Author Topic: Plug reader needed.  (Read 2304 times)

Offline HP2

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Re: Plug reader needed.
« Reply #15 on: September 12, 2007 - 02:23:44 PM »
So did you change the ignition at the same time as changing the carb? I'm just trying to isolate the problem to one side or the other, but if both were changed at the same time, you may have multiple problems.

I'm a little unfamiliar with the original AVS carbs, but the nice thing about Carters is that you can adjust the idle, power, and cruise circuits independantly. Although there are some differences, I recommend you go to the Edelbrock web site and download their manual on their AFB carb. There are some very good tips in there that will help you working on you carter. Also, the jets and rods are interchangable between the two, so there is almost no need to start drilling things.

It sounds like you have an issue with the cruise circuit. This could be a change in rod size to allow more fuel in around the 3300 rpm your missing at. The rods are typically a two step sizing that allows fuel to flow based on throttle position and vacuum signal. The rod fills the hole in the jet to regulate the fuel flow. Bigger jet is the same as a smaller rod in total fuel flow, so there are actually multiple ways to address the issue. The rods are held by a plunger which is controlled by a spring which reacts to a vacuum signal.  This spring allows the rod to slide up and down throughthe jet and add or subratct fuel. If this spring is too strong/weak and/or your rods or jets are too small/large, you will run into these types of transitional problems.




Offline 71bigblock

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Re: Plug reader needed.
« Reply #16 on: September 12, 2007 - 05:26:41 PM »
HP2, I put in the pertronix early this spring, March maybe.  Never had a problem winding out till I put the carb on. 

Are the rods you speak of the ones that stick up when I take the cover off?  (I'm a carb dummy)   :bricks1:

Offline matt63

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Re: Plug reader needed.
« Reply #17 on: September 12, 2007 - 07:56:50 PM »
I'm still thinking it's ignition related.  I would check your timing, condition of wires, etc.
Matt in Edmonton

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Offline 71bigblock

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Re: Plug reader needed.
« Reply #18 on: September 12, 2007 - 08:23:29 PM »
I'm still thinking it's ignition related.  I would check your timing, condition of wires, etc.

Timing has been adjusted by ear, but I guess it wouldnt hurt to do it again.  I replaced all the plug wires and coil wire a few months ago.   :walkaway:

Offline HP2

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Re: Plug reader needed.
« Reply #19 on: September 13, 2007 - 06:51:27 AM »
HP2, I put in the pertronix early this spring, March maybe.  Never had a problem winding out till I put the carb on. 

Are the rods you speak of the ones that stick up when I take the cover off?  (I'm a carb dummy)   :bricks1:

So there was no problem until the carb swap. I'd say we concentrate on  getting the carb adjusted.

Yes, the rods are the things sticking out of the cover when you pull it off. These slide into the primary jets when it is all assembled. There are numbers on the jets and rods that correspond to their size. While Carter and Edelbrock use a different numbering system, the parts do swap. If you can find the rod numbers, I can tell you what size they are. Or you can just measure the two steps with a mic.

Offline 71bigblock

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Re: Plug reader needed.
« Reply #20 on: September 16, 2007 - 09:45:19 AM »
Well, I took it to a show last weekend, and got it warmed up.  Now, when I kick it down, at about 65 it will start to miss, but not nearly as bad, but it still does it.  I think its just that the secondary jets are too small.  After it was warm, I adjusted the idle screws again, and you guys were right, it was a touch lean, the RPM came up some after I screwed them out about 1-1 1/2 turns out.  I still wonder why I have black all over the shed floor though.   :clueless:

Offline moper

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Re: Plug reader needed.
« Reply #21 on: September 21, 2007 - 12:01:51 PM »
When you start the car, even if you dont have a choke, you pump the pedal. That soot is the result of the over-rich condition when it's cold. If you snapped the trottle a few times, you might see that when it's warm on a concrete floor too.

Offline vinb

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Re: Plug reader needed.
« Reply #22 on: September 21, 2007 - 09:06:59 PM »
You can take the .089's and put them back in the secondarys and put the .082's back in the primary's . If that helps your high speed miss then you can either drill out the .082's or get a jett kit from Eldebrock and start messing with jetts until you get the plug reading you want. Also get a caliper and measure the metering rods and subtract the difference from the jett and thats what you have. The metering rods I looked up are #6-575, .062 middle & .052 bottom end.
I doubt it is the fuel pump, but it could still possibly be ignition. Just because it new doesn't mean it working correctly..
(By the way the plugs do look like there on the lean side....)

Offline Grancoupe

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Re: Plug reader needed.
« Reply #23 on: September 23, 2007 - 06:47:23 PM »
Wouldn't installing a pyrometer gauge take a lot of the guess work out of tuning the engine. Especially without a a dyno.

Offline Chryco Psycho

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Re: Plug reader needed.
« Reply #24 on: September 23, 2007 - 10:34:19 PM »
yes & no the pyro would show change but not nessiasrily gains in tuning

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Offline Grancoupe

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Re: Plug reader needed.
« Reply #25 on: September 25, 2007 - 09:37:56 PM »
But dosen't exhaust gas temp indicate the air fuel ratio. High temp lean/ low temp rich.

Offline Chryco Psycho

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Re: Plug reader needed.
« Reply #26 on: September 26, 2007 - 02:42:00 AM »
yes to a point , increased temp is leaner mix but not nessisarily increased power

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