All Big Six 300 build for towing 12k lbs

Relates to all big sixes

fox81

Active member
Hello,

Just wanted to get yous guys opinions and insight on a 300 built for towing abuse.

Ive got an 81 f350 dually cab chasis (from the factory) with a 300 in it. dana 70hd with 4.10 rear end. t18 4speed tranny.

Im wanting to tow my mini excavator and dump trailer weighing around 12k. I know its gonna be slow but has anyone hauled this kinda weight with a 300? Also im trying to find a 300 to rebuild and replace the existing motor. What would you guys do to beef up the motor to handle said abuse?

Thanks!20211025_152512.jpg20211025_152519.jpg20211025_153120.jpg
 
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THE FRENCHTOWN FLYER

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There's lots of info on this site.
I'd build it with a RV/towing cam (or the stock cam advanced 4 degrees), low restriction exhaust, metal cam gear, hypereutectic pistons, and head work as outlined on several threads on here. No need for hi compression, better ignition, or lots of carb.

That body looks clean.
 
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HitmanX

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Some DRW Alcoas (8x6.5 sounds right) will help with dead unsprung weight removal you can ditch and make the truck easier to accelerate. They are about 21lb less than the steelies per my scale. Truck looks very clean indeed!

Otherwise, listen to the guys here on what to do.
 

pmuller9

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It takes power to tow 12K.
You would be working the engine between 3000 and 4000 rpm to make the power you need.
At that rpm range you can make good power and still have longevity with the right parts.

The stock head is good for power between 2000 and 3000 rpm.
To extend the power band to the 3k to 4k rpm range the engine would need a ported, big valve head.
The Tried and True cam profiles that has been used for this power band have had the .050" durations in the 220 degree range.
The four cams that have been used are the following:

Schneider 140H (13912) .496”/.496” 222/222 280/280 110deg
Howards 280996-10 .501”/.501” 221/221 275/275 110deg
Crower 284HDP (19205) .509”/.517” 220/222 284/290 110deg
Erson E270321 (Hi-Flow AH) .504"/.504" 220/220 284/284 110deg

Erson cam is no longer recommended as we had a quality issue that was not resolved.

You can port and install larger valves in a head yourself or purchase the Promaxx CNC ported head.
At these valve lifts it is highly recommended to use the Harland Sharp roller rocker arms.

Use one of the 4 bbl intakes with a 4 bbl carburetor in the 500 cfm range or the Holley Sniper 2300 which will have less of a problem with the heat this engine will generate.

If you already have long tube headers keep them. They will produce the best overall torque.

Because this engine will be working hard and generating a lot of cylinder heat limit the compression ratio to 8.6 for 87 octane pump gas.

The second option is turbocharging.
 
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fox81

Active member
It takes power to tow 12K.
You would be working the engine between 3000 and 4000 rpm to make the power you need.
At that rpm range you can make good power and still have longevity with the right parts.

The stock head is good for power between 2000 and 3000 rpm.
To extend the power band to the 3k to 4k rpm range the engine would need a ported, big valve head.
The Tried and True cam profile that has been used for this power band has had the .050" durations in the 220 degree range.
The four cams that have been used are the following:

Schneider 140H (13912) .496”/.496” 222/222 280/280 110deg
Howards 280996-10 .501”/.501” 221/221 275/275 110deg
Crower 284HDP (19205) .509”/.517” 220/222 284/290 110deg
Erson E270321 (Hi-Flow AH) .504"/.504" 220/220 284/284 110deg

Erson cam is no longer recommended as we had a quality issue that was not resolved.

You can port and install larger valves in a head yourself or purchase the Promaxx CNC ported head.
At these valve lifts it is highly recommended to use the Harland Sharp roller rocker arms.

Use one of the 4 bbl intakes with a 4 bbl carburetor in the 500 cfm range or the Holley Sniper 2300 which will have less of a problem with the heat this engine will generate.

Use the stock EFI exhaust manifolds.

Because this engine will be working hard and generating a lot of cylinder heat limit the compression ratio to 8.6 for 87 octane pump gas.

The second option is turbocharging.
Thanks!
This is good advice ill be refering to for sure!
 

fox81

Active member
It takes power to tow 12K.
You would be working the engine between 3000 and 4000 rpm to make the power you need.
At that rpm range you can make good power and still have longevity with the right parts.

The stock head is good for power between 2000 and 3000 rpm.
To extend the power band to the 3k to 4k rpm range the engine would need a ported, big valve head.
The Tried and True cam profiles that has been used for this power band have had the .050" durations in the 220 degree range.
The four cams that have been used are the following:

Schneider 140H (13912) .496”/.496” 222/222 280/280 110deg
Howards 280996-10 .501”/.501” 221/221 275/275 110deg
Crower 284HDP (19205) .509”/.517” 220/222 284/290 110deg
Erson E270321 (Hi-Flow AH) .504"/.504" 220/220 284/284 110deg

Erson cam is no longer recommended as we had a quality issue that was not resolved.

You can port and install larger valves in a head yourself or purchase the Promaxx CNC ported head.
At these valve lifts it is highly recommended to use the Harland Sharp roller rocker arms.

Use one of the 4 bbl intakes with a 4 bbl carburetor in the 500 cfm range or the Holley Sniper 2300 which will have less of a problem with the heat this engine will generate.

Use the stock EFI exhaust manifolds.

Because this engine will be working hard and generating a lot of cylinder heat limit the compression ratio to 8.6 for 87 octane pump gas.

The second option is turbocharging.
Curious how you know it would be working in the 3000-4000 rpm range. I dont have my tach wired up yet but that seens like it would be accurate.

Is there some math to figure that out or is it just from experience?

Thanks!
 

fox81

Active member
Some DRW Alcoas (8x6.5 sounds right) will help with dead unsprung weight removal you can ditch and make the truck easier to accelerate. They are about 21lb less than the steelies per my scale. Truck looks very clean indeed!

Otherwise, listen to the guys here on what to do.
Those seem expensive!
 

sdiesel

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my heaviest recorded weight behind a 300 was 25,600 gross-way overloaded equipment and somewhat light on brains (and brakes).
the very same hill at 25,400 behind a 460 auto both dually 4x4, i LOST 2 mph going over the hill. the six will do just fine. the 4 speed will make your life miserable though. a zf 5 would be an improvement. the mentioned EFI exhaust will be found on 87 and newer fords. if your anywhere near longview wash. you can come pilfer parts from me if needed.

i would also go to 4:56 gears. heavier brakes would be nice if you can make it work. i use a dually axle from a 2006 gmc, because they are disc and the axle is a better design. but they are not common in CC config. yes to aluminum wheels they enhance the ride on a truck whose springs are
a. not worthy of the term spring, steel axle locator is more accurate, and, b. are too short in the rear to actually "spring".

here is an idea and cheap too . find an 88 or newer fsuperduty. it has the rear axle you need in good gears and its bolt in save for the u joint. build a zf 5 speed with transmission park brake, but you will have 10 hole wheels in back. no big deal really. but the 300 will pull like hell with 4.88 or 4.56 gears

a ranger cab in C/C is a rare thing
 
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THE FRENCHTOWN FLYER

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Somebody already did a nice job with the dual exhaust. Does it hook up to EFI dual exhaust manifolds? It may be a tad loud for my tastes for hours at a time.
 
Another vote for deeper gears and more speeds in the trans. Stock 300 should be fine otherwise.

Throw a big muffler in each of those pipes. Reducing engine noise will make it a ton less fatiguing.

Swapping an axle is no more expensive than changing out gears. An axle from an E-350 box truck or motorhome will be 8x6.5 to match your front and have disc brakes and will likely already be 4.56. If you find a screaming deal on a 99+ Superduty rear axle you can swap your front to 8x170 with nothing more than new rotors so don't rule that option out. There are a TON of F350 DRW trucks being parted out at any given time because of how popular they are as work vehicles.
 
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Sevensecondsuv

Well-known member
I'm building something similar, but for a SRW F-250. A link to my build thread is below. No results yet obviously, but might be some interesting reading for you.

I'll go against the grain here on the trans. Mine currently has a ZF but I'm switching to a T-18. Really the only difference between the ZF S5-42/47 and old granny 4-spd like the T-18 is the ZF has an overdrive gear. My thinking is that a 300 built to make power north of 3000 rpm while towing 12k won't have much use for overdrive. Beyond that, gears 1-4 in the ZF are only marginally different than the T-18. The only other significant difference is the reverse gear. In the ZF it's not enough ratio for a 12k trailer and you'll end up slipping the clutch. The T-18's reverse is a good 30% lower.

To actually improve the trans, you'd need a 6-speed like the ZF S6-650 or NV5600. Another option is a gear splitter or o/d unit added to the 4-spd to make it an 8-spd and cut the gaps between gears in half.

Here's the link to my build thread:
 

HitmanX

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Supporter 2021
The Alcoas were factory option on the later Aeronose 92-97. I will try to post a pic of mine, worst part is finding the damned things in DRW form. SRW are so easy to find it is not funny in five and eight lug. I paid $100/ea for my set which is not bad for a reasonable price.

Dude I know in Canada has a small block gasser ZF kicking around he would probably sell. I THINK he is over in B.C. problem is how to get the thing across the border to you if you go that route.
 

sdiesel

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be careful the box truck van thing. those i have encountered have like, 42" frame rails.
the flip side is a rear axle with wider stance. especially shuttle vans.
most were dana axles, inferior to the sterling or especially the AAM axle.
if you can get the fronts to convert to metric , thats a super option.
the best way to go.
and likely the cheapest alternative too.

brakes and gears are a bigger deal than engine power.
just never expect to go anywhere quickly, and if you dont enjoy manipulating the 300 six for its torque over h.p., style of driving, then a 460 is in your future....or a turbo , hehe.
yes to t-18 over ZF, except for lacking 1st synchrony. t- 19 might be an option as it is full synchro.
anything built by BW is worthy of consideration.
including turbos transfer cases etc
 

BigBlue94

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To actually improve the trans, you'd need a 6-speed like the ZF S6-650 or
The ZF6 is a towing monster. I love mine behind a 5.4L V8. All those forward gears would be great to keep the 300 in the right rpm range. I've pulled 8500 lbs with it from Kansas to Michigan and back with it. 4.10 gears with 35" tires.

My 300 lives at 3000-4000 rpms. It does it on the highway for hours on end. Just need to make sure you have a good oil and oiling system, a good cooling system, and free breathing for the engine. I have the schneider 140H cam and 9.75 compression fed by a 450 cfm 4 bbl.
 

pmuller9

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Curious how you know it would be working in the 3000-4000 rpm range. I dont have my tach wired up yet but that seens like it would be accurate.

Is there some math to figure that out or is it just from experience?

Thanks!
3000 to 4000 rpm is where you need to operate the engine in order to pull the 12K load up a grade or shifting through the gears to accelerate up to speed. The goal is to move peak torque just above 3000 rpm to make the horsepower needed to get the job done.
The engine build I described above makes power from 1000 to 5000 rpm with over 300 ft lbs of torque.

The stock engine has a much shorter power band and quits making power just above 3000 rpm.
The above engine will easily work over 4000 rpm and make an additional 100 hp over the same year stock engine.

There is no reason to expect to move the load slowly just because it is a 300 six.
 
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BigBlue94

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3000 to 4000 rpm is where you need to operate the engine in order to pull the 12K load up a grade or shifting through the gears to accelerate up to speed. The goal is to move peak torque just above 3000 rpm to make the horsepower needed to get the job done.
Agreed! This isnt just true for the 300. The 5.4L V8 in my 08 does best in that same rpm range. It would accelerate up a decent grade with 8500lbs (fullsize lifted bronco) in tow and the 6500lb truck itself. I think its output is 300hp & 400 ft/lbs. It would have pulled even better if the 35" tires were 31s or if i had 4.56 gears.
 

fox81

Active member
Somebody already did a nice job with the dual exhaust. Does it hook up to EFI dual exhaust manifolds? It may be a tad loud for my tastes for hours at a time.
It has long tube header on it. It sounds pretty good. I have 48" glass packs on it. Its not really that loud but its pretty throaty. It had dual cherry bombs but was way too loud. Sounded like a japanese airplane. lol
 

fox81

Active member
my heaviest recorded weight behind a 300 was 25,600 gross-way overloaded equipment and somewhat light on brains (and brakes).
the very same hill at 25,400 behind a 460 auto both dually 4x4, i LOST 2 mph going over the hill. the six will do just fine. the 4 speed will make your life miserable though. a zf 5 would be an improvement. the mentioned EFI exhaust will be found on 87 and newer fords. if your anywhere near longview wash. you can come pilfer parts from me if needed.

i would also go to 4:56 gears. heavier brakes would be nice if you can make it work. i use a dually axle from a 2006 gmc, because they are disc and the axle is a better design. but they are not common in CC config. yes to aluminum wheels they enhance the ride on a truck whose springs are
a. not worthy of the term spring, steel axle locator is more accurate, and, b. are too short in the rear to actually "spring".

here is an idea and cheap too . find an 88 or newer fsuperduty. it has the rear axle you need in good gears and its bolt in save for the u joint. build a zf 5 speed with transmission park brake, but you will have 10 hole wheels in back. no big deal really. but the 300 will pull like hell with 4.88 or 4.56 gears

a ranger cab in C/C is a rare thing
An axle swap is definately something i want to do as the dana 70hd is kinda an odd ball. Only one option that i could find for a limited slip/posi.

Also im new gearing. But i feel with out even towing that the gearing should be different. Maybe its just the t18. Im set with my new tire size. would that play into choosing different gearing? I think its the stock tire height
 

fox81

Active member
Thanks for all the input guys! I appreciate it.

So a cam, gear swap and brake upgrade seem to be in order.

Ill just run my motor till it quits, which might never happen.. lol. I recently started using 15w40 oil. A friend recommended using it as i thought i was getting some blow by. Also i put some lucas in there. But after installing the new yfa I think it just dumping an ubsurd amount of gas the whole time. No more blue smoke.
 
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