More motor...

[william_7900]

My 71 Blazer has a moderately tired 350 with a shoe-horned in NV4500. I would like more torque. Thought about going the 6.5 diesel route but have decided against it. Spoke to the best builder in the area and he suggested I go with either a stroked 350 or even better in his opinion would be a 400 cu in if I could find one. I want to put in a 700r4 at the same time.

What do u guys think? Is the 400 torque'y or would u do something different? I have 411's in it currently.

Do I need something special to mate a 700r4 to my transfer case?

So two questions: engine thoughts and needs for mating a 700r4.

Looking forward to your thoughts.

William

 

[resurrected_jimmy]

What transfer case are you currently running? A 700R4/NP241 assembly should be pretty easy to come by.

I am not a 400 sbc fan, I would go for the 383 stroker motor

 

[Mike82K5]

I have an '82 that came stock with the 700R4. I bought it with a bad diesel motor. I switched it over to gas and I am running a 406(400 bored .030 over). It makes 425 hp and 475 lbs of torque. I love this set up. Its very fast for a 4300 lb vehicle. If you want any other info send me a pm.

Mike

 

[72blazerguy]

I'm running a stroked 350 in my 72 (383 stroker). No complaints, excellent torque. Wish that I had upgraded to 700r4 w/ NP241 at the time, but wanted to keep the 205 and had limited funds. Will be upgrading to 700r4 in the future.

 

[william_7900]

It has a 205 in it. I've read a bit on the required changes to mate a 700r4 with the 205. Is it easier to use a NP 241? If so, where are the best places to look for a NP 241? I'm assuming some other changes may be necessary with an NP 241 such as drive shafts, input shaft?

The reason I'm pursuing the 400 is because of the cost to stroke a 350. I spoke with a performance engine shop yesterday and he indicated it was about twice the cost to upgrade a 350 to a 383 than a typical rebuild of a 400.

So two more questions - merits of a NP 241 over using the 205?
Am I correct in the cost differences of rebuilding a 400 over upgrading my 350 to a 383.

Thoughts?

William

 

[resurrected_jimmy]

the 700R4/NP241 combo is a stock setup from 89-91 K5 or burban. You won't need to swap the trans output or T-case input for them to mate. The 241 is an aluminum case, chain drive, with a 2.72 low range ratio. It is a very stout T-case, just don't smack it into rocks or the aluminum will shatter.

 

[manchildau65]

Either way you go, I think you'll be dissapointed with a stock 700 behind any SBC with more than stock power... I've personally gone through 3 of these trannies with mildly built sbc's (coincidently, 2 - 350's and 1 - 400)

Are you sure your 350 is getting tired or could your 700 actually be the one getting tired? Don't get me wrong, 700's are awesome when built up!

 

[william_7900]

I have a nv4500 standard in it now.

 

[smalltruckbigcid]

What kind of use? daily driver or trail only. Build the engine for what you will use it for.

I's stay with the manual setup over a 700r4 anyday

 

[Hogback Fabrication]

It has a 205 in it. I've read a bit on the required changes to mate a 700r4 with the 205. Is it easier to use a NP 241? If so, where are the best places to look for a NP 241? I'm assuming some other changes may be necessary with an NP 241 such as drive shafts, input shaft?

Pull your NV4500 and NP205 and sell them, they are desirable and worth quite a bit. You should be able to find a 700R4/NP241 for relatively cheap, most people want to swap the other way around.

Be aware that 700R4's don't really hold up too well in stock form and many rebuilds are not done right.

So two more questions - merits of a NP 241 over using the 205?

The 241 is lighter and has a deeper low range gear (2:1 vs. 2.72:1). The 241 is an aluminum, chain drive transfer case which can break but isn't super weak. The 241 also uses a slip yoke style driveshaft.

The 205 is basically unbreakable but it's heavy with a high ratio low gear. Most 205's use the desirable fixed yoke rear output.

The 205 is generally considered the better transfer case.

The reason I'm pursuing the 400 is because of the cost to stroke a 350. I spoke with a performance engine shop yesterday and he indicated it was about twice the cost to upgrade a 350 to a 383 than a typical rebuild of a 400.


Am I correct in the cost differences of rebuilding a 400 over upgrading my 350 to a 383.

Thoughts?

William

Well, depends on what you want to do.

The 383 will cost more than a stock rebuild on a 400 because the 383 requires new pistons, flywheel/flexplate and harmonic balancer.

If you're looking for performance out of this motor (383 or 400) you'll be replacing the pistons anyway and likely the flywheel/flexplate too.

The 350 block that you would use for the 383 is better in basically every way. Really the whole idea of a 383 is to get the longer stroke from the 400 into the better block that the 350 has.

The 400 uses siamesed cylinders which can cause overheating problems, especially when its bored out during a rebuild and its cylinder heads use steam holes so if you put any other SBC head on it you'll have to drill those holes into them. The 4 bolt main bearing caps on 400's are also prone to cracking.


400's aren't all bad and lots of people use them with success but the 350 block is better and that is why 383's are so popular.

 

[max 02]

Wouldn`t it be cheaper to put a big block in it? I did that in my old 78 c10 and I SURE LIKED IT!!

 

[K85 Octane]

^^^ some people don't like big blocks, weight is a factor for me, but overall it depends heavily on the type of offroading you do. Mud bogs = big blocks

However, I have a junk 350, 30 over, and was going to do a 383 using an early 90's 3/4ton 350 4 bolt, with 1 piece main seal. That is until my machiniest (who is also my uncle haha) said he had the parts for a 400 and has built them with great success in the past. My decision was made lol

 

[COCHEV]

Wouldn`t it be cheaper to put a big block in it? I did that in my old 78 c10 and I SURE LIKED IT!!

I sure like mine too...

the sbc 400 is a nice motor too, but still not a big block.

i'll take the nv4500 off your hands too...

 

[rob h]

I built a 350, would of liked a 400 but the 350 was free. I thought building one was a good idea but i build one a little too stupid. Watch how high on compression you go with it so you dont need race fuel . I cant say that its not neat having 12.5:1 but its expensive to drive. It does run like a race car with 39s but hard with the wallet. A mild 350 or even on worked up pretty good with no more than 10:1 would be more practical. Or if you have the cash a nice crate motor with a warranty. Depends tho will you dd it or not will tell ya how far to go. I also like the idea of an injected 454 or the 5.3-6.0 newer swaps...

Please pitch the idea of ditching the 4500 for a 700 r4...the 700r4s ive never seen one last to a good worked up motor.

 

[william_7900]

You guys have helped me a ton - as usual.

It is not super easy to find a car that has a 400 in it that is or has been recently running, take everything out, sell the car, rebuild the 400 and put it in my Blazer. It may be much easier to just stroke the 350. I really don't want to put a big block in it but that may ultimately be the best option for what I want - not a ton of $'s but more power and more torque but much worse gas mileage.

I've read where I may have to modify my firewall and motor mounts as well as other parts to get a 454 to fit????

You guys are also causing me to rethink my desire to switch the NV4500 for the overdrive automatic...

Is the consensus that it is just as good an option to stroke the 350 - may cost a bit more but less hassles - than try to find a 400 and rebuild?

Thanks again for all the advice.

William