Carbs, Mountains, fuel/air mixture... lets talk

[Longhorn Man]

Vehicle;
Bone stock 72 burb, 402/TH400/quadrajet carb. only mod, brand spankin new HEI. Fresh tune up, plugs wires, whole dist with cap/rotor/coil.
Will be towing about 3000 pounds of spare parts, gutted parts truck, and mountain dew.
I'm having concerns of the air to fuel ratio getting too rich when I go through the mountains. I'll be leaving from Seattle, which is pretty much sea level... give or take a few feet, going through the mountains and the high plains, and ending up here in Ohio, which Columbus area is 900-ish above sea level.

Questions;
1. Would I make it through the mountains without messing with the carb? I know it won't be optimized, but would it do it without fowling out the plugs every 10 miles?
2. Been recomended (by non car guys) to travel at night, cool air = dense air... makes sence, would it be enough though?
3. Same guys as above, said ditch the stock restrictive air cleaner... even go without for a leg of the trip, let it take in all the air it can
4. Lower octain fuel would be better in a rich condition right... les resistant to ignition, try and get a quicker burn out of it?

Is there anything I am forgetting?

I have NEVER messed with a quadrajet, I could probably screw one up in short order, so i'd rather leave the sucker alone if it'll make it through the thin air and just get worse MPG.

[StingRay]

We had a 69 GMC Longhorn with a 350 when I was a kid. Dad hauled a 2800 lb camper, a boat, 7 people and all our crap every year for 10 years all of the way from Saskatoon to the BC Southern interior and sometimes all of the way to Vancouver Island ( over 1000 miles) going through all of the mountain ranges. I've perspnally driven my 72 with a stock q jet over the rockies a couple of times. If it's basically stock mixture, reliability and performance will all be fine. Mileage will suck no matter where you are.

[WorkinLonghorn]

I had a '69 1/2 ton with a carb tuned for power (rich) and when I took it up the local mountains,4-5000', it would lose TONS of power and would make black smoke.Didn't foul though.This was a 350 (which may have been stroked because it went like a bat on meth at sea level.

[Longhorn Man]

LOL on the mileage! I'm only hopin for 8 MPG.
I like what you're saying... anyone else have anything to add, or want to argue the testiment given?
I just don't like surprises.

[samwise68]

my dad drove his '68 C20 with a 283, 2 bbl, headers, etc., from Rhinelander, Wis, to Oregon, taking 2 from Duluth, Mn., across N. Dakota, Montana, trhough the mountains, into Washington and down into Oregon. granted, this was in January, but he said he didn't have any problem with his fuel to air ratio. (i asked just because i knew he had experience).

so, with that said, i think you'll be ok.

or. atleast i'll be crossing my fingers for you along the way.

-Sam.

[Longhorn Man]

you and me both Sam.
Thanks guys

[jeffspower]

Around '89 I made my first trip to Denver, going to Pikes Peak in a Buick with a mild built 455 & original Q-jet. ZERO problems, even at 14,000 ft. This was in July 90+ heat. No humidity there though. Years later, I made the same trip in a '88 Grandless Am. The 3.0 MPI would fall on it's face with every altitude change, and take MILES to adjust for it. Stupid thing even vaporlocked at about 7,000 ft.

So not all FI is better- but I do consider myself a pretty good tuner on a Q-jet

[CCCC]

Hello Longhorn Man:
I have some info in response to your questions, and have read a few of the posts about your Burb purchase and upcoming driving adventure. You certainly are well-known and obviously well-liked in this crowd, probably because you have been unselfish and have helped a lot of folks - like me once. Opinion -you are in for a great trip. BTW, Bob Cowan gave some good tips on pre-trip check if you are not certain of how this truck has been maintained.

I live at 8,000 ft. elevation and have a bunch of these 67-72 Chev/GM small blocks, one 402 BB and a BIG V6. I drive most of them all over this high country and often some of them all the way up through Colorado, Wyoming, Montana and over to Washington (we have some kids and grandkids near Monroe, WA). Fuel burn is not much of a problem at speed - idle can be a different story. At times, when on good highway with almost zero traffic up here, I have run without air cleaner to get better breathing - it helps a little bit. Also, I have put taller air filters inside the stock can - just let the paper filter stick up above the can and clamp the lid on top - may need a longer stud.

The Q Jet is probably not going to give you any trouble at altitude if it is clean and set up correctly before you start. That carb, in good shape, is quite adaptable. Actually, pulling a load with throttle more open may help matters in the mountains What you are more likely to get is some roughness at idle.

However, depending on 1. the degree of timing advance; 2. the octane rating of the fuel. 3 the operating temp - you may get some pre-ignition on the uphill grinds. One trip probably won't hurt anything, but you might consider the following:

1. Make sure timing is no more than 8 degrees adv. and maybe back it off a bit for this trip.

2. Consider some octane booster for the mountain portion (don't buy any of that canned stuff at Auto Zone, etc. - very weak mix and no real help). There is a less-expensive and very effectiveway to do this boost with toluene mix, and if you have two fuel tanks on the rig, you could have some of the high oct in one for use when needed. I use a formula gotten from a fine article on this. Will try to find the article if you really want it.

3. Consider an add-on auto trans fluid cooler (not a difficult add) - will take some of the heat load from your radiator/cooling system, and if the block has a high temp thermostat maybe change it to 165 or so (although I really do not think that a thermostat change would have much effect overall). If the rig starts to heat up near the top of a hill, run your heater inside the cab on high air and it will drain off a little bit of heat.

As soon as I close this out I will think of one more thing - or two - but probaly not any better than the mundane stuff above. Have a great time.

Paul (CCCC)

[BCOWANWHEELS]

ANDY, GO AS IS. dont fool with it. when you start pullin the rocky drop a gear and dont make it pull hard. so what if alot pass you. just fall in behind a semi and take your time. run premeum gas till you clear the rockys. watch your temp gauge constantly and keep it below 200 degrees. runnin at night will lower operating temps too but you not going in the mid summer and fall is hitting now in the rockys. every fuel stop check trans and oil levels and lok under vehicle for fluid leaks. wouldnt hurt to carry some jugs of water and a gallon of oil, qt. of power steering fluid, qt. of trans fluid. check fan belts & hoses b4 leaving . go easy is the ticket. set a pace the burb is comfortable with. rig up some temp. tail light for the back of the towed vehicle. checkeverything when you stop. feel the hubs for hi-temps ( bearings).
Also if you can drain the diff and fill with clean lube b4 you leave. bet its old as the hills. probably wouldny hurt to pop off the front dust caps and check grease in ft. wheels too. might save you from burnning a spindle & bearing. of course check tire pressure also .. remember a flashlight too.....
bob


P.S.
IF IN QUESTION STOP...... AND CHECK IT OUT........

[dan42]

I had a '72 Blazer that I took to Alta, Utah (about 9200 ft) from the coast of California, and parked it up there all winter - 350, stock Q-jet, automatic. Never messed with it, always started, ran great up and down the mountain. I'm guessin' you'll be fine.

[GMC Jim]

used to live in Montana and travelled to the Pacific coast many times. Now live in Oregon, but still visit friends in Montana and Minnesota most every year. Never a problem across the Rocky mountain divide... As altitude increases; less HP is produced by any engine ( unless supercharged ) as I am sure you know. Pulled a 16ft fiberglass boat over the mountains once with a 1979 Cad Seville ( 350 engine ).... No problem but somewhat sluggish' at higher elevations which is to be expected....
As most any owner will agree, the 402 engine is a real gas hog... You might want to check the timing to optimize for max power and fuel economy. Also, you might want to check radiator, radiator shroud and cooling fan clutch for proper operation. Weather has cooled down across your planned trip, which is a good thing also. Have been across the mountains at temperatures of near 100 degrees,, also in winter temps of 10 degrees on the Montana side.... As you might imagine, an engine feels like it has gained or lost 50 hp or so, at the extremes of temperature and altitude on your extended journey.. from the flat lands thru mountains....and the lush vegetation of the Pacific northwest........... Jim

[special-K]

My experience with taking my`71(402) out to the southern Rockies/Grand Canyon was:
I timed it to specs before leaving and when I was climbing north off of I-40 is started running like a rag.Once I got to Taos,NM I advanced and leaned by ear and it ran good again.I got up into Chama,NM/CO line I adjusted again to where it ran nice,by ear.Basically leaned it out and advanced to where it wouldn`t ping.This was hauling the camper on back with four of us and gear.Not a real hefty load,but something there.
We went all over,Mesa Verde,Monument Valley,Glen Canyon,North Rim Grande Canyon,Sedona,Prtrified Forest...all over.9,000-2,000' and all was good.Coming back east it ran fine,so I never reset it and it stayed that way for years.
I`d say set it as lean and as advanced as you`re comfortable with there in Washington and see how it goes,should be fine.You know to listen for the ping and if you start hearing it,crank the timing back.The carb should be fine if temp stays right.
Just let that BBC roll and it`ll be happy.Don`t get anxious and start pushin` it,not hard to dew.

[Longhorn Man]

all very good info. CCCC, if you could get me that article, My dad and i are always looking at ways to improve the fuels, and if he can save a panny a gallon (even if it costs him 3 cents a gallon to create) he'll jump all over it My e-mail is cockroach93@yahoo .com
Thanks again everyone.

[weasel29gm]

Heck Andy, flip the lid and let 'er suck air !!! Thats the ''hillbilly'' way LOL!!!!

[glock35ipsc]

Andy,

I live at ~5300'. Before I got my 02 GMC, I use to pull my snowmobiles with my stock 70 K10. Cameron Pass is right at 11,000'. The truck never had any troubles pulling the snowmobiles up the pass at all.

I say the HEI and the tune up will be a bonus. Run it and forget it. If the Q-Jet is in good condition, I doubt you will have any problems related to it.

[eedgell]

I agree with Tim. You sould'nt have any trouble, but if you do, advance the timing at altitude, and lean a bit. Dont lug on the hills. Drop that gear and keep your revs up. You will be fine. Just remember that high altitude likes a little more timing advance than lower altitude. This will help with the carb from wanting to load up, and help with heat. Good Luck!!

[68C15]

thin air equals to faster combustion. go up a few points on octane. if it starts to ping drop back a couple degrees on the timing.
I would leave the carb alone as any changes would require extensive work. unless you are keen on the idea of drilling out the air bleeds, tapping the holes to install hard to acquire ones from BG and changing them ever 1000 ft. above sea level and back again all while enroute.

[Stocker]

I have read that the Q-jet is very adaptable, and that has been my experience.

Years ago I took my stock truck (in my sig, with q-jet) from NorCal to eastern Kansas and back, in winter... thereby crossing the Rockies twice. No issues at all, just normal loss of power at higher elevations.

[eedgell]

Originally Posted by Stocker

I have read that the Q-jet is very adaptable, and that has been my experience.

Years ago I took my stock truck (in my sig, with q-jet) from NorCal to eastern Kansas and back, in winter... thereby crossing the Rockies twice. No issues at all, just normal loss of power at higher elevations.

Nothing personal, but you dont cross the Rockies in Kansas. You must make it a bit farther west to Colorado for that. FYI the Rockies run from Montana to Wyoming to Colorado to New Mexico. North and south.

[Stocker]

Originally Posted by eedgell

Nothing personal, but you dont cross the Rockies in Kansas. You must make it a bit farther west to Colorado for that. FYI the Rockies run from Montana to Wyoming to Colorado to New Mexico. North and south.

Is this a test?? Nothing personal, read my post and special-K's post, and check your atlas.

I've crossed the Rockies quite a few times over the last 38 years, and they still run through Colorado -- which lies between Kansas and the west coast.

[glock35ipsc]

Originally Posted by eedgell

Nothing personal, but you dont cross the Rockies in Kansas. You must make it a bit farther west to Colorado for that. FYI the Rockies run from Montana to Wyoming to Colorado to New Mexico. North and south.

Hmmm, I've lived in Colorado all my life, and I've always crossed the Rockies whenever I've headed to California.

Of course, I've only made it there once. I seem to get sidetracked and end up in Vegas. In which case, I've still crossed the Rockies.

[eedgell]

Originally Posted by Stocker

I have read that the Q-jet is very adaptable, and that has been my experience.

Years ago I took my stock truck (in my sig, with q-jet) from NorCal to eastern Kansas and back, in winter... thereby crossing the Rockies twice. No issues at all, just normal loss of power at higher elevations.

My bad. Did'nt catch on to the NOCAL thing. When I briefed over the post I thought you were coming from North Carolina. [dont ask why] That would be the reason for my post. Just a miss read.

[special-K]

NorCal to Kansas runs east/west passing across the north/south running Rockies,right.I-80:San Francisco CA,Reno NV,Salt Lake UT,Casper WY,I used to drop down I-25 to I-70 by way of Denver CO,Topeka KS.

[special-K]

I was heading to California and ended up in Bamf,lol.Still was the Rockies,though.Never did found California that time.
I`ve been across The 10`r and missed the Rockies.Skeeters were rough and the gators ran me off(was that a bull?Nope!It`s a frickin`GATOR!!!!).Never saw Kansas that trip.

Hey!!Let`s ask Miss South Carolina.

[Stocker]

Originally Posted by special-K

Hey!!Let`s ask Miss South Carolina.