Nothing Special's '71 Bronco

[Gary Lewis]

I don't have any guidance.  But I've seen some, so did some Googling as well as looking on my book shelf and found these:

Holley Motor Life:  The rule of thumb is for every 5000 ft. change in elevation, compensate by 3 jet sizes.

ITSTILLRUNS: Adjust the jets one size for every 2,000 foot change in elevation or for every 35 degree change in temperature.

Super Tuning & Modifying Holley Carburetors: I have a copy of this book, by Dave Emanuel, and it says "As a rule of thumb, in order to maintain the same air/fuel calibration as was present at standard temperature and barometric pressure (70F and sea level), jet size should be dropped one number (.002") for each 35 degree increase in temperature or 2,000 foot increase in altitude."

I found plenty of other seemingly authoritative statements, but they all seem to point to the same thing: 1 size per 2000 feet or 3 sizes for 5000 feet.  And those are essentially the same.

[Nothing Special]

Gary Lewis wrote

....

Super Tuning & Modifying Holley Carburetors: I have a copy of this book, by Dave Emanuel, and it says "As a rule of thumb, in order to maintain the same air/fuel calibration as was present at standard temperature and barometric pressure (70F and sea level), jet size should be dropped one number (.002") for each 35 degree increase in temperature or 2,000 foot increase in altitude."

....

I hadn't recalled how Holley jet sizes worked, but Autolite/Motorcraft jets are sized simply using the ID.  So one jet size is .001".  So that would seem mean one jet size in an Autolite/Motorcraft would be equivalent to 2 jet sizes in a Holley, which would get closer to the 1 jet size per 5000 feet.

I think for Moab next month (4000') I'll go with one jet size because a little too rich is better than a little too lean.

But next time I go out to Colorado (typical elevations from 7,000' to 14,000') I'll probably start around 2 jet sizes, but maybe plan to experiment a bit.  But I don't think I'll plan for more than about 4 jet sizes (which should be good for about 9,000' per the Holley guidelines and 17,000' if Autolite really does double it)

[grumpin]

Nothing Special wrote

Does anybody have a rule of thumb for how many jet sizes to drop for how much change in elevation?  I've found a few different suggestions ranging from 1 size per 2000 feet to 1 size per 5000 feet.  I'm thinking the difference is due to what engine/carb they are talking about.  But I'm wondering if anyone has any suggestions for a 2100 on a 302?

I ended up calling Holley, but I ended up where you and Gary are in my research.

I was thinking two numbers, and Holley agreed. But, now I’m thinking it’s lean at lower elevations. I was thinking of going back to what came on the carb when I bought it. It’s a newer 4160. I live at 4100 feet of elevation.

Now you got me thinking of ordering one number up. I also think I should quit thinking!

[Nothing Special]

I think for now I'm going to call the carb good!  Last night I put the check ball weight in and switched the jets back to the 52s.  Now it's running smoothly with no discernible misfire.  It will feel just a bit flat if I push the choke in right away, but I don't have to keep it out very long either.  So I thhink I'm pretty close on the mixture.

Also I'm able to do something with it that I haven't been able to do for a few years: let the clutch out without giving it gas or stalling the engine!  Even on a slight uphill I can start with it at a 900 rpm idle!

There are two minor driveability issues now.  I don't think the first one is carb related.  When the engine is at idle (900 rpm) and I hit the hydroboost brakes fairly hard the idle speed will drop to about 700 rpm.  If I also turn the steering it'll drop a bit farther.  A week or so ago it would die sometimes when that happened.  Now it just makes me think it might die.  But apparently the power steering pump is putting a bit too much load on the idling engine.  For now I'm going to live with it.

The other I guess really isn't a driveability issue since it's not when I'm actually driving.  But when I shut the engine off and try to restart it about 30 seconds or more later it's flooded.  It'll start easily if I clear the flood, but I can't just start it without hitting the throttle.  I don't know if gas is leaking through somewhere or if it's heating up, expanding and pushing somewhere.  But gas is getting into the intake manifold while the engine isn't running.  I'd like to get that taken care of, but I probably won't before Moab.

I think I'll probably try the 50s in it for Moab, but I'll definitely bring the 52s along.  I might order the sizes to fill in my jet collection.  But then again, I might not.


The other thing I did today was fix the passenger door latch.  It's been getting harder and harder to open, especially from the outside.  I didn't think Lesley was going to appreciate fighting with it for a week on vacation.  So I took the door panel off, hoping I'd see something I could address.  I didn't so I decided to just spray a bunch of lube on it.  Voila!  About the easiest fix I've ever had!


Oh, and the power steering noise I was complaining about right after getting it out of the garage (with a new power steering pump) this spring?  It's pretty much gone.  It took "filling" it about four times before it stayed full (I think I had air pockets).  But now that it's full it's quiet.


I might still find a few things to do to it before the trip.  But I need to open my folks cabin and get the motorhome ready too.  So the Bronco might just be done!  (for now...)

[Gary Lewis]

Yippee!  Moab, here we come!  

Sounds like you have most of the issues sorted.  But remind me what PS pump you are running?  I haven't noticed any change in idle speed with the Sag, whether I keep hitting the brakes or turn the wheel.  But then I have a 460 not a 302.  Still, I would expect to notice something.

And the lube does sound like and easy fix.  She's gonna like that.

When do you leave?

[Nothing Special]

We talked about the power steering pump back at the bottom of page 6 in this thread.  I had identified it as a stock pump from a '76 Bronco.  You had pinned it down to:

Gary Lewis wrote

Interesting.  Learned something.  In this thread on FTE Bill/Numberdummy says:

1965/66: Ford/Thompson P/S pump (1965/66 misc. cars & 1966 F100/250 2WD) had a much larger filler neck and dipstick than...

1967/77 Ford/Thompson "pencil neck" P/S pump (Most FoMoCo vehicles except 1975/77 Econolines & 1972/77 cars with Hydro-Boost).

Has a steel reservoir, P/S pressure hose threads onto the pump.
------------------------------------------------------------------------
1978: FoMoCo introduced the new C-II P/S pump, installed on most everything well into the 1990's (and beyond for some) except Econolines & 1978/79 cars with Hydro-Boost.

C-II pump has a plastic reservoir, P/S pressure hose connects to the pump w/a qwik connect fitting.
---------------------------------------------------------------------------------------------------------------
Eaton P/S pump: 1953/64 (edit: except M-E-L engines w/Vickers Drive pump) & some 1965/66 Passenger Cars (mostly 200/289 Mustang/Falcon/Fairlane/Comet).

Depending on applications, the separate reservoir was either mounted on top of the pump or remotely mounted on the left fender inner apron.

As for the running, maybe it'll clear up when it warms up - both the engine and the outside temps....

As to the 302 vs the 460, this 302 isn't what the original one was.  When I bought this Bronco it had the original engine with a little under 200,000 miles.  I could drive around my residential neighborhood never taking it out of the 1:1 high gear.  It would easily pull away from a 10 - 15 mph corner like that.  Then I replaced that engine (twice actually).  I bought the engine it now has from a local engine rebuilding shop.  They were pretty proud of their build that would be stronger than the original.  It may be at some speeds, but I've never been thrilled with it off idle.  Now pulling away from a corner in my neighborhood I have to downshift to at least the 1.4:1 3rd gear of my NV3550, and sometimes even that isn't enough.

I suspect this engine is cammed wrong for what I want.  Not only for driving in my neighborhood, but also when 'wheeling.  When I was first 'wheeling it I found it was much worse at crawling than my old '75 CJ-5 (that had the same crawl ratio), because I couldn't keep the engine running below about 1200 rpm while the Jeep's 258 six would crawl at about 600 rpm.  After putting the 4.3:1 Atlas transfer case it's actually good at crawling (quite a bit better than the CJ-5).  But I know the engine's power curve could be a lot better for what I want.

Some time I might do something about that.  But with the Atlas I can live with it, so for now at least I do.  But the point is that it's pretty anemic at idle, so I'm not too surprised that the power steering pump can pull it down

[Gary Lewis]

Yes, now I remember!  I wonder if the Sag is more efficient than the older pump.

And I understand the issue with the cam since my new 460 doesn't have the low-end torque the old one did, in spite of having more compression.  But, like you, I'll live with it.

[FuzzFace2]

Little late to the party
On the hot restart do you have a spacer between the intake & carb and if so what is it made of?

It sounds like what all us carb motor guys run into with today's gas blend.
It is made to vaporize easier and that makes it boil, read heat up, easier also.
When it boils the vapors come out the vent tubes and because they are heavier than air they fall into the intake floor and causes a flooding issue.

I have seen it posted to help fight this issue is to use a spacer between intake & carb that will not transfer heat (plastic?) and to add something to the fuel.
They say a little diesel helps but I have not tried it.
Add a qt to no more than a half gallon to s tank of fuel at fill up. Start little and work your way up.
Now if you have a cat on your truck then I would not do this.

Why I say I have not done this is because when I drive my truck its to/from work or the dump (dump is only a few miles down the road so motor dose not get that hot either) with no stops in between. One or 2 time I have it has "flooded" so foot to the floor ans it starts up with a little more cranking.
Dave ----

[Nothing Special]

Don't worry about being late, the party's gonna keep running for a while!

I do not have any spacer.  The carb is just bolted to the cast iron intake manifold with a standard  gasket between them.

Someone on another forum pointed me to an extra thick gasket that insulates a bit.  I might look into that.  And a guy I work with said he had similar issues with a 351W in his '79 Mercury Capri drag car.  He found an aluminum heat shield that went between the carb and manifold, with a gasket on each side, that theoretically directed the heat out away from the carb.

But in an early Bronco there isn't room for anything very thick there.  The hood is pretty close to the air filter.

On mixing diesel in, that sounds risky to me.  Reducing the volatility might be good, but reducing the octane?  Maybe not so much.  But maybe I should try some non-oxy fuel in it?

Like you, I find it pretty easy to deal with it in general, so I'm certainly not looking for an expensive or complicated fix.  But I could see it being a little bit bigger problem when 'wheeling.  Not horrible, I can always open the throttle to restart it.  But if I stall it a few times trying to get over a rock that can get old.  So I think I will try some non-oxy fuel at least for this trip.

[Gary Lewis]

An extra thick cork gasket and an aluminum heat shield might do the trick.  And it sure can't hurt - unless that little bit causes the air cleaner to hit the hood.

As for the fuel, Chris Tubutis put me onto this site years ago for finding ethanol free gas.  Looks like there is a station in Moab that has it.

[ArdWrknTrk]

I think I'm the one who found the Jeep rubber insulator.
But if hood clearance is an issue it might be too much.

[FuzzFace2]

I think I know of this thick gasket you talk of, it has plastic spacers at the bolt holes so you cant tighten down the carb to much ans warp or crack the carb base.
If you can use that and the heat shield plate with a thin gasket might work and worth a try.

As for lowering the octane when diesel is added do you think adding say a qt to 20 gallons would cause that? What about starting with a pt and see what that would do?
They say you only have to change the properties of the gas a little.
Dave ----

[Nothing Special]

I looked at that site and found the 1 station it lists for Moab.  Then looked it up and saw reviews.  Apparently it's an unattended self-service only station.  It has very mixed reviews, with several saying they had trouble with their card either bring refused or being double billed.  (The nice thing about the internet is that it's so easy to find out anything about anything.  And some of it is even true!)

Anyway, I think I'll fill with non-oxy gas when I run this tank out (still trying to burn up the gas that was in the main tank over the winter).  If it makes a difference I may try to stick with non-oxy until the trip is over.  But if not, or if I can't get non-oxy in Moab , it's not hard to live with.


On the hood clearance, I don't know how much I have, just that in general it's tight in early Broncos.  I don't think you can fit a 351W in without a body lift.  I do have a 1" body lift and am still running a 302, so I should have a little room.  But I also have an aftermarket open element air filter (otherwise known as a Hot Air Intake on the performance world) which I think sits higher than the stock Bronco air filter housing.  Going back to a stock air filter is also on the list (I'd like to reduce the intake noise of the open element) and if I do I'd certainly have enough room for a spacer.  But in the mean time I might try the thicker gasket (it looked like that would only add ~1/8" or so).  Or I might just keep living with it.

[Nothing Special]

FuzzFace2 wrote

I think I know of this thick gasket you talk of, it has plastic spacers at the bolt holes so you cant tighten down the carb to much ans warp or crack the carb base....

Yep that's the one.

FuzzFace2 wrote

As for lowering the octane when diesel is added do you think adding say a qt to 20 gallons would cause that? What about starting with a pt and see what that would do?
They say you only have to change the properties of the gas a little.
Dave ----

It's probably safe.  It just seems weird to me I guess.  And a bit of a hassle.  When I had my '29 Model A I had a bottle of fuel additive I was supposed to use since I couldn't get leaded gas for it.  It was always a bit of a pain to add that every fill, and that was only an ounce or so, so I could carry a bottle with me.  I don't think I want to be carrying a few quarts of diesel around to be able to add it at every fill, so that would mean finding a station that has diesel (I know, not that hard, I drove a diesel pickup for 5 years) and get a little from that pump before moving to a gas pump and filling up.  It's certainly doable.  But if that's what it takes I know I'll prefer to live with the lesser hassle of holding the throttle open on hot restarts.

[Gary Lewis]

Yes, some of what you read on the internet is true.  

But I think getting the old gas out has to be a priority.  You may find it runs much better when you get fresh gas, of any persuasion, in there.

As for the clearance, put a blob of Silly Putty on there and gently close the hood.

[ArdWrknTrk]

Adding diesel isn't going to do anything about the fuel fraction that has very high vapor pressure.

Refineries today use catalytic cracking to make whatever is highest on the spot market.

Gasoline today is not a fraction that boils off between X and Y temperature.
It is a chemical blend that when combined with 10% ethanol winds up at 91 or 89 or whatever R+M/2 octane.
I smell all kinds of stuff.
Often toulene, which has a very high octane too.  (so the rest must be garbage)

I hear people add enough water to get the ethanol to fall out. And then they think they have "pure fuel"
Ahh , NO.  It doesn't work that way.
But I get real tired to trying to explain facts to the willfully ignorant.

[Gary Lewis]

ArdWrknTrk wrote

Adding diesel isn't going to do anything about the fuel fraction that has very high vapor pressure.

Amen!

I'm no chemical engineer, but I have spent a bit of time working with the process to distill petroleum - enough to know that the "light ends" evaporate/distill quickly.  When those are put in a mixture they won't go away if you add something else.  All of those molecules are still there waiting to evaporate whenever the right temp is reached.

So the only way adding diesel fuel to the mix can cut down on the evaporation is if there's enough diesel to significantly reduce the percentage of volatile molecules.  And adding a small amount isn't going to do that.

[FuzzFace2]

Gary Lewis wrote

ArdWrknTrk wrote

Adding diesel isn't going to do anything about the fuel fraction that has very high vapor pressure.

Amen!

I'm no chemical engineer, but I have spent a bit of time working with the process to distill petroleum - enough to know that the "light ends" evaporate/distill quickly.  When those are put in a mixture they won't go away if you add something else.  All of those molecules are still there waiting to evaporate whenever the right temp is reached.

So the only way adding diesel fuel to the mix can cut down on the evaporation is if there's enough diesel to significantly reduce the percentage of volatile molecules.  And adding a small amount isn't going to do that.

From what was posted it did not mask or cover the "light ends" from evaporating it makes them just a little heavier to slow it down.
Well I guess it does then?

If I was to have this hot start issues I would give the diesel a try as I would not have anything to loose at that point.
Dave ----

[ArdWrknTrk]

Chemistry and physics are against you Dave.

Plenty of people put oil in their gas (MMO) but it is not going to change how quickly the lightest fractions boil off.

Keeping the float bowl cooler will help.
That's what insulators, heat shields, radiators and plastic bowls all do.

[Nothing Special]

On the recommendation of some people on the Bronco forum I got this insulating gasket.  The first issue I had was that my mounting studs weren't long enough for the added thickness (~3/8"). I had some 5/16-18 ready-rod so I made new studs (maybe I'll get real studs for it some time).

Next issue I had was that I believed the website that called it a gasket. It didn't feel like a gasket to me, and I doubted it's ability to seal. But I put it between the carb and manifold anyway and started it up.

Spraying carb cleaner around the base of the carb showed a whole lotta vacuum leaks. Fortunately I had a couple of stock gaskets. So I put one on either side of the new "gasket" (more of a spacer really) and tried again. No leaks this time!


It's definitely better now, but not perfect.  I stopped for gas (engine definitely up to temp) and when I restarted it took quite a bit of cranking, but did start without my needing to hold the throttle open.  (This was running on the aux tank that was empty over the winter and filled a few weeks ago.  So it was fresh-ish regular 87 octane E10)

At the gas station I filled it with non-oxy premium and switched to the main tank (which had been empty), so the next test was with fresh non-oxy.  Again with a hot engine I leet it heat soak while I ran in to NAPA to get pads and rotors for my son's car.  And again it started without holding the throttle open, but with a lot of cranking.

So like I said, better but not perfect.  I'll live with it like this for the foreseeable future.  And I now know that there's no point in chasing down the much more expensive non-oxy fuel.