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1991 K5 - What engine and tranny to buy?

M

Mass91

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I have lurked here for over a year. I finished a restoration of a 1991 K5 to the point it basically looks brand new. Paint, all new trim, moldings, grille, interior upholstry, rebuilt AC system, MT Rims with 33" Goodyears, new window motors, stereo, headliner... basically everything it needed to look new. (I'll post some pics when I figure out how). It was a southern truck so no rust. It has 145,000 original miles on the engine and tranny.

The engine is shot. It needs a rebuild or replacement. The tranny I had rebuilt but it still has it's quirks. I know this truck well as I bought the identical model year and color truck new in 1991, so I know how it "shou'd" run and feel.

What I want to do is keep it legal but put a new motor in it. I am debating rebuilding only to keep it all original, or just buy a new crate motor and maybe even a tranny to go with it so I don't have to deal with the quirks of the existing one. Basically, I can spend what I want. I don't want to break the bank, but I guess I would be willing to place a max budget of $10K if it meant getting the best.

I worry about going to powerful (maybe 300-350hp max?) as it may cause for new rear end/driveshaft etc. Also, I don;t like the TBI, but if I make a change I need to be able to pass emissions in New Hampshire.

Any advice, suggestions knowing what you know would help. I know this is a general question. But also keep in mind, this truck is really, REALLY nice and worth doing right.

Thoughts? What would you experts do? Also, I am not looking to beat this thing offroad. The occasional dirt road in Maine and NH and snowstorm.

Appreciate your input.
 
Honestly, in your case, it sounds to me like dropping in an exact replica (rebuilt or new) is the way to do it.

Anymore, either a diesel swap or the LS-series is the way to go, IF you are going to go with something else. But those bring a whole host of other problems, and it sounds like you are not trying to get into that.
 
RamJet 350 from summit, or jegs, or anyone of those places. I think it's 350 horse out of the crete, if I remember right. That would be pretty sick. I always said if money wasn't a real problem, I would purchase that motor and never look back.
 
If it is more original, like you say, then I might just rebuild what you have.

But you could look at my build I did a 5.3L/4L65E

You may want to pay the $25 for a membership to post and see pics.
 
I thought in New Hampshire vehicles '95 and earlier don't have to pass emissions?
 
From your post it seems you don't want to get into any heavy mods, but you want quality. If that's the gist of it, then I'd say crate motor and if you want a little more power and better operation, you can put an aftermarket EFI setup on it like FAST.

But if you're willing to do a little more modification, you can go with an LS motor. They are highly regarded. My Blazer will get one one day, I'm just waiting on an excuse.
 
If your budget really is that high and you want to do it right the first time....

LS swap all the way. Get a donor engine/trans with all of the accessories and PCM out of a low mileage truck and install with custom engine mounts. Buy a custom harness, widely available from many sources, plug it in, hook up a few wires and done. Well, except for swapping out a higher pressure fuel pump in the tank and maybe some adapters for the fuel lines at the engine.

The power, driveability, reliability, and mileage will all be worth it in the end. 5.3 for a better power upgrade (even though it's smaller) over your 350. 6.0 for a much torqueyer feel, it'll feel like big block power in an old K5.
 
Chevy305 said:
I thought in New Hampshire vehicles '95 and earlier don't have to pass emissions?
Click to expand...

You are right! I just moved from the communistwealth of Mass and should have known Live Free or Die didn't have mass laws. So NOW what should I get?
 
Mass91 said:
You are right! I just moved from the communistwealth of Mass and should have known Live Free or Die didn't have mass laws. So NOW what should I get?
Click to expand...


Mass is the same. 95 and older is safety only. Been that way for years. That's not to say you won't get some dick inspector who looks under and fails you for no cat(s). You may not have to pass a sniffer but some places may look for the proper equipment.

Regardless of what you can/can't do, i still say LS swap for your intended usage of the truck.
 
An LS swap will be cleaner burning then what you have now.
Your power choose is way more unlimited with an LS. A 5.3 tuned with headers would start in the 350hp range all the way up to a 6.2 with headers and a cam swap in at over 500hp.
With your budget you can do a real nice swap.
I will be glad to answer any question you would have on doing one.
 
496truck said:
Mass is the same. 95 and older is safety only. Been that way for years. That's not to say you won't get some dick inspector who looks under and fails you for no cat(s). You may not have to pass a sniffer but some places may look for the proper equipment.

Regardless of what you can/can't do, i still say LS swap for your intended usage of the truck.
Click to expand...

You can keep the cats on an ls swap but most people don't.
 
I would stick with a GEN I SBC, if it's as nice as you say. Rebuild your short block, go with a roller cam, buy some good heads, and have it tuned on a dyno.

Martin
 
The tbi engine management will hold you back. You can fight with it to get more power from an upgraded gen I if you want. I didn't want to, so I went with a new GM 350 tbi, for my 88 K5. It runs nice, but is slow with 35" mud tires and a lift. My 79 C20 pickup has a hot little gen I 406-full roller and built for low end torque. It halls but, even with the 600 cfm carb. My mom and brother have 2005 silverados with the 5.3.

I vote for a 5.3 or 6.0 LS. They haul but and get better mileage. They can be upgraded pretty easily, and they should pass smog if you keep them as they came out of the original vehicle. I have to pass smog here in Cali. I would love to have a 5.3 in my K5. My Gm 5.7 tbi was $1700 from summit racing, two years ago. I have at least 4 times that amount of money into my 406 and it gets at most 10 mpg and is estimated at 400+hp and 525tq. A 5.3 could be upgraded to pass that up, and it would probably still get better mileage, and you might be able to do it for less money.

The LS is the new Gen I sbc. They are everywhere and it seems to be easy to find parts and do upgrades. The technology is better.
 
496truck said:
Mass is the same. 95 and older is safety only. Been that way for years. That's not to say you won't get some dick inspector who looks under and fails you for no cat(s).
Click to expand...

Thought I was going to have to deal with that once, even had the bribe money ready, but the guy decided that his knees weren't up to getting down on the ground :D
 
I believe in Ma its 1997 and older that dont need smog tests now,only safety..every year it goes one year up more...but they are supposed to do a visual to ensure the converter and other things like the gas tank "flap" is intact...
 
I had a guy offer me an 04 dmax and anything related to drive train and wiring that was left this morning. II'mnot financially or mmechanically sound enough to find anythingto swap it to. That would be a good donor. I'm in amarillo and can get it for anyone if they are interested...
 
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