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replacing Idle jets in weber 45DCOE...


Guest Anonymous
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Guest Anonymous

I have the idle jet holder/idle jet out, but I'm wondering how to get it apart. It seems the idle jet is pressed into the holder.

I'm replacing my 55f8s for 65f9's. I have an otherwise stock motor, and I normally drive at high alts if that matters. I'm doing this because steve from these boards suggested it, I'm wondering what the reasoning is and what others are using (not second guessing you at all steve, I'm just wondering why ;).

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Guest Anonymous

The choice of idle jets is partly governed by the diameter of the main venturis (chokes). I have an otherwise stock motor with 45DCOEs, and with 34mm chokes I run 50F8 idle jets. I had 45F8s, and they were too lean. I suppose I could stand to go up a little bit, but I suspect that unless you are running 36mm or 38mm chokes ( which probably won't give any improvement over 34's for a stock cam ), the 65F9 idle jets would be too rich.

Mike

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Guest Anonymous

so would 65f9 idle jets be right? Also, keep in mind I'll be doing most of my driving at 5000+ feet, over a mile up. Doesnt this mean I should run slightly leaner then normal? So maybe I need 60f8s or something, or with these 36mm chokes are my 65f9s gona be ok?

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Guest Anonymous

I guess I'm not really qualified to say what will work at high altitude with different chokes than I'm running. All I know is that you'll probably fiddle with it for a few years until you're happy with the settings. I'm told that unless you put it on a dyno or at least set up a air/fuel ratio meter on the exhaust, it's really difficult to get it exactly right.

Mike

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Guest Anonymous

hows the difference in performance with 45's? I was given them, so thats why they're going on-I know they are probably too big for stock

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Guest Anonymous

I picked up my vintage 45's at a bargain price, so I was saved the hassle of fretting over 45's vs. 40's, vs 38/38 downdraft, etc. Supposedly you can't see the performance advantage of 45's relative to 40's until you get up to about 7k rpm, which of course will never happen with a stock motor. Also, with a stock motor you will not be losing any top-end power (cause the top end is so low) if you go with smaller main venturis, like 34's, and this makes it much easier to tune the idle and lower end of the band.

I haven't really clocked my car, or dynoed it, or anything like that, and prior to the 45's I had a single barrel Weber 34mm downdraft on it, so the difference is night-and-day. I've been told that for a stock or mildly modified street motor (up to about 150-170hp?) you can actually get the same power out of a 2-bbl Weber downdraft (38/38 or 40/40) that you will out of sidedrafts, if you know what you are doing. But IMHO, half the appeal of sidedrafts is their character. They have great throttle response, lovely sounds, and they are so flexible that you can set them up for any type of motor. They leave plenty of room for future modifications to the head, cam, compression, etc. Also I like their modularity; it's easier to pull off a sidedraft carb or two than it is to unbolt a downdraft manifold, so you get wonderful access to the starter. I'll never go back.

Mike

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