the float NOW floats in petrol and move the collar on the needle accordingly.

Similarly, to lower the petrol level, make some washers out of cork jointing sheet and put them in the hollow UNDER the float. Then adjust as above.

This way there are no tricky soldering or unsoldering jobs until you know what is needed, and if you find the problem IS elsewhere, then no irreversible changes have been made to the original arrangement.

Any comments from wiser men?

[AlanBartlett]

Hello Ian,

According to the Pitmans Jowett book
Quote
Popping Back in Carburettor

When the car gets away badly and pooping back occurs in the caburettor when accelerating, the compensating jet is too small.

If popping back occurs at irregualr intervals and the engine has little power and cannot drive the car at hight speed, fit a larger main jet until these explosions in the inlet pipe dissapear, and then test un the right jet has been found. Popping back is very often due to defective sparking plugs or valves not closing properly. Popping back in the silencer when coasting down hills is a sign the slow running mixture is too weak, caused by the slow running jet being choked and can be remdied by cleaning.


Now I'm not sure what they mean by fitting a larger jet, I mean are they still available or still made? And as for the sparking plugs and valves, my plugs are new, and all valves have been set up for clearance many times and ground in also.

As you say Ian any Wise men care to comment?

[ian Howell]

Alan: -

We must expect that the car was running OK when your father used it, so the effects should be adjustable without resorting to new jets etc.

Wait for the wise men to respond!

[AlanBartlett]

Hi Ian,

This is totally different engine, the orginal i found stripped down, unknown of his plans, as this was 10 years ago, I was about eight at the time, so my memory doesnt recall. The engine in there at the moment, is the 8hp he aquired through a friend working for maff, the foot and mouth people, so history of the current engine is unknown, but what I do know is it was cut out of its last chassis, as cutting marks on the clutch rods that were on the gearbox that came with it.

[Keith Andrews]

popping...common on old classics..

Wise men? here is one

We must expect that the car was running OK when your father used it, so the effects should be adjustable without resorting to new jets etc.

pooping is caused by a lean mixture , most noyicable when going down hill or lifting your foot off the throttle..
Most common cause is worn butterfly bushes in the carb...give the them a shake, there should be very little or no movement...
Or a intake manifold leak...

Neil Moore pionted out to me on the bradford many yrs ago, and emphasied it...when mounting the manifold, looesen off the cylinder bolts, mount the inlet manifold, torque down...THEN torque the cylinder bolts.
Neil said this has been a common issue for decades...From the design I believe once again he is right on the money.

[AlanBartlett]

[quote="Keith Andrews"]
Most common cause is worn butterfly bushes in the carb...give the them a shake, there should be very little or no movement...
What do they look like? And where are they located?

Also the mixture screw is all the way down, to a rich mixture.

Or a intake manifold leak...

As for the intake, double gasketed and tightened up as you described, brainwashed into that lil trick from when I first started.

[ian Howell]

I had forgotten that this was not the previous engine - sorry!

"Mixture screw is all the way down" not good news, but nil desperandum!

It sounds more and more like air is getting in where it shouldn't, so check the butterfly bushes.

These are the two 'bearings' - actually just the holes in the carburettor body - one at each end of the rod that is attached to the accelerator linkage and which carries the circular flap just inside the inlet port of the carb.

Also, check that the circular flap actually closes the hole through the carb. This may be adjustable if the flap is held onto the (split) shaft by a couple of screws. (I am not familiar with carbs other than mine and Javelins'). Also it may have worn ridges where it touches the carb body.

Just have a look for wear, give the rod a 'rattle' and perhaps try squirting a few drops of oil onto the outside ends of the rod with the engine 'ticking over' (Difficult when driving!). If the engine pitch changes or clouds of BLUE smoke come out the back end, there's your problem!

Otherwise . . well others will be sure to have other ideas. Watch this space!

[Tony Fearn]

Also the mixture screw is all the way down, to a rich mixture.

Just looked at a spare 30VEFH carb and the mixture screw lets more air in as you unscrew it, but I'm surprised Alan needs to turn the mixture screw all the way in.

Tony.

[Forumadmin]

Try Google on 'Zenith VEFH'; what do you get?

[Keith Andrews]

Fixing butterfly bushes:
unless u have the right tools to remove butterflys and realign during reassembly, remove and replace bushs....AND know what u are doing
DONT attempt the repair yourself

U can put the carb in for rebuilding to a crab specialist...which involves everything from cleaningf re cadding, jets gaskets etc..
OR do most of the stuff yourself and 1/2 the price
Rebushing the throttle body in NZ is about $60 to $70 including clean, and new butterflys

The biggest mistake, and often the demise of a carburetter is the common attitude most have to the unit...be it a simple Zeneth , IMpco 425, or a 4 barrel spread bore double pumper 850 holley.

A carburetter is a VERY high precision instrument, with design ond tollerancs measured in fractions of 1/1000"...
Practices like drilling out jets is bad...in some cases even drilling out and making bigger has the reverse effect!! due to the orginal design and chamfer of the jet...

2 things make an engine 'Go' be it an old worn engine or a new engine
1/Correct air fuel ratio
2/Timing the main flame front of the explosion about 15degs after TDC
Espec on old small low performace engines.

[AlanBartlett]

Today I had my first spark plug failure, I thought something terrible had happend, as i was only getting one cylinder the big pounding boom,boom as one cylinder was in movement instead of 2. I looked at the plug it was a little black, so i cleaned it off with petrol and still no joy, swapped the plugs over, and the plug still didnt work on the otherside, so i'm pretty sure its dead. Do plugs just fail like that? Because the night before I was driving around fine with no problems. Then went to start it up last night the pound of one, wasn't in a situation to sort last night so had ago tonight and found out it was a duff plug. Because the plug was sparking but not firing. If that makes sense.

[Keith Andrews]

Spark plugs are very sensitive components..
Drop a plug on the ground...throw it way...one can bet if it doesnt fail then it will not to far into the future
NGK plugs tend to just fail when they are worn. most other brands seem to slowly deteriate un noticablly for a long time...
Plug reading with a magnifing glass will tell you so much about your engine
mixtures, timing, ring, valve guides, carb condition, mixtures, electical condition.

A well tuned or close to well tuned engine, even a well worn engine, there should never be any need to clean plugs...If u have the correct heat range (note heat range has noting to do with the temp the enhine runs at)
Its more throw the old ones away, new plugs...rather than clean

Reading plugs is not just colour soot, but where it is, microscopic metal despots, the heat burn (blueing) of the center electode and how much, electode wear, and understanding the combinations of the above.

[AlanBartlett]

A change shall be sought, I'll change both at the same time.