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Yes Ed. That was helpful, but I kept wondering why I was playing on various dynos whe I could have been either driving or racing? Those same pulls work on the track (or street) just as well. Years ago Ron Neal at Prototype Engineering, spent quite a bit of dyno time with a GTA engine I built with 80 mm 2 ring GTA forged pistons and 12:1 compression. We were sorting through the "best" cams and after hours of running noted a slight drop in high rpm oil pressure. We shimmed the relief valve spring (bad practice, I've since learned) and I went racing. It was quite an engine, but at my first bearing check, I found the rod journals on the GTA nitrate hardened crank were begining to hourglass. It took a few years before the mains followed, but the long and short was I needed a new GTA crank. I still have the engine, and now with a 79 mm bore and 10.7 compression with three ring pistons, use it on the street. GTA crank #2 has now been replaced by #3 built by Marine Crankshaft through John Norman.
I've learned over the years to spend much less time in diagnostic tuning, and more time driving as I get older. Most professional dyno shops don't really like to wear out vintage engines in testing, preferring to get close and a tad rich, and let the driver wear out the engine. Seems a reasonable plan using Webers. With FI (tuneable) I revise the above as once set, the electrons make adjustments impossible with my favorite Webers!
 

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My AFR cost about the same as a couple of hours on a dyno and I get the thrill of going fast on bumpy country lanes while I collect data. As I keep on saying to friends, it beats working for a living.
 

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Idle jets

The Zeitronix has helped me now with idle jets. I was running 55F17 when I took the car to the dyno. I swapped in leaner 55F21 to try to lean out the low end. I then bought some size 50 idle jets - 50F17, 50F21 and 50F18. I then learned that they have no effect on the AFR in the power band so I went back to 55F17 - the fattest of the collection. It was clear from the AFR that the engine was not picking up as well as it could in the progression range due to lean mixtures. It was around 15 when cruising at around 4000 rpm. So I converted the 50F17's to 60F17 by drilling out the fuel orifice with a 0.60 mm drill. It was so small that I had to work under a magnifier.

It worked. My AFR is now around 13 at 80 mph in 5th and the pickup is much better. I have a small hesitation when I feather the gas pedal and the AFR is 17 or so on the over run but it picks up cleanly if I floor it. I have increased the idle speed a little from about 600 to 800 rpm and maybe that will help.
 

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But Mad North-Northwest
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Yeah, 600 is way low. I was always told with Webers to set the idle at 900-1000 and that's been working well for me.
 

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It will idle at 500 - pretty impressive for a motor with racing cams.
 

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I'd like to get and AFR and test mine. A low idle is better for gear changes I think, much easier to get into 1st at the lights no doubt. That is the drawback of a fast idle.
 

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This is a great thread! I've got a baseline and will see what changes with the new intake cam I'm installing.
 

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This is cam timing as it relates to weber tuning so I hope I can put it here. I've superimposed a degree wheel over cam caps superimposed over each other. The timing mark on the right is the intake and left is exhaust. If my scales are right the marks on the caps are several degrees thick. How one would get it exact with them seems impossible to me. The caps are 74 so the marks should be at 102 for the exhaust and 114 for the intake. Using each for a starting point I've put red and green lines where I think 104 should be. Am I close? Do I need to move them, if so which way? Thanks maybe this will help others check against the templates.

 

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Trained (ex)Professional, , 1953-2018 RIP,
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One must keep in mind that the 102, 104, 114, etc cam timing numbers (a format not used by Alfa, BTW) refer to degrees of crankshaft rotation, not the cams. For example, timing an intake cam to 114 means that the intake valve will be at maximum lift when the piston is at 114 degrees After Top Dead Center (ATDC); an exhaust cam at 102 means the exhaust valve will have max lift at 102 degree Before Top Dead Center (BTDC). Since the cams turn at one half crankshaft speed, one needs to calculate this into the equation.
Conveniently enough, a straight up vertical line on the cam cap is 100 degrees (or zero on your degree wheel). A mark on the cap one degree to the right of vertical equals TWO degrees of crankshaft rotation. This results in a cam timing of 102 (1 x 2 + 100 = 102). To time the intake cam to 104, your mark needs to be two degrees right of vertical (2 x 2 + 100 = 104). Same formula applies to the exhaust cam; for a 104 cam timing, the mark on the cap needs to be 2 degrees left of vertical.

Take note of where the factory marks on the caps are; 7 on intake and 1 on exhaust. This equates to 114 and 102 respectively.
 

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Thank you! !00 straight up really helps and I was pretty sure about the ratio but for sure is way better than pretty sure:) The marks being as wide as they are sure isn't exact but short of taking the motor out and setting up a degree wheel they will have to do. At least I did check TDC against the pointer when it was on the engine stand.
 

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Trained (ex)Professional, , 1953-2018 RIP,
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The marks being as wide as they are sure isn't exact...
For a street engine, a degree or two either way would be, IMO, extremely difficult for most drivers to even tell the difference. IOW, ballpark close is good enough. Using a degree wheel will get you in the right section while adjusting the lash of each valve so the valves are all timed the same puts you in the correct seat.
 

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I once spent some time playing with LC's in my prevoius motor and I agree that it is hard to tell the difference. I did stop watch runs on a section of road to make comparisons. It think that I could do it better now as the Zeitronix records time as well as rpm and AFR. So if I did WOT runs on exactly the same stretch of road under similar weather conditions then I should be able to measure accurately the acceleration.
 

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Speaking of weather and tuning here in the afternoon making a run is like trying to get a Cessna 150 off the ground with two heavy people in the ****pit with full tanks, on a 100 degree day. The difference in the way my motor runs between the early morning and 98 degree high humidity afternoons is quite noticable. On idle jets which would be considered leaner than a 45 F9. a 45 F8, or a 40 F9? I'm assuming a 45 is leaner than a 50, right?
 

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Trained (ex)Professional, , 1953-2018 RIP,
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A 45 has a smaller fuel orifice than a 50 but that does not necessarily make it leaner (the two digit number is the diameter of the orifice; a 45 is 0.45mm, 50 is 0.50mm, etc). The other part of the equation is the 'f' number. This designates the number of and the diameter of the air bleeds. Thing is, the f numbers are not in any particular order according to size so one needs to look at a chart of Weber idle jets.
 

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40 is very small for your motor. Des Hammill makes the following recommendations for fuel orifices
40 - 250 to 350 cc/cylinder
45 - 350 to 420 cc/cylinder
50 - 420 to 490 cc/cylinder
55 - 490 to 560 cc/cylinder

Alfa fitted 50F8 in 2L motors and that should be close, even with bigger cams.
50F11 is one step leaner and 50F9 is one step richer. I would be surprised if you had to go outside of that range.

Here is a copy of the Weber tuning manual. http://www.lainefamily.com/images/WeberTuningManual.pdf

You will find dimensioned drawings of all idle jets. It may be possible to drill out an orifice to make a different idle jet if you do not have it on hand.

the list of idle jet air bleed suffixes from rich to lean is F6, F12, F9, F8, F11, F13, F2, F4, F5, F7, F1, F3
 

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Thanks! My webs came with 45 f9 and I put 45 f8's in which is what I have now. I did see where the 2L euro motors came with 50 f8. I guess what I was asking was is moving from 50 to 45 give the same amount of lean condition as going from f9 to f8?
I've got a set of 50 f8's comming just to see what they do. It would be richer than a 45 f8 or 9? For 15 bucks and free shipping it's cheap at twice the price, maybe:).
 

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At idle or on the first progression hole 45F9 may be a lot like 50F8 but 50F8 will supply more air/fuel emulsion at the top of the progression range and that will influence the transition.
 

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To see how the F numbers relate to mixture really helps understand whats going on. We're getting there slow but sure, thanks!
 

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4th gear at a 3700 cruise was giving me right around 13.2 afr and the motor sounded happy. I thought I had a 6500 rev limiter plug in the msd which led me to believe my tach was way off but it turns out it was a 7000 plug. I ordered a couple of 6500 plugs from msd for three fifty each and put one in. What I need to do now is a good run at speed and look at the plugs. Now that i have the cams timed as close to 104 as i can get I'd really like to log with rpm and add vacuum in there as well.
 
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