625 AFB on 340 too rich, kinda long...
#591437
01/23/10 11:49 AM
01/23/10 11:49 AM
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Posts: 154 Winlock, Wa
fshd4it
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Car runs way too rich at an idle, maybe all across the rpm range, too. I'm talking burn your eyes kind of thing; always has, I've just never felt comfortable/knowledgeable about dialing in carbs/timing/plugs,etc. So I've let it run "rich" assuming I was erring on the side of safety. But no more! Time to confront my fears! Here's my combo: '72 340, 1.88 j heads, 8.5 +/- comp, .474 lift/228 deg @ 50 cam, hooker super comp headers. 4 speed car. Ignition is MSD 6al, stock dist (w/15 deg adv. plate and orig springs), rn12yc champions gapped @ .045. Idles about 900, 13" vac, timing is set at 12 initial, 38-40 total at about 3500(I know that's probably too much- I'm either going to order FBO's plate & spring kit or weld up my slots). Carb is stock from the box (9 years ago).I don't have an A/F meter and I'm a bit nervous about getting the thing too lean. My first impulse is to step up the "big end" of the metering rods (71 to 73 to 75) but leave the power size alone.Good idea? Could a plug heat change help? What do I need to watch for/look at while I'm doing this? As stated above, it's been this way for years; I'm just tired of making excuses for why it doesn't seem to run right!
In order to know what you want, you'll probably have to find out what you don't want.
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Re: 625 AFB on 340 too rich, kinda long...
[Re: stumpy]
#591439
01/23/10 12:12 PM
01/23/10 12:12 PM
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fshd4it
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I set the idle screws the best I could (rpm & vac), but with the rumpity-rump it's kind of hard to be positive. Backed out about 2 turns from closed. When I pulled the plugs, the bottom threads were wet & smelled like fuel. I'd have to pull them again to tell you any more than that, tho.
In order to know what you want, you'll probably have to find out what you don't want.
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Re: 625 AFB on 340 too rich, kinda long...
[Re: minnesota guy]
#591442
01/23/10 02:20 PM
01/23/10 02:20 PM
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Jets are supposed to be .098 primary, .095 secondary (according to info I've found); I'll pull the top to make sure & check float level per Dodgem's post.Just want to make sure I can get a new gasket today before I start,in case I can't re-use the old one.
In order to know what you want, you'll probably have to find out what you don't want.
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Re: 625 AFB on 340 too rich, kinda long...
[Re: fshd4it]
#591443
01/23/10 03:23 PM
01/23/10 03:23 PM
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Joined: Jan 2003
Posts: 9,436 Blair County,PA
62maxwgn
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Quote:
Jets are supposed to be .098 primary, .095 secondary (according to info I've found); I'll pull the top to make sure & check float level per Dodgem's post.Just want to make sure I can get a new gasket today before I start,in case I can't re-use the old one.
Are you sure the primarie's aren't supposed to be .089? The secondarie's are usually larger than the primarie's.
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Re: 625 AFB on 340 too rich, kinda long...
[Re: solarguy]
#591445
01/23/10 03:52 PM
01/23/10 03:52 PM
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Joined: Mar 2003
Posts: 15,478 the boonies
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try opening the gap a to .050. thats what MSD recomends for cars with less than 10.5:1 compression
It's got a cop motor, a 440 cubic inch plant, it's got cop tires, cop suspensions, cop shocks. It's a model made before catalytic converters so it'll run good on regular gas.
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Re: 625 AFB on 340 too rich, kinda long...
[Re: 62maxwgn]
#591447
01/23/10 04:08 PM
01/23/10 04:08 PM
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fshd4it
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That's what I always thought,too. But I just pulled them out & measured them, .098 primary,.095 secondary. And the float level is right on spec @ 9/32, per Dave Emanuel's book. The springs look more pink than orange(stock app. from allcarb.com's site),but they're definitely one of the two. Anything more I should do before I button this back up? Man, I type too slow. It's an aftermarket carter competition from Federal Mogul before they quit making them. Drivability is key right now, as this is mainly the wife's car, but I do have a new comp. 750 AFB I could swap in. Figuring how to read plugs is next on my learning curve.
Last edited by fshd4it; 01/23/10 04:17 PM.
In order to know what you want, you'll probably have to find out what you don't want.
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Re: 625 AFB on 340 too rich, kinda long...
[Re: minnesota guy]
#591450
01/23/10 05:04 PM
01/23/10 05:04 PM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
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burn your eyes kind of rich I'm thinking:(1)need weaker metering rod springs (2) floats (level/pinhole). Holler when you find it. EDIT what do your plugs look like? I'd get a strip kit & toss in the weakest springs & you'll know in 2 minutes if that's it. MORE EDIT No strip kit? Take the springs out completely & idle it. You'll know in less than a minute. I'm assuming that you dont have too much fuel pump psi @ idle, eddys cant take much.
Last edited by RapidRobert; 01/23/10 06:05 PM.
live every 24 hour block of time like it's your last day on earth
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Re: 625 AFB on 340 too rich, kinda long...
[Re: RapidRobert]
#591451
01/23/10 05:52 PM
01/23/10 05:52 PM
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OK then,here we go. 1, I pulled the plugs & they are all dk brown to black w/ coloring on the insulators. Damp/wet around the bottom of the threads. Note: the Chall has not been driven for months, only run in the garage to test & tune this past week. After I get it running today it'll get a good wringing out. Maybe show something new? 2, I'll gap the plugs to .050 before reinstalling. 3, I'll pull the metering rod cover plates @ idle to check operation. 4, a friend of mine has several strip kits, so I have access to different rods & jets. 5, get my distributor fixed up so timing can be set correctly. 6, move the 'puter out to the shop.Too much walking back & forth.
In order to know what you want, you'll probably have to find out what you don't want.
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Re: 625 AFB on 340 too rich, kinda long...
[Re: fshd4it]
#591452
01/23/10 06:34 PM
01/23/10 06:34 PM
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RapidRobert
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Rereading your post if you have a genuine carter competition series AFB it would be jetted on the rich side plus possibly an altered idle circuit but I sure wouldn't think eye burning rich. If you toss the springs for a check do replace the flat covers then idle it and I'd glass bead the plugs or get some new ones. Fuel pump psi is not excessive correct?
live every 24 hour block of time like it's your last day on earth
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Re: 625 AFB on 340 too rich, kinda long...
[Re: RapidRobert]
#591453
01/23/10 07:08 PM
01/23/10 07:08 PM
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fshd4it
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I don't believe the fuel pressure is excessive- I'm running a carter mechanical pump (one of the ones that bolt together), but again not sure of psi. I checked the rod plungers/springs, they're pulled down at an idle. I gapped a new set of plugs .050 & installed them- it actually seems to be a little better, odor/smoke wise. And a bit snappier when I blip the throttle. Only concern is they are rn 14 yc plugs, and I don't want to run too hot. I'm going to go get a new set of 12s right now & try them,too.
In order to know what you want, you'll probably have to find out what you don't want.
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Re: 625 AFB on 340 too rich, kinda long...
[Re: fshd4it]
#591455
01/23/10 07:37 PM
01/23/10 07:37 PM
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Joined: Feb 2008
Posts: 711 Montana
Posest
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Quote:
I don't believe the fuel pressure is excessive- I'm running a carter mechanical pump (one of the ones that bolt together), but again not sure of psi. I checked the rod plungers/springs, they're pulled down at an idle. I gapped a new set of plugs .050 & installed them- it actually seems to be a little better, odor/smoke wise. And a bit snappier when I blip the throttle. Only concern is they are rn 14 yc plugs, and I don't want to run too hot. I'm going to go get a new set of 12s right now & try them,too.
Check your pressure. I have had fits like this when the fuel pump was stock. It is hard to tell without a gauge what psi you have. I had a carter pump on mine also that was too much pressure. I have had this problem on my 340 and several smallblock Chevrolet's. Now I just automatically put in a regulator. I hate fighting carb troubles and almost every time is is over pressure on a carter or edelbrock.
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Re: 625 AFB on 340 too rich, kinda long...
[Re: Posest]
#591456
01/23/10 08:41 PM
01/23/10 08:41 PM
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as noted above...check that the metering rods are staying down while it idles..
step up springs could be too stiff.
Tony
70 AARCuda Vitamin C 71 Dart Swinger 360 10.318 @ 128.22(10-04-14 Bakersfield) 71 Demon 360 10.666 @122.41 (01-29-17 @ Las Vegas) 71 Duster 408 (10.29 @ 127.86 3/16/19 Las Vegas)
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