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With my "special sauce" 33mm venturi profiles and bumping up to 135 mains from 32 venturis and 130 main jets I went from 8.5 secs to 8.16 secs. It also and I don't say this lightly has beginning at 6300 rpm significantly more "kick" and revs to 7200 fast. I wasn't used to it hitting that so fast and shifted out of fear and surprise more than anything else.
I began with:
130 mains
F11 emulsion tubes
32 venturis
200 AC
50 f8 idle jets

Now:
135 mains
F15 emulsion tubes
33 venturis turned from cast 32's
200 AC
50 f8 idle jets
My afr's went way lean with the 33's and 130 mains so I didn't do any timed redneck dyno runs until I put the 135's in.
Now the AFR's are at WOT through the gears in the mid 12's but go to 13's at 7000. I need to get the rev limiter in the msd repaired so the 6.5k or 7k plug works. I really don't see much advantage in taking it past 7000 but if it made the difference between victory or defeat in a drag with Ed you can bet I would:)
 

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Weird aint it?
 

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I really don't see much advantage in taking it past 7000 but if it made the difference between victory or defeat in a drag with Ed you can bet I would
It might make sense to go close to 7000 if your peak power is around 6200 as mine is. Shifting at peak power rpm will almost always result in slower acceleration because you have dropped too far out of the power band in the next gear. You want to maximize the combined area under the power curves. Based upon my dyno curves my optimum shift point from 4th to 5th is 6800 rpm. It is higher in the lower gears that are wider spaced. As my tach over-reads by 10% I have marked it with a red line at 7500. It impresses folks who see it and don't know the whole story.
 

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I reported in the EGT thread that the Weber settings that I thought were ideal for torque and power from my motor produced very high exhaust gas temperatures when running at a steady 5200 rpm in 4th gear - 80 mph. They were more reasonable in 5th. Installing bigger main jets,150 to 155, dropped the EGT at 5200 by 100 degrees but it made the AFR too fat in the high power zone so today I ran with 200 air correctors instead of 170's. It did the trick. The EGT's were pretty much the same as with 170 AC's and the AFR's in the high speed/part throttle were also about the same but the AFR in the high power zone was returned to where it needs to be.
So the message is that air correctors affect the whole of the WOT range but have little effect at part throttle, even at high rpm. Main jets influence part throttle even when the throttle plates are barely open if the rpm's are high.

And now to brag about the car. I did a rolling start 7 to 100 mph pull in 21.5 seconds up a gradient of about 2%. That was with 3 gear shifts. I think that says almost as much about RJ's gearbox/clutch/flywheel as it does about his influence on the motor.
 

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But Mad North-Northwest
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That's pretty good. Usually it takes me 21.5 seconds to shift from 1st to 2nd gear. Alfa pause, you know.
 

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More data

I was happy with 150MJ/170AC until I measured the high EGT’s at high cruising speeds. 155MJ/200 AC fixed that but now my WOT mixtures are fat below 5000. They were fat below 4000 before. That costs torque – I know that from the dyno. The torque drops off when the AFR drops below 11. So I want to lean out that area and I decided to block the lowest row of holes in the F34 emulsion tubes. When I went to block these holes I “discovered” that I had already blocked two of them before I got the EGT sensor. Now with all 4 blocked there is no noticeable improvement on the WOT mixture but my cruising temperatures have gone up – the exact opposite of what I was looking for. So I unblocked all 4 holes and now my cruising temperatures are much lower and my high power AFR is a little bit fatter. So the next step is to return to 150MJ/170AC and see if my cruising EGT’s are acceptable. If they are not then I will drill some more low holes in the emulsion tubes. This confirms what John Passini wrote - that emulsion tubes have a small effect at full throttle and a large effect at part throttle.

I had done a 7 to 100 mph rolling start pull up the hill in 21.3 last week. I do not do standing start pulls because I don't want to abuse the clutch. Today I did 17.1 going down the hill. The two way average is 19.2. I figure a good driver could go from zero to 7 mph in 1 second so my 0 to 100 is about 20.2 seconds – 1 second faster than a stock Montreal in the 1973 R&T European test.
 

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I'm with you on the rolling start. now I'm curious what I'll get from 3500 in 1st to 100 with a 410 rear end. Weather is perfect here to hit my favorite strip of road.
 

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I'm with you on the rolling start. now I'm curious what I'll get from 3500 in 1st to 100 with a 410 rear end. Weather is perfect here to hit my favorite strip of road.
Go for it!

You will not be in 1st gear very long if you start at 3500. I went from 2000 to 6000 in 1.4 seconds today.
 

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Emissions 40's vs Classic 45's

I posted several AFR curves while I was tuning my 40DCOE116/117's and they had an S shape. I have swapped them out for a pair of 45DCOE152's and here are comparison curves of WOT runs in 3rd gear. The black one is the best torque/HP with the emissions carbs. The brown one is with the 45's with 150 MJ/200 AC/F16 ET and stock accelerator jets. The red one is the same setup as the brown but with "0" accelerator pump bleed back valves. The difference in the shape of the curves is striking. I made no other changes to the engine.
 

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Richard Jemison
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Jetting

Before changing ACs swap the main jets to something significantly smaller (140s, then 145s) see what happens in the blend area from 3000 to 6000 where the rich dip is currently.
If you have "adequate" size jets then there should be enough fuel supply for the higher RPMs.

I`m afraid that changing IJs will lean out "tip-in" AFRs which are good.

Like we talked about yesterday, see what "cruseing" AFRs are at 2500 to 5000 which is typical hwy driving. On a race car this isn`t as important and WOT is AFRs are critical.
 

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Thats interesting that the emission carbs are richer in the low speed circuit.
Not what you would expect. Emissions carbs give better fuel consumption but the gains are clearly not at WOT.
 

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Both the above are what I've suspected reworking the emission Webers for years. I've had a feeling these were funstioning as you have shown.The ease working with non-emission is now explained, as well as RJ comments on my set-up for non emission.
These last two posts are IMPORTANT for those following this thread.
At least three of us share the same opinion here.
 

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Make that 4 :)
Just how common are "emission" webers and how can one tell the difference? I've heard of Weber carburetors since I cleaned my first butterfly but have never heard of, except here, and Ed's are the only ones I know of. Scratching head
 

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Just how common are "emission" webers
They were in Shankle's conversion kits and maybe some others. I bought mine from a guy in Italy. They were OE on a number of European Afa's in the 70's and 80's. They would still be my choice for a 160 -170 HP motor for road use.
 

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Before changing ACs swap the main jets to something significantly smaller (140s, then 145s) see what happens in the blend area from 3000 to 6000 where the rich dip is currently.
Just out of curiosity; wont that shift the whole AFR curve leaner? Why not adjust the AC's to target that RPM range?
 

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I had a few problems with the 45DCOE152's, mainly due to inferior manufacturing. Two of the threads in the carb body for the emulsion tube holder were not completely tapped and were causing the threads to bind before the main jet was seated. Both float needle valves were damaged and I encountered fuel starvation at high speed that was only corrected by setting the pressure regulator to 5 psi. 140 main jets were too small and they caused the AFR curve to take a big shift upwards and I have settled for 145's. The unexpected result is that I have to run big air correctors. Here are curves for 200, 220 and 280 which is pretty good. I will probably stick with this combination and then play around with pump jets. I bought a couple of sets off Ebay and they don't quite fit so I will have to reduce the diameter of the spindles until they will slide in.

I tried 50F8 idle jets are they were much too lean. I now have 60F8 and they are pretty good. The car drives very well except for some lean hesitations when I get on the gas.
 

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Whoever had the carbs before you must have had a fit with them with the main jet not seating. Glad you got that sorted! I guess it's time for a drive to the dyno you used last time? I for one can't wait.
 
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