New k10 4x4 help

[70k10fourby]

Hi guys. I've been an old car guy for a while but recently sold my newer Silverado and bought a 1970 k-10 4x4. Tired of paying high registration and insurance and smog in California, and buying vehicles that just depreciate. I found a nice truck, original paint, great body with factory A/C. I've got some questions about the motor that would be right for this truck to be my daily driver that i offroad on the weekends. I need it to get good mileage but still be fun to drive. It's got a 3/4 drive train, 60 in the back and 44 in front. 4.10 gears and 33's, and an np205. It had a built 350/th350 that i just yanked out. I bought a 700r4 for it and am researching motor stuff right now. A friend has a tpi 305 out of a 1990 IROC camaro that is brand new (has 200 miles on it before car was totaled.) Would this be a good motor for my truck. I know these made a lot of torque. Or should i spend some cash and builder a nice 350 to do just what i want. Any thoughts would help, thanks.

[FLDBRED]

It would be hard to beat one of the modern LS style motors.They are starting to become cheaper and the swaps are becoming easier!It is about the only motor that will get you decent fuel mileage in our trucks!Other than that I would go for a roller 383 with Vortec heads and a mild cam!Welcome to the site!

[70k10fourby]

Yeh, an LS would be great. But the TPI 305 is free. I can get great mileage out of my carbed chevelle with 400 hp, but the 4x4 thing is new to me. It seems like if you under power these heavy vehicles sometimes you can end up getting worse mileage though.

[fencepost]

IMO I hate 305's I think you will like the 350 better maybe even a mild 383 built for torque. 3/4 running gear, you might want to do some towing some day and if you ever decide to sell it the 305 will get frowns. I say 350 or 383. You could go with a TBI 383 build there are some folks on here who have done the TBI swap on your type truck.

[70k10fourby]

Cool, maybe i can find that thread. I may be able to bolt the tpi intake to a 383. I'm really shooting for 20mpg.

[fencepost]

Originally Posted by 70k10fourby

Cool, maybe i can find that thread. I may be able to bolt the tpi intake to a 383. I'm really shooting for 20mpg.

Would opt for an after market intake better flow. They sell adapters to install TBI on carb intake, look em up on e-bay. Also try tbichips web site that guy is very helpfull. I'm thinking of doing a 383 in my 94 Z71 and keeping the factory TBI.

[mrein3]

I would and did go with a 383.
I did not go with a roller block. I wish I would have. I have a 99 Suburban 350 on the stand that would make a great start for another 383, this time with a roller cam and the vortec heads that are already on it.

Advanced Adapters makes an output shaft for a 700r4 that will allow you to bolt it directly to the NP205 adapter you already have behind your th350. you'll have to move the engine forward almost 2 inches to make up for the longer 700r4. Lots of people on here have done that.

If the previous owner didn't already convert that front axel to disc brakes, that would be another good upgrade. Stock 70's had drums up front. I've read on here that 71-87 fronts are a direct exchange. Just make sure you get one with the same gears your rear and current front have.

Roller 383, 700r4, 3/4 ton drive train, California body - man I'm envious.

[msgross]

Originally Posted by 70k10fourby

Cool, maybe i can find that thread. I may be able to bolt the tpi intake to a 383. I'm really shooting for 20mpg.

I wouldn't plan on that... be happy with 15... My 2005 Tahoe gets 19-20 MPG with better gearing and a modern LS 327...

Free is good, but the 4.10's won't help the mileage, but will help the torque... even with the 700R4 I think 20MPG is dreaming...

[67/72junkie]

No way I would run a 305 in a 3/4 4x4.My 72 3/4 4x4 as a 400 small bock 350 turbo and 4.10. it averages 13 to 14 mpg around home with alot of stop and go driving.It will get 16 mpg on the open road and tow anything I care to put behind it without a problem.

[70k10fourby]

Do you guys think going from 4.10's to 3.73's would kill it?

[70k10fourby]

The trucks got discs in front. Also, the 700r4 i got was built by Phoenix transmission in Texas using the output shaft from advance adapters for the np 205. It's a super sweet truck. Just got to make it a little more driveable. I'll be posting pictures soon.

[mstrav1973]

unfortunately good gas mileage in these trucks isnt going to happen. overdrive will help, but you have 4:10 gears with the 33's. big tires eat gas milleage. if you go with to small of tires your rpms will be up to high doing 65 ish down the freeway. I have 35's with 3:73's and was getting around 10 mpg. with some recent upgrades hopefully it improves a little. 15 - 20 aint gonna happen. I have an 07 gmc with a 6.0 that gets 13 mpg with 285's (32's) on it.

Matt

[mrein3]

Originally Posted by 70k10fourby

Do you guys think going from 4.10's to 3.73's would kill it?

No.

With a 700r4, 3.73's and that first gear will still be a stump puller.

My truck has 3.73s and can pull like crazy.

I've never seen over 13mpg on the open road. I get 10 pulling my boat around.

[BluTrukker]

The best way to get good mileage out of an old heavy truck is to swap in a diesel. A lot of guys have done it, and if you can find a late model donor, there is a huge aftermarket to make power and mileage.

[70k10fourby]

With the 3.73's do you think youre bogging it down on the highway ever? or when towing your boat?

[Murphy IRE]

I'll have to double my mileage, but the last time I checked; I was getting about 11 mpg ( but I had a lot of vacuum leak). 400 sb with a 700r4 tranny. I haven't checked but I think I have 3.73 gears. The few Times I've towed something, I never knew I was towing anything. I'm getting better milage than my friend with a 350 /350th.

[PowerPro]

I think running 33's and expecting more than 15mpg is more than a little hopeful, but good luck and let us know how it works out! Truck sounds great! POST PICS!!!!!!

Oh, and suggestion for good gas mileage would definitely be an LS swap. I get 12-14 with my 472, but I love the power.

[mrein3]

Originally Posted by 70k10fourby

With the 3.73's do you think youre bogging it down on the highway ever? or when towing your boat?

No. Never. If anything I'm spinning it way too fast when I'm going 70+ on the interstate.

If/when I get a 700r4 I won't be towing in overdrive but the 3rd gear in the 700r4 is the same as my final gear in my th350 - however with a lock-up torque converter it will slow the engine down some on the freeway.