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Weber DCOE40 questions

bugedd

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So I picked up a second hand Weber DCOE tuned for a pumped 1380, so my relatively stock 1275 will need less fuel than its probably tuned for. After reading a number of articles online, and feeling most of the info is over my head, I am looking for advice. Now, I don't really know much about my 1275. It sounds like it has a slightly lumpy cam, has a crappy header, thats about all I know. So with that, what might be a good starting point for selection of idle jets, emulsion tubes, venturi, main jet, etc. I am just looking for a starting base line, then I can go from there.
 

twas_brillig

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check this thread:

https://www.britishcarforum.com/bcforum/u...948_#Post540937

and (humbly!) my post from that thread:

found my "Tuning the A-Series Engine" by David Vizard and he has a chapter on Webers. For a stock 1275, he suggests:

"45 DCOE
35 mm = Choke
4.5 = Aux Venturi
150 = Main Jet
180 = Air correction Jet
F2 = Emulsion Tube
40 = Accelerator Pump Jet
50F2 = Idle Jet

And make sure you read Hap's comment just below mine regards Webers."

And (touch wood) I'll be trying to figure out this spring what to do with a DCOE 45 bought in a parking lot, and applied to a stock 1275.
Doug
 
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twas_brillig said:
And (touch wood) I'll be trying to figure out this spring what to do with a DCOE 45 bought in a parking lot, and applied to a stock 1275.
Doug

IMO too big. Sell it and get a 40. I have 30's in it and am considering going down to 27's. This on a 1500.
 

racingenglishcars

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I'm afraid I am going to have to agree that the 45 is probably too big for a street 1275, however I had friend who bought a brand new '75 1500 and it ran beautifully with a single 45 DCOE.

If it idles rough because it has a racing cam, the eingine will breathe better than stock and utilize the Weber carb better, though mostly at high engine speeds. If it idles rough because of other failures such as carbs, vacuum leak or ignition system, the DCOE won't do anything for you.
 
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bugedd

bugedd

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Thats a great thread, gives some good info.
As for the rough run leading me to believe the car has a cam, the ignition has been gone through and there is no known vacuum leak. And the car scoots pretty decent which leads me to believe its modded.
 

BlueMax

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If you think your car has a cam in it then why speculate? Take the rocker assembly off and leave one pushrod in the number one lifter, set your magnetic base on the head holding the dial indicator in the center of the push rod and rotate the engine to measure the cam lobe height, my ears are not micrometers I have do it the old fashion way. Then you will know a little of where to start your jetting from. Or you can speculate and run in both directions with hope of hitting it in one of the directions you go in, Expensive!
 
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bugedd

bugedd

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Well, I wouldn't be too upset if I did cook the motor. Its a bit tired and could use a some love. As is the rest of the car :smile:
 
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BlueMax said:
If you think your car has a cam in it then why speculate? Take the rocker assembly off and leave one pushrod in the number one lifter, set your magnetic base on the head holding the dial indicator in the center of the push rod and rotate the engine to measure the cam lobe height, my ears are not micrometers I have do it the old fashion way. Then you will know a little of where to start your jetting from. Or you can speculate and run in both directions with hope of hitting it in one of the directions you go in, Expensive!


Even better, the engine is already together and running, don't remove the rocker arm assembly, just set a dial indicator up on the valve retainer, and take valve lift readiing there, instead of lobe/cam lift. valve lift is cam lift x rocker arm ratio, which if you have stock rocker arms is around around 1.25 ratio.

You fellows have fun with those side draft webers, I always thought they lacked low end and mid range grunt, and only if the jetting was perfected, offer a small top end advantage. People that love those carbs, love them alot, I'm just not one of those people :driving:
 
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bugedd

bugedd

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Yesterday I got the DCOE in the mail, all looks good. Now I am trying to figure out linkage. Can ya'll our there with DCOE's post pics of your throttle linkage so I can get some direction?
 
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bugedd

bugedd

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That would be great. I can't find any good images of cable routing/linkage. I am thinking a different throttle arm than what is on there would help.
Thanks
hamiltonedd@yahoo.com
 
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Give me a few hours to see if I can hold lunch down and I'll get you some.
 
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sasdwe

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I've got a 1500 with DUAL DCOE 45s with 32mm venturies. It has headers, a Kent racing cam, milled head, 9:1 pistons, MSD, Mallory dual-point, double valves springs, roller rockers, aluminum flywheel and a few more tricks that don't immediately come to mind. If the 1275 is totally stock, then maybe a single 45 would be too much carb, but I doubt it. With just a few mods to improve breathing - cam, headers, a single 45 should do just fine. These cars have been set up to run with dual SUs with comparable barrel sizes to a DCOE45.
 

Westfield_XI

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Teglers site is useful, but not very current. I have found that the best information today on Webers is at sidedraftcentral at yahoo.com/groups.
 
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sasdwe said:
These cars have been set up to run with dual SUs with comparable barrel sizes to a DCOE45.

One needs to also consider the DCOE doesn't have varible venturis and will flow whatever the throttle plate dictates. SU's are demand sensing.
 
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bugedd

bugedd

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So I have a question on the numbers on the carb. Some are "40DCOE18", mine is "40dcoe31". what does that last number refer to?
And I am working on restoring its finish. Its an older carb, so its looks are not the best. Thoughts on brightening up the aluminum?
 
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Last number is series if you will. Google it and you'll find out about the progression holes.
 
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bugedd

bugedd

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didn't come across that in my search, let me check again
 
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Doc will know but IIRC, that's an OEM carb and the 31 is venturi size. Fiat probably.
 
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