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‘85 Ford Bronco 4.9L or 300 inline 6

4K views 23 replies 12 participants last post by  Warriors_Breakfast 
#1 ·
The old war horse is wearing down and the boiler maker needs an uplifting. Come to find rebuilding is a lost art. No one rebuilds anymore! Just buy a reman they tell me. Ok the reman is $2k. WHAT!!! A rebuild kit is $395. What’s going on here? I’m thinking about jumping in (I’m no grease monkey) and rebuilding it myself. Anyone out there got a better idea? I’ve thought about buying a used but that could be a crap shoot. I need ideas boys and girls!!!
 
#3 · (Edited)
Rebuild all the way... Unless u can find an inline 6 at a good price... The 4.9 is weak (edit correction, I meant 4.6). Had that in my 99 Expy (within 500lbs of the same curb weight as the BKO) and it was a dog. @biggum has some great info on his build thread from when he rebuilt his motor. Worth checking out.
 
#8 ·
Rebuild all the way... Unless u can find an inline 6 at a good price... The 4.9 is weak. Had that in my 99 Expy (within 500lbs of the same curb weight as the BKO) and it was a dog. @biggum has some great info on his build thread from when he rebuilt his motor. Worth checking out.
I think you had a 4.6..... the 4.9 went away in 96....

How many miles are on that thing, and what makes you say it’s worn out? Burning oil? Leaking? Knocking?Low compression? Depending on the exact issues, it could be something a lot easier than a motor rebuild. There isn’t much to go wrong or wear out unless there are a million miles or it was abused and not serviced
 
#4 ·
A rebuild kit is fairly inexpensive as you've mentioned, but that's not including any machine work you may need. I asked my local machine shop how much a standard rebuild would run me on a 460 I have.

I was given a rough estimate reusing all the factory parts (block, heads, crank, etc). With all the typical standard machine work (valve job, bore and hone, etc) and with an engine rebuild kit I was told I could rebuild it with my own labor for just under $2,000. Having them build it would be like another $600-800 I think, can't remember. I'd imagine your straight six would run a little less being that is has 2 less cylinders and 1 less head.

You may or may not be better off getting a reman, but it sounds like their price is somewhere in the ballpark of what it would cost to have an engine rebuilt back to factory specs. You could hit up a junk yard and take a shot at a used engine or looking at local ads for trucks being parted out. Depending on the yard I go to I can get an engine anywhere from about $200-600 depending on what engine it is.
 
#5 ·
@BigBlue 94 and @AbandonedBronco have given their 300ci motors some good attention. I've got the later 4.9L and love it, though I'd like to freshen it up with a rebuild in the next few years. I rebuilt the inline 4 in my first truck back in high school... well worth the effort, and bragging rights to your less mechanically inclined friends
 
#6 ·
Rebuild it. The 300 is a real stump puller, especially with the right mods. There's a guy on fordsix.com with a turbo 300 in his Maverick and some formidable times in the 1/4 mile.

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#12 ·
By the way, between me, abandoned bronco, nick oille, and warriors breakfast; theres a lot of 300 knowledge here.

The HD exhaust mentioned above is a single 2.5" outlet with 3 bolts on the flange. Its a great piece, but hard to find.
 
#13 ·
I think finding that would really just be a matter of right place at the right time. I got some interesting stuff in the works Blue, like a US Shift Quick 4 and paddle shifters for the 4R70W . Sorry for the hijack.

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#15 ·
$2k is a decent price, and is almost guaranteed less than what you'd spend on rebuilding it yourself.
The $395 is just the parts. That doesn't take into account all the machine work to get the block back in order. Boring and honing the cylinders, cleaning up the crank, all the valve guides, time, and assembly, etc. etc.
That said, you never know what corners may have been cut on a purchased reman. Rebuilding it yourself, you'll know.
Plus, if you rebuild it yourself, you can pump it full of goodoes. :D

Rebuild all the way... Unless u can find an inline 6 at a good price... The 4.9 is weak. Had that in my 99 Expy (within 500lbs of the same curb weight as the BKO) and it was a dog. @biggum has some great info on his build thread from when he rebuilt his motor. Worth checking out.
Ha I was about to chastise you! My 4.9 er 300, is a tank! And so was my 4.6, but it was a 4cam and in a 3200 lb mustang, not a 5000lb expy.
Hehe, me too! The 4.9, even stock, isn't weak! And it was discontinued before 99. :D

I went fairly radical with mine, and spent about $6000 on it.
That's about what I spent on mine, and it is FUN.

These changes will get you to about 175hp and make it more reliable than the feedback ignition.
Don't forget the torque! (Which is where it's at).
Probably around 300 - 325 at that point.

I’ve seen reproduction ones on eBay.
A set of tri-y’s off an efi truck is pretty good too
Same. Plenty of reproductions on eBay. But, if it were me, I'd go with the EFI manifolds.
 
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#16 ·
Hehe, me too! The 4.9, even stock, isn't weak! And it was discontinued before 99. :D
Well... Ford stopped using it after 97, but then sold the rights to another company that still produces the mighty 300 to this day. Its still used in industrial and agricultural applications. 1965-2020+ is a hell of a run!

Agree on the torque figures. I still wanna get mine dynoed. I have no idea what it makes. Maybe 275HP and 400 ft/lbs? Feels stronger than the stock 460 in my 95 F250.
 
#17 ·
Yup, so awesome they still make them. It says a lot!
Isn't that Oxx Power?

Of course, I was referring to Ford putting them in production vehicles.


I'd love to have mine dynod. I think I'm going to here in a month or so. Mainly to have the Sniper professionally fine tuned to the engine, with a bonus of knowing what it's putting down.

Dyno numbers always read lower than expected though, as you have about 15% - 20% loss through the drive train.
 
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#18 ·
It is oxx power now, I think they were named differently previously. Many a grain auger and pivot irrigation system have been powered by the 300.

Yeah crank vs wheel HP is always different. Good thing we have manual transmissions that only have about half the parasitic loss of an automatic.
 
#20 ·
Get the rebuild kit. Until you break it down there's no telling whether you'll need machine work or not.

Machine work can include boring/honing the cylinders, align-boring the crank journals, and valve work (not to exclude some others). I've NEVER found it necessary to align-bore any engine I've rebuilt, and unless you have scoring in the cylinder walls, it is unlikely that they'll need boring at all.

Unless you want to buy the tools to do so yourself, you'll need a machine shop to replace the cam bearings, and for a valve job (should it be needed). Unless your valves or valve seats are burned, you can grind them yourself with a cheap plunger and some valve grinding compound.

You can get a ridge-reamer and a cylinder hone relatively cheap and do the cylinder work on your own.

Keep in mind that you'll need to lay out some cash for tools. The ones that come to mind are a cylinder hone, ridge reamer, valve lapping tool, and a valve spring compressor. I'm sure there might be a couple of other ones, but nothing that will break the bank.
 
#21 ·
There are many great ways to resolve this, however, not all are equal. During a rebuild, you can have the head, intake, and exhaust port matched for a fairly reasonable fee. I've always noticed gains in power and fuel economy from a good port match and cleaning up where the valve seat meets the casting.

I've been doing my own porting for years now, it's easy as long as you remember less is more, avoid sharp transitions, and do NOT hog out the passages. That being said, I still pay my machinist for an hour or so of finish porting. The results speak for themselves, we got a full interior, fully optioned 240SX to run 14.6 in the 1/4 mile, on 15 year old 185 width all season tires and a passenger. Oh, I forgot to mention that was after I bent a valve. So yeah, porting gives you a lot of bang for your buck. I also gained a mpg or two.

The 4.9 in my 1992 F150 was rebuilt before I got it, It atleast had the standard cam timing set, possibly higher compression, it got 17 mpg and ran great even with a blown head gasket that was drinking water.
 
#22 ·
There are many great ways to resolve this, however, not all are equal. During a rebuild, you can have the head, intake, and exhaust port matched for a fairly reasonable fee. I've always noticed gains in power and fuel economy from a good port match and cleaning up where the valve seat meets the casting.

I've been doing my own porting for years now, it's easy as long as you remember less is more, avoid sharp transitions, and do NOT hog out the passages. That being said, I still pay my machinist for an hour or so of finish porting. The results speak for themselves, we got a full interior, fully optioned 240SX to run 14.6 in the 1/4 mile, on 15 year old 185 width all season tires and a passenger. Oh, I forgot to mention that was after I bent a valve. So yeah, porting gives you a lot of bang for your buck. I also gained a mpg or two.

The 4.9 in my 1992 F150 was rebuilt before I got it, It atleast had the standard cam timing set, possibly higher compression, it got 17 mpg and ran great even with a blown head gasket that was drinking water.
@twofortyz well said. My 300 has already got the port matching done and intend on getting the head flowed so I can make good use of the power of the cam and motor itself. Sage advice... [emoji120] 6=8, all day long.

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#23 ·
Porting a u-port 300 head is not as straight forward as a crossflow v-8 head. For the 300, do not touch the floor of the runners. Only the sides and roof. The exception is the radius dumping into the valve bowl can be smoothed out a small bit. More can be accomplished with going to larger valves and enlarging the valve bowls. In fact, my 85 head has no work done to the head runners. It does have larger valves and valve bowls were enlarged and smoothed out. The head is the choke point of the 300. But the runners themselves are quite adequate. The issue is the extremely sharp 90° turn the air has to make to pass through the valves. Making that turn as lengthy as possible is the best solution.

SI sells the enlarged valves. But a machinist will have to do the work.

The 300 is so choked from the factory in 85, its not even funny. What other engine can add 50% more power just with an intake and carb swap? Add a cam and some compression, and you can add 100% of the factory HP rating.
 
#24 ·
I already have oversized valves, so I wouldn't have much headwork to be done as it is. I really lucked out when I found and purchased this motor from the PO who had wrecked his truck by getting t-boned. Motor hasn't even passed the break-in period yet.

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