whats better?

[noJeepshere]

starting after the summer semester of college here im going to begin a buildup of my 81 k5. the body is largely rust and cancer free and the frame lacks cracks. the rig is a fairly light one at just over 3500 lbs. (as indicated by the scale at the dump) its a completely plain jane rig. the first item of business is the engine. its a 79 350 thats completely junk. my question is, what would be better, a vortec 305 or a 250 straight six? my idea is to keep it light and get a good amount of torque out of it. are there fuel injection kits for the 250, or does it hve to stay carbed? im going to do all my own work and want something unique. in my plan is a 2-3" lift with 33in tires. also front and rear lockers with 3.73 gears. it has the sm465 and np 208 (both need rebuilding) itll do mostly mountain trails with some mud and crawling. high horsepower and speed is not a concern. just a somewhat economical machine capable of getting out there.
thanks in advance!

 

[Hogback Fabrication]

the rig is a fairly light one at just over 3500 lbs. (as indicated by the scale at the dump) its a completely plain jane rig.

I don't buy that, that's likely at least 1000 pounds too light.

the first item of business is the engine. its a 79 350 thats completely junk. my question is, what would be better, a vortec 305 or a 250 straight six? my idea is to keep it light and get a good amount of torque out of it. are there fuel injection kits for the 250, or does it hve to stay carbed?

The 250 is marginally lighter than a small block, a 305 and 350 weigh the same. There's no reason to use any of the old L6's IMO.

TBI from a late 80's to early 90's Chevy truck will work fine on the 250, 305 or 350.

im going to do all my own work and want something unique. in my plan is a 2-3" lift with 33in tires. also front and rear lockers with 3.73 gears. it has the sm465 and np 208 (both need rebuilding) itll do mostly mountain trails with some mud and crawling. high horsepower and speed is not a concern. just a somewhat economical machine capable of getting out there.
thanks in advance!

That all sounds good.

 

[jonrpick]

starting after the summer semester of college here im going to begin a buildup of my 81 k5. the body is largely rust and cancer free and the frame lacks cracks. the rig is a fairly light one at just over 3500 lbs. (as indicated by the scale at the dump) its a completely plain jane rig. the first item of business is the engine. its a 79 350 thats completely junk. my question is, what would be better, a vortec 305 or a 250 straight six? my idea is to keep it light and get a good amount of torque out of it. are there fuel injection kits for the 250, or does it hve to stay carbed? im going to do all my own work and want something unique. in my plan is a 2-3" lift with 33in tires. also front and rear lockers with 3.73 gears. it has the sm465 and np 208 (both need rebuilding) itll do mostly mountain trails with some mud and crawling. high horsepower and speed is not a concern. just a somewhat economical machine capable of getting out there.
thanks in advance!

The only factory EFI available for the 250 was TBI that was only sold in Mexico AFAIK. I've never actually seen it, just heard about it. You can get a 4bbl intake and an adapter to stick a standard TBI unit on there, along with the other standard stuff (O2 sensor and what have you). TARussell put TBI on his 292.

A TBI unit from a 4.3L would probably be close enough in displacement to work with no problems.

I've yet to sign up, but I hear inliners.org has a lot of awesome info on doing custom things. I personally want a port-injected, turbo-charged 292. Since these motors have siamesed intake ports, I'm thinking using 3 injectors (one per pair of cylinders) is how I'd pull it off, then control the whole thing with something like a Megasquirt.

I've heard good things about the 250's. I'm going 292 for the extra cubes and really long stroke (longer than a stock 454) and the low-end torque that'll come with it.

 

[dyeager535]

How about an LS-series motor? I suspect all of them, cast iron or AL block, are lighter than gen1 stuff. Not necessarily economical, but when you start putting together EFI, it gets closer, especially with the performance of them.

I agree, GM SBC is a SBC, might as well get decent displacement if you go that route. If the 6 is marginally lighter, forget it.

No way that dump scale is right, sorry. My K5, stripped, sitting on 31's and 10 bolts, was at 5000lbs. I've heard of very few under that, complete. And even if they were within a couple of hundred pounds, that's probably a normal margin of error in the scales.

 

[noJeepshere]

I don't buy that, that's likely at least 1000 pounds too light.

ok there's a disclaimer here: it was 3625 without me and an empty tank, i had somewhere around two gallons left. 30 gallons of gas at 7 lbs a gallon = 210 lbs + weight of truck = 3835 sounds better, but still kinda light, huh? with me in there it goes to about 4075. it has no interior panels or headliner or backseat or carpet and light duty 30" tires. and that was when it originally had a six in it. now it has the 350. i was cheep and didnt rebuild it nicely. i put 67 camaro z28 heads on it and that blew out the bottom end (along with driving it without headers)

I've yet to sign up, but I hear inliners.org has a lot of awesome info on doing custom things. I personally want a port-injected, turbo-charged 292. Since these motors have siamesed intake ports, I'm thinking using 3 injectors (one per pair of cylinders) is how I'd pull it off, then control the whole thing with something like a Megasquirt.

i had actually thought of something like that, but i think id have to get an overdrive tranny to go down the freeway. that was back in high school, but still like the idea. depends on how much it is. i thought the original six that was in there had much more "torque-ability" then the 350 ever had, it was hard to kill that thing! if i could find a good pre-emission 250 and an efi kit for it, i think ill do that.

 

[jonrpick]

i had actually thought of something like that, but i think id have to get an overdrive tranny to go down the freeway. that was back in high school, but still like the idea. depends on how much it is. i thought the original six that was in there had much more "torque-ability" then the 350 ever had, it was hard to kill that thing! if i could find a good pre-emission 250 and an efi kit for it, i think ill do that.

OD tranny is no problem... the bellhousing pattern on the 'six' block is the same as the V8 pattern, so a 700R4 will fit with no problems. That's the combo I plan to run.

 

[noJeepshere]

i want to stick with a manual if i can. my late friends widow has a 5 speed od tranny out of a mid-60's school bus that had a 454. at least thats where it came from i think. maybe mid-70s. i hope she still has it, as it would fit right in. my idea is a lightweight and durable rig, hence the desire for low horsepower

 

[jonrpick]

i want to stick with a manual if i can. my late friends widow has a 5 speed od tranny out of a mid-60's school bus that had a 454. at least thats where it came from i think. maybe mid-70s. i hope she still has it, as it would fit right in. my idea is a lightweight and durable rig, hence the desire for low horsepower

I don't know how light you'll get it in stock form... Ditching the hard top will help some, but as others said, the straight six is some lighter, but not drastically lighter than a small block. There is a guy casting aluminum blocks for the 'sixes', but they're very hard to find and expensive. You may want to see if usbody.com has a race-weight hood or something. I know they offer thinner fiberglass body panels for certain vehicles, and that may be a way to shave a few pounds. Think about getting some quick-release hinges for your doors and pop on some tube doors when you're hitting the trail, again, it'll save quite a bit of weight.

Regardless of what others may think or say, a 250 can do well on the trail. There's guys out there in Toyotas using 4-cylinders and turning 40" tires, although again, those are lighter rigs that our K5s.

Remember, horsepower is a function of torque AND RPM. You can still have torque without high RPMs, and the result is a lower HP number. Straight sixes are known for having good bottom-end torque, so I believe if you plan accordingly and gear properly, you can have a pretty functional rig.

Keep us posted.

 

[noJeepshere]

how 'bout this... iirc, there was a pickup down at the boneyard that had the vortec 4.3 v6. my thoughts are to have a spacer custom machined to fit between the intake manifold and head to ft the injectors. both are very nearly the same displacement, but the 292 would be a torquer. i could get the truck fairly cheep and have all the parts to do the work. btw, i found a 292 freshly rebuilt for $800. that sounds like something unique and light and efficient.

 

[Hogback Fabrication]

Why not just take the 4.3?

 

[jonrpick]

how 'bout this... iirc, there was a pickup down at the boneyard that had the vortec 4.3 v6. my thoughts are to have a spacer custom machined to fit between the intake manifold and head to ft the injectors. both are very nearly the same displacement, but the 292 would be a torquer. i could get the truck fairly cheep and have all the parts to do the work. btw, i found a 292 freshly rebuilt for $800. that sounds like something unique and light and efficient.

292's are cool, that's what I want. The biggest issue with one is that they quit breathing and peak early in stock form. Stock form means a 1bbl carb. With a 4bbl intake and a real carb, it should keep revving a while longer. Consider getting the ports cleaned up on the head.

Also, make sure the head doesn't have the intake/exhaust manifolds "built in". Those bring teh suck.

 

[noJeepshere]

Also, make sure the head doesn't have the intake/exhaust manifolds "built in". Those bring teh suck.

im not sure what you mean "built in" as in the intake and the exhaust manifolds are part of the head? that would suck. maybe thats what "intagrated heads" means when i read up on these things.

 

[dbabicky]

Yes, that's what integrated head means, intake /exhaust are one with the head on the 250. Not all of the 6's were that way though. Not even all the 250's were that way. That was something they pulled in the late 70's-early 80's.

 

[noJeepshere]

what about 292's are they mostly integrated or "traditional"?

 

[jonrpick]

what about 292's are they mostly integrated or "traditional"?

Well, there's fewer 292's to choose from, since it was a truck-only engine. It's not hard at all to find the better head. They're all over eBay, rebuilt, with a warranty for a few hundred bucks. The ones with integrated heads don't turn up very often.

 

[K5dreamer]

if you have a choice, rebuild the 350 you have.

the 4.3 is a great motor if its what you have to work with. basically its a 3/4 350, so all 350 performance gear will fit it in regards to rods, pistons, valves, and porting and polishing is all the same, rockers, etc. you just order 3/4 as many parts as you normally would. But from all the guys i know that run them, you wind up with a 3/4 350, which gets the same gas mileage as a 350 would have. for a full size blazer, its kinda confusing why you would pull the 350 out and put a 4.3L in, unless you just want something different, in which case i applaud you there is even a company that makes engine mount brackets that make the swap a no brainer.

in regard to the strait six, the only thing i have to say is that they have a reputation for being immortal. i know people who TRIED to kill them, and couldnt.

other than that, if you really just dont want that 350, then i suggest you go with the 305. But as i said, if its at all an option, rebuilding that 350 would be the cheapest, easiest, and IMHO the most effective option.

oh and that weight is realllllly light for a full size. mine weighs 5200lbs, or at least thats what i was told by the previous owner, i havent put it on a scale yet.

 

[noJeepshere]

in regard to the strait six, the only thing i have to say is that they have a reputation for being immortal. i know people who TRIED to kill them, and couldnt.

that was me i originally had a 250 in it, and tried EVERYTHING to kill it. my dad told he wouldnt replace a running motor and i wanted a 350 bad. i put two bottles of 7-up in an empty tank (ran the tank out), 1st geared it through town (@ 25mph+), floored it in a gas station parking lot (5 min stationary), let it burn all its oil...(ran dry over 20 mi!) lets see, what else... forced it down a gear at way too fast a speed (overrev galore!), raced it from a cold start... i cant think right now what all i did, but you get the idea. when i finally pulled it out, the crankshaft moved back and forth 1/4 inch! the crankshaft bearings were blue from overheating, and it still ran! i think what finally did it in was when i swapped it into a 79 chebby, i drove it to the boneyard without coolant. its still there.

 

[noJeepshere]

Why not just take the 4.3?

a v6 in a fullsize doesnt quite sound right by me. besides, having a vortec'ed 292 with a 5 speed manual tranny would be unique. thats what im going for, is something unique. at least to america. the rest of the world gets by on 4-bangers and 32's.

 

[K5dreamer]

... the rest of the world gets by on 4-banger DIESELS and 32's.

there, fixed that for ya

but naw man, if you wanna do something no one else has, im all about it. Just dont expect unrealistic things from it. typically if youre doing something no one else is doing, with old parts like these trucks, theres a reason no one does it. But im all about unique. Actually check out ebay, there is a super clean first gen, i wanna say a 70 or a 71, bright yellow, fully resto-modded truck with a strait six. i was very surprised, but thought it was very cool non the less.

 

[BGKYK5]

i want to stick with a manual if i can. my late friends widow has a 5 speed od tranny out of a mid-60's school bus that had a 454. at least thats where it came from i think. maybe mid-70s. i hope she still has it, as it would fit right in. my idea is a lightweight and durable rig, hence the desire for low horsepower

That is prolly a 2WD Clark transmission. It may bolt up to the engine, but it will take some major work to hang a t-case off the back.