hey, i have a few questions for some experts. i am looking at a 1979 bronco that i might buy. i've only dealt with 80's trucks and broncos so i don't know much about these. i do know it has a 351m that will turn over. i'm not worried if it runs or not because i can make it run. the guy wasn't sure about the transmission though. what trannys were available for '79? it's an auto. it has a 9" rear and i think a dana 44 front. also, the guy said that the tranny will go in first gear but none of the others. what problems could this be? is it something expensive or something i can do? he wants $800 for it but he will take less. just wondering if its worth the money and time. thanks for any help.

 

if its a C6 auto then its probably the vacum modulator. it controls shifting of the tranny. if its a manual tranny then probably has some bad synchros. i would talk him down if you can but otherwise seems like a good find

 

its an auto and he said its probably the modulator. what i want it for is for a mud truck. do you think the engine and tranny are good for mudding, or should i find something else.

 

For mudding I'd swap to a manual personally but of all the autos that went in the Bronco the C6 is by far the sturdiest of them in my opinion.

 

okay, so the tranny will be okay as for as punishment, but what about the engine? is the 351m a good engine for mudbogging? i will be able to modify it a little. i have an edelbrock 750 carb i can put on it and i can get other things too. what would be some good add ons for a lot of torque? basically what i'm asking is will it be able to pull itself out of a hole.

 

A 460 will bolt to your c6 that is behind the 351m.That will give the torque for mud-bogging.A 750cfm carb will be too big for the 351m,you will loose all your low end power.I don't think a 351m can rev high enough to use 750cfm.
This would be a good carb for a 460.

 

I've allways been told the 351M is junk, because it is just a 400 with sleeves in the cylinders to down size it, and that caused all kinds of problems. From what I've heard of the 400 itself, It wasn't a great engine either. Of course with enough money and time you can make anything good, but most people seem to think it's better to do a 460 swap. If it were my choice, i'd get a late model EFI 460 with a harness and computer for a manual tranny, and put that infront of that C6. That just my opinion though, I won't have a carbed vehicle. As for the tranny,BIGFOOT has a C6 n it, so yeah it's pretty strong. You should have a dana 44 in front unless its been changed out, the only thing i've heard about it is that the axle tubes coming out of the pumpkin are weak and can crack, so you may want to upgrade those with some stronger ones. Most of this is opinion and stuff i've heard from other people, but I hope it helps you make your choice.

 

Never heard of sleeves in the 351M, the only difference between a 351M and 400M is 1/2" of stroke. Whoever told you about sleeves, must be a cummins mechanic.
I would give 600 and build it.

 

As a matter of fact the person that told me does drive a 3/4 ton Dodge with a 24 valve............guess that explains that.

 

The difference between the 351m and the 400 is the crank and pistons.You can make a 351m into a 400 by changing the crankshaft and pistons.Same goes for the 429s and 460s.

 

Cool good stuff to know, I need to expand my knowlege of internal engine stuff.

 

Since we are on the subject of 351M I have one that I did a simple rebuild on(Edlebrock econo series 600 carb, intake, cam, lifters and timing set, headers, rebuilt stock heads and new gaskets all the way around) in my 83 F150 4X4. It just does not have enough oomph to spin the 33x12.50. I'm running 355's. Will going to 410 do it? I need suggestions.

 

your rebuilt 351m won't turn 33's? sounds like something is wrong. i have an '85 with a stock 302 efi and mine mud boggs fine with super swamper SSR 35's. its a little slow to get going but it'll pull you down the road as fast as you want. mine has 3.55 gears too.

 

I think he was talking about burnning rubber.

 

okay, i get you. yeah, mine will burn tires, but only cause its a manual. if i had an auto i don't think it would. besides, super swampers wear fast enough without burning them up.