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New guy with a Bugeye

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Nader said:
Good to know, I'll keep an eye on it. I can weld up the Al. for reinforcement if necessary.
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That's mounted upside down. It was originally designed to mount on the "long" side. That's the top adjustment part, it was NEVER designed to be the fulcrum point which takes the majority of load.
 
kellysguy said:
That's mounted upside down. It was originally designed to mount on the "long" side. That's the top adjustment part, it was NEVER designed to be the fulcrum point which takes the majority of load.
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You're right, but it's been mounted this way for years. And it only has to survive a couple more weeks until I install a 5lb mini alternator.
 
David_Doan said:
What are the specs./model number of that battery?
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It's an Odyssey PC680. You can Google it for specs.

Just got the mini alternator. It needed some modifications to fit. Again, I had to mill down (this time the appropriate) pivoting lug by a few mm. Also had to machine a bushing to reduce the 10mm hole to 8mm to fit the 5/16ths bolt hole on the engine side. Threw a pistachio in there for scale. The last pic shows the miniaturized electrical system together.
 

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So I just came back from some tuning, and here's what I learned about Weber DCOE jetting on the 1275: Following the guidelines to use 135 main jets is no good. It gives you the notorious mid-throttle stumbling on acceleration that I've read about from multiple posts. I could dial some of it out by richening the idle mixture screw, but still sluggish on acceleration. So I decided to go big and put in 155 main jets (and left the air correctors alone at 180). Man! Did that liven things up! No stumbling or flat spots, just hard acceleration and a fuel gauge that visibly drops. I'm going to weld an oxygen sensor bung into the exhaust so I can plug in my Innovate air/fuel meter for finer tuning.
 
Nader, there is a Mazda alternator that is almost that small. Off of a B2000 pickup from around 1990.
I have a DCOE setup for a Datsun engine and will be following your carb tuning exploits. I would kinda like fuel economy as well as decent acceleration.

Kurt.
 
Nader said:
It's an Odyssey PC680. You can Google it for specs.

Just got the mini alternator. It needed some modifications to fit. Again, I had to mill down (this time the appropriate) pivoting lug by a few mm. Also had to machine a bushing to reduce the 10mm hole to 8mm to fit the 5/16ths bolt hole on the engine side. Threw a pistachio in there for scale. The last pic shows the miniaturized electrical system together.
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Is that alternator internally regulated? If so 1 wire or 3 wire hookup?
 
I just welded up an oxygen sensor bung to the exhaust to use with my Innovate LM-2 AFR meter. It's fun to mess around with jetting when you have real numbers that quantify the flat spots and smoky grey exhaust. Before the meter, I thought the car was running well with chokes of 34, relatively large main jets of 155, and the idle mixture screw opened up a fair bit. Fuel consumption was ridiculously bad, funny at first, but now annoying.

Now with meter in hand, I jetted back down to 130, fattened up the idle jet, and predictably re-developed that flat spot under hard acceleration starting around 2500 rpm. Meter indicates that AFR starts around 11 (rich, but okay), spikes up to the 20s in the flat spot (dangerously lean), then back down to 11-12 after 3500 rpm. I'm thinking it needs richer accelerator pump jets, but now I'm questioning the choke size. I imagine that snapping open the throttle with these oversized chokes results in a sudden drop in manifold vacuum and intake velocity, more than the current accelerator pump jet can accommodate, thereby resulting in that big lean flat spot I experienced.

I've just ordered chokes in 32 and 30, and also fatter accelerator pump jets. With those size chokes, I'm firmly in DCOE 40 territory. In fact, it was only after ordering up all this carb stuff that I discovered an old, unproven Weber 40 with chokes of 30 down in my basement. Spares from my Alfa stockpile. I might as well just slap that one on and see how it runs.

Tuning this setup would be more fun if it wasn't so expensive. Then again, the new smaller chokes may pay for themselves in fuel savings. I have to use that justification because I'm too stubborn to go back to the perfectly adequate SU setup.
 
Swapped out the 34 chokes for a pair of 32s, and fattened up the accelerator pump jets to 60. Still some mid-throttle stumbling, but better. Going to swap in the size 30 chokes tomorrow.

Are there supposed to be internal sleeves between the Weber intake manifold and the head?
 
kellysguy said:
They have some 28s, 27s and 24s on ebay.
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Not for a DCOE 45. The smallest choke on a 45 is a size 30. I heard 28s were once available, but they're NLA.

Been enjoying a couple of rare sunny winter days here outside of Seattle, so I'm going to test these newly installed size 30 chokes.
 
So, yeah, size 30 chokes in a single DCOE 45 is the ticket, along with 130 main jets. 175 air correctors, 50 F-8 idle jets. Idlle adjustment screw is about one turn out. This is for a 1275 with a mild cam and a shabby 3:1 header. Drivability and power are great, AFM reads 12-13 through the entire rev range.

Having tested the different chokes and jets and confirming results through an air fuel meter, I'm having a hard time understanding how is size 34 choke ever became the default for a single DCOE 45 for these little engines.
 
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