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I have a 1996/1979 Ronco (a 1979 Bronco with a 1996 ranger body on it)
this truck will be used primarily in mud bogs and a few trail rides
the 351M is over 400HP C6 and 205 case with twin sticks.

the question is about the diffs................

I have open 3.55s front and rear, i was thinking of re-gearing to 4.56 s with lockers.
I am running 35/14.50 15 Boggers.
can I stay with the 3.55 gears, spool the rear and lock the front if i drive it in 4 low?
I would only use 4 High on the street(almost never)
would this put too much strain on the axles or drivetrain?
I am on a budget and this would be cheaper.
or should i re-gear to 4.56 or better???
 

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With the gears you have now, 4low wont be low enough for what you're going to be doing. Also factor in the strain on you're drivetrain from the high gears. A lower gear will also let you take advantage of 4hi and low. 4.56s are reasonable for what you have now but if you plan on going with bigger tires later I'd say go with 4.88s.
 

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Most of the strain will be in you're axles and trans, especially with the wider tire. I'm not sayin it will be a huge amount of strain and that you'll be breakin things left and right, just that over time the higher gears will take their toll.
 

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Good choice. Although there will also be a big difference with you're axles locked, so you'll find yourself trying to keep your wheel speed up.
 

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I am over 400 HP and gobs of torque
I'm not being a dick or anything but I have to ask, " Have you had the engine on a dyno ? " if not how do you come up with a number ?, I know when you first started your build there was a big debate on this very same subject,
now if I am correct ?, the 351M is known for its torque but not its horse power, and also known for its poor oiling system and taking out the bearings at high RPM's, so if I am correct in this statement? this is why you get so much crap for claiming a high H/P #, people want to see the facts on how it was achieved, I am just trying to " Help A Brother out ! "
 

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I'm not being a dick or anything but I have to ask, " Have you had the engine on a dyno ? " if not how do you come up with a number ?, I know when you first started your build there was a big debate on this very same subject,
now if I am correct ?, the 351M is known for its torque but not its horse power, and also known for its poor oiling system and taking out the bearings at high RPM's, so if I am correct in this statement? this is why you get so much crap for claiming a high H/P #, people want to see the facts on how it was achieved, I am just trying to " Help A Brother out ! "

Actually the only REAL problem with the 351M is there are no high compression pistons available like the 400. (you can't use the 400 pistons because the wrist pin location is different.)

Now a 400, I have no doubt, can make those numbers but a 351M.......not without some one off pistons or other custom work and if thats the case I wanna know more. :toothless
 

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I dont know you guys, 400hp is pretty easy to get out of these stock 351s nowadays....















200 shot of laughing gas and you're making big power. Most likely it will only work once though...
 

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I dont know you guys, 400hp is pretty easy to get out of these stock 351s nowadays....















200 shot of laughing gas and you're making big power. Most likely it will only work once though...
LOL. I've personally owned/built maybe 6 engines in 35 years as a builder and automotive machinist that made over 400 HP, proven on a dyno. Out of mayeb..I dunno..300 engines built by me over that same period? None over 500HP..even the 671 blown 460 in the shop now is not expected to got over 485HP.

Can it be done?..sure..all the time. 600HP engines abound...howver short-lived they might be. What I'm saying is I know what it really takes..and its one heck of lot more than the ole 'internet keyboard dynos' would have you believe.

I was at the Carlisle All-Ford Nationals a couple years ago and there were a ton of evil Fords that put on shows on teh chassis dyno they had in the show field. Lot of 427 side oilers..and some radcial bi-turbo custom 'stangs..once of which was hyped big time before finally going on the 'truth roller'. What a joke...after three cough and backfire filled attempts to demonstrate that their placard's 650 BHP was a real number..they bailed. For giggles, I put my trail-dented '69 EB with the Oz-408 EFI engine turning 39.5 IROKS on the rollers soon after that sad show and the crowd went wild.:toothless The dyno guy 'driving' said it was the most fun he had all day long.
 

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I would regear it.

Contrary to popular wisdom on this board 3.50 gears will strain running gear LESS than the correct 4.56 gears you need. (HH might say go 4.88 & call er good). That's because of the crappy 1.96 to 1 in the 205.

300 RW horse is about all I would expect from this motor. Hav2 - a 600 cfm carb would be PLENTY to make 400 HP.

The pocketprotector slide rule types like bmc can elaborate if necessary. Tim Meyer & others have flow tested every concievable head & those numbers are available on the internet.
 
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