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Leaning out/tuning a Weber on a 1275

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drooartz

drooartz

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So the new Morris has a Weber of some sort (I believe it's a 40) on a 1275 engine. I don't know anything about Webers, but I do know that this car is set up for sea level and I'm at 5550' so it's running quite rich. Tried to take the car up a local pass road and somewhere around 8000' it bogged down completely and I had to turn around.

Eventually I want to do a set of SUs on it, but for the immediate future I'd just like to get it running better as is.

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Drew, undue the brass wing nut and take a common screw driver and remove the larger headed jet. That will be attached to your emulsion tube. Separate the top cap and you’ll see the air jet, try increasing the jet size about 15% and see how that works. If you see improvement but still a little rich try another 10% and see. The jet will be embossed on the side of jet.
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Thanks!
 
Buy the book titled Weber Carburettors by John Passini tuning and maintenance and save yourself some time while learning.
 
Thanks for the book recommend.
 
Grantura_MKI said:
No worries. You could always fit a Shorrock blower to it?
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Nah, though the Bugeye may get a supercharger some day. The Morris is destined more for touring duty so I'm keeping it simple. I'm keeping an eye out for a decent set of SUs and a manifold, but want to be able to drive it now.
 
drooartz said:
Nah, though the Bugeye may get a supercharger some day. The Morris is destined more for touring duty so I'm keeping it simple. I'm keeping an eye out for a decent set of SUs and a manifold, but want to be able to drive it now.
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Drew, If you'll be removing the Weber in lieu of SU carbs, you'll be better off with a single SU, either and HIF44 or HS6. They will perform better than twin HS2's and be much less maintenance. I've done that setup on several MM's and also on my A35, and there is a noticeable difference over HS2's I've removed from the same cars.

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Thanks, Gerard. Was wondering about doing a single SU for this one. Now I just need to find the carb and manifold...
 
drooartz said:
Thanks, Gerard. Was wondering about doing a single SU for this one. Now I just need to find the carb and manifold...
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I can get you all that if you want... rebuilt too. I've done several and have another one upcoming for a Traveller I'm restoring, including a complete engine rebuild.
 
Gerard said:
I can get you all that if you want... rebuilt too. I've done several and have another one upcoming for a Traveller I'm restoring, including a complete engine rebuild.
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I'll be in touch...
 
Drew,
If you decide to go with dual SUs I have a rebuilt set with manifold that I'll swap.
Rut
 
Drew
I am kind getting into the same set of circumstances as you are with my B/E. The H1 carbs have been a pain, the 4 speed transmission makes the car sound like it going to explode a speed on the back roads. So I found a Datsun 5 speed and will put that in with Gerards' Kit and have a 40 dcoe carb to put on the 948. How does your MM handle the vacuum advance line (does it even have one)? My 2nd gear synchro might also be bad so I will be following your rebuild closely. My thought is to get the car running well with the old 4 speed and the Weber. When the weather cools I will pull the motor and do the transmission and possibly a disc brake conversion.
Regards
Paul
 
No vacuum advance line on my Morris -- it's running a Pertronix of some sort and the dizzy doesn't have a vacuum advance on it. Don't know if that's optimum, but that's how it's setup now.

I have decided to swap to a single SU on the Morris. The Weber is getting traded for a carb set that will go on my Bugeye. I'm sure the Weber could be setup for my Morris, but I'm happier keeping things similar between the two cars and I know what to expect with the SU.

Your plan to get the car running with the 4-speed sounds like a good one. You could also try swapping in a 3.90 rear end -- if your 948 is built nicely it could probably pull it okay and it's an easy thing to swap in.

My 5-speed at least needs bearings, though it seemed to be shifting just fine. Found some metal bits in the gearbox oil, though, so it's got to be done. Still contemplating if I'm going to do it myself or hire out the work.
 
Drew
Thanks for the info. The MM must have a mechanical lucas 25D . Not ver common. The differential idea is also a good one. I will have to check my parts source. Gerard tells me that the second gear synchro problem might be addressed sometimes by changing the oil in the trans. I will see when it comes in. Maybe Gerard will chime in on how to handle the vacuum advance with a weber.
Regards
Paul
 
apbos said:
Drew
Thanks for the info. The MM must have a mechanical lucas 25D . Not ver common. The differential idea is also a good one. I will have to check my parts source. Gerard tells me that the second gear synchro problem might be addressed sometimes by changing the oil in the trans. I will see when it comes in. Maybe Gerard will chime in on how to handle the vacuum advance with a weber.
Regards
Paul
Click to expand...

One of these days I'll have to look into exactly what dizzy I've got in the MM and see if it's set up properly for the rest of the system. It runs pretty well at this point, though, so I'm unlikely to mess with it too much.

The 3.90 is pretty common to find, and might be the ticket for you. I had one in my last Bugeye with a 4-speed (but also a 1275) and it was a pretty good match.
 
Drew, I believe your PCV is set up to feed just the front port of your head and likely leaning those cylinders out WAY too much. Try plugging that inlet and letting the PCV vent to atmosphere to see if it will run better. If it does you can make up a restrictor for the line or continue to vent to atmosphere.

Kurt.
 
Thanks, Kurt. I'm swapping out that Weber anyways (for a single SU), so I'll be figuring out a new PCV concept with the new manifold. Good to think about, though -- I'll make sure to keep that in mind when I'm setting up the SU.
 
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