1984 Bronco build thread

[mat in tn]

very cool but would have opted for the 4bbl.one is as simple as the otherand a small four would possibly get better mpg although not with me driving.

[StraightSix]

to each their own I suppose. Ive seen several people have a real rodeo trying to get a holley 4 barrel to run right on their 300, sorta scarred me off. Especially when I bought a motorcraft carb and rebuild kit for a cumulative $60. If I really wanted the engine to rev and make power past about 3500 RPM a bigger carb, probably a 4 barrel, would be required. But Im happy with it running well, making good torque and fuel economy, and sticking around at 3000 and down. I cant deny, Id be very interested to see the dyno results of a swap from something like my 287 CFM 2 barrel to a holley 390 (or similar).

I also take a bit of silly pride in being able to point out how few truly aftermarket parts my truck has. the Intake manifold is aftermarket but almost everything else is a ford part from a different engine or model year. Nifty.

General updates - the engine is almost completely dressed. it all went together pretty smooth, so far the transfer case, transmission, coolant jacket and engine oil are not leaking so thats good. I filled the carb bowl with 93 and poured the rest of five gallons in the gas tank (which was dry). Ill add about another five gallons before startup and may attempt to prime more of the fuel lines, Im not sure yet (mechanical pump on block)I got my custom pushrods installed last night and the valves set, 3/4 turn past zero lash (my valve train is now fully adjustable). The exhaust manifolds and walker Y pipe gave me some trouble, it was taking a lot more work to get the rear manifold pulled up than it seemed like it should. I loosened the rear studs and collector bolts, shifted everything around a little and then it all bolted up fine.

the only mandatory thing left to do before startup is get the water pump pulley installed, set up the belt drive and drop on the mechanical fan.

I also need to make my oil pump priming tool. the one I bought has a female 5/16 hex drive and I need male so Ill be cutting a bit off of an allen wrench and either pinning or welding it into the shaft. if I had a mig machine weld would be a no brainer but I only have stick at the house.

I also need to get something worked out on my slave cylinder for the clutch. I ordered a new one and was about to install it when I notice that the entire thing is made of plastic including the ears that retain it in the steel bracket on the bellhousing. Im very skeptical to say the least. this got me crawling around on the floor and looking at the original again. I think what went wrong with it is that the clutch pedal got pushed in while the slave cylinder wasnt in a bracket thus allowing it to extend beyond its intended travel? now, in current state the clutch pedal does nothing to the slave cylinder while in the bracket. you can use your hands to compress the piston back into the body with some force, and if you let go the piston slowly advances back out. it makes me wonder if there is just air inside the slave cylinder or line somewhere which is why you can compress it by hand (just compressing the air) but it doesnt do anything when in the bracket if you push the clutch pedal. Im going to atleast try bleeding it before putting the plastic one in :(

I dont need the clutch to work for cam break in, I plan to have the engine and transfer case in gear with the driveshafts out. this should give me a chance to do a no load bearing break in on all of the fresh bearings and also guarantees that everything inside the gear boxes is getting lubed as designed.

[StraightSix]

Turns out my slave cylinder was fine - the metal rod that runs from the clutch pedal to the master cylinder is snapped in half. one would think I would remember the moment something like that happened, but I am really at a loss. Ill have a new one installed today.

the engine is effectively ready for startup. Im pulling my thermostat back out to drill a small air bleeder hole in it, and Ill spend the next day thinking over everything, trying to catch anything I may have missed. weather allowing we will start her up for cam break in tomorrow afternoon, otherwise Saturday morning.

[mat in tn]

I agree with your opinion on the two barrels as the way you planned it out. not many understand how carburetors are sized for the engine, but I think you got it right.
limiting the cfm of the carb is a way of protecting an engine from overrevving. just changing to a good two barrel should improve things a lot. no single venturi can meter precisely across its total range of operation. each has a "sweet spot". this is my only real complaint with the 1 barrel. mine has been great all along other than mpg. it may be tuned at 2k rpm, yet I run the highway at 2750. no overdrive in bubba.

[StraightSix]

I was really fairly pleased with the driveablity of my one barrel, but I cracked an intake runner and had a lean burn issue. I reasoned that a full mechanical conversion with performance oriented parts wouldnt be much harder in the short run (and easier in the long run) than keeping it factory. When I lost the cam I was getting 16 mpg highways, and ut responded much better to throttle around 1500-2500 with usable breathing up to about 3500.

Im really excited to get to learn to tune it with the afr meter. There is some chance that having live afr will prompt me to look for a carb with a little more adjustability than the 2150.

[mat in tn]

did I mis read something? you lost a cam? if so pleaseexplain that

[StraightSix]

sorry, I should probably use more descriptive words and phrases, "lost the cam" could mean a lot of things I guess.

#2 intake lobe wiped out. I started it up, had a lot of valve noise in the front half of the block, pulled valve cover and ran the engine, #2 intake valve wasnt getting any oil. ran a compression test and #2 was much lower than the others (and much lower than when I had performed the same measurement months earlier). I attribute the low compression on #2 at that time to low intake valve lift. swapped in new lifters, no change. all of this is what prompted me to pull the engine out last July. once I got it out of the truck it failed leak down test an all cylinders, and I just generally didnt know the history or condition of the block. I thought about just doing a cam and an oil pump but settled on a full rebuild.

I know this is a hotly debated topic, but Id encourage anyone running a flat tappet cam to do some reading about zddp.

[ArdWrknTrk]

There's really no debate about ZDDP and flat tappet cams....

There is a lot of snake oil sold and misconception about products sold today.
You need a true racing/break-in oil (like Brad Penn) or an additive that spells out exactly how much ZDDP is in it.

Any street oil sold since the advent of catalytic converters in the '70's is suspect.
Definitely any that meet API specs after leaded fuel was phased out.

[StraightSix]

Couldnt agree more Jim. Im running Joe Gibbs br30 for breakin on the cam, a fresh fill after cam break in through 50 miles, and a 3rd fill to get from 50-500. I actually havent selected the oil Ill run long term, Ive had too much other stuff on my mind.

[ArdWrknTrk]

I've never had any problem with filters clogging from cam break in.

Maybe I'm just cheap....  

[StraightSix]

Hi Guys! I think cam break in was a success. between a new mechanical fuel pump and a gas can on the ground in front of the bumper fueling was a non issue. seems like the thermostat worked fine, top hose got hot a few minutes into the run. hot oil pressure at 3000 rpm was around 45-50 psi, hot oil pressure at idle speeds was 15 psi or so which is less than I expected. the AFR read 16.5-18.5 for most of the run but that could be the result of leaky intake or exhaust. A few heat cycles to make sure the manifolds are sealed up right will be necessary before swapping jets. The oil didnt have any water in it and didn't smell like gas.

I did have a few runs of oil down the adapter plate, but I previously had some oil coming out of side covers and may have leaks on the valve cover too. Im not going to get worked up about a main seal/oil pan leak until I have a little more info. I can always re-click the pan bolts after a few heat cycles I suppose.

The road worthiness list is - Install driveshafts, torque two problem xmember nuts down, figure out my fueling issue (pretty sure its a crumbly spongy jumper I found the other day), run a few heat cycles to get manifolds sealed up and then potentially swap jets, set base timing, and then it should be ready for a ring break in drive.

[mat in tn]

I'm not sure that i would be happy at 15 psi. it is enough and 45-50 is certainly enough, but I like oil pressure.  it really does depend on how the engine was built and how it is intended to be used.

[StraightSix]

Its a 5w30 break in oil too, it very well may make more pressure with something like a 10w30 or 10w40.

[StraightSix]

Well, after a long and often stressful two weeks of drive line installation, engine rework, fitting fighting and fretting, I think its mostly alright.

I retorqued my manifold nuts after the first heat cycle, most turned 1-2 flats before clicking. I fired the engine back up and got the base timing and idle roughly set. It idles at 600, 19inhg, and about 14.5 on the afr.

I got the fuel system patched up (it wouldnt run off the gas tank for cam break in so I swapped on a new pump and pulled suction from a jerry can on the ground). It was a rotted out fuel hose just forward of the rear axle.

I have an odd sound or vibration every now and again, it always scared the daylights out of me.

I still need to fix those x member nuts, install driveshafts,and fashion a hold down solution for my new optima battery before the ring break in drive.

The Frenchtown Flyer has suggested that I not swap jets just yet. Im lean at part throttle with zero load, around 16-17 afr. He suggests I try out a full load WOT pull before jet swaps. The AFR meter does add a whole extra level to tuning.

I made a small but definitive win by finishing wiring in my new amplifier and powering it on for the first time. Even with the cheap speakers it sounds a lot better than before and the bluetooth will make listening much more convenient in todays world. Not a lot of bass response, but its crisp and clear. Between tgat and the new cab seals it should be quiet when I want and Willie Nelson when I dont.

My rear glass motor doesnt seem to have the "stuff" to get the rear glass up against the resistance of my new tailgate window seals. Im not sure if I should be looking into a replacement motor, rewiring with larger conductors all the way back, or something else. Id welcome input. It worked fine before but the seals were basically nonexistent.

[Gary Lewis]

It sounds like you are making really good progress.

I agree that you want to tune under load. But I think your idle AFR is a bit lean. Try closer to 12 and see if it doesn’t idle as well as tip-in better.

Willie sounds good in a truck. Seems right at home there.

On the rear window, you might try silicone spray on the seals. Should help it crank up easier.

[StraightSix]

Thanks Gary! It feels good. the more pieces it was in the more frazzled I felt. having it mostly put together feels really reliving.

I richened up my idle a bit and its now floating around 13-13.5. baby steps.

Ill see if I can find some silicone spray.

I have been having rough running, odd sounds, and just generally sorta worrisome stuff happening. today, I fired it up to run another heat cycle for the manifolds and noticed that it was indeed running rough and occasionally giving a small shake, but I also noticed that the tach was behaving a little oddly and the noise seemed to be coming from the exhaust in a way I hadn't previously realized. I shut it down and swapped in a different DS2 box. when I fired it back up, it was a whole different engine. it runs smooth, no odd noises and no shakes or shudders. it dropped a full 2 points across the board on AFR which I attribute to getting good ignition on all cylinders. perhaps it wasnt even firing consistently before resulting in excess oxygen in the exhaust gasses.

I was pretty worried, but not Im feeling a lot better.

I got those rust welded xmember nuts off today and tapped them. I know this makes them no longer a lock nut. Ill apply loctite when I put them back on. the way I see it, atleast heat will get that off. rusted lock nuts... they nearly stumped me.

assuming I can get to town to pick up a spare good DS2 box and get the xmember nuts retorqued, and hang my drive shafts, I should be able to drive it tomorrow for the first time since July. If all goes well I plan to di a ring break in drive.

any advice on how to perform a ring break in drive? I wish we had hills around here (and we do have some) but most of them are nothing too steep.

for anyone who is following along since the transmission rebuild, she shifts beautifully now.  

[Gary Lewis]

Yes, baby steps is the way to do it.

And a bad DS-II box will do that.  I had a bad box when I broke the cam in on Big Blue.  Wouldn't hardly rev over 2K in neutral, and the tach went wonky at that point.  So I kept it running for thirty minutes and then changed out the box - fixed everything.

Plus, it certainly messes up the AFR readings.  So disregard all of the previous readings as everything has now changed.  But I find that idle AFR needs to be around 12:1 to make the engine easy to start and provide good tip-in.

To break in an engine, inc rings, you need some significant acceleration.  Don't lug it, but don't go full throttle in 1st gear.  And don't take it too high in RPM.

On Big Blue I used heavy throttle in 3rd and 4th gears when turning between 2K and 4K RPM.  And I didn't allow the RPM to stay the same for more than a couple of minutes in the first 100 miles or so.

[StraightSix]

Hi! I just took a drive up and down the road. all seems reasonably well with nothing major to report mechanically. Maybe 3 miles.


hot idle AFR - 12.5

In 1st and 2nd, Im not sure you can really put much load on the engine and AFR stays moderate (no more than 16, normally around 15) regardless of throttle position.


any more than 1/2 throttle in 3rd and you get pretty lean, around 17.


any more that 1/3 -1/2 throttle in 4rth and it gets really lean, 17-20 and then the engine cuts out.


any time you pull from 1500ish in 3rd or 4rth its going to run very very lean.


Current - MC2150 1.08 w/ 47F jets. I have 48, 49, and 50s. I think Ill swap jets before the next ride. is there potentially something else wrong? lean out is almost immediate in 3rd and 4rth as soon as the throttle plates open. I can cruise in 4rth and hold 16 - 17 on flat ground so long as Im not accelerating or at more than about 1/3-1/2 throttle.

does anyone know roughly how many jet sizes I should be moving at a time? Ive heard that you should always go atleast 2, but I think that was in reference to Holleys.

[Gary Lewis]

The power valve in that 2150 should open at 6” or so, depending on what one you have, and bring the AFR back to 14ish.

What vacuum readings are you seeing?

[StraightSix]

I wish I had a vacuum gage in the cab so I could record that too. then again, I need at least some attention to look at the road with.

I swapped the power valve and went on another spin.


part throttle is still really lean in 3rd and 4rth. past 1/2 throttle both richen up considerably to 14.5 - 16 in 3rd and 15 - 16.5 in 4rth. right when you hit 4rth, if you put the pedal on the floor on level ground you get 18 for a second and then it richens up.


part throttle cruising in 4rth may be fairly lean, like 16.5 - 17. im still running 93. Im tempted to take it on the break in drive.


it fell flat on its face once rolling out of second. Im not sure if Ive lost my touch with a clutch or if the pumpshot isnt doing what I think.


it feels a lot like it did before with one major caveat - I was pushing it hard up  hill in 3rd to see what the AFR would read and I didnt notice that I was rolling nearly 4000 rpm! I dont know if it would have free spun that fast before. on the bottom it feels sorta like I remember, on the top it is going to have a lot more breathing room. not to mention that its lean and the ring seat may improve some.


at this point Im inclined to wonder if Im not a little lean on jets, and if I might not need "more power valve". I dont know if those are still made in multiple spring tensions.