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general notices, announcements, invitations, & social stuff (like meets & car shows)

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rficalora
Rob Ficalora
Cypress, TX
(2386 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

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British V8 Colorado meet - Altitude planning
Posted by: rficalora
Date: April 18, 2014 12:24PM

Been thinking about altitude change from my current, effectively 0' above sea level to Colorado Springs' 6,000 feet. I talked with the guy who tuned my carb for me & he advised I'll need to plan for ".001" reduction in jet size for every 2000' ft gain of alititude. If you intend to run up Pike's Peak , we need to add jet extentions and a double slanted, slotted float at the rear. Otherwise you will experience a severe lean condition as you accelerate on a steep incline."

I don't recall, is there a Pikes Peak (or partial Pikes Peak) run planned? What about other places we're going?

Net - what elevation changes do we need to be planning for?

And yeah, I know, EFI takes care of this -- I've renewed my research into what I need, but very unlikely I'll have swapped over before July.



Edited 1 time(s). Last edit at 04/18/2014 12:24PM by rficalora.


Moderator
Curtis Jacobson
Portland Oregon
(4309 posts)

Registered:
10/12/2007 02:16AM

Main British Car:
71 MGBGT, Buick 215

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Re: British V8 Colorado meet - Altitude planning
Posted by: Moderator
Date: April 18, 2014 01:34PM

Yes, Pikes Peak is on the agenda. Its summit is 14,115 above sea level.

I drove from Longmont (5000ft) up to Breckenridge (9600ft) for MG2009 without a jet change, and it was a mistake. I had forgotten my jet kit at home. I couldn't enjoy my car with it running like that. It would barely idle. I had to get by with just twisting the idle-air screws, but that's not the best solution.

How many of you guys have fitted a wideband air/fuel ratio gauge? I installed one several years before converting from carb to EFI. It really helped me get my Edelbrock dialed-in. It was also eye-opening on cross country road-trips, in that it showed me just how much fuel mixture changes with altitude.

The good thing about an Edelbrock carb is that a needle change can be accomplished in minutes without spilling a drop of fuel. The bad thing is that you should plan on changing needles (and idle-air screws) along your route to Colorado, not just once you get here, IMHO.

Take notes with each change. If you have a GPS, you have an altimeter, so you can include the elevation in your notes. I suggest marking the heads of idle-air screws with magic marker or paint or whatever so you can differentiate "one o'clock" from "seven o'clock". With jetting changes, I recommend trying to get away with a needle change instead of a jet change wherever possible because the brass jets are easily buggered by a screwdriver tip. Also, be alert not to overtighten the screws that hold the needle covers down. I had a screw head pop off once! That's something you don't want to experience mid trip. In fact, it was the straw that broke the camel's back and gave me great incentive to complete my EFI conversion.


rficalora
Rob Ficalora
Cypress, TX
(2386 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: British V8 Colorado meet - Altitude planning
Posted by: rficalora
Date: April 18, 2014 05:46PM

No O2 here. And I have a Holley so changing jets is slightly more work.


Jim Stabe
Jim Stabe
San Diego, Ca
(603 posts)

Registered:
02/28/2009 10:01AM

Main British Car:
1966 MGB Roadster 350 LT1 Chevy

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Re: British V8 Colorado meet - Altitude planning
Posted by: Jim Stabe
Date: April 18, 2014 06:23PM

Summit has some reasonably prices units

[www.summitracing.com]

[www.summitracing.com]


74ls1tr6
Calvin Grannis
Elk Grove,CA
(1112 posts)

Registered:
11/10/2007 10:05AM

Main British Car:
74 TR6 / 71 MGB GT TR6/Ls1 71 MGB GT/Ls1

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Re: British V8 Colorado meet - Altitude planning
Posted by: 74ls1tr6
Date: April 18, 2014 06:23PM

If we go all in a big group, we should stop every 2000 ft up or down the hill for adjustments :-) and photo/video time!

Jim has your situation changed where you might be able to attend the meet?



Edited 1 time(s). Last edit at 04/18/2014 06:25PM by 74ls1tr6.


MGBV8
Carl Floyd
Kingsport, TN
(3235 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

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Re: British V8 Colorado meet - Altitude planning
Posted by: MGBV8
Date: April 18, 2014 06:30PM

Rob,

If I were heading to CO with a Holley, I would invest in some of those quick jet change metering blocks like RapidJet, etc. A stock Holley from TX to CO & back would be a pain in the a$$. Enough to convince even me to switch to EFI.


Jim Stabe
Jim Stabe
San Diego, Ca
(603 posts)

Registered:
02/28/2009 10:01AM

Main British Car:
1966 MGB Roadster 350 LT1 Chevy

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Re: British V8 Colorado meet - Altitude planning
Posted by: Jim Stabe
Date: April 19, 2014 02:34AM

Sorry Calvin., unfortunately I won't be able to make it. Several things have come up which have delayed the car and my daughter is expecting our first grandchild in that time frame. I would truly like to meet everyone but it doesn't look like it's in the cards this year.


74ls1tr6
Calvin Grannis
Elk Grove,CA
(1112 posts)

Registered:
11/10/2007 10:05AM

Main British Car:
74 TR6 / 71 MGB GT TR6/Ls1 71 MGB GT/Ls1

authors avatar
Re: British V8 Colorado meet - Altitude planning
Posted by: 74ls1tr6
Date: April 19, 2014 10:17AM

Jim, congrats on your first grandchild in your family. I wouldn't miss that for anything either. Enjoy your time together. There will be another year that you can make a meet in the near future.

Again Congrats!


302GT
Larry Shimp

(172 posts)

Registered:
11/17/2007 01:13PM

Main British Car:
1968 MGB GT Ford 302 crate engine

Re: British V8 Colorado meet - Altitude planning
Posted by: 302GT
Date: May 02, 2014 08:02AM

The biggest concern with high altitude driving should be with the cooling system, not the fuel system. A rich fuel mixture is relatively harmless, but a failed cooling system can destroy an engine. The problem is that water boils at a lower temperature at high elevations. Thus, for a given engine temperature, the cooling system pressure is going to be higher. Preparations should include checking and replacing hoses, probably a new radiator cap, and maybe new coolant (antifreeze raises the boiling point as well as lowers the freezing point). Consideration should also be given to adding a coolant recovery tank if not already equipped with one. Another help is to advance the ignition timing once at a high elevation. If running vacuum advance it may be possible to simply switch from ported to manifold vacuum; otherwise the static timing could be advanced a few degrees.

If still using a stock MGB (or other British) radiator there may be a problem with the radiator cap (but I do not know for sure). Some British radiators have a longer neck meaning that a standard radiator cap fits, but is does not reach down far enough to seal the radiator opening. In such cases, it is necessary to use a genuine British radiator cap.

In terms of jetting, it is not as big a problem as it is sometimes made out to be, and it may be possible to get by reasonably well without changing jets. First of all, main jets play no role in idle or even level road cruising. They only come into play during acceleration and higher power situations. Idle screws are easily adjusted to smooth out the idle, and during cruising, the fixed jetting of the transition circuit largely controls the mixture. This is relatively insensitive and, in any case, can only be adjusted on carburetors that have replaceable idle air bleeds. But most likely, drivability will not be an issue, only a slight decrease in fuel mileage. A rich mixture under power will reduce engine output somewhat (making the dyno session useless without a jet change), but with modern high energy ignition systems, the plugs will still fire the mixture. It is only a problem if a plug fouls causing raw fuel to wash the cylinder walls. But this is very unlikely; though switching to hotter plugs will help if this is a concern.

Holley type carburetors are equipped with a power valve on the primary side which enriches the mixture under high power (low vacuum conditions). Normally, the valves are set to open below 6 or 6.5 inches of vacuum. It is possible to put in a valve that does not open until the vacuum drops to 4 inches, and this will delay the richening. Setting the secondaries to open later (assuming vacuum secondaries) will also help to keep manifold vacuum up and keep the power valve from opening. It might be useful in some cases to use a weaker accelerator pump cam, or to set the existing cam to deliver a lower output if it is normally set on the high output position.

Constant vacuum carburetors such as SUs are unaffected by altitude. I have some experience with this…. When I moved from Denver to NJ I drove my SU equipped Morris Minor. It got 44mpg on the high altitude leg and 44 mpg on the low level parts of the trip. The only adjustment I made was retarding the timing a little once I reached Kansas. After settling in NJ I never even changed the mixture needle. I also had a Honda 600 sedan; this had a 600 cc motorcycle engine and motorcycle carburetor that worked on the SU principle. I bought the car in Texas and also had it also in Colorado. The drivability and fuel mileage were unaffected by the altitude change. I bring this up because Edlebrock carburetors seem to have a somewhat similar mechanism to an SU with a moving mixture needle and may have some altitude tolerance. But I admit, I have never used an Edlebrock so I may be totally wrong.

Anyway, keep in mind that at the British V8 meet in Townsend, TN, the excursion into the mountains reached over 5000 feet, essentially the same altitude as Colorado Springs, and none of the cars had any significant trouble. Pikes Peak is more of a challenge. Some additional advice there is if the engine has a front sump to make sure that it is completely full before beginning the ascent.

Finally there us a 50 + year history of carburetor equipped family cars successfully ascending Pikes Peak and Mt. Washington so no one should fear that their carburetor equipped car will suddenly stop running beyond a certain elevation…


ghornbostel
Greg Hornbostel
Nebraska
(72 posts)

Registered:
09/02/2013 01:41PM

Main British Car:
1957 TR3 Buick 231 evenfire V6

Re: British V8 Colorado meet - Altitude planning
Posted by: ghornbostel
Date: May 06, 2014 10:56AM

What goes up must come down. You have to change all that jetting back and if you don't you will be running lean and that causes holes in pistons. 99% of all automobiles that go to Colorado from lower altitudes suffer reduced performance but still function for the short time they are there. Now if we are going to race to the top of Pikes............... My Bultacos (2 cycle) really wouldn't run above 9000' with jetting for 1500'. However the BSAs would work to the top, not the best but work. I have above 8000' jetting for all of them and change back ASAP. The point is that a lean condition is much more serious than a rich condition that will change back on its own with lower elevation. Be very careful.
Regards
Greg Hornbostel


lars49
Larry Barnes
Colorado Springs
(176 posts)

Registered:
06/11/2009 02:12PM

Main British Car:
1980 MGB GM LA1 3400 V6

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Re: British V8 Colorado meet - Altitude planning
Posted by: lars49
Date: May 07, 2014 04:27PM

You can expect to see these altitudes

Hotel location - 6575

Monument Hill on I-25 between Colo Spgs & Denver - 7100

Mountain Dive @ Woodland Park & Pine - 8500

Will Rodgers Shrine - 8200

The Peak - 14114


One other note -- regular gas here has an octane rating of 85, other grades are similarly reduced.



Edited 2 time(s). Last edit at 05/07/2014 06:45PM by lars49.


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