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Discussion Starter #1
Now, I love instant gratification but.. I can hear what sounds like the starter catching on the running engine. I just installed a euro intake cam and made sure cam timing was set properly (102). I set the engine timing to 37 degrees at 5000 RPM using an advance timing light. Now the engine starts immediately and seems to catch on the starter, with no delay after turning the key - its too fast. Is the timing too advanced?
 

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How advanced is it at idle? A lot of advance makes it hard to start, not easier, but it might be so advanced it's kind of "kicking" against itself as the early spark tries to push the piston back down before it goes over the top.
As a test, maybe set the timing so it's like 3-6 BTDC at idle, see if it starts better. A car with carburetors, if set up right, starts almost immediately, unlike an injected car that needs a few spins.

And you didn't make any changes to the starter?

Andrew
 

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Discussion Starter #3 (Edited)
And you didn't make any changes to the starter?

Andrew

I did not.. I did synch the carbs. It turns out that the rear carb was 4kg/hr lower than the front at idle. I'll look into it more tomorrow night. It ran great and sounded even stronger than before.

Before tonight it would take about one-two seconds to start.

Oh yeah, I almost forgot that I switched from 50F11 to 50F9 idle jets. I'm trying to resolve a transitional hesitation between idle and main circuit (DCOE2s). It must be this combination of factors.. Perhaps I just lucked into the correct settings.
 

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I did not.. I did synch the carbs. It turns out that the rear carb was 4kg/hr lower than the front at idle. I'll look into it more tomorrow night. It ran great and sounded even stronger than before.

Before tonight it would take about one-two seconds to start.

Oh yeah, I almost forgot that I switched from 50F11 to 50F9 idle jets. I'm trying to resolve a transitional hesitation between idle and main circuit (DCOE2s). It must be this combination of factors.. Perhaps I just lucked into the correct settings.
its worth noting that those " advance " type timing lights are notoriously inaccurate. you might want to set the light to 0 advance and see where the idle timing really is... and 37 sounds like a lot to me i would think 34 or so would be a better number but your combination might want more...
 

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Richard Jemison
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You are just slow on the key.....

If you are running a low compression engine you might get away with 37 degrees. As mentioned 34 is approiate.

However, engines with high dome high compression race motors need more advance to comphensate for poor flame travel and slower burning race fuel.
This does not apply to engines with 10.5 or lower CR ratios.
 

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Discussion Starter #6
It must be me being used to turning the key for longer before yesterday's upgrades. It was running so well it would strike me as odd for the timing to be extremely over-advanced.

The 37-40 degrees was from the book values for a European 2000 Spider with Webers. Why is it considered too far? Is the engine not the same as the US Spica? Is the book value incorrect?
 

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The book values are correct. But please keep in mind that it was written 40 years ago with the then available fuels. Todays fuels, and your particular setup, may need a slightly different value.
As points of comparison, I'm running a warmed over 2L on Webers at 43 degrees on New Jersey mandated E10 fuel while a friends hot 2L pings at anything over 38 with it's current (lean) jetting.
 

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I can tell you that on the dyno earlier this year my hot 2L motor made max power at 34 and 36 degrees. It made less at 32 and I did not advance it beyond 36. That is at a genuine 10.6 to 1 CR. With a previous motor with nominally 10 to 1 pistons and high performance cams I advanced the ignition in steps up to 38 degrees and I could not induce observable pinging on 91 octane fuel. I used to believe that the most advance that did not produce pinging was correct. Now I am not so sure. But I don't see why your ignition timing should be causing problems unless you have a short advance curve.
 

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Discussion Starter #9
I'm trying to understand cam timing more - what would result in a lack of low end torque? Cam timing too advanced?
 

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I'm trying to understand cam timing more - what would result in a lack of low end torque? Cam timing too advanced?
Lobe centers too close - low LC numbers - too much overlap could be the problem. I think that RJ generally recommends 104/104 for factory cams.
The factory timing marks on a US '76 were 114/114 according to the Shankle catalog. Download the timing templates from Centerline if you plan to adjust the cams. Also make sure that the clearances are correct.
 

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If it's not rich enough it'll feel weak on the bottom end too, and if advance is not coming in right. There are many variables. And how big are your carb chokes? Smaller gives better response lower down.
Andrew
 

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Discussion Starter #12
DCOE 2
Choke: 33
Emulsion Tubes: F16
Main Jets: 120
Air Corrector:180
Idle Jets: 50F9
Pump Jets: 40
Aux Venturi: 4.5

Exhaust: 50
Starter-circuit: 65F5

Yeah.. I just need a good long saturday to try some different things out, I think.
 

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Richard Jemison
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weak low/midrange

Leave the jetting as is unless this isn`t a stock engine.

The cam timing on all Alfa 4 cyl Weber motors were changed in a TSB to 104/104 None of these cams are very good at lower RPMs by design. (too slow a ramp rate to reduce wear which increases overlap killing low end torque) Spreading the LSAs helps that problem. Actually I suggest moving the intake cam to 104 and the exhaust to 106LC. That brings the LSA to 105 degrees and advances the cam timing events which will enhance lower RPMs.

Cam timing as above will help if currently set at the 102 marks.

But, most likely it is distributor advance curce.

On some thread someone mentioned similar issues. The distributor was a Marelli 103B. But as I recall they had "changed the advance weight control springs" as "suggested". (??? By who and for what application???)
Actually the Marelli 103B had a fast advance off idle (good) which was probably killed by the advance springs installed.

Marelli distributors have more issues with returning to "no advance" at idle than Bosch. That can be corrected often by cleaning and lubricating the advance mechanism. Advance at lower speed/RPM can be inproved (increased) by adding weight to the centrifugal advance weights (welding a bead to each about 1/2 inch long).
You can also limit total advance by limiting how far out the weights can go by adding metal to the hook of the weight that stops the outward movement. This will allow more initial advance without exceeding max advance at high RPM (36 degrees)

The best "stock type" distributor(s) for a street driven car seems to be the Bosch 0 231 110 044. or 041, or the 0 231 129 032, or 034.

Most distributors are "full advanced" by 4K to 5K RPM. The advance curve is very important on a street motor where constant RPM driving at lower RPMs need a stable ignition timing at the best amount of advance. Unlike race motors that need correct max advance, and only enough retard to make the engine easy to start without "kicking back".
 

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Those Webers were originally for a BMW. I agree with Richard that the Jetting is generally good except the main jets are too small for 33mm venturis. I would try 130 or 135.
 

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Discussion Starter #15 (Edited)
I moved to 130 main jets. I reset the cam timing, chain tension, and set the engine timing to 30 at 4k rpm. My city driving is now even better than before (pre-euro cam). I'll have to see how it behaves on the highway. Webers were popping often at idle after I installed the new cam, but all popping is gone now, as well as the flat spot. It sounds great! Thanks for the tips gentlemen!

Note: I would like to note that according to John Shankle's Alfa jetting chart the jetting for DCOE2s in a 1750/2000 Alfa is 120 main, 180 air, F16 emulsion, 35 pump jets, 50F9 idle jets, 55 exhaust. I'll have to see how the 130 behaves.
 

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Note: I would like to note that according to John Shankle's Alfa jetting chart the jetting for DCOE2s in a 1750/2000 Alfa is 120 main, 180 air, F16 emulsion, 35 pump jets, 50F9 idle jets, 55 exhaust
Can you post that? I thought that I had all of the Shankle information. Alfa never specified 120 main jets for a 2L. I have 150's in my hot motor and that is a result of dyno testing with high quality AFR instrumentation.
 

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funny carbs,you can never get perfect,set them up for sea level,go up 2000 feet,now they aren't,lol fuel injection is so much better,o2sensor makes shu're that you at a perfect fuel air ratio ,carbs leak fuel in at3-5 psi, fuel injection sprays it in at 35-45 psi,even higher with direct injection, carbs have no feedback if you are using toomuch fuel ,and at different films,and engine load,the carbs just leak fuel in. fuel injection,well you know the rest
 

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sorry for spelling,typing on my cell phone
 

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I see the data on page 61 of the Shankle catalog. That is wierd. I think that it is a mistake. 40DCOE2 was supplied by Weber to BMW for the 2002. Shankle must have got some and sold them for Alfas./ The BMW setup is 33 venturi, 4.5 auxillary, F16 ET, 120 main, 190 AC, 50F8 idle 40 pump jet 175 needle valve. AFAIK, Webers of the same series require jetting specific to the engine and your DCOE2's should be set up the same as 40DCOE32's which were supplied to AR for 1750/2000 Alfas. But maybe there is a feature of the 40DCOE2 that I don't understand that requires the use of much smaller main jets. I look forward to be enlightened.
 

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Discussion Starter #20 (Edited)
I see the data on page 61 of the Shankle catalog.

Thats the page I was talking about. I'd also like to correct my post above - it was an air correction of 150, which I'm assuming with the 120 main jet would produce a more fuel rich emulsion than the 130 main/200 combination? But who knows..?
 
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