Re: [Chrysler300] C hemi dual quad idle
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Chrysler300] C hemi dual quad idle

I also have the four-bolt manifolds, so I have clearances of 1/4" left,
1/4" right, and 1/4" to the hood (measured with a squished baggie of
grease). It's crazy close, but it does work out.

Keith Boonstra

On Mon, Nov 9, 2015 at 2:29 PM, John Grady <jkg@xxxxxxxxxxxxxxxxx> wrote:

> A further complication on air cleaner contact is we put the rare 4 bolt
> “truck” exhaust manifolds on this car, which almost forces some jacking up
> of drivers side…( how they did it, per reports /recommendations of the day)
> ---the manifolds hit the large 57 steering box, and inner part of upper
> control arm parts  . If anyone else goes this way, some pretty aggressive
> grinding of back of suspension parts should be done to get 3/8” or so
> there. Looking at it installed , the parts of suspension that interfere do
> not look structurally important  to me. Your opinion may vary. Some of
> these big flange manifolds have flats cast there . I researched that pretty
> well at the time, how to get those in a 300C, and no where was the air
> cleaner issue at the hood mentioned. I wanted 2.25 exhausts,  and if you
> look at pretty bad stock 300 “log” exhaust manifolds and tiny exhaust pipes
> on converts, a lot of what the hemi is all about is very obviously lost in
> the overall 57 exhaust design. We opened the frame cutouts in the X too.
> On the carburetors, we ground off that fast idle cam end so throttle
> plates are now sitting as closed as they get. However a new and unexpected
> complication arose; the front carb idle air screw has no real impact on the
> idle; we think the carbs may have been apart at the throttle plates
> /shafts, (extremely tight tolerance fit at manufacture to throttle bore)
> and although now closed mechanically till they touch, air is still getting
> by front carb, more air than is allowed in by the screw , in the first few
> turns  . So adjusting the screws(air screws) to same turns out per  300C
> dual quad set up instruction gets you nowhere. Both idle stop screws on the
> linkage are now not touching, (correct) both air screws were initially 4
> turns out  to get reasonable idle speed,--but after figuring out front one
> is not working right, it was turned in 2 turns , then went for vacuum
> readings on 4 mixture screws.   The front mixture screws do impact idle
> vacuum, so front cab is contributing OK, irrespective of air screw setting
> . The factory setup suggests 1 turn out on air screws, it would not idle
> there at all. Rear one acts normal. This experience and thoughts about it
> might help someone else…
> Someone mentioned using a carb air flow balancer /unisyn on this . This
> really makes sense to me now… (I did not have one) ---you cannot depend on
> counting turns on the air screw to sync carb air flow ..too many mechanical
> fit variables in that.
> It seems happy now, stable idle and no bang engaging torque flight, no
> stalling. Not real happy with what I know now, one carb not closing 100%
> right, but it is information. But take away is probably best to NEVER  take
> off staked screws holding throttle discs on throttle shafts. ..ever …even
> if shafts are a little loose.  Note that on single quads with throttle
> linkage stop screws  holding the carb open for idle, all this is no
> problem/does not matter....
> On to next problem….
> john
> *From:* Keith Boonstra [mailto:kboonstra.zeegroup@xxxxxxxxx]
> *Sent:* Friday, November 06, 2015 6:20 PM
> *To:* John Grady
> *Cc:* chrysler300@xxxxxxxxxxxxxxx; Chouinard JY
> *Subject:* Re: [Chrysler300] C hemi dual quad idle
> The drivers side air cleaner on my C also rubbed a groove in the hood pad
> that another owner had installed. Maybe that's why Chrysler didn't put a
> pad on the '57 hoods out of the factory.
> Without the pad there now there's no rub, but it's really close (about
> 1/4"); and I know if I ever snap the left side engine mount, I'll have a
> pretty big zit on my hood.
> Keith Boonstra
> On Fri, Nov 6, 2015 at 5:16 PM, John Grady jkg@xxxxxxxxxxxxxxxxx
> [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:
> More info after previous post on this issue of setting idle correctly --
> or understanding intent .
> It turns out that although both idle screws are obviously there on the 2
> carbs and linkage ... They are NOT to be used to set idle . The factory
> supplement image is marked "do not adjust" at each screw . It should say
> screw should not touch anything .. Or be removed .
> On these setups,only ( and not on WCFB in general ), there are two air
> bleed screws for idle air, like the large ones on ram cars , but these look
> like large mixture screws. They are on drivers side of each carb, to rear
> of secondary throttle shaft .The back one is hidden behind the vacuum
> fitting/ neutral switch . A few guys emailed me,suggestions about this
> setup , unaware of this idle air screw deal .. as I was too . So setting
> idle by front carb idle stop screw is wrong idea . But that screw will
> change idle .
> Further the carbs have to close 100 % or air will go by throttle plates
> like a normal carb at idle . On my car the fast idle cam tang when off the
> cam (warm engine ) was hooking under the cam end ---holding the carb from
> closing 100 % . I am going to add clearance there by bending or grinding
> end of cam disc . Then carb will close 100 % . Then air is set by bypass
> air screw . There is no fast idle adjustment except bending that same tab,
> which would hold carb open resting on cam until choke pulls off . Supposed
> to be about 1350 rpm. Once all this is working , balancing 2 air screws and
> 4 mixture screws ( count turns to start ) ought to have it idling as
> designed . It uses both carbs at idle . They suggest one turn open on 4
> mixture screws to start . The 300 supplement explains all this , but to me
> anyway , is not specific about the idle screws . I have learned something
> here.. Want to share it . The idle screws are not idle screws . A new issue
> , my air cleaners are rubbing on underhood pad . That is close !!
> More later , ! Progress!!
> John
> Sent from my iPhone

[Non-text portions of this message have been removed]

Posted by: Keith Boonstra <kboonstra.zeegroup@xxxxxxxxx>

To send a message to this group, send an email to:

To unsubscribe from this group, send an email to bob@xxxxxxxxxxxxx or
go to

For list server instructions, go to

For archives go to

Yahoo Groups Links

<*> To visit your group on the web, go to:

<*> Your email settings:
    Individual Email | Traditional

<*> To change settings online go to:
    (Yahoo! ID required)

<*> To change settings via email:

<*> To unsubscribe from this group, send an email to:

<*> Your use of Yahoo Groups is subject to:

Home Back to the Home of the Forward Look Network Archive Sitemap