Alfa Romeo Forums banner

1 - 20 of 28 Posts

·
Registered
Joined
·
183 Posts
Discussion Starter #1
I was going to add this to the header thread where folks are emphasizing the importance of a catalytic converter, but I figured it was better to put it in its own thread. My car originally had SPICA, an air pump and a cat. Now it has Weber clones and both air pump and cat are gone. I've got it tuned pretty well, but nowhere near as clean as a modern fuel injected car. It tends to run rich.

I'd like to have it burn cleaner. Just because. I'd also like to avoid having it run poorly due to a plugged cat. Is there something I can add to my mostly-stock exhaust (4-2-1 headers, a short connector pipe, then the original two mufflers) that will help with this?

Thanks
 

·
Registered
Joined
·
820 Posts
I was going to add this to the header thread where folks are emphasizing the importance of a catalytic converter, but I figured it was better to put it in its own thread. My car originally had SPICA, an air pump and a cat. Now it has Weber clones and both air pump and cat are gone. I've got it tuned pretty well, but nowhere near as clean as a modern fuel injected car. It tends to run rich.

I'd like to have it burn cleaner. Just because. I'd also like to avoid having it run poorly due to a plugged cat. Is there something I can add to my mostly-stock exhaust (4-2-1 headers, a short connector pipe, then the original two mufflers) that will help with this?

Thanks
adding a cat is not going to actually fix anything. all it will do is clean up one part of the terrible emissions the car is making because its running rich
( according to you ) . fix what wrong with the car and forget the cat unless its an enforcement issue.
 

·
Premium Member
Joined
·
14,025 Posts
It is OK to run the idle circuit lean - you are not going to damage anything. The price may be flat spots. It is my experience that a strong spark will help you run with leaner idle jets. For me that means an ignition that will handle a coil with a low primary resistance, say 0.7 ohms. I use an MSD box to fire an MSD Blaster coil. You can then open up the plug gaps to .040" and get big sparks.

What idle jets are you running?
 

·
But Mad North-Northwest
Joined
·
10,527 Posts
Generally you can't add a cat to a car with Webers. The Webers just run too rich. You'll end up with the converter getting quickly damaged and potentially overheating.

In general Webers tend to be set up a bit on the rich side. You get more power when the engine is a little rich (max power is at AFR ~12.5:1) plus the power/mixture curve is flatter in that region so small variations in mixture don't translate to big variations in power. It's also safer to have them a little rich at the baseline as extended lean running can cause damage.
 

·
Premium Member
Joined
·
14,025 Posts
It's also safer to have them a little rich at the baseline as extended lean running can cause damage.
Yes at higher rpm and power but not at low-mid rpm and cruising. I see my AFR meter read 15 or so at times under light throttle and around 17-18 on over-run. A lean idle mixture helps to keep the plugs clean. I have been doing it for many years and tens of thousands of miles.
 

·
Premium Member
Joined
·
14,025 Posts
Also remember that Weber made "emissions" carburetors. They would not enable a Spider to comply with US regulations but they are much cleaner than the classic Webers. I have a pair on my Spider. They make good power and give lower fuel consumption than classics.
 

·
Registered
Joined
·
183 Posts
Discussion Starter #8 (Edited)
Mine are set lean at idle and slightly rich when on the main jet. Idle jets are 50 F9, which may be too big since the mains that came with it were also too big (140). The current main jets are 130, which is slightly smaller than the 132s that were on cars that came with stock Webers. I've ordered a set of F8s ($15 a set from Czech Republic)

I'm going to go with Gubi's recommendation and keep the exhaust as-is.
 

·
Premium Member
Joined
·
14,025 Posts
50F9 are richer than "normal". Try 50F8 and if they are good you could try 50F11. I ran 50F11's in a strong 2L motor.
140's are also bigger than usual. 130 is usually big enough for classic Webers with regular cams. What size are your air correctors?
 

·
Registered
Joined
·
183 Posts
Discussion Starter #10 (Edited)
The air correction jets are marked CA 205. Maybe I should step down to 180?

I'm kind of disappointed that these are so poorly set up. When they were purchased from IAP, they were allegedly jetted for the Alfa Romeo 2000 engine.
 

·
Premium Member
Joined
·
14,025 Posts
205 should be OK. 200 is standard. Bigger numbers on AC's weaken the mixture throughout the main circuit but they have most effect at high rpm and that is where you don't want to be lean. Smaller main jets will lean out the middle. The Emulsion tubes can be F16 or F9. I doubt that you will notice much difference between them.

IAP don't disappoint me as my expectations are not so high.
 

·
Registered
Joined
·
183 Posts
Discussion Starter #12
205 should be OK. 200 is standard. Bigger numbers on AC's weaken the mixture throughout the main circuit but they have most effect at high rpm and that is where you don't want to be lean.
I do get a hiccup of some kind around 5K RPM when I push it hard. From what I've seen in other posts, air corrector jets are generally around 50 above main jets. As long as I'm swapping things out, I might as well see what a set of 180 air correctors does.
 

·
Premium Member
Joined
·
14,025 Posts
I have 140 mains and 160 air correctors and they are right for my engine. The 50 difference is a starting point if you don't know where you are. The Standard jetting for a 2L Spider with Webers with 32mm venturis is 130 mains, 200 air correctors and 50F8 idle jets. That is the way that the factory set them up.
 

·
Super Moderator
Joined
·
10,623 Posts
I've ordered a set of F8s ($15 a set from Czech Republic)
Would you share the name of your jet supplier in the Czech Republic? Buying Weber jets tends to get sort of expensive; paying $3.75/jet sounds pretty reasonable.

I'm kind of disappointed that these are so poorly set up. When they were purchased from IAP, they were allegedly jetted for the Alfa Romeo 2000 engine.
Not that it matters toward solving your problem, but are you running those OER carburetors, or are you saying that you replaced them with a set of Webers purchased from IAP. Or to speak in code, does IAP now sell OERs? Perhaps you are running OER's and they take the same jets as Webers.
 

·
Registered
Joined
·
183 Posts
Discussion Starter #15
Would you share the name of your jet supplier in the Czech Republic? Buying Weber jets tends to get sort of expensive; anything for $3.75/jet sounds pretty reasonable.
Carb.deals on Ebay.

carb.deals on eBay

I have no idea where he gets his stuff, but no one has ever complained about the quality.
 

·
Registered
Joined
·
4,187 Posts
I must admit I'm still scratching my head on this one. Unless you just enjoy chasing your tail, if you want a cleaner engine why don't you just convert back to the oem SPICA configuration?
 

·
Registered
Joined
·
183 Posts
Discussion Starter #18
I must admit I'm still scratching my head on this one. Unless you just enjoy chasing your tail, if you want a cleaner engine why don't you just convert back to the oem SPICA configuration?
Mostly $$$. I have a partial SPICA system that someone took off--probably because it wasn't working. The cost and time involved in undoing the conversion to Webers, obtaining all the missing parts, and re-attaching everything using a pump which may not (probably doesn't) work just doesn't make sense to me. If I were to go that route, I'd buy a complete car with the SPICA system already installed.
 

·
Premium Member
Joined
·
14,025 Posts
Thanks! Interesting stuff - carb.deals sells yet another brand of Weber knock-off: FAJS. See: New 40DCOE Carburetor with Horns Replacement for Weber Solex Dellorto | eBay
I saw their 45DCOE's and they looked too good to be true. Then I realized they were not Webers. Who knows what is inside them or the quality? I would not touch them with a long pole. Weber's reputation was built on quality.
I bought some "Weber" idle jets from Italy that did not conform to the Weber drawings.
 
1 - 20 of 28 Posts
Top