Best Choice for Drivetrain

[vicnation]

I have a low mileage 1976 K10 shortbed. It has a 350, TH350, NP203 and 3.08 gears. I need more lower end torque, the reliability and efficiency of fuel injection and would like to be able to comfortably drive it down the road at highway speeds. Everything is stock except for headers. I have 32" tires and a 2 inch lift. I do plan to add A/C. Speaking financially, I am looking for the best value option.

Option 1: Using the original engine, add aluminum heads, a towing cam, Edelbrock Pro-Flo 4 port fuel injection, update the fuel tank and add an electronic fuel pump. Add a 700R4 and keep the stock transfer case. Not sure about gear ratios.: Opinions welcome.

Option 2: Get a crate 383 long block, add the before-mentioned cam and fuel injection system and other items. Add a 700R4 transmission and keep the stock transfer case. Opinions welcome on the gear ratio.

Option 3: Get a used or crate 454, add the fuel injection system, 700R4 transmission and keep the stock transfer case. Opinions are welcome on the gear ratio.

Option 4: Get a used LS 6.0 with a 4LXXE transmission. Not sure what to do about the transfer case or gear ratio.

Any other suggestions?

The truck will not be used off road and will be driven a few times a week. I understand that I will need to change the driveshafts as well depending on the selected option. Am I missing anything?

Thanks...

 

[dsteelejr]

Instead of just throwing a pile of cash at the problem you could make incremental changes until you get the results you want. Since you said you’re towing I’d start with ditching those 3.08s and install some 4.10s. If you want more power put an RV cam in that engine. I don’t see how installing a 700R4 is going to help. I had one in my ‘84 K5 years ago and it was a piece of ****. My ‘73 C20 has a TH350 and it’s only been rebuilt twice in it’s life due to ordinary wear and tear. I’d rather have a TH350 or TH400 for towing than a 700R4. I’ve seen several members on here mention that you can’t use OD on a 700R4 without cooking the son of a b!tch.

 

[vicnation]

Thank you for your suggestions. Rochester makes a good carburetor but mine needs a complete overhaul. I would prefer fuel injection for better starting, smooth power and better fuel efficiency. Would I need to change valve springs if I installed an RV cam? I'd like an overdrive transmission to keep my RPMs lower at highway speed.

It is not my intent to build a performance monster. I just want to update the truck for occasionally pulling a boat but more for just driving on today's roads at today's speeds.

 

[dsteelejr]

First, I meant to say that TOWING while in OD on a 700R4 will cook it. I should start proof reading before I hit post.

Going fuel injection is your choice. It’s your money and your truck. Do what makes you happy. While carbs will never be as efficient, you can get plenty of power out of a new or freshly rebuilt, well tuned carb.

I’ve never heard of changing valve springs when upgrading to an RV cam, but I would defer to someone with more engine experience for a definite answer.

I’m running 4.10s in my ‘80 K25 with stock size tires. In top gear 1:1 no OD I’m running at about 3250 RPM at 70mph. Kinda high, but not too bad. You said in so many words the truck is not a daily driver so it might be worth putting up with the higher RPMs. My ‘80 K25 is my off road truck and my work horse so I wouldn’t want any high gears. You can also go with 3.73. I think that’s a good middle ground ratio.

If you really want more engine power I’d look into the 454 option. I dunno how savvy you are at engine swaps, and I’m certainly not, but having read posts on here about LS swaps there is a lot to it. Different motor mounts, adapting to the tranny, computer module, more wiring harnesses, etc. Unless you have the knowledge and resources or can pay someone to do it its a lot to take on. Swapping a 454 in there would be a better option.

 

[AyWoSch Motors]

I'll say this, I'm a carb guy, think Fuel Injection is more hiped up that it should be.
My 86 had a 305, with a slightly bigger cam, edelbrock performer large port intake, edelbrock avs2 650cfm carb, sm465 4 speed manual, np205, and 3:73 or 3:90 something gears cant reminder. Anyway, that is a great setup. Itd do 75mph happily around 3k rpm. It could haul a bed full of rock, no issue, beat kids between stop lights with ease, lol. Got pretty good mileage too, for a squarebody.

I'd say, start with the rear gears. A 3:73 would be a good upgrade, better than you have, but not so high it'll be screaming.
I'd say leave the trans and transfer as is. A th350 is a good trans. And as previously said if you plan on towing, I wouldn't use an OD capable trans. 1:1 is what you'd like. A TH400 or a 4l60e would be an acceptable upgrade as well, with little changes.
Engine wise, I'd say start small. stock block, stock heads are a solid setup.
A higher flow intake, dual or single plane 4bble intake, with a better carb. Something bigger and better than the stock Rochester, but not so big that it guzzles fuel, around 650 is good.
If you still wanted to change the cam after that, I wouldn't go straight to something as big as an RV cam, I'd just go a little bigger than stock.
And as weird as it sounds, the air cleaner makes a big difference. The more air you get, the more power it makes, but the more gas a it drinks. I air cleaner with tiny little hole, will choke power, but be good on gas. If you have a fully open filter or even double stack them like I have, you be allowing it to get a lot of air, with results in more power, but image milage will suck.

It's hard to get good power and good mileage. You want a happy medium, not to much of either.
A regular old SBC 350 has alot of potential.
If your looking for any sort of milage, DO NOT GO BIG BLOCK. I love them but they got a drinking problem for sure.
If you want both excellent mileage and good power, LS is a good upgrade, but you'd have to change almost everything. It costs alot and it's a pain. Not a huge fan of LS personally...
Start with changing the little things before you make a big expensive change.

My 2 cents...

 

[oldretiredafguy]

Instead of just throwing a pile of cash at the problem you could make incremental changes until you get the results you want. Since you said you’re towing I’d start with ditching those 3.08s and install some 4.10s. If you want more power put an RV cam in that engine. I don’t see how installing a 700R4 is going to help. I had one in my ‘84 K5 years ago and it was a piece of ****. My ‘73 C20 has a TH350 and it’s only been rebuilt twice in it’s life due to ordinary wear and tear. I’d rather have a TH350 or TH400 for towing than a 700R4. I’ve seen several members on here mention that you can’t use OD on a 700R4 without cooking the son of a b!tch.

First hand knowledge here of towing with a 700R4----DON'T. Put a quality rebuilt TH400 in and never look back. Save yourself a thousand dollar bill+ to spend on something else.
Mike

 

[shiftpro]

First hand knowledge here of towing with a 700R4----DON'T. Put a quality rebuilt TH400 in and never look back. Save yourself a thousand bill+ to spend on something else.
Mike

Towing your dirt bike maybe....

 

[CalSgt]

I built a K-10 33" tires, plain 350 W/quadrajet & dual plane manifold, RV cam, 3.30 gears, 700R4 W/208 TC... It hated 55 mph, if fact it didn't like going under 70 mph on the highway. The tall tires + high rear end gear + overdrive + high rpm range cam (2000+ IIRC) wanted to almost idle at 55 mph and would constantly downshift to get some power. If I wanted to haul ass & keep the rpm's up it loved it, I always wished I would have chosen a smaller cam.

I agree with @AyWoSch Motors saying to go to a lower gear ratio for starters, and to do it a step at a time and assess where it needs to go from there.

I would think a bone stock 5.7L L31 vortec crate motor would pair really nice with a Holley or Edelbrock EFI setup. They make great power, run cool, have great heads, and come with a roller cam. Thats my recommendation if you are dropping coin on a new motor. Slight differences from your '76 350 but are easily overcome compared to the LS swap.

I'm a big fan of EFI with the modern fuel we get at the gas station, new gas has lower vapor pressure than what was available when factories still produced carbureted engines. Not saying carburation is bad, just a fan of EFI.

I'm a fan of the 700R4 too, if built right and TV cable set up correctly they hold up fine. Dad ran a super early 700R4 in his '76 k-25 with a 454 and had no issues, it was his daily driver from about 1982-2002.

I hate the 203 TC though, super heavy and not really that stout for as much as they weigh. A 208 is light weight and would pair nice with a 700R4, they aren't very tough but you said you don't plan to offroad it anyway.

Good luck

 

[vicnation]

I appreciate all of your suggestions. It has given me a lot to consider which is exactly what I was hoping to get from this community. Thank you! If anyone else has suggestions, please offer them.

 

[Vbb199]

All these hate posts regarding a 700r4, and yet here i am = towing easily 7,000 pounds or less on hills and winding roads with it, good ****.
And have done it, many many times, and im stilling doing it, no burnt fluid, no excessive ashing, no slipping.
I think @bucket Will agree too.
Just treat it right, downshift on hills back to 3rd.
You see, what burns a transmission up when towing in 4th is insufficient line pressure because the tranny fluid pump is spinning slower (.7:1 ratio, OD), if you have a well tuned TV cable via a pressure gauge, and you have the right gear ratio to assist it, even in 4th, the pump will still spin fast enough on flat ground or slight grades to keep it oiled.
When i tow heavier **** like my offroad rig + trailer to the national forest, on hills, i dont ever see spikes in temps..... the magic secret to prevent clutch glazing, then ultimately; failure is to keep the fluid cool, and keep the pressure high... if you go towing with a 3.08 ratio, you really are gonna destroy it.
If you go lugging the tranny and just be a vehicle operator instead of downshifting and letting the motor do the labor, you're gonna destroy it.


Just stay away from the 82-86 units , they really are the crap, which is where they get a majority of the bad rep from.
If you intend on towing more than that 7-7500, you should consider other alternatives like the th400 or a 4L80e

 

[Bextreme04]

If all you will be towing is an occasion boat, a 5.3/4l60e combo from a junkyard would be cheaper and easier to do than the other options. Hell, you can get the motor, trans, wiring harness, and ECU for less than what just the Pro-flo would cost you and make more power with better fuel economy. You would have to make the same fuel system improvements regardless. The only other thing you would need for the LS is the motor mount adapters. 700R4 or 4l60 should have no issues with towing a boat or small travel trailer as long as you have a nice BIG trans cooler.

 

[Vbb199]

To answer the question, i say tune your current motor, swap heads, look into fuel injection if you wish, toss that 700r4 in, or whatever you really want. If you go with the 700r4, i would at least recommend 3.73 minimum ratio.

But thats really based on your tire size.

 

[Raider L]

Man!! What advice! I wish I was @vicnation!

 

[shiftpro]

All these hate posts regarding a 700r4, and yet here i am = towing easily 7,000 pounds or less on hills and winding roads with it, good ****.
And have done it, many many times, and im stilling doing it, no burnt fluid, no excessive ashing, no slipping.
I think @bucket Will agree too.
Just treat it right, downshift on hills back to 3rd.
You see, what burns a transmission up when towing in 4th is insufficient line pressure because the tranny fluid pump is spinning slower (.7:1 ratio, OD), if you have a well tuned TV cable via a pressure gauge, and you have the right gear ratio to assist it, even in 4th, the pump will still spin fast enough on flat ground or slight grades to keep it oiled.
When i tow heavier **** like my offroad rig + trailer to the national forest, on hills, i dont ever see spikes in temps..... the magic secret to prevent clutch glazing, then ultimately; failure is to keep the fluid cool, and keep the pressure high... if you go towing with a 3.08 ratio, you really are gonna destroy it.
If you go lugging the tranny and just be a vehicle operator instead of downshifting and letting the motor do the labor, you're gonna destroy it.


Just stay away from the 82-86 units , they really are the crap, which is where they get a majority of the bad rep from.
If you intend on towing more than that 7-7500, you should consider other alternatives like the th400 or a 4L80e

There's one in every crowd... the guy on 44s with a 12 bolt and never breaks anything. Oh well.

But seriously V you're right. Thanks for the detailed post, making a couple of great point.
Who are transmission repair shop's biggest customers..? OLD LADIES. Well I just pulled that out of my and hope it helps make my point... which supports your point.
And you warned not to lug these units. Spot on... big blocks eat these guys not because of total power, but from cranking the torque
from idle up... or holding 4th gear on the highway or hill. Lower rpm will lower pressure and there's the risk. Slip those plates once... twice... they're never the same.

 

[Vbb199]

There's one in every crowd... the guy on 44s with a 12 bolt and never breaks anything. Oh well.

But seriously V you're right. Thanks for the detailed post, making a couple of great point.
Who are transmission repair shop's biggest customers..? OLD LADIES. Well I just pulled that out of my and hope it helps make my point... which supports your point.
And you warned not to lug these units. Spot on... big blocks eat these guys not because of total power, but from cranking the torque
from idle up... or holding 4th gear on the highway or hill. Lower rpm will lower pressure and there's the risk. Slip those plates once... twice... they're never the same.

Ive burned up a couple from not setting the tv right, and ive burned up one from treating it poorly, and to that end, i (for a long time) was permanently disgusted with the 700r4, but i agree, there is always "that one guy" LOL

Like i said, if you're just an operator, and treat the 700r4 like everyone who owns an automatic, (putting it in drive, and never messing with the shifter again except to put it in park) its gonna quit.
You develop an ear for these things, even on my empty suburban, if im going up a hill, and i can HEAR the thing lugging, i downshift it, let the motor wind out.
My sbc makes its torque like a bbc, low rpms, and like a sbc, makes high rpm HP, its ideal for getting a load rolling down the line with the 4.10's and 31's.

When i got it loaded down,
I hold 1st manually until shes wound out to 4,500 and moving about 15mph, then manually shift, keep the load rolling, etc etc.... i let my engine do all the labor, and let the ol' 700r4 just keep the truck going faster, and nothing else.
I control when it shifts, and downshifts, and as a result, its much happier towing.