New guy with some questions.

[UTAH90YJ]

Hi all, new to this forum. Been lurking old Chevy forums for about the last 6 months while I've been shopping for a truck. You guys seem like a solid bunch.

I just picked up a 79 GMC K25 Sierra Classic Trailering Special with what I believe has a 400 BBC, Turbo 400, NP203 Full time, 10 bolt/ 14 bolt. Got it for $650

I can wrench on my vehicles, but I'd like to keep the custom work and modding pretty minimal on this truck. I know from experience on my Jeep that once you start doing crazy mods all hell breaks loose. I want a reliable pickup that can work and play. Budget for this truck is below 2k.

I can't seem to find too much information on this trim or model, does anyone have any good sites where I can read up all I can on this truck?

It needs some seats. I have a seat bracket on order, and I'll probably head to a junkyard for some seats. Any Chevy/ GMC pickup seats from 73-87 should bolt right in right? Or is there better options out there?

The 400 Big Block, from what I hear it is just a slightly bored out 396? Any concrete information on this motor? What is the mpg and power I can expect (haven't been able to drive it much, has no seats so not registered yet). Can anyone recommend a good exhaust setup for it? Not looking for something blaring, just want some good sound.

How much benefit would I gain from a 205 part time swap or a 203 part time kit? The truck will be used a decent bit for daily driving, quite a bit in the winter (Rocky Mountain Region), and some casual wheeling trails that don't require lockers (not too crazy, I am in the process of building a 90 Jeep YJ for rock crawling).

I am on the fence about lifting it. Don't want to put too much money into it, but I want it to look good and be semi capable offroad. But it still needs to be able to be used as a work truck and towing occasionally. Not a ton, just my Jeep or sometimes a small excavator. I was thinking of getting an ORD Shackle flip kit in the rear, and some 4" leafs for the front? Tires will most likely be some 35" Treadwright Guard Dogs in E load rating. Airbags later on if it sees lots of towing.


Here is a bad picture, I can take more if you guys want em. Its nothing special, but It's my first truck and boy am I excited about it.

[walkerb]

Nice truck welcome to the board. Looks really solid.

[81rado210]

Looks like good start for the price

[dieseldawg142]

welcome!
your 400 bbc should actually be a 402 bb. chevy didn't want to toss a hallowed nameplate like 396 when they bored it out. unless you got the sb 400.
hp is rated at what your wallet can handle. if your casual wheeling, i would just part time your 203, there still plenty strong. ran a converted 203 with a 400 sb in my 76 k5 with 35's alot more than casually & never had a prob with it.
and 4by squares are meant to be lifted!

[UTAH90YJ]

Originally Posted by dieseldawg142

welcome!
your 400 bbc should actually be a 402 bb. chevy didn't want to toss a hallowed nameplate like 396 when they bored it out. unless you got the sb 400.
hp is rated at what your wallet can handle. if your casual wheeling, i would just part time your 203, there still plenty strong. ran a converted 203 with a 400 sb in my 76 k5 with 35's alot more than casually & never had a prob with it.
and 4by squares are meant to be lifted!

Awesome. I can't seem to locate any casting numbers to get a positive ID on the motor. It has "GM Goodwrench 350" Stickers on the valve covers, but the VIN and labeling on the front clip all say it is a 6.6l 400.

[rich weyand]

sounds like it's a replacement crate engine.

[dieseldawg142]

^^^agreed, sounds like a crate replacement
the 400 sb is not to bad an engine, just not alot of meat between the bores, so a clean-up is about as far as you go. they do make good torque though.

[UTAH90YJ]

Thanks everyone. So just to clarify, you guys think it is a 400 small block crate motor?

[rich weyand]

No, I think it's a GM Goodwrench 350 crate engine #10067353. Most of the other crate engines would have GM Performance on the valve covers.

If you could pull the numbers on the block we could tell you for sure.

The engine ID number on the front is the most useful. You can get at that pretty easily by moving the alternator (or AC compressor) on the passenger side of the engine.



All is not lost, though. One, it means that the engine has fewer miles on it than the truck, which is a good thing. Second, you can put a Comp Cams 12-235-2 in it, with the recommended lifters and springs, and for a few hundred bucks you could get 290hp and 415lbft (at 2500!) out of it, which will be a HUGE improvement over stock.

[cadillac_al]

Looks like a very solid truck; good score.

[Vintage Windmills]

Good deal! I actually saw this one for sale online and thought about having it shipped here! Like the paint color on it and it seems pretty rust free!

[Eug396]

I found this site the other day when I was looking for some information on my GMC's history. This guy does a pretty good job of breaking up the model years and differences. Lots of extra information too. May check it out. http://www.chuckschevytruckpages.com/models.html

[willett]

The 203 is alright if its part timed, I've been running one for a good many years. If you want to swap to a 205 your going to have to swap your output shaft to a longer one which means dropping your tranny and ripping it right down to nothing. Not the best of your trying to keep cost down.

[rich weyand]

The NP203 is fine.

One note: The oil for the rear output shaft bearing is provided by the chain spinning and throwing oil up into the ways to keep the reservoir filled, and the chain does not turn if the front driveshaft is not turning. So when driving around with the hubs unlocked, put the transfer case in HI LOC the first time you drive every day, for the first couple miles, then you can switch from HI LOC to HI while on the roll. When driving long distances, put it in HI LOC every time you stop, for the first couple miles, and again switch from HI LOC to HI on the roll. This will keep you from eating up output shaft bearings.

Not running around in HI LOC or LO LOC on clean dry pavement with the hubs locked will keep you from eating up chains and tires.