timing and weber again....

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joe27979

joe27979

Well-Known Member
Posts
1,354
Location
west Norfolk
so I set my carb as per book today:



Set timing to 6 DBTDC with strobe
connected Tacho
mixture screw 2 turns out from stop
idle set 1.5 turns out

engine to running temp
adjust mixture to smoothe running
adjust idle to 850rpm
adjust mixture again etc etc

runs smooth and great, but after 30 mins driving it cuts out at junctions

what gives?? do I need to advance timing a bit more or set higher idle?

please help as I've got a long journey 2m
 
Long time since I ran a petrol, I have always had better results setting weber at higher revs than 850 idle. However it seems more like another problem. I know you have gone through the stuff but I would start again. Valve clearances, any fuel lines getting hot/to close to exhaust and vapourising fuel. Should there be an insulator plate carb to manifold? Try spraying WD40 around manifold/carb join when on tickover to see if revs alter indicating an air leak.
 
Had something similar with Weber turned out it was air leak. Fitted a new seal kit in carb and she ran mint. Also had issue with electric fuel pump was mounted to engine block and when up to temp evaporated fuel.
 
Did have a cracked carb insulater aswell. Think person that fitted carb tightened mounting bolts up too tight.
 
no carb insulator on mine, new carb and gasket have been fitted.

my fuel line runs over front of engine behind thermostat into an inline filter so fuel is cooled by engine fan.

I'll try squirting carb cleaner all around inlet tomorrow..any other idears why it would cut out when coasting to a stop? once I flick key it starts ok and idles fine with no issues
 
think I'll adjust dizzy by ear tomorrow too, it was running slightly faster at about 10DBTDC, when I turned it to 6DBTDC it ran a bit lumpier-I smoothed it out by unscrewing mixture screw (does this make it richer?)

what if I unscrew mixture 2 turns out from when it bottoms out, idle 1.5 turns and then set timing if dizzy by ear rather than strobe?
 
At 10BTDC you'll probably find it sounds terrible and pinks under load as soon as you start putting on revs it will advance quite rapidly (you can watch this with your timing light).

I'm pretty sure you do need a carb insulator for a Weber, that might be the problem. I'd fit one and check round for leaks (spray brake cleaner around the manifolds and carb joints and if it the revs change its sucking in somewhere. However I doubt it is that in this case.

Where have you got the vacuum advance pipe connected and do you disconnect it when setting the timing?
 
at 10 it sounded lovely!! and revved through the range nicely.

I'd better look for a carb insulator then.

vac advance is off a stub on carb to a 2" long silicon tube-then it's solid metal pipe around back of engine to another 2" piece of silicon pipe to the dizzy

I didn't disconnect it doing timing..is that bad?
 
joe27979 said:
at 10 it sounded lovely!! and revved through the range nicely.

I'd better look for a carb insulator then.

vac advance is off a stub on carb to a 2" long silicon tube-then it's solid metal pipe around back of engine to another 2" piece of silicon pipe to the dizzy

I didn't disconnect it doing timing..is that bad?
Click to expand...

no
 
joe27979 said:
at 10 it sounded lovely!! and revved through the range nicely.

I'd better look for a carb insulator then.

vac advance is off a stub on carb to a 2" long silicon tube-then it's solid metal pipe around back of engine to another 2" piece of silicon pipe to the dizzy

I didn't disconnect it doing timing..is that bad?
Click to expand...

6deg is for static not dynamic. You have vac amd centrifugal advance when running so at 850rpm you will well advanced compared to base. So 10 is not a million miles off at 850 rpm. To time dynamic base properly requires vac advance off and rpm at 450.
Oh yeah I had no isolator thing on my weber worked great. Just up the idle speed leave the timing at what sounds best no pink uphill in 4th. Is your throttle rod thing all oiled and taught? It does sound like fuel delivery so maybe vapour lock as was said. Just insulate the fuel line.
 
Last edited:
I set static TDC when I did my dizzy skew gear and valve clearances but dynamic when it was all back together..

so u saying I should disconnect vac line-adjust idle to 450rpm and then dynamically tune dizzy with my strobe?

throttle linkages is nice and tight.. we have a lot of bumpy roads round here and I
noticed slight knocking of my foot against accelerator peddle promoted
lots of mini bunny hop type jerking while
I'm driving over road imperfections-is throttle usually that sensitive?
 
joe27979 said:
I set static TDC when I did my dizzy skew gear and valve clearances but dynamic when it was all back together..

so u saying I should disconnect vac line-adjust idle to 450rpm and then dynamically tune dizzy with my strobe?

throttle linkages is nice and tight.. we have a lot of bumpy roads round here and I
noticed slight knocking of my foot against accelerator peddle promoted
lots of mini bunny hop type jerking while
I'm driving over road imperfections-is throttle usually that sensitive?
Click to expand...

they all vary slightly but i set 6 degrees at idle 750 ish with vac on,throttle linkage needs setting correctly as you can end up with little pedal and great movement of throttle as all levers in system travel through an arc
 
I got it warm this morning and then listened to exhaust, it was puffing a lot rather than smoothe... I turned dizzy clockwise a gnats tadger (advanced it) and all the puffing stopped and now smoothe again.

looks like it's happy at that, prob 9 or 10 DBTDC

All the exhaust ports warmed up together

I unclouded fuel pipe from bracket on dizzy now so fuel pipe is away from all hot stuff

sprayed carb cleaner all over carb and no change in engine rpm

left it idling at 1000rpm, will let you know how journey goes
 
It might stationary or on the flat but try a steady incline at 35 in top and it will probably start crackling and pinking...not good for the engine. Or do you add octane boost? Best I can manage is 8 degrees with 98 octane.

Where on the dizzy get us a picture, might be worth checking that, if it leaks it can cause troubles too but not usually too bad.

PS: Sorry had missed a load of posts!
 
Looks ok but I'd get one or two spacers - these are just to stop the carb getting too hot WEBER 34 ICH/ICT CARBURETTOR BASE BLOCK GASKET | eBay

And that vac pipe looks to be from the correct port but looks like it is probably going to cause bother get a proper one they're only a few quid Classic Mini Vacuum Advance and Retard Pipe Kit NEW inc ends rover austin 998 bl | eBay - I always buy two for when I forget to put it on properly and it burns off on the exhaust!

Apart from that I'd have a feel of the coil when its running rubbish it might be getting over hot and could be the cause...
 
Oh, and it looks like you're missing the PCV setup - there should be a pipe and tee piece from a spacer below the carb to the pipe from the "dalek's head" crank breather, that does make a bit of a difference but probably nothing to do with your current problems...

[edit]
Sorry, scratch that, you've got the older oil filler
[/edit]
 
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