Wideband Results

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it's more important that you aren't exposing progression holes at idle. If your are backed way off, don't sweat it.
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[Casting Timmy]

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one other obvious thought; the throttle plates don't have any holes in them do they? If they do (common on center mount set ups), close them.
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[Motor60]

No. Throttle plates do not have holes in them.
With my current :
52
145
200
44idfs
36 vents

Motor falls on its face like it has no fuel. From a hard start.

[[email protected]]

photo down carb throats?
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[tzepesh]

Starting again with engine specs: 1584cc engine, W100 cam, 4-in-1 exhaust, Megajolt ignition based on MAP, Dellorto DRLA36, 30 vents, 52 idles, 180 airs, 9164.2 emulsion tubes, 122 mains.
I sorted out the ignition, so that remains fixed, similar to the one below but with some changes (at 800 I have 8 degrees at 60-77KPa, and the RPM bins are a bit different because of the tuning software):

I followed the whole carb tuning procedure again while driving, starting with main stacks out and no accelerator pumps etc. until I got it running right. I want to understand why it behaves like this:

With #52 jets it is running very well, but wideband shows too rich, around 10, plugs also read rich (black with smoke).
I switch to #50, is is running very bad, it accelerates ok but does not want to maintain speed, it seems to lose power, sometimes with backfire through the carbs, but AFR shows around 13-14.
If I install #48 jets, it is very lean, around 18, so it does not run well and does not have power (it was clear, it was just to be sure about the 50s).

It seems odd that it does not want to run good with 50s, but it really does struggle.

And one more small question: it seems that when I switched to 52s (so larger jets) the mains also read a tad richer, is this normal?

PS. I know Jet Doctors created me a lot of issues, I will remove them as soon as I get the occasion. Now I need the car running and can't afford a few days off to remove the lead plugs I installed. What is the best technique to remove those plugs? I remeber the air holes were initially 2.2mm diameter, but I bon't have such a drill and I fear if I mess with the holes the whole circuit will be affected. Maybe drill with 1mm and pull them out somehow (I'll see if I find an 1 or 2mm tap...)?
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'74 1303S, L98B Viperngrun (extra glitter), German Look
'64 1200, Sea Blue, under restoration

[Motor60]

Ok. I've tried every possible combo
I have 170-220 air jets
120-150 main jets

I have 52 idles and light cruise is 14.7-15.1 on the dot. I know that's the bad zone. I need 50s. But that seems small for 44s with 36 vents.

From a HARD start, motor hesitates before it takes off. I've adjusted timing from 28 to 26. Can't figure this out. Please help

[stan_tichomirov]

My 2276 didn't like 52 idles in 44IDFs. I'm running 54s, they are a bit rich but work well overall, better than 52s. I have 53s but haven't tried them yet.

Stan
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My 1835cc build
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[Motor60]

Gonna try 50s but not sure it's gonna like it. That's small for 36 vents in 44s. To get to 16-17 afr for light cruise at 1/3 throttle. Does it matter that my svda is hooked up to 1/2 side carb? I was gonna T it up to both carbs. And probably get a pulse valve from John.

[stan_tichomirov]

I ran 50s with 40IDFs in this thing, but the 44s do not seem to like the smaller idles.

Stan
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Jansen Enterprise
My 1835cc build
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[Motor60]

Ok so I think the problem is I have the vintage speed exhaust. I took it off, bought a merged header and welded a bung into it. Just with a stinger but hope that work for now. It's 100 degrees out right now in SoCal so I'll wait to start tuning again till it's about 90 degrees.

[Motor60]

Ok based on my new exhaust, I'm running 17.7-18.5ish light cruise 1/8 throttle 55 mph. 57s was about same 17.2-18.3.
60s woke it up but low 13s. All this without main stacks.

2054cc
Dual 44idfs with 36 vents
Svda distributor
8/28 timing
40x35 heads

Gonna wait till motor cools and try again but with 32 vents.
I'll say that tuning with vintage speed exhaust was definitely not working out. It was telling me that 52 idles were good (based on wideband). And new exhaust tells me 55s too lean.

[jason]

Changing exhaust changes the way it breathes. You will have to tune it again when the stinger comes off for optimum tune.

[Motor60]

32 vents are in. Got the 55 idles to run 16-17s at cruise 1/8-1/4 throttle. Stays mostly in low 17s

So started playing with airs. I started with drilled out main (prob 160-170) and 170 airs. Bug takes off great from hard start and wideband doesn't go lean when I transition to mains. Goes from 17 to 11s without a lean spot.
I went thru the airs up to 210. The 210s gives me a hesitant from a good start.

I thought I was supposed to be at like a 200. Am I seeing something wrong with the 170? Or am I misreading this whole thing

[[email protected]]

If the engine likes 170 airs, run them.
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It's just advice, do whatever you want with it!

Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net

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[67rustavenger]

[Motor60]

2054. Dual 44 IDF
32 vents
55 idles
130 mains
170 airs

Weird combo? Very responsive now. No more bog from a hard start.
This is with new merged header.
If I put my vintage speed back on, will this combo still work?

[modok]

I don't think your jetting is odd at all, it's what I'd have recommended for a started point.

The carburetors are a good judge of character. It might need subtle adjustment with a different exhaust.
If it's WAY off, then, the carburetors are telling you.... don't bother, just take it back off

[Motor60]

I put back on my vintage speed exhaust and it still runs smooth, with aircooled' proper jets (only buy jets from him). Only advice I can give for guys running VS exhaust, is DONT try tune with it. It's way off.
Last night I went out for a drive with VS exhaust without changing the jetting just to see how it reads.

55 idle
130 main
170 air

Merged header w/ stinger: was 16-17 on progression
12.8-13.2 WOT with no lean hole

VS was 13.2 on progression and 10-11s at WOT

But bug performed same. Trying to jet with VS exhaust was exhausting and it was never gonna be right if I used it with wideband. Was easier to buy merged header, weld a bung, and tune with that.

[stan_tichomirov]

Ok, weird issue with these Italian 44IDFs -- they idle rich. I went down from 54 idles to 53 idles and can feel the extra snap, but idle AFR is at 12. Idles very smooth around 900RPM, but stinks. Cruises in mid to high 13s, accelerating part throttle in the 12s, WOT starts in 12s, then goes to high 13s (still trying to figure out why). Throttle plates are closing, timing at idle is at 8, mixture screws are only out 1/2 turn to a point where it starts popping while decelerating with throttle closed, but I can't get the AFR to be lower. Power is good, transition is smooth, 52 idles gave me hesitation before so I went richer to 54s, now came back down. Other than the rich idle, it runs pretty damn good IMO.

2276 with 40x35.5 heads, small ports
Web 109 with 1.1:1 rockers, 9.3:1
1 5/8 BP merged header with A1 phatboy
locked out 009 with Blackbox, vacuum lines from each throat to MAP sensor

Italian 44IDFs with 36mm venturis, F11 tubes, 53 idles, 143 mains, 210 airs. Fuel pressure too high? Floats are at 10.5mm.

Stan
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Jansen Enterprise
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