1984 Bronco build thread

[StraightSix]

Hi Guys!

Here is a walk around tour of the bronco. I should have made something like this a long time ago.


I got a permanent vacuum gauge intsalled, and the new gauge shows more like 16 inHg at hot idle. Im inclined to believe the new Ashcroft instead of the cheap Chinese gauge I had ziptied to the hood. The low vacuum reading prompted me to look around for vacuum leaks. I did find a leak in the hot air choke mechanism that I was able to resolve, and the engine no longer responds to spraying stuff on likely leak points. I dont think I have any more vacuum leaks. currently, hot idle is around 16inHg, 650ish rpm, and Ive been trying out different idle AFR ranges between 12.5-13.5 to see if any produce more vacuum. so far, that doesnt seem to be the case.

I check the coolant reservoir every time I cold start the engine, and there is pretty reliably about 2-3 tbsp missing every time. there is no coolant anywhere under the bronco, I cant find any on the engine (including the back, head gasket, freeze plugs.. everywhere). the oil on the dipstick looks great.

 I had the plugs out last night and this morning. I scoped all six cylinders, I cant see any evidence of coolant in the cylinders or being burned. #5 plug was wet with gasoline last night, but was dry (and not so rich looking) this morning when I pulled the plugs back out. in the photo, one is on the left, six is on the right.



I ran a compression check this morning, with all six plugs out, the throttle and choke fully open, and the engine cold, 255 miles on the block, the compression test results were 145PSI on 1, 150 -2, 150 - 3, 150 - 4, 145 - 5, 140 - 6. the static CR is about 8.6:1, dynamic is about 7.0-7.1:1.

at this point, the missing water is what has me most worried. I cant explain where its going. Im afraid that Im burning it, but it seems hard to believe Im buring a tablespoons of coolant every 10 miles but I cant find any liquid water in the cylinder after cooldown with a bore scope, or tell by the plugs. conservation of mass.. it has to be somewhere. perhaps the block is still working air pockets out?? the engine is at 255 miles, Id guess about 7 hours of run time.

[Gary Lewis]

Liked the video.  Nice Bronco.  

At 200+ miles you are still doing break-in and I think the vacuum will come up as things wear in.  And the compression readings are good.

But I don't know what to suggest on the coolant.  It would be surprising if you lose about the same amount each drive.  But it is possible little air pockets are being worked out.

Have you driven it on the highway?  If so, does that change the amount of coolant you lose?  Highway use would cause the pressure to come up, which should cause it to use/lose more coolant.

[StraightSix]

Thanks Gary!

I guess that depends on what "highway" means. Sustained periods under certain load conditions or engine speeds ?

[Gary Lewis]

It was more that the engine was under load and got thoroughly warm.  Around town doesn't necessarily do that.

I find that it takes 20 - 30 miles at highway speeds for my engines to get everything warm.  I judge that by the oil pressure, which drops a bit at idle after the engine is fully warm.

Also I've had a bad head gasket and it wouldn't leak at less than 45 MPH.  Below that it would run forever w/o losing coolant.  Above that it lost coolant very consistently.  I'm not saying I think you have a head gasket leak, but just wondering under what conditions you are losing coolant.

You could do a leak-down test to see if the head gasket is leaking.  Or put a pressure tester on the radiator cap and see if the system loses pressure.  And there are litmus tests for products of combustion in the coolant.

[Pete Whitstone]

StraightSix wrote

at this point, the missing water is what has me most worried. I cant explain where its going. Im afraid that Im burning it, but it seems hard to believe Im buring a tablespoons of coolant every 10 miles but I cant find any liquid water in the cylinder after cooldown with a bore scope, or tell by the plugs. conservation of mass.. it has to be somewhere. perhaps the block is still working air pockets out?? the engine is at 255 miles, Id guess about 7 hours of run time.

I went through this with my truck recently, even put dye in the antifreeze to try to spot where it was going. I was smelling antifreeze all the time, and going through a lot more than it sounds like you are. Like a cup every 30 miles. It was driving me nuts and I couldn't find it. I was also concerned with the thought it might be going through the motor and burning.

Finally one day while I was driving it, I was at a long stoplight and saw wisps of steam coming from the radiator area. Got to inspecting everything very carefully and finally found the culprit at the lower radiator hose/radiator junction. I tightened the clamp that was on there, then threw a second clamp after it, right on the "ridge" on the radiator hose boss. No more leaking.

Not saying that's where yours is leaking, but I am saying that I would bet a lot of money that it is leaking it somewhere, rather than burning it through the engine. You just have to find it. After it's hot, shut it down and then start wiping shop towels or paper towels on the bottom side of everything - hoses, water pump, and so on. Sooner or later you will figure out where it's going to.

[StraightSix]

Gary and Pete -
I think my next move will be to pressurize the radiator. Ive had several people share stories like yours, Pete. I suspect thats the only way Ill find it.

Check out what followed me home last night

it was absolutely filthy, I think a few generations ( or 50) of mice had been reared in it. Ive scrubbed it down with hot soapy water to get it clean enough to work on.

it came off of an 85 302. surprisingly, at the right orientation it fits on my carb and over my hot water box.


I dont have the cold air duct that runs from the grill to the air cleaner. I also dont have any of the temperature control/vacuum devices. I just have an air cleaner housing.  I do still have the factory style 1bbl air cleaner off of my 300. It has a ..reasonable looking.. temp sensor in the top of it, part number 9E607. I dont have a 9E897 (the check valve?) or a 9A995.

oddly enough, the 302 air cleaner didnt have a metal snorkel on it, and it doesnt appear that it ever did. the piece riveted onto the air cleaner is plastic and apparently designed to clamp the cold air duct onto.

my original 300 air cleaner has the metal snorkel on it with vacuum motor and damper attached. unfortunately, the vacuum motor no longer seems to work.

at this point, my rough plan is to take the metal snorkel off of the 300 air cleaner and rivet it onto the 302 air cleaner over the old PCV hole (pointed towards the passenger headlight in the photos above). Ill need to close up the hole for the original snorkel which will now point at the firewall. there is another quarter sized hole Ill need to close up in the rear unless it houses one of the sensors, In not sure yet.

I know I need some parts to include - the soft cold air snorkel duct, a new vacuum motor to fit my 300 air cleaner, and probably new 9E607, 9E897 ,9A995.

for now Im more concerned with getting the cold air side running. Georgia summer is coming and we may not see ambient temps below 40 degrees for 24 hours between now and October. I thing getting the cold air side running will be mostly finding and installing factory style parts. the hot air side will require some minor fabrication/MacGyvering to get going and probably wont be too important other than cold start until fall.

when it comes to moving the snorkel to a new spot, or closing up a hole that will no long be used, do we have best practices? Im sure rivets are the easiest and one of the most durable ways. what about sealing it all up? ofcourse, it doesn't need to be water tight but you dont want a LOT of air flowing through.  expanding foam? adhesive foam strips?

[Gary Lewis]

I think pressurizing the radiator would be my first choice.  I'll bet over time you find a leak, but it may take a while to find it.

The kits are fairly expensive from what I've seen, but I think the parts stores "rent" them.  If not, I've considered making one out of an old radiator cap.

As for the air cleaner, I think you are on the right track.  But I am not sure I'd rivet the snorkel to the base.  Instead I've used 1/4-20 screws, nuts, and washers to spread the load.

And do you really need to cut a new hole?  Most of the air cleaners I've looked at have a tab that orients it with the carb, but you could bend or cut that tab to let you orient it differently and get the existing hole pointed where you want it.

The ~1" hole is for another sensor, the Cold Weather Modulator IIRC.  You can see how the system works on the Operation tab at Documentation/Fuel & Air Systems/Air Cleaners.

[StraightSix]

Gary,
unfortunately, interference with the hot water box is what drives the need for certain orientations of the air cleaner. I only have two orientations that will work, one is with the original opening pointed to the fire wall and the other is with the original opening pointed towards the driver side head light. this is even with my considerable stack of adapters and spacers for the carburetor :( I can try to get a better photo showing off the interference issue later today.

noted on the 1/4 - 20 hardware

Ive been reading on the air cleaner page. From what I gather, the "bimetal sensor" is 9E607 and lives in the air cleaner lid. I have one of those that looks reasonable. The "cold weather modulator" is 9A995, and it lives in one of the quarter sized holes in the side wall of the air cleaner. Ill need one of those for sure.

The 300 air cleaner diagrams show a small piece in line just before the vacuum motor, 9E897. it looks like the Windsor air cleaners didnt have this part. does anyone know what it is?

[Gary Lewis]

Ok, I think I understand about the orientation.

As for the thing in the vacuum line, do you mean like in the illustration below?  Here's the writeup from the "Other" tab:

Check valves were used in many places in the vacuum systems on these trucks, and one place was on the air cleaner to keep the vacuum to the vacuum motor that controlled the air temp to the carb.  One example of that is in the illustration to the right.

[StraightSix]

Yep, that would be the one. Thanks Gary! with any luck I can find the few missing parts I need and get this going fairly quickly.

[StraightSix]

Well, I had a productive lunch break. First, something caught my eye from the bottom of the parts pile..

the cold air duct is the original from my factory intake set up. I hadnt seen it in a while so I assumed it was gone.. Score! The air cleaner is off of my junkyard 82 block. it just so happened to have a seemingly ok cold weather modulator in it. I have two reasonable looking bimetallic sensors now. I still dont have a good vacuum motor to control the damper, but the list is getting shorter.

I took some better photos of the options for arranging the air cleaner. there are two options that will clear the heater core box.

option 1 - original snorkel pointed to the firewall.


Benefits - This orientation allows me to eliminate the 3/4" air cleaner spacer that goes between the carb and the intake. the air cleaner could sit directly on the carb. the new snorkel location would be over the original PCV location so I wouldnt need to patch the PCV hole closed.
anti-benefits - the Cold weather modulator is in the back far from my vacuum source (base flange of the carb, driver front). it seems like it would make getting the lower portion of the air cleaner off a bit of a pain.

option 2 - original snorkel pointed towards driver side head light


benefits - vacuum modulator is in a very convenient location.
anti-benefits - the 3/4" spacer is required between the carb and the air cleaner to prevent interference between the air cleaner and the heater core box.


assuming I dont take the whole thing apart 5-10 per week, Id prefer option one. I think it will look cleaner. I sure do take it apart a lot these days though.. Input is welcome.

option 3 - use the orientation from option #1 (original snorkel points to fire wall) and make a new hole for the cold weather modulator if it really bothers me that much.

[Gary Lewis]

I like option 2 better. I think you could put a short snorkel on and get to the cold air opening in the radiator support from there with the hose - assuming there’s an opening on the driver’s side. That way you wouldn’t have to cut a new opening.

[StraightSix]

Gary,
I hadnt considered using the original snorkel and running to the air inlet on the driver side (I do have the cutout with pre drilled holes). If my only goal was a cold air intake, that would be by far the fastest and easiest thing I could do. I do think it would make accomplishing hot air/ thermostatically controlled air temp pretty difficult as the snorkel would be right over the valve cover, or on the driver side of the block far away from the exhaust manifolds.

as silly as it may sound to our more northern members, I do think I want functioning hot air. we pretty reliably have a few days a year with day time temps in the low 20s and it may be driven many many miles per year in ambient temps below freezing. I dont want it to be a fair weather only vehicle. since the penalty for too cold air is risk of lean out and detonation, I dont want to forgo the opportunity to have hot air. also, its pretty cold natured at start up. it could use some help in that department

[Gary Lewis]

Good point, I forgot about the heat issue.  

So you could do it right and go the other way.  Or do it quick and dirty for now and plumb up the cold for the summer.  Me, I'd do it right.  

[StraightSix]

Ive got atleast a few weeks before it gets hot and maybe two months before it gets really hot. getting just the cold air side working with option 1 or 3 is probably a one day project assuming I have everything I need handy. I dont really even have to get the vacuum modulator, vacuum motor, bimetallic sensor, or hot air stove figured out for quite a while. for now, laying the foundation in fab work is probably a good start.  

its just about always easier and faster to do it right the first time.

[Gary Lewis]

I agree it is "just about always" better to do it right the first time.  And if you have the time to do it that way now then you'll save time in the long run.

But it would be easy to get cold air to it the "quick and dirty" way.  

[StraightSix]

Here is what I was able to get done in about an hour this evening. I have a usable example of both sensors, the 84' 300 intake snorkel (with busted vacuum motor) and a stripped upper and lower 302 air cleaner. I marked the new location for the snorkel on the air cleaner with a marker. Ofcourse, thats the outside profile, not the actual line to be cut on.

I still need to cut out the spot for the new snorkel and patch the old snorkel hole. I need a few extra short 1/4 bolts for the attachments. After drilling out a few rivets, I see why you used bolt Gary. I think I may expirement with some kind of foam product to help seal off the snorkel holes. Im not sure if Ill get away with bending a lip to fit inside of the snorkel the way the factory spot works, but I guess I can try and cut it off later if it doesnt work out.

Once the cutting and patching is done Ill put it all together to verify fit then take it all apart and get everything truly clean. Then paint, then final assembly.

[Gary Lewis]

Good luck.  That aluminum is not very fun to work with as it is brittle.  I did the cutting on a steel lower and it wasn't bad.

And use washers on the inside to spread the load.  With the vibrations of the six I'm guessing the bottom will crack pretty quickly if you don't.  They cracked pretty easily on the V8's, so...

[StraightSix]

Good advice on the washers for sure.

My lower section is magnetic. Go figure. Does this perhaps mean it isn't original to a 302?

[Gary Lewis]

Interesting!  It is doubtful it was original on a truck. Only the 351HO and 460 air cleaners had steel bottoms from what I’ve seen. But there was a smaller Mustang air cleaner that had a steel bottom.