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40 and 45 DCOE WEBER JETTING info!


Guest Anonymous

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Guest Anonymous

I see alot more DCOE discussion lately - so here's my chance to pipe in what I've been tinkering with. I won't touch a thing on the 40s - they're as perfect as I could ever want - but I'm still dialing in the bigger 45s.

I've actually started a file folder FULL of Weber info. I write notes in it to record results with different varieties of jets, air correctors, etc. Hope this can work as a starting point for others:

40DCOE with "ti" manifolds (shorter than most aftermarket ones) and factory "ti" 1/8" spacers. Long 60mm velocity stacks from 45s - but grafted to the inner sleeves of chopped 40mm stacks: GREAT, immediate throttle response from down low to up high. Best when stomped at around 3500 rpm though. Thoroughly smooth around town - like any Motronic BMW! 20-21 mpg at 80 mph cruising, who cares about city mileage? Currently on stock motor with 9.5 pistons (E12 head)

needle/seat valve 1.75

Emulsion tubes F16

air correctors 170

Main jets 120

idle jets 55 (no f number on these)

pump jets 40

main venturi/choke 33

aux venturi 4.5

exhaust valve/jet (bottom of float bowl)55

The 45 DCOES I've rebuilt and have spent hours getting them to perform as well as the smaller 40s did. I'm almost there - probably try slightly richer idle jets though. Power occurs about 300 rpm higher than the smaller carbs (3800-4200rpm). Maybe a bit better top end (5800rpm and up). I tried 180 air correctors - and it introduced a flat spot like hell around 3000rpm...so here's where I am now (same engine, same car, same manifolds, same size stacks except for 45s, same spacers*)

* Without spacers - there was a definite loss of low end power - very disappointing, so I put them back in. With aftermarket (longer) manifolds - this may not be an issue.

45DCOE set up currently:

needle/seat 2.00

emulsion tubes F9

air correctors 170

main jets 125

idle jets 55 (no f number)

pump jets 40

main venturi/choke 34

aux venturi 5

exhaust valve/jet (bottom of float bowl)70

float level with brass floats 7.5mm / 14mm dropped.

I'm tempted to try larger mains and then larger air correctors with 'em - but it's so close to perfect (for my needs) that maybe I'll just let it be.

I'd love to know what works for others - but would REALLY like to know what mods have been done to your engines - as this will certainly affect the "best" internals of the carb....LEE??????

Hope this helps somebody out there....I've smelled like gasoline since THURSDAY night, playing with these things!

Paul

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Guest Anonymous

I will learn. ANyone in the bay area (San Jose) willing to come over and help me tune mine.

Would say that I would buy you beer like everyone else does but I'm way underage so I can supply you with sodas?

Thanks

Darius

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Guest Anonymous

I have settings pretty close to yours on my 45s. Engine has 10:1 and a cam.

I run:

needle/seat 2.00

emulsion tubes F9

air correctors 200 (Paul runs 170)

main jets 130 (Paul runs 125)

idle jets: I now run 45 (too lean) and aim at 50

pump jets 45

main venturi/choke 34

aux venturi 5

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Guest Anonymous

Get the book "Weber Carburetors" by Pat Braden

ISBN 0-89586-377-4

Even if you get someone to set them up for you - it'll keep you from having the "deer in the headlights" look on your face while they describe exactly what their doing to your carbs.

It discusses theory on just how a carb works (A little physics won't kill a young lad like you) - it's GOOD for ya! (and I was a FINE ARTS MAJOR!) It contains detailed descriptions on how each part of the carb works, it's purpose, where it's located, tips and precautions, and overall operation of Webers in general.

Bolting on a set of dual carbs can damage your motor if not set up properly - too much fuel being dumped into the engine can rinse essential oil from the cylinders - destroying piston rings. Too little fuel can cause lean / over heated combustion temps - and do the melty melty to the head and pistons.

It requires a few basic tools to get "good" at them:

Synchrometer - for synchronizing them - measures air flow from barrel to barrel - cheap and very easy to use tool.

small flat blade screwdriver - 8"-12" long

fairly wide flat blade screwdriver - medium length

needle nosed pliers

compressed air - if available.

Get high quality screwdrivers - they make the tweaking of the carbs a much nicer experience (Mine are fancy Snap-On brand - and I bought them for carb use only - only about $13-18 each though.) Nice tools make you feel like an artist at work.

Tuning requires a disciplined methodical approach, patience, and a sensitive ear/eye. Practice will only make it better.

Paul

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Guest Anonymous

Someone mentioned checking the current set up of carbs - even NEW ones for inconsistencies and wrong parts - and YES! I have found different idle jets from carb to carb on new units right out of the box (!)Most carbs have woefully inadequate idle jets from the factory, for our cars - causing hesitation off-idle, and popcorn noises at any rpm below full throttle. WHY? Who knows!

On my used 45s - I found one MISSING air corrector, one BENT idle mix screw, one slightly bent throttle shaft (fixed it!) - and a freeze plug glued to the top of one, and spraypainted inside and out (yeah...INSIDE!) instead of the mickey mouse hat. They were a mess. If I had to calculate how many hours it took to get them "right" - I'd say about 20+. Add about $160 in rebuild kits and assorted jets / parts.

Paul

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Guest Anonymous

I'll second Paul's comments about checking what is in them. I bought mine from a supplier that specialized in '02 parts, told them exactly what my engine tune was, elevation, etc. They sent a nice little sheet listing the jets and chokes - which wasn't even close. One float was so far off that raw fuel would run out the barrels. Check 'em before you bolt 'em on.

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Guest Anonymous

if you have an uncurable flat spot at 2500-3000 drilling a small hole (1/32) on each throttle plate on the bottom part seems to cure most of it.......

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