| Re: [GMCnet] 403 vs 455 [message #302037] |
Sun, 12 June 2016 01:59  |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
Karma: 11
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Haven't been on since you asked the question. So I'm not up on what's been covered. I'm sure you've heard both are fine. They are. The HP, and torque ratings are very close. I prefer the 403. Had both. On our last 3800 mile trip. And pulling Linda's 5,000 LBS Chevy Uplander. We averaged 10.2 MPG. My 78 Royale has the 3:70 from Applied GMC. I pull trailers a lot. With a GVW of 17, to 21,000 LBS. most of the time.
So I don't know if this was mentioned. One thing to think about is that the 77, and 78 have all the final up dates. Were painted with Dupont Imron. It's extremely durable. And these years have better front A/C units. Our first 78 burned last Aug due to a frig that had a fire recall on it that we didn't know about. Building another 78 Royale now under the Restoration subject heading. It's going to the GMCMI Rally in Branson in 11 days. If you have any questions. Feel free to call anytime. CDT. Bob Dunahugh Cell. 319-521-4891
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| Re: [GMCnet] 403 vs 455 [message #302054 is a reply to message #302037] |
Sun, 12 June 2016 14:10  |
mrgmc3
Messages: 210
Registered: September 2013
Location: W Washington
Karma: 2
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I am probably in the minority here, but I have a '78 with 403 and 3.07 final drive, and am perfectly happy with it. I don't tow anything, nor do I haul a lot of gear, but it goes down the road fine, and will pull any western grade in 2nd gear without fuss. In 2nd the overall drive ratio is more like 4:50:1 so you have the benefit of torque multiplication and the ability to shift into 3rd on the flat land. It's the closest thing to overdrive!. I've done a fair amount of carb tuning to get it to cruise at 70 mph at 15.5:1 A/F, but I can get 10 mpg with the dash air on running 65-70.
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] 403 vs 455 [message #302056 is a reply to message #302037] |
Sun, 12 June 2016 14:22 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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I just got Cinnabar 3.42 made in USA installed and i'm still getting used to it, just the 50 gal or so of run time home. The launch in stop and go is better with less convertor slip but I do miss the 3.07 on the flats. 3.07 just not optimal for all the other scenarios. I don't think I would ever want above 3.42 though with speed limits at 75 in a lot of states. (Sorry JimK, I just can't drive 4000 miles round trip to get work done. Wish you were closer than the far left coast.)
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] 403 vs 455 [message #302061 is a reply to message #302056] |
Sun, 12 June 2016 17:43 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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At least you're running lower than the stock 3.07.
People that understand gear ratio tell me that it is the way to go and
there is nothing wrong with the 3.07, just not as desirable whether your
pulling or going 70-80 mph.
Your vacuum gage will tell you and the carb will run leaner with higher
vacuum.
That was a test question on the ASE test I took few years ago.
On Sun, Jun 12, 2016 at 12:22 PM, John R. Lebetski
wrote:
> I just got Cinnabar 3.42 made in USA installed and i'm still getting used
> to it, just the 50 gal or so of run time home. The launch in stop and go is
> better with less convertor slip but I do miss the 3.07 on the flats. 3.07
> just not optimal for all the other scenarios. I don't think I would ever
> want above 3.42 though with speed limits at 75 in a lot of states. (Sorry
> JimK, I just can't drive 4000 miles round trip to get work done. Wish you
> were closer than the far left coast.)
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
> Source America First
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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