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I found a major thing about this, Mike..and may be your problem. It was mine. J-Y had one carb that would not “come in” on an F of mine we had worked on. Screws did nothing for him on one carb . He subbed a 300 carb he had , all OK. But later I took weird one apart, and after fixing it , put back on and returned his carb. What I found was the needles had been over tightened by a not so bright guy in distant past, and then played with unmercifully, probably constant tweaking “tuning the carb”..probably to no avail--- for following reason. When I bought this F 20 years ago, in DC, guy told me it “never idled right”—not a car guy, he gave up.. What this over tightening and playing does is ,first, puts a noticeable deformed / worn ring, like a step, around the needle itself where it contacts the carb..If you take needle out , you can see it. This changes it to “on –off” action at the critical point where you adjust it . The taper is not in play, and the hole or needle restriction in the carb is probably enlarged / damaged significantly. NOW! Before a BIG Oh NO ; I found that replacement Edelbrock AFB needles available cheap at Summit, are not only much beefier/bigger, they are enough different in taper or where taper is, to get you a whole new life on this adjustment. Best news? They screw right in . Carb acts like new. When you think of it, what can pro rebuilders do to a carb, beyond cleaning small openings, installing a carb kit , setting floats (and possibly bushing loose throttle shafts ? –have to fix that air leak, if shaft is loose) not black magic. But I think this wrecked needle / needle seat problem is common on ram cars , the needles have been tweaked a million times. “turn all the way in, then back out 1.5 turns” Well yeah, but not 50 ft/lbs “all the way in”. Once that happens, 1.5 turns no longer works. Hope this helps. It is not you, it is the carb needle ! John From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of Michael Moore mmoore8425@xxxxxxx [Chrysler300]
Thanks for the tips. I may well end up doing exactly that. I will try to get my idle closer first by using the vacuum gauge. My problem is that I am able to turn idle mixture screws entire turns without seeing a difference in rpm. On my E Type Jag, one trick for setting idle richness is to lower the idle almost to stall speed because the minute changes become more obvious. I will try the vacuum but will likely end up at a carb shop. Best, Mike Moore Morgan Hill, Ca On Sep 4, 2014, at 5:36 AM, Henry Schleimer <henry.schleimer@xxxxxxxxxxxxxxx> wrote: Just thought I’d pass on my experience with vacuum gauge tuning. I did this with my 78 Australian Valiant with a 265 Hemi six and two barrel Carter not long after I bought it around 15 years ago. Got the best idle vacuum and thought everything was sweet! I was then involved with setting up Queensland Transport’s random on-road emissions testing where Inspectors would pull over cars and do an idle check for HC and CO. No fines – just educational to help combat pollution. As part of trialling the mobile 4 gas analysers we were using, I had an Inspector test my Val. I found the emissions were off and more surprising was the significant effect that just 1/16 of a turn of the idle screw would have. That small change didn’t show up on the vacuum gauge. The car ran better after that and I haven’t touched it since. My experience was that vacuum tuning gets you in the ball park but having a mechanic put a probe up your exhaust pipe is a small cost for savings in fuel, reliability and peace of mind. Also, my previous Val had a two barrel Carter on a 318. I tossed the Carter for a new 4 barrel Holley along with other mods. (4 barrel Carters were rare as hens teeth over here.) I had that dyno tuned and found the jetting was set up rich straight out of the box. Obviously, dyno tuning can give air/fuel ratio throughout the rev range and under all types of load – not to mention spark timing for max power. Back then, the testing and fitting new jets cost me $75 when the carb cost me $350 - so it was a relatively good investment. For my 300C, I have religiously followed the factory manual for carb set up. But once it is going (and I have confidence my transmission rebuild won’t blow up) I’ll probably still get it dynoed even if it is running well. Be interesting to see if it really has 375 HP! All the best from Henry in Brisbane Australia where it is now Spring and 24 degrees C. From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of 'John McAdams' clafong@xxxxxxxxxxxxx [Chrysler300] Michael: Back in the fifties, I used this tip on my first car, a flathead Plymouth six with 2 carbs. When adjusting the idle screws, I watched (or felt) the front edge of the open hood to see when it was shaking or steady. You have the advantage of the long hood pivoting from the cowl. Sometimes I held my forehead or temple against the edge of the hood. From Big John Mc Adams (In SoCal) From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of Michael Moore mmoore8425@xxxxxxx [Chrysler300] Rick, I just watched a video about how to adjust idle mixture screws using a vacuum gauge, so I will try that. Thanks! Mike Moore 300H On Sep 1, 2014, at 12:54 PM, Michael Moore mmoore8425@xxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote: Rick, Thank you for your informative note. I have religiously followed the workshop manual to adjust my carbs (300H). Many years ago (I've owned it since 1966) I had no problem tuning it up. In recent years, it sat idle for a number of years and I finally had the time to get it back on the road. I was not happy with how it ran, even less so with how it stopped. I fixed the stopping problem then worked on the running problems. A friend who is most impressed with his mechanical skills spent some time helping me. That got a bunch of linkages bent up. I later replaced the distributor which helped immensely and had a top shop rebuilt the carbs with all new linkages. Suspecting the damper and timing mark, I had it rebuilt. I also adjusted the valves hot,and running, measured them, and for reference later checked them cold and found ca .002 difference between hot and cold. Dwell is correct, timing is correct-but I still do not like the way it runs. I have followed the work shop procedure several times, always dissatisfied with the results, My professional mechanic (not the genious who bent up the linkages) , who owns a Corvette, also with dual AFBs says its just because of the gasoline. One thing I am unsure of is tuning the 4 idle screws and looking for rpm increase or decrease, I can sometimes turn a considerable amount and not see it go up or not. How do you use a vacuum gauge for that? Because we have owned the car so long, and do enjoy it, I have been wondering about installing a single 4-barrel carb on another manifold for normal driving-but then what? Why would I ever install the 2x4 manifold again? 1. What would you do. 2. What do you use the vacuum gauge to adjust the carbs. (I am using a tach only) Thanks, Mike Moore 300H On Sep 1, 2014, at 12:28 PM, 'Rick Vitek' rpvitek@xxxxxxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote: With respect to Q1, are you sure if it’s too much fuel or not enough? Mark’s post is more likely, namely it’s a vacuum management issue. Lower engine rpm’s and thus less vacuum combined with braking (and thus with power brakes actuating and affecting vacuum). __._,_.___ Posted by: "John Grady" <jkg@xxxxxxxxxxxxxxxxx> To send a message to this group, send an email to: Chrysler300@xxxxxxxxxxxxxxx To unsubscribe from this group, send an email to bob@xxxxxxxxxxxxx or go to http://autos.groups.yahoo.com/group/Chrysler300/join and select the "Leave Group" button For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm For archives go to http://www.forwardlook.net/300-archive/search.htm#querylang __,_._,___ |
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