Home » Public Forums » GMCnet » [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system.
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Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system. [message #324201 is a reply to message #324160] |
Fri, 22 September 2017 11:57 |
mrgmc3
Messages: 210 Registered: September 2013 Location: W Washington
Karma: 2
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You can get away with 16:1 A/F at light load up to say a 65 mph level road cruise load. I'd suggest dialing in with the benefit of at least one exhaust thermocouple and someone with real good hearing if you don't have a knock sensor. You'll likely need to go richer with any headwind or grade load.
Chris Geils - Twin Cities / W Wa
1978 26' Kingsley w/ very few mods; PD9040, aux trans cooler, one repaint in stock colors, R134a, Al rad, Alcoas, 54k mi
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Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system. [message #324205 is a reply to message #324196] |
Fri, 22 September 2017 12:33 |
Justin Brady
Messages: 769 Registered: April 2015 Location: Bell Buckle, TN
Karma: 11
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Kosier wrote on Fri, 22 September 2017 11:00Dick Balsley, who spent his whole career with GM, said that Gm calibrated
carbs for a 16.2 ratio. They liked 16.5, but production tolerances
kept them at 16.2. The Q-Jet on my Cadillac engine has been running at that
figure for 10+ years. Call it "dumb luck" if you want>
Gary Kosier
77PB w/500Cad
Newark, Ohio
--------------------------------------------------
From: "Bob Dunahugh"
Sent: Thursday, September 21, 2017 10:37 PM
To:
Subject: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the
Howell/GM system.
> Randy Van Winkle is extremely knowledgeable on that topic. And has data
> that shows it's fine with our 403, and 455. You have to remember that this
> system controls the ignition timing. Bob Dunahugh
> _______________________________________________
> GMCnet mailing list
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Do you have an afr gauge installed? I've never seen a carb run that lean Intentionally even at cruise.
Justin Brady
http://www.thegmcrv.com/
1976 Palm Beach 455
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Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system. [message #324206 is a reply to message #324205] |
Fri, 22 September 2017 12:41 |
Keith V
Messages: 2337 Registered: March 2008 Location: Mounds View,MN
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The other variable is the E10 gas we run now.
What does that do to EGT and AFR?
I did try rejetting my carb up one step and it made a huge difference, it went to around 14:1
Maybe I should see what that does to my MPG...
________________________________
From: Gmclist on behalf of Justin Brady
Sent: Friday, September 22, 2017 12:33:50 PM
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system.
Kosier wrote on Fri, 22 September 2017 11:00
> Dick Balsley, who spent his whole career with GM, said that Gm calibrated
> carbs for a 16.2 ratio. They liked 16.5, but production tolerances
> kept them at 16.2. The Q-Jet on my Cadillac engine has been running at that
> figure for 10+ years. Call it "dumb luck" if you want>
>
> Gary Kosier
> 77PB w/500Cad
> Newark, Ohio
>
> --------------------------------------------------
> From: "Bob Dunahugh"
> Sent: Thursday, September 21, 2017 10:37 PM
> To:
> Subject: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the
> Howell/GM system.
>
>> Randy Van Winkle is extremely knowledgeable on that topic. And has data
>> that shows it's fine with our 403, and 455. You have to remember that this
>> system controls the ignition timing. Bob Dunahugh
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
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Do you have an afr gauge installed? I've never seen a carb run that lean Intentionally even at cruise.
--
Justin Brady
http://www.thegmcrv.com/
1976 Palm Beach 455
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Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system. [message #324207 is a reply to message #324201] |
Fri, 22 September 2017 13:22 |
Gary Worobec
Messages: 867 Registered: May 2005
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I concur, I have a WB A/F gauge with my Howell FI and routinely get that reading on lean cruise.
Gary
> On Sep 22, 2017, at 9:57 AM, Chris Geils via Gmclist wrote:
>
> You can get away with 16:1 A/F at light load up to say a 65 mph level road cruise load. I'd suggest dialing in with the benefit of at least one
> exhaust thermocouple and someone with real good hearing if you don't have a knock sensor. You'll likely need to go richer with any headwind or grade
> load.
> --
> Chris Geils - Twin Cities
> 1978 26' Kingsley w/ very few mods; Headers, Progressive Dynamics 9040, aux trans cooler, one repaint in stock colors, R134a, Al rad, 50k mi
>
> _______________________________________________
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Gary Worobec
garytwmw@gmail.com
(o) 951-763-0518
(cell) 773-230-6226
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Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system. [message #324214 is a reply to message #324207] |
Fri, 22 September 2017 14:40 |
johnd01
Messages: 354 Registered: July 2017 Location: Sacrameot
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This is kind of off topic but why should I switch to FI?
Does it pay out or is more of a nice toy to add the bigger toy we drive?
On Fri, Sep 22, 2017 at 11:22 AM, Gary Worobec wrote:
> I concur, I have a WB A/F gauge with my Howell FI and routinely get that
> reading on lean cruise.
>
> Gary
>> On Sep 22, 2017, at 9:57 AM, Chris Geils via Gmclist gmclist@list.gmcnet.org> wrote:
>>
>> You can get away with 16:1 A/F at light load up to say a 65 mph level
> road cruise load. I'd suggest dialing in with the benefit of at least one
>> exhaust thermocouple and someone with real good hearing if you don't
> have a knock sensor. You'll likely need to go richer with any headwind or
> grade
>> load.
>> --
>> Chris Geils - Twin Cities
>> 1978 26' Kingsley w/ very few mods; Headers, Progressive Dynamics 9040,
> aux trans cooler, one repaint in stock colors, R134a, Al rad, 50k mi
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> Gary Worobec
> garytwmw@gmail.com
> (o) 951-763-0518
> (cell) 773-230-6226
>
>
>
>
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--
*John Phillips*
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Johnd01
John Phillips
Avion A2600 TZE064V101164
Rancho Cordova, CA (Sacramento)
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Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system. [message #324218 is a reply to message #324215] |
Fri, 22 September 2017 15:56 |
Ronald Pottol
Messages: 505 Registered: September 2012 Location: Redwood City, California
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Well, where do you use your coach? Are you never going to altitude (Jim B
thinks you should stick with the carb, but he's in Florida, tallest
mountain east of the Mississippi is on about 6600' in New Hampshire, in the
past month, I've been over a pass that high 3 times). Are you running below
freezing (I remember my dad having fun getting our cars started in the snow
at altitude, not fun)? Do you drive a bunch (so the gas savings might pay
off)?
On Sep 22, 2017 13:09, "Justin Brady" wrote:
> Really just depends.
> I did it for faster starting, more reliably running, tuneability with a
> handheld instead of jets, more control, vapor lock elimination, etc.
> It won't make your coach run better than a perfectly tunedcarb (except at
> large altitude changes) but I just prefer fuel injection to carburetors.
> plus who among us has a perfectly tuned carb? :d
> --
> Justin Brady
> http://www.thegmcrv.com/
> 1976 Palm Beach 455
>
> _______________________________________________
> GMCnet mailing list
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Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system. [message #324221 is a reply to message #324218] |
Fri, 22 September 2017 16:13 |
Emery Stora
Messages: 959 Registered: January 2011
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Ron - I lost a bet once with someone from North Carolina when I said the highest mountain east of the Mississippi was in New Hampshire.
Actually it is Mount Mitchell in North Carolina at 6684 feet. You can reach it from the Blue Ridge Parkway.
Emery Stora
77 Kingsley
Frederick, CO
> On Sep 22, 2017, at 4:56 PM, Ronald Pottol wrote:
>
> Well, where do you use your coach? Are you never going to altitude (Jim B
> thinks you should stick with the carb, but he's in Florida, tallest
> mountain east of the Mississippi is on about 6600' in New Hampshire, in the
> past month, I've been over a pass that high 3 times). Are you running below
> freezing (I remember my dad having fun getting our cars started in the snow
> at altitude, not fun)? Do you drive a bunch (so the gas savings might pay
> off)?
>
> On Sep 22, 2017 13:09, "Justin Brady" wrote:
>
>> Really just depends.
>> I did it for faster starting, more reliably running, tuneability with a
>> handheld instead of jets, more control, vapor lock elimination, etc.
>> It won't make your coach run better than a perfectly tunedcarb (except at
>> large altitude changes) but I just prefer fuel injection to carburetors.
>> plus who among us has a perfectly tuned carb? :d
>> --
>> Justin Brady
>> http://www.thegmcrv.com/
>> 1976 Palm Beach 455
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
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Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system. [message #324225 is a reply to message #324221] |
Fri, 22 September 2017 17:06 |
Jerry Wheeler
Messages: 246 Registered: January 2013
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Glad you chimed in Emery as I now don't have to correct the statement about
the highest mountain east of the Mississippi.
JR Wheeler 78 Royale NC/OR
On Fri, Sep 22, 2017 at 5:13 PM, Emery Stora wrote:
> Ron - I lost a bet once with someone from North Carolina when I said the
> highest mountain east of the Mississippi was in New Hampshire.
> Actually it is Mount Mitchell in North Carolina at 6684 feet. You can
> reach it from the Blue Ridge Parkway.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>
>> On Sep 22, 2017, at 4:56 PM, Ronald Pottol
> wrote:
>>
>> Well, where do you use your coach? Are you never going to altitude (Jim B
>> thinks you should stick with the carb, but he's in Florida, tallest
>> mountain east of the Mississippi is on about 6600' in New Hampshire, in
> the
>> past month, I've been over a pass that high 3 times). Are you running
> below
>> freezing (I remember my dad having fun getting our cars started in the
> snow
>> at altitude, not fun)? Do you drive a bunch (so the gas savings might pay
>> off)?
>>
>> On Sep 22, 2017 13:09, "Justin Brady" wrote:
>>
>>> Really just depends.
>>> I did it for faster starting, more reliably running, tuneability with a
>>> handheld instead of jets, more control, vapor lock elimination, etc.
>>> It won't make your coach run better than a perfectly tunedcarb (except
> at
>>> large altitude changes) but I just prefer fuel injection to carburetors.
>>> plus who among us has a perfectly tuned carb? :d
>>> --
>>> Justin Brady
>>> http://www.thegmcrv.com/
>>> 1976 Palm Beach 455
>>>
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
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Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system. [message #324236 is a reply to message #324201] |
Fri, 22 September 2017 18:00 |
George Beckman
Messages: 1085 Registered: October 2008 Location: Colfax, CA
Karma: 11
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mrgmc3 wrote on Fri, 22 September 2017 09:57You can get away with 16:1 A/F at light load up to say a 65 mph level road cruise load. I'd suggest dialing in with the benefit of at least one exhaust thermocouple and someone with real good hearing if you don't have a knock sensor. You'll likely need to go richer with any headwind or grade load.
I concur with Chris. I do run 16.2 and 16.4 and have for years. THe Exhaust temp runs cool at 16.4. Lots of air. Not much fuel. The worry, whether you have a carb or EFI, in my opinion, is not lean cruise but "Does the unit go into Power Enrichment (Power Valve on a carb) soon enough." 12.8:1 or richer. EBL will increase fuel until it is 11.8 on a long pull.
I don't see high exhaust temps in lean cruise. I don't see high exhaust temps in Power Enrichment. At the sweet spot 14.7, light (and I mean slight) pull caused by a bit of upgrade or wind and exhaust temp starts to rise quickly. Like 150* in thirty seconds. (This increase does not show up on the temperature gauge.)
The heat is not a good thing. But for those of you who are familiar with cutting with an acetylene torch know, you heat the metal, but it is when you add oxygen, the metal "burns" away. Same with exhaust valves and pistons. Hot is bad. Hot with too much oxygen is catastrophic. So, we cheat and put in too much fuel, so we use up as much of the oxygen as possible. You can heat the combustion so much things break and melt but it is when parts of valves burn away, that we have sudden and catastrophic events.
The second problem heat causes is detonation. (pinging) Detonation can blow crevices in pistons if you let it rattle long enough.
(Thanks to Matt Colie for tutoring me on these matters over and over until it finally got through my thick skull)
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system. [message #324238 is a reply to message #324221] |
Fri, 22 September 2017 18:30 |
Ronald Pottol
Messages: 505 Registered: September 2012 Location: Redwood City, California
Karma: -2
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Well go update Wikipedia please
;-)
On Sep 22, 2017 14:14, "Emery Stora" wrote:
> Ron - I lost a bet once with someone from North Carolina when I said the
> highest mountain east of the Mississippi was in New Hampshire.
> Actually it is Mount Mitchell in North Carolina at 6684 feet. You can
> reach it from the Blue Ridge Parkway.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>
>> On Sep 22, 2017, at 4:56 PM, Ronald Pottol
> wrote:
>>
>> Well, where do you use your coach? Are you never going to altitude (Jim B
>> thinks you should stick with the carb, but he's in Florida, tallest
>> mountain east of the Mississippi is on about 6600' in New Hampshire, in
> the
>> past month, I've been over a pass that high 3 times). Are you running
> below
>> freezing (I remember my dad having fun getting our cars started in the
> snow
>> at altitude, not fun)? Do you drive a bunch (so the gas savings might pay
>> off)?
>>
>> On Sep 22, 2017 13:09, "Justin Brady" wrote:
>>
>>> Really just depends.
>>> I did it for faster starting, more reliably running, tuneability with a
>>> handheld instead of jets, more control, vapor lock elimination, etc.
>>> It won't make your coach run better than a perfectly tunedcarb (except
> at
>>> large altitude changes) but I just prefer fuel injection to carburetors.
>>> plus who among us has a perfectly tuned carb? :d
>>> --
>>> Justin Brady
>>> http://www.thegmcrv.com/
>>> 1976 Palm Beach 455
>>>
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
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1973 26' GM outfitted
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Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system. [message #324241 is a reply to message #324205] |
Fri, 22 September 2017 20:01 |
Kosier
Messages: 834 Registered: February 2008
Karma: 1
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Yes I do. I installed it when I installed the Cadillac. I'd heard so many
horror stories
about Cadillacs and heat that I also installed the aluminum radiator. No
problems!
I think it's important to have a heavy enough spring under the power
enrichment
piston that you get more fuel quickly when the vacuum drops. Since I'm
rather
deaf, I purchased the J & S Knock Eliminator. Maybe it really is dumb luck.
Gary Kosier
77PB w/500Cad
Newark, Ohio
--------------------------------------------------
From: "Justin Brady"
Sent: Friday, September 22, 2017 1:33 PM
To:
Subject: Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the
Howell/GM system.
> Kosier wrote on Fri, 22 September 2017 11:00
>> Dick Balsley, who spent his whole career with GM, said that Gm calibrated
>> carbs for a 16.2 ratio. They liked 16.5, but production tolerances
>> kept them at 16.2. The Q-Jet on my Cadillac engine has been running at
>> that
>> figure for 10+ years. Call it "dumb luck" if you want>
>>
>> Gary Kosier
>> 77PB w/500Cad
>> Newark, Ohio
>>
>> --------------------------------------------------
>> From: "Bob Dunahugh"
>> Sent: Thursday, September 21, 2017 10:37 PM
>> To:
>> Subject: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the
>> Howell/GM system.
>>
>>> Randy Van Winkle is extremely knowledgeable on that topic. And has
>>> data
>>> that shows it's fine with our 403, and 455. You have to remember that
>>> this
>>> system controls the ignition timing. Bob Dunahugh
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> Do you have an afr gauge installed? I've never seen a carb run that lean
> Intentionally even at cruise.
> --
> Justin Brady
> http://www.thegmcrv.com/
> 1976 Palm Beach 455
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system. [message #324242 is a reply to message #324238] |
Fri, 22 September 2017 20:00 |
johnd01
Messages: 354 Registered: July 2017 Location: Sacrameot
Karma: -1
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Ron,
Not sure how I am going to use my MH yet. We have about 10 hours on it. I
have had fuel problems. Replaced the fuel filters and fuel line between the
pump and carb. It had a section of hose. Need to replace the pump because
fuel blends back to the thanks. It stalled on me about 12 times, before I
changed the filters, all but 1 of them I was able to restart while costing.
I am in Sacramento but I do not see us going North or South much. Most
trips will have 2 to 4 passes over 7000 feet. We may go to Portland OR. a
few times. 80 from Sacramento to Reno is probably the hardest climb we will
do very often. We like to vacation near Jackson WY just over 6000 feet most
the area there.
We are on a limited retirement so we will be limited by fuel and
maintenance costs.
I know, it is like talking to airplane people where fuel is the cheapest
thing you put in your plain. Jet fuel is expensive but when you look at
overhauling 2 engines at $500,000 each every 3000 hours along with all the
other costs, the fuel does not look that bad.
On Fri, Sep 22, 2017 at 4:30 PM, Ronald Pottol
wrote:
> Well go update Wikipedia please
>
> ;-)
>
> On Sep 22, 2017 14:14, "Emery Stora" wrote:
>
>> Ron - I lost a bet once with someone from North Carolina when I said the
>> highest mountain east of the Mississippi was in New Hampshire.
>> Actually it is Mount Mitchell in North Carolina at 6684 feet. You can
>> reach it from the Blue Ridge Parkway.
>>
>> Emery Stora
>> 77 Kingsley
>> Frederick, CO
>>
>>> On Sep 22, 2017, at 4:56 PM, Ronald Pottol
>> wrote:
>>>
>>> Well, where do you use your coach? Are you never going to altitude
> (Jim B
>>> thinks you should stick with the carb, but he's in Florida, tallest
>>> mountain east of the Mississippi is on about 6600' in New Hampshire, in
>> the
>>> past month, I've been over a pass that high 3 times). Are you running
>> below
>>> freezing (I remember my dad having fun getting our cars started in the
>> snow
>>> at altitude, not fun)? Do you drive a bunch (so the gas savings might
> pay
>>> off)?
>>>
>>> On Sep 22, 2017 13:09, "Justin Brady" wrote:
>>>
>>>> Really just depends.
>>>> I did it for faster starting, more reliably running, tuneability with
> a
>>>> handheld instead of jets, more control, vapor lock elimination, etc.
>>>> It won't make your coach run better than a perfectly tunedcarb (except
>> at
>>>> large altitude changes) but I just prefer fuel injection to
> carburetors.
>>>> plus who among us has a perfectly tuned carb? :d
>>>> --
>>>> Justin Brady
>>>> http://www.thegmcrv.com/
>>>> 1976 Palm Beach 455
>>>>
>>>> _______________________________________________
>>>> GMCnet mailing list
>>>> Unsubscribe or Change List Options:
>>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>>
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
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> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
*John Phillips*
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Johnd01
John Phillips
Avion A2600 TZE064V101164
Rancho Cordova, CA (Sacramento)
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Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system. [message #324243 is a reply to message #324205] |
Fri, 22 September 2017 20:15 |
Kosier
Messages: 834 Registered: February 2008
Karma: 1
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Senior Member |
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Yes I do. I did a lot of twiddling with the carb, but I think the jets are
still stock. I think
you need a heavy enough spring under the power piston that it raises the
needles as
soon as the vacuum drops very much. I also have the J & S Knock Eliminator
since
I'm rather deaf. Maybe it is really "dumb luck".
Gary Kosier
77PB w/500Cad
Newark, Ohio
--------------------------------------------------
From: "Justin Brady"
Sent: Friday, September 22, 2017 1:33 PM
To:
Subject: Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the
Howell/GM system.
> Kosier wrote on Fri, 22 September 2017 11:00
>> Dick Balsley, who spent his whole career with GM, said that Gm calibrated
>> carbs for a 16.2 ratio. They liked 16.5, but production tolerances
>> kept them at 16.2. The Q-Jet on my Cadillac engine has been running at
>> that
>> figure for 10+ years. Call it "dumb luck" if you want>
>>
>> Gary Kosier
>> 77PB w/500Cad
>> Newark, Ohio
>>
>> --------------------------------------------------
>> From: "Bob Dunahugh"
>> Sent: Thursday, September 21, 2017 10:37 PM
>> To:
>> Subject: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the
>> Howell/GM system.
>>
>>> Randy Van Winkle is extremely knowledgeable on that topic. And has
>>> data
>>> that shows it's fine with our 403, and 455. You have to remember that
>>> this
>>> system controls the ignition timing. Bob Dunahugh
>>> _______________________________________________
>>> GMCnet mailing list
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>>
>>
>> _______________________________________________
>> GMCnet mailing list
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>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> Do you have an afr gauge installed? I've never seen a carb run that lean
> Intentionally even at cruise.
> --
> Justin Brady
> http://www.thegmcrv.com/
> 1976 Palm Beach 455
>
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Re: [GMCnet] 16.5 to 1 lean burn cruise isn't a problem with the Howell/GM system. [message #324246 is a reply to message #324206] |
Fri, 22 September 2017 21:08 |
mrgmc3
Messages: 210 Registered: September 2013 Location: W Washington
Karma: 2
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Senior Member |
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Keith V wrote on Fri, 22 September 2017 12:41The other variable is the E10 gas we run now.
What does that do to EGT and AFR?
Do you have an afr gauge installed? I've never seen a carb run that lean Intentionally even at cruise.
Justin Brady
Keith,
E10 will run 4% leaner than E0 (no ethanol), and so I kind of split the difference in jetting since you can't count on one fuel or the other. There is no direct affect on EGT due to E10 other than the slight enleanment. Spark advance has a much greater impact on EGT than small changes in A/F. This is why I urge everyone to make sure both their vacuum and centrifugal advance are fully functional. Retarded timing increases EGT a lot, in addition to lowering power and economy.
Justin,
My quadrajet runs about 15:5 at 60 mph level road cruise but drops to 13.5 for slight grades or speed 70 and above (and 11.5 at WOT). There is a lot of tunability with a quadrajet. Most people change main jets but the power piston spring controls when enrichment occurs from cruise and light throttle, so changing to stiffer spring will push the primary rods out of the jets from a higher vacuum starting point (i.e. smaller increase in load to gain some enrichment - i.e. Lean out the cruise point but make sure it rapidly enriches with load).
An AFR gauge or monitor and the patience to make numerous small changes can provide good results. Start with a tool box full of spare jets, power piston springs, a notebook for all changes and a good quadrajet book (like Doug Roe's) and you can make a lot of improvement.
I would not recommend this for a novice as there are many variables that can end badly, but if you read up and understand the basics of engine performance and the limits of where an engine should run for A/F and spark you can make significant gains.
Chris Geils - Twin Cities / W Wa
1978 26' Kingsley w/ very few mods; PD9040, aux trans cooler, one repaint in stock colors, R134a, Al rad, Alcoas, 54k mi
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