I posted a while back on two complete trucks I have access to.

Transmission ID (http://www.pirate4x4.com/forum/showthread.php?t=527604)

I want to build one of these motors for Propane, somewhere in the 11.5-12:1 compression range, to build my Scout around. There is an '81 with a 351 and an '86 with a 460. Both have a C6 which I will also use.

I have been told by a good friend who has built a few 460's that the early - mid 80's Fords were detuned badly, the compression was in the 8:1 range, and that the heads would be nearly useless for what I am trying to do.

Question #1: What would be the better of the two motors to work with and how would you recommend getting the proper compression ratio, ie headwork, new heads, etc.?

Question #2: (New topic that I cannot find an answer to) Is there a suitable passenger side drop transfercase that would mate to the C6 for the same project? Dana 300, GM np205? I need to be able isolate the front and rear axles.

Thank you kindly!

Both were badly de-tuned but both are suitable for what you want with a change of heads.

I guess an 81 would have a 351W, if so theres tons of suitable after market heads. Stock 69-70 351W heads have big valves and small chambers so they would be a good choice, especialy if you have a tight budget.

If it's a 351M use Australian 302C closed chamber heads, that will bring the cr up. While your at it use a 400 crank to gain 50 cubic inches free.

Look for C8VE, C9VE, or D0VE heads for the 460, they'll bump your cr way up and they flow decent too.

My personal pick of the above 3 would be the 351W. Light, good aftermarket support with cheap parts, easy to stroke to 400ci and they make good power. 400hp should be easy with propane.

Odds are that 81 will have a 302 or a 351m, but yeah find early w heads and likewise for the 460, DOVE or older.

You are probably right, 351M. Most people don't like 351Ms or 400s but they are a good motor. Not so much the 351M, don't even waste time or money on it. Use the 351 crank as a core and get a 400 crank. Look here for some good ideas:

http://www.tmeyerinc.com/400stroker.html

http://www.barnetthighperformance.com/home.htm


Odds are that 81 will have a 302 or a 351m, but yeah find early w heads and likewise for the 460, DOVE or older.

No replacment for displacement but the 351w has a way better aftermarket cause of mustangs it will be harder to feed a 460 if you use impco.

Your engine q's are pretty much answered, so about the t-case- it SHOULD be possible to utilize a GM or Dodge 205 case with a Ford input to get what you need- would have to drill and tap the proper bolt pattern in the case too. Another possibly better option would be to use a divorced GM/Dodge 205 and a Ford 2wd tranny, but if you have to use a married case setup, the divorced one might still be the better way, as you could still put the Ford input in it and drill and tap the mounting bolts without the original bolt pattern that would be on a married case getting in your way. (i might not have explained that very well)

Good points. You have lead me on a 351/400M internet chase.

351/400M Performance (http://www.projectbronco.com/Technical_Articles/351m400_performance_build_up.htm)

I think I am leaning toward the 351 block and finding a 400 crank and harmonic balancer. It seems that detuned is an understatement in describing how this motor left the factory. Weight will also be a saving compared to the 460.

Another good point on the Propane feeding a healthy big block. More of a reason to head toward the 351/400.

It seems likely the motor in question is a 351M, how do I know for sure? It is an '81 351 in an F-250 with a 2bbl carb. It all looks original.

Thanks to all.

Your engine q's are pretty much answered, so about the t-case- it SHOULD be possible to utilize a GM or Dodge 205 case with a Ford input to get what you need- would have to drill and tap the proper bolt pattern in the case too. Another possibly better option would be to use a divorced GM/Dodge 205 and a Ford 2wd tranny, but if you have to use a married case setup, the divorced one might still be the better way, as you could still put the Ford input in it and drill and tap the mounting bolts without the original bolt pattern that would be on a married case getting in your way. (i might not have explained that very well)

Is there enough material to drill and tap for a gm case? I agree the divorced would be easier, but space is limiting as far as I see it. I don't know that I've seen a passenger side drop divorced case??? Are you suggesting that I clock a divorced Ford case and drill and tap it freshly? That might be a fair option if I can figure how to shift it. I will need to look at a divorced case. Thanks for the thought.

the round bolt pattern chevy np205 with a ford input will be close to the round ford c6 bolt pattern
I would look at that option

there is no denying a 460 is a better power producer then a 351M, you will need to use a dual 4 intake with dual mixers to feed it properly.
better aftermarket as well.

I like the 400M motors and you can get great power from them as well.

I wasn't suggesting reclocking a ford 205- just redrilling the tranny to t-case bolt pattern into the front of a GM or Dodge case. I could be wrong on this, as I am no GM expert, but I believe the round pattern GM 205 is a rare bird. They mostly had what is called a figure 8 or racetrack pattern- for obvious reasons when you see one. Pass. drop non married 205's should be plentiful- GM, Dodge and IH all used em'. What I would consider the ideal setup if you HAD to have a married case, would be to find a GM/Dodge/IH divorced case, then put the Ford input into it, and drill and tap the appropriate bolt pattern into the case- you wont have any previous bolt patterns causing problems with the Ford 6 bolt circular pattern you are trying to put in. Only problem with my idea is that maybe not all divorced cases have an appropriate flat surface on the front to drill, tap and seal against your C6 tailhousing adapter. I am only basing my idea on a divorced 203 I have lying around- it has the flat area on the front that would be perfect for a bolt pattern in it- other divorced cases might not have that, so check them out before you start throwing money at it. Just food for thought.

I like the 400M motors and you can get great power from them as well.

How do you feel about the standard (non M) 400 motors?

How do you feel about the standard (non M) 400 motors?

I do not like Chevys or Mopars much at all.

just redrilling the tranny to t-case bolt pattern into the front of a GM or Dodge case......Pass. drop non married 205's should be plentiful- GM, Dodge and IH all used em'. What I would consider the ideal setup if you HAD to have a married case, would be to find a GM/Dodge/IH divorced case, then put the Ford input into it, and drill and tap the appropriate bolt pattern into the case.

That is worth investigation. My mind was actually working through that all night. Now to find a good divorced np205.


I like the 400M motors and you can get great power from them as well.


I think that is where I am headed. A 351 rebuild with the 400 crank should be feasible for me and quite affordable with some solid ebay work.

This is some good daydreaming.

Comp cams does not make 4x4 Extreme cam for the 351M/400 but they will grind them all for about the same as a regular cam. Because if you go with 351M/400 the cam shaft should be one of the first things on the list of things to change. One way to know if it is a M vs. W is the W will only have 6 valve cover bolts and the M has 8 bolts.

That is worth investigation. My mind was actually working through that all night. Now to find a good divorced np205


I think that is where I am headed. A 351 rebuild with the 400 crank should be feasible for me and quite affordable with some solid ebay work.

This is some good daydreaming.

you have no choice for pistons other then customs or Tim Meyers, so ebay isnt going to help.
for heads you will have a very tough time beating the $1075 for set up Aussies from powerheads.
the machining for screw in studs and the big valves will exceed what they sell them for.

I do not think a divorced 205 is going to help you, find the round pattern chevy or use a ford front axle and a matching ford case

you have no choice for pistons other then customs or Tim Meyers, so ebay isnt going to help.
for heads you will have a very tough time beating the $1075 for set up Aussies from powerheads.
the machining for screw in studs and the big valves will exceed what they sell them for.

I do not think a divorced 205 is going to help you, find the round pattern chevy or use a ford front axle and a matching ford case

mj, sometimes the truth hurts. I'm glad I have some time to do my homework. Fortunately, the Tim Meyers pistons are reasonably priced. The heads, however, I am going to have to do some hunting on.

For clarification, what is the limiting factor on tapping a divorced 205 to mate up to the c6?

Thank you kindly.

for pistons the old trick was to rebush the rods to accept 351C forged pistons
but I think the deck has to be cut down to get the quench where it shoud be. I haven't done it yet but I do have all the parts here.
trw2379 forged flat tops, aussie heads, 351m block, 400m crank

I have been pondering if the quench is as important with lpg gaseous fuel as with liquid gasoline

For clarification, what is the limiting factor on tapping a divorced 205 to mate up to the c6?

Thank you kindly.

I would say it all boils down to whether or not the case in question has the flat machined surface around the input. I only brought the idea up because I noticed that a divorced 203 that I have sitting around does have that surface-other divorced cases may not, and if I was a betting man, I would bet they dont- just an idea I thought should be investigated. What you should really do is post your t-case question in the general 4x4 forum- perhaps someone there has more knowledge of GM/Dodge/IH versions of the 205. If the 6 bolt pattern GM 205 is the same as a Ford pattern then that would definitely be the way to go- if you can find one.