Home » Public Forums » GMCnet » [GMCnet] GMCs, Mountains, Fuel Injection, Electric Blowers, Gears
| [GMCnet] GMCs, Mountains, Fuel Injection, Electric Blowers, Gears [message #180133] |
Mon, 13 August 2012 11:20  |
Gerald Work
Messages: 102
Registered: June 2010
Karma: 0
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Senior Member |
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Hi Gene,
We are now on our own having left the other cross Canada rolling rally folks. We came over BC 6 from Kelowna to the free ferry crossing at Needles, BC. Around a 4000 to 5000 foot pass with very long ups and downs and it is very hot. We still have a carb and had no issues. We did have to go into first on some very twisty up hill hair pin turns, but the norm was second or third. I did turn on the epump on the long uphill runs but don't think it was needed. This wonderful 94 octane gas with no alcohol is great. Not all that much more than crap gas.
From here we will mossy slowly through this very scenic region and then go down to Wallowa lake in NE Oregon. That will take us down the very long and steep Hells Canyon grade and then back up a long steep run into the Eagle Cap wilderness area. Given the really hot weather there and the fact that we will be back on alcohol gas I suspect we will have to use the epump a bunch. We certainly will need to readjust the rear brakes by the time we get home! Can't ask more out of this old girl than she is giving us on this trip. The other coaches all made it to Kelowna, albeit with a bump or two along the way for a couple of them.
Based on our experience here and with the direct comparison to about a dozen different coaches of different make up, I think it is safe to say that the most important things for reliable travel in such rugged mountain terrrain are 1) 3.5 or lower gearing on a strong trans, 2) the large one ton front brakes, 3) the aluminum radiator and 4) some form of epump to supplement or replace the mech fuel pump. All this stuff is well known and well vetted but seldom can it be seen so clearly as it has been on this trip. Not everyone elected to run the 94 octane good gas but is sure looked to me like it made a large difference.
Our coach is set up with a strong 455 that has lived its 80k life on a diet of syn oil, Manny trans with 3.5 power drive (also living on syn oil), Manny one ton front end, aluminum radiator, Jim K larger cooling lines from the trans to the radiator, no external trans cooler (I took it off to replace the weeping rubber hoses and never put it back), a Patterson ign, a non-stock Rochester Qjet carb, a Jim K. Epump and filter kit installed outside the frame rails with a manual switch by my left leg which I only turn on when needed, tanks coated with white elastomeric and newish rubber lines with no socks on the pickups. The stock mech fuel pump is the one with the bypass for a Toro with AC which I plugged (can't see any difference from when I had it plumbed back into the tanks. The vents are at the high point under the drivers side hood and at the DS wheel well. No charcoal canister and no Christmas tree. Also, no smog inspections where we live. So far, so good. By the time
we get home we will have done something around 3000 miles on this trip with very little on the level. Great fun and quite challenging.
Jerry Work
The Dovetail Joint
Fine furniture designed & hand crafted
in the 1907 former Masonic Temple building
in historic Kerby, OR
Http://jerrywork.com
..............
Message: 17
Date: Sat, 11 Aug 2012 14:30:38 -0500
From: gene barrow <barrowgene@gmail.com>
Subject: [GMCnet] GMCs, Mountains, Fuel Injection, Electric Blowers,
Gears
To: gmclist@temp.gmcnet.org
Message-ID: <2be99.5026b2dc@gmc.mybirdfeeder.net>
Content-Type: text/plain; charset="ISO-8859-15"
I've been reading the net too much recently. Many different but related topics.
"PS - The lack of performance out of this engine at altitude has made me decide that the Paterson engine I have in Houston will be
fitted with EFI" Rob Mueller
"Anyone out there who has any input on how a GMC runs at 12,000+ feet? " Mark Hickey
"Your last post on EFI reminded my of my conversation with James. He said it made the most incredible difference traveling over Eagle Mountain or Mount Eagle. He fooled with his carburetor and finally threw in the towel.
I suspect the carb in his coach was never exactly right, but others have said that the EFI really makes a difference in higher altitudes." Stick Miller
" 13% grades both up and down, lots of 6 to 11% stuff, some 20 to 40 km long. The coaches are holding up well for the most part. It is a real testament to Manny trans, Manny one ton from ends, alum radiators and the large cooling lines from trans to radiator. Lots of smelly brakes from the coaches without the larger one ton from rotors and calipers. A few with over heating issues on stock radiators, but for the most part every one is making it." Jerry Work
The quotes above all relate to Gmc's performance in the mountains.
I live in the mountains @ 4500' and have to climb to 6000' before getting down to 300' on the Sacramento River at Red Bluff.
Seventy miles of up and down grades with many slow (15 to 25 mph) curves.
About once a month I go to So Cal over the Grapevine @4144'. every 2 to 3 months I go north to Oregon over the Siskiyou Summit @4310'.
I have driven 5 different GMC's over various mountain passes including Deadman Pass 8047", Conway Summit 8143' Tioga Pass 9943' all in California and Monarch Summit in Colorado 11312'
Coaches were:
23' 455 3:07
26' 403 3:07
26' 455 3:07
26' 455 3;07
26' 455 3:07 and 3:70
All had carbs- none had Mark's electric blower. All made it up the grades; slowly and in 2nd gear.
I suspect that neither fuel injection nor electric blowers will make a "significant" difference in power/performance when coaxing a 12,000 pound brick up a 7 mile 6% grade.
Long steep grades and or slow switchback curves seem to have more effect on performance than thin air at higher elevations.
Last week I traveled to Florence, Oregon to see the newly completed shrine to Mr.ERF at Mickey D.'s He's honored as their most regular customer.
Coach, 1976 Palm Beach has 455 w/carb and 3:70. coach weighs~11,000 lbs.
Northbound on I-5 between the Oregon border and Canyonville (about 100 miles) you encounter Siskiyou Summit 4310' (highest point on I-5) 7 miles of 6% grade on both sides, Sexton Pass (named for GMCer Dennis Sexton?) 1960', Smith Hill Summit 1730', Stage Road Pass 1830', Canyon Creek Pass 2020'
All of these hills except Canyon Creek Pass required downshifting to second for part of the climb. Plenty of air volume available at these elevations.
When speed drops below 50 mph and rpm drops below 2500 and vacuum is 5" or less I manually shift to 2nd.
Any of you Great North West Netters travel this route? With FI or carb? What is your experience?
We are all hoping/trying to improve performance but it seems that many "upgrades" don't actually improve performance (headers come to mind) and some have unexpected issues.
The 76 Kingsley that I drove from Boston to San Francisco last Sept. had OEM exaust. It generated substantially less heat and noise in the cockpit than my daily driver 76 Palm Beach with headers.
Enough rambling.
Hope to hear more from the Cross Canada Ramblers on their experience in the mountains. Good opportunity to compare a variety of coaches over the same terrain at the same time.
Comments please.
--
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
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| Re: [GMCnet] GMCs, Mountains, Fuel Injection, Electric Blowers, Gears [message #180204 is a reply to message #180133] |
Tue, 14 August 2012 10:42  |
 |
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Jerry,
Since this is the first time I've driven Double Trouble into the mountains I thought I'd comment on your observations:
1) 3.5 or lower gearing on a strong trans
Comment: Double Trouble has a 3.21 to 1 planetary final drive and while it does help performance at "sea level" it doesn't help much
pulling up mountains. Agree 100% on the strong trans with Mobil Synthetic Trans Fluid- USE SUPER / LOW range! I have a Switch Pitch
/ Power Drive Manny Tranny sitting in Houston that will get installed behind the Patterson engine.
2) the large one ton front brakes
Comment: Double trouble has OEM disks with 80mm calipers on the front wheels, Caddy disks with 80mm calipers on the middle wheels,
and OEM drums on the rear. The pads and shoes are carbon metallic. I have absolutely NO braking problems at all with this setup. No
smelly pads / shoes. With JimB's sensitized booster I just touch the pedal and I slow down or stop as quickly as I want to. I have
yet to lockup the rears.
3) the aluminum radiator
Comment: I agree 100% the aluminum radiator is well worth the cost, in fact the only problem I have with it is that it cools the
engine TOO WELL! When it was installed I switched from a 195 to a 180 thermostat and now when it's a cool day the engine will run
below 180. I've got an auxiliary gage and Digi-Panel and I note temps down around 165! I'm going to change back to 195 as I reckon
165 is too low.
4) some form of epump to supplement or replace the mech fuel pump
Comment: While at JimB's COOP a couple of years ago Jason installed a little 1-4 psi Facet pump in between the AUX tank and the
selector valve which comes on when you switch to AUX. It works great in flat terrain. Unfortunately with the configuration of the
GMC fuel tanks (rear = MAIN / front = AUX) when your going up and down mountains it takes you longer to UP than it does to come down
so eventually you wind up with more fuel in the MAIN tank than the AUX so when you switch to AUX with the fuel pickups near the
center of the tank a vapor lock problem may or may not be avoided. Once I figger'd this out we began to stop for gas more frequently
to keep both tanks as full as possible. This action also resulted in keeping the fuel temps down and the problem got better. It did
not resolve it; it just made it better. BOTTOM LINE - put pumps in the tanks!
5) Jim K larger cooling lines from the trans to the radiator
Comment: Agree 100% - Quite frankly I don't understand why GMC didn't use 3/8" OD lines in the first place. Cost reduction?
6) fender wells removed - (Last email)
Comment: You (and KenB) noted that you have removed your fender wells with no ill effect. I just took a look at mine and noted that
they come all the way down to the frame. I think I'll do it in stages. Cut most of the vertical section out leaving just the inner
curved section. I'll bet that'll be the best of both worlds as it will allow air to flow out "sideways" and help cool the engine /
exhaust manifolds yet protect the Marcus McGee ceramic insulation blanket I have to install on the bottom of the floor.
Regards,
Rob M.
USAussie - Downunder
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Gerald Work
Sent: Monday, August 13, 2012 10:20 AM
To: gmclist@temp.gmcnet.org
Subject: [GMCnet] GMCs, Mountains, Fuel Injection, Electric Blowers, Gears
Hi Gene,
We are now on our own having left the other cross Canada rolling rally folks. We came over BC 6 from Kelowna to the free ferry
crossing at Needles, BC. Around a 4000 to 5000 foot pass with very long ups and downs and it is very hot. We still have a carb and
had no issues. We did have to go into first on some very twisty up hill hair pin turns, but the norm was second or third. I did
turn on the epump on the long uphill runs but don't think it was needed. This wonderful 94 octane gas with no alcohol is great.
Not all that much more than crap gas.
From here we will mossy slowly through this very scenic region and then go down to Wallowa lake in NE Oregon. That will take us
down the very long and steep Hells Canyon grade and then back up a long steep run into the Eagle Cap wilderness area. Given the
really hot weather there and the fact that we will be back on alcohol gas I suspect we will have to use the epump a bunch. We
certainly will need to readjust the rear brakes by the time we get home! Can't ask more out of this old girl than she is giving us
on this trip. The other coaches all made it to Kelowna, albeit with a bump or two along the way for a couple of them.
Based on our experience here and with the direct comparison to about a dozen different coaches of different make up, I think it is
safe to say that the most important things for reliable travel in such rugged mountain terrrain are 1) 3.5 or lower gearing on a
strong trans, 2) the large one ton front brakes, 3) the aluminum radiator and 4) some form of epump to supplement or replace the
mech fuel pump. All this stuff is well known and well vetted but seldom can it be seen so clearly as it has been on this trip. Not
everyone elected to run the 94 octane good gas but is sure looked to me like it made a large difference.
Our coach is set up with a strong 455 that has lived its 80k life on a diet of syn oil, Manny trans with 3.5 power drive (also
living on syn oil), Manny one ton front end, aluminum radiator, Jim K larger cooling lines from the trans to the radiator, no
external trans cooler (I took it off to replace the weeping rubber hoses and never put it back), a Patterson ign, a non-stock
Rochester Qjet carb, a Jim K. Epump and filter kit installed outside the frame rails with a manual switch by my left leg which I
only turn on when needed, tanks coated with white elastomeric and newish rubber lines with no socks on the pickups. The stock mech
fuel pump is the one with the bypass for a Toro with AC which I plugged (can't see any difference from when I had it plumbed back
into the tanks. The vents are at the high point under the drivers side hood and at the DS wheel well. No charcoal canister and no
Christmas tree. Also, no smog inspections where we live. So far, so good. By the time we get home we will have done something
around 3000 miles on this trip with very little on the level. Great fun and quite challenging.
Jerry Work
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GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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