Mess of questions...

[Daks]

I am in the middle of performing a swap to big block in my 72 Cheyenne K20 with little to no knowledge on what this really takes to accomplish...

As I understand it from everything I have been able to gleen from the boards here is I need to move the entire drive train forward a little bit in order to gain the clearance that I need to make things fit. Well, I have a couple options and questions that I was hoping someone might be able to give some insite into...

I have an trade out where I can get a 700R4 tranny for a littlle side work that is being completely rebuilt and was thinking about using it for the overdrive. As I understand it, the 700R4 is about 2" longer then a TH350. Can I just bolt that 700R4 directly to my np205, use the 2" in lenght difference to place my engine far enough out front to clear everything without making a headache (or more of a headache as I have learned...) with headers? Or do I need to change the shafts and get spacers and mess with drive shafts and all of that... At one point, I saw a decent thread that had some info on a 700R4 in a 4x4 truck, but I can find it anylonger... Also, does this mean that I have to move the engine stands farther forward as well to make this work? Or mess with any of the cross members?

If I stay with my TH350, do I need to do anything besides moving things forward a little bit? I do not really want to mess with changing the sizes on the drive shafts... And I definitely do not want to be beating in the firewall to get this to work.

You have to forgive me, I really know very little about engines, and working on any automobile, but I tell you... this working in the grease, barking your nuckles, and trying to figure out what the hell your doing is the most fun I have had in a long long time. =) Any help and insight would be greatly appreciated.

Thanks!

[4x4Poet]

I can give you a philosophical approach (i.e., wordy). Since the driveshafts can easily be shortened or lengthened and the tranny crossmember can be slid forward or rearward with new holes drilled thru the frame, the more crucial placement involves having enough fan clearance before the radiator and valve cover clearance in front of the firewall. Work those out first before drilling eng crossmember or tranny xmember holes in the frame. You also potentially can use a big block or 2wd fan shroud instead of the 4x4 (K10/K20) shroud that extends farther back than the other two.

As for avoiding driveshaft work, how close you can get to the original holes in the tranny crossmember without having to bash the firewall or place the fan too close or to far from the radiator is probably anybody's guess. Maybe someone here knows. We have had a few folks put BBCs in 67-72 4x4s.

BTW, in your research did you read of using a 73-8? engine crossmember instead of the stock, K20 eng xmember? The 73up eng xmember bolts right up with only a few extra holes to drill and it eases and expands oil pan choices. Uses the common clam shell motor mounts, too. Of course, it can be placed foward or aft of the original eng xmember to some degree. I don't know how it would affect engine placement if left in the original position.

Glad you're having fun.

[GMC AMI]

I exchanged a 350 with a 396 from a car and bolted it right in with the only mod was cutting the 4x4 shroud down to size. This was a 71 GMC 4x4 1/2 ton.

[Yukon Jack]

I put a 454 in my 69 K20 using the existing small block engine crossmember and towers along with new stock type engine mounts. Oil pan clearance was very close. I ended up using a couple washers to raise up the engine slightly. I had major firewall interference even with a body lift.

If I were to do it over I would definitely move the engine forward and then work through moving the transfer case and tranny. A problem with moving the engine forward is you are shortening the front driveshaft. You want it to be as long as possible to keep the angle from being too severe. If you used a longer tranny that would help.

You will find some people have installed bb's in the K trucks with absolutely no modifications. Some just need to massage the firewall a little, others like me have to make major firewall modifications. Don't ask me why it varies.

Burt4x4 recently put a bb in his K5 and just had to do minor firewall mods. He has a body lift and he did switch to the 73-up crossmember. You might want to pm him so he can chime in with his thoughts.

I don't have info on the tranny to transfer case issue but I would imagine you will need some type of adapter to use that tranny with an NP205.

[ckhd]

Well, here's my 2¢. I haven't done both at the same time, but I have put a big block in a 4 wheel drive, and I have put a 700r4 in a 4-wheel drive. I *might* have done the post with the 700r4 conversion. I made a big long one with all my troubles/experiences with it after I did it.

My experience with a big block in a 4-wheel drive and no 700r4 (In a '72 K5): There are major firewall issues. We had to "massage" the firewall with a big hammer until it fit. After that, all is well. Used the same motor mounts and everything.

My experience with a 700r4 and a small block: I moved the engine forward. It's 1 3/4" if I remember right. I did have to trim the fan shroud to let the power steering pump fit, and the radiator hoses. It took drilling 8 holes for the new location of the crossmember. I was originally going to do the driveshaft deal, but two things made me change my mind. First, the transfer case mount looked like it was going to be way to big of a headache for me to relocate, plus I was low on funds and didn't want to have to pay for driveshaft mods. Second, I would like to someday put in a big block, and remembering the experience I had with the '72 blazer, I decided that moving it forward would allow the clearance needed to put a big block in.

So, in my opinion, move the mounts forward, leave the driveshaft alone. You will gain the needed firewall clearance, and you won't have to jack with driveshafts, tranny mounts, and t-case mounts.

[ckhd]

Forgot to address the 700r4 to the 205 issue:

It will not bolt right up. The reason is the output shaft on the 700r4.

If you have a NP205 from an automatic pickup, you can get an output shaft that will allow you to bolt it right up. When I did my 'burb, I bought the tranny with the output shaft already installed (I got mine from Bowtie Overdrives). It did literally bolt right up. No mods, no worries. I have no idea if anyone makes a 700r4 output shaft that will spline with a 205 from a manual transmission pickup.

Bowtie Overdrives, and Advanced Adapters both sell the output shaft seperately. I don't know who else does. When I found out B.O. had the shaft, I stopped looking.

[402Bowtie]

Is this the thread you were looking for?
700R4 w/ NP205

[Daks]

Ooh, thanks for all the great information, I do have a couple more things I am having trouble with resolving that I couldnt dig out during the course of reading the threads and replies here. I am feeling a bit more confident about actually doing this now then I was yesterday hehe.

So.. If I go with the 700R4, it should put the front crossmember out to a position that will work just fine for the big block. Also I should be able to just use the same tail end of the 350 I have now. And as the 700R4 is being rebuilt, I can tell em to just put a 4x4 output shaft on it so I dont need to make any modifications to anything else. At least this is the picture I gathered...

Now, in regards to shifting linkage geometry.... Should this all remain the same and I dont need to mess with that stuff at all? The kickdown should work the same as with the 350 I assume, as well as the fluid tube? I guess since I have just a 3 speed column indicator that the linkage probly does need to change, any suggestions on that?

Thanks again for the great knowledge base you all share openly!

[mrein3]

Originally Posted by Daks

So.. If I go with the 700R4, it should put the front crossmember out to a position that will work just fine for the big block. Also I should be able to just use the same tail end of the 350 I have now. And as the 700R4 is being rebuilt, I can tell em to just put a 4x4 output shaft on it so I dont need to make any modifications to anything else. At least this is the picture I gathered...

On factory 4x4s, the "Adapter" is the part bolted between the transmission and the transfer case. The company Advanced Adapters makes an output shaft for the 700R4 specifically designed to be put in a 2 or 4wd 700R4. This shaft then mates up with the factory NP205 to th350 adapter. If you start with a 2wd 700R4 you leave the tail cone off the tranny. The bolt pattern on the back of the main body of the 700R4 will bolt to the adapter on what you have if you started with a factory th350 and NP205. Two and a half years ago when I swapped my manual out for an automatic the NP205 to th350 adapter was still available over the counter at the Chevy dealer.

I believe Advanced Adapters makes an output shaft to mate a 700R4 to a 10-spline manual transmission to NP205 adapter. However the overall length of that setup would be quite a bit longer than the extra 1.5-2 inches you get when swapping a 700R4 for a th350.

I would also highly recommend that you replace the "drive sleeve" while you have the 700R4 laying on the ground. This little piece couples the output of the tranny to the input on the x-fer AND seals the fluids in the tranny. I got a new one of them over the counter at Chevy 2.5 years ago too.

[ckhd]

Originally Posted by Daks

So.. If I go with the 700R4, it should put the front crossmember out to a position that will work just fine for the big block. Also I should be able to just use the same tail end of the 350 I have now. And as the 700R4 is being rebuilt, I can tell em to just put a 4x4 output shaft on it so I dont need to make any modifications to anything else. At least this is the picture I gathered...!

You almost have it. Don't tell them you want a 4X4 output shaft, they will give you one that would fit in whatever piece of crap aluminum t-case that came in the late '80s. You need the specific special non-gm adapter output shaft. The only places I know of to get these are Advanced Adapters and Bowtie Overdrives. With this output shaft, the tail end of the 700r4 will bolt directly to the spacer that is currently between your TH350 and the NP205. Make sure you specify that it is going to be bolted to a NP205 that used to be bolted to a TH350.

Originally Posted by Daks

Now, in regards to shifting linkage geometry.... Should this all remain the same and I dont need to mess with that stuff at all?

You might be able to make the original stuff work, but I got a shift linkage kit from Bowtie Overdrives and it made the linkage install a piece of cake. It has nearly infinite adjustment. I definately recommend you go that route.

Originally Posted by Daks

The kickdown should work the same as with the 350 I assume, as well as the fluid tube? I guess since I have just a 3 speed column indicator that the linkage probly does need to change, any suggestions on that?

There is no "kickdown", it's a TV (throttle valve) linkage. Kinda the same thing, but absolutely CRITICAL in a 700r4 that it is right. If it is wrong, your 700r4 will last 10000 miles, then self destruct. Some people get linkages off newer vehicles and fit them to their applications, or if you have one of several applications, Bowtie Overdrives has a "TV kit" that has linkage that hooks directly to the carb, and brackets to hold the cable. That's the route I went.

The fluid tube is different. MAKE SURE you get a locking dipstick. I have seen 8-10 vehicles that have had SEVERE fire damage before they came up with the locking dipstick. Last summer, I stopped a motor home from burning to the ground. What happens is that when you are pulling a load, or going up a steep hill, or getting the tranny hot, then it builds up pressure, and for some reason it ends up puking fluid out the filler tube... all over hot exhaust manifolds, creating instant fire. The locking dipstick prevents this from happening.