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Vortec 5.7 is basically a bolt in for a gen 1, right?

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urbex

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Recently popped a head gasket in the '86 K5. Bought the truck a couple months ago from a guy that claimed the motor was recently rebuilt, but this thing is such a dog that I doubt his claims, or whoever built it didn't have a clue of what they were doing. I'm hesitant to put any money in this motor, and leaning towards a full motor replacement.

I know the 5.3 is the big thing now, but I have zero desire to deal with that swap, and the changes needed for it. I'm fully capable of doing it, I just don't want to. Really looking at the quickest way of getting this thing driveable again, outside of just putting head gaskets in my current motor, as I could just as easily find a cracked head or block, and don't want the truck immovable until I find another motor for it.

I've been googling for a while now, and keep coming up on hits for swapping a 5.3 in, or swapping Vortec heads on, but nothing for swapping in the whole 5.7 Vortec motor into the K5 and still using the carb. I know I need to get the Vortec specific intake, but outside of that, a '96-'99 Vortec motor would otherwise be a bolt in swap, right? I'll be reusing my existing built 700r4 trans with it as I've already sunk quite a bit of money into the trans, and also don't want to deal with a standalone set up to run the 4L60E/4L80E trans. I'm already running an electric fuel pump, and I have a full dual exhaust with long tube headers as well.
 
Yes. Intake is the only real difference if you just plan to get an engine and bolt it in.

There are obviously other differences (timing chain cover/CPS, centerbolt valve covers, roller cam, no fuel pump provisions) but if just bolting it in, from what you describe, I can't think of anything else that might be an issue. I suppose the bracket for the TV and accelerator cables could be an issue but that would be more related to the intake I would think, depending on what their bracket(s) bolt to.

Depending on what your funds are, the four bolt L31 GM crate engines run around $1800, which is pretty much a steal. I'd be real hesitant to run a used Vortec because the heads are just too prone to cracking, and coolant in the cylinders can wreak all kinds of havoc that may or may not be immediately obvious, even if the heads had been replaced.
 
brand new 4 bolt main L31 on ebay @ radley chevy shipped for 1779.99 .

I have one on the stand new ready for drop in my truck.

also if using another distributer you need a melanized gear for it to be friendly with roller cam .

I even reused the 88-95 serp belt drive on my engine . all bolt holes lined up .
 
sweetk30 said:
brand new 4 bolt main L31 on ebay @ radley chevy shipped for 1779.99 .

I have one on the stand new ready for drop in my truck.

also if using another distributer you need a melanized gear for it to be friendly with roller cam .

I even reused the 88-95 serp belt drive on my engine . all bolt holes lined up .
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I keep going back and forth on whether to buy a donor truck, and sell other parts to make this a close to free swap, or buying the crate with a warranty on it. Then again, if I end up having to rebuild the donor, I'll probably end up right back at the cost of the crate anyways.

I did replace the distributor last month with a $50 HEI Amazon special, though I don't have a clue what kind of gear is on it, nor on the Accel distributor it replaced. I did forget to mention that I'm also running a serp belt drive, though I'm sure it would just fine on a Vortec motor, lol.

I installed a TCI cable bracket a while ago that mounts on top of the carb studs to handle the throttle and TV cables, works fine. I can't imagine why it wouldn't work on any other carb intake.
 
A rebuild on a donor, if the block and heads are good, will run you more than a new warrantied engine. With no warranty. I am running a non vortec version of that engine. Been in the Jimmy for 12 years now. Only upgrade I have done to it is screw in rocker studs. I float the valves on a regular basis and a couple of studs started pulling. So I fixed it for good. I should just back off of the skinny pedal a little.
 
sweetk30 said:
also if using another distributer you need a melanized gear for it to be friendly with roller cam
Click to expand...

I suspect any stock roller cam gear will work. Unless there is something I don't know, if you got your hands on a used car roller cam distributor I don't see why you couldn't just swap the gear?'

No idea what a cam gear runs nowadays, I just got sick of trying to understand what went with what. My 1988 TPI distributor has played nice with at least three different roller cams for 30 years.
 
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dyeager535 said:
No idea what a cam gear runs nowadays, I just got sick of trying to understand what went with what. My 1988 TPI distributor has played nice with at least three different roller cams for 30 years.
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Given that my distributor was $50, brand new..I'm assuming it's probably a standard iron gear. Then again, I know it's generally recommended to not put an old gear on a new cam, regardless of material, so I'll be putting on a new gear anyways. Turns out the Summit Racing branded gears are only $17, so that's a non issue now.

The stock L31 isn't really where I want to be, power wise, and as soon as I crack it open to put a different cam in, the warranty goes out the window anyways. Ideally I'd like to be putting down at least 400lb/ft of torque at the flywheel. From what I've been reading, that's nearing the upper limit of the stock Vortec heads. Part of me is tempted to pull my current motor apart anyways to see if the lower end is still usable, then just do a heads/cam package on it using something with a bit more headroom than the Vortecs.

I've been going back and forth on this for a week, and I'm still not sure where I want to go with it....
 
If you know it won't make the power you need, then absolutely don't settle.

There are crate motors out there that are rated for what you need, and if you could use the existing short block with some better heads and cam, that would certainly save some money.

I just know that the L31 crate was less than having machine work done and acquiring parts to get a used engine to L31 specs, and as soon as I started to get away from the L31, cost increased exponentially. It took a lot of time for me to figure out which way to go as well. More power is always appealing, and you don't want to be disappointed.

I don't know if it's cheaper to assemble a non-stock combination or to buy a crate engine that is more inline what what you are looking for. If you know 400ft lbs is your minimum, at least when searching for crate engines, that will make selection a bit easier.
 
It's that whole "need vs want" thing. I suspect that the stock L31 would be OK, but I've never built a motor for a truck this big and heavy before. My only real frame of reference was the Dodge 318 in my Grand Cherokee. Factory rated at 300lb/ft, and it did OK spinning 33s in the mud, but the Jeep was a solid 1,000lbs lighter than the K5 and was running through a 5 speed manual.

So I'm making an assumption that to equal the performance in the heavier K5 with the 700r4 trans, I'll likely want to be closer to the 400ft/lb mark. I think I also need to dig out the Desktop Dyno and start running combos through that again.
 
I can tell you that towing ~2000lbs, I could use more power. I still consider myself a novice at tuning the TPI, and while some of the lack of power could be due to lack of my skills, the combo I'm running may not be perfect for the engine either

It is perfectly fine on flat ground or unloaded up hills, but from what I'm calculating as 5% grades, the power just isn't there. MAYBE if I wanted to run around 4000RPM I could keep the speed limit. If I had OD, I could probably gear it a bit different so that it wasn't quite so ridiculous on downshift, but for the amount I use the truck, not worth it. I'll just live with 55MPH climbing grades with the trailer.

It feels like it pulls pretty hard unloaded, although the 465, 3.42's and 33's are probably less than optimal for acceleration, but oh well. Probably getting a bit of knock on downshift. Generally, I still need to play with timing under load more:


The one piece rear main seal, roller cam, and centerbolt valve covers are all positives IMO, if you can get a crate that has those, with the power you are wanting, I think you'll be happy with all the benefits the L31 has, and then some. But unless you increase displacement by a fair margin, the only way to make that power is to spin the engine faster.

FWIW, it looks like the ZZ6 is the "first" crate SBC in GM's lineup (I assume that means lowest cost) that makes 400HP. It's also around three times what the L31 one is. :(
 
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Whoops, I went the wrong way. I read HP vs. Torque. The ATK does seem to bump the cam up a bit, and .040" bore.

The GM SP350 does 407ft lbs for $~3300.
 
dyeager535 said:
Whoops, I went the wrong way. I read HP vs. Torque. The ATK does seem to bump the cam up a bit, and .040" bore.

.
Click to expand...

Yes, that's been one of my big issues for many years when looking at builds and motors....everyone focuses on peak HP, and virtually nothing else. 1000hp at 7 grand doesn't do me a whole lot of good. The other side of this is that I don't necessarily need stump pulling torque right off idle, which is seemingly what most assume when one says "truck" or "4x4". My main focus is on building a high torque number, and HP will fall where it falls. I don't mind running a looser converter, rough idle, and having the power start around 2 grand if that's what it takes. Ahh...who am I kidding...we're all little kids inside that WANT the nasty idle, lol.

The reality is that from an off road rock crawler standpoint, even a well worn bone stock 305 TBI motor is generally plenty enough power once one is in low range. The TBI 350 motor I'm running now, but with a carb up top is also generally enough power off road. Of course, it will fall on it's face pronto on the pavement in high range, lol.

The biggest problem I run into now is with throttle response, and acceleration rate even at higher RPMs. Not so much that I'm trying to create an off road drag truck, but rather that if I need to "bump" up a rock ledge, it's impossible because the motor revs up so slowly. It's like running my diesel tow rig...there's just NOTHING there until the RPMs come up and it starts to build boost. I'm shooting for more of an all around 4x4 with this truck, and although it will likely see some rock trails here and there, I'm not building it with a focus on rock crawling, as it will also see mud and sand from time to time, as well as some extended freeway driving. Jack of all trades, master of none, so to speak, and I know it will be a compromise, some of which will be on the side of likely driving me nuts. It is what it is.
 
Realistically it sounds like a big block is what you need.

I'm not a big block guy, but increasing the output of the SBC means more RPM. No way around that. You can up the displacement of an SBC, but you can only go so far without getting exotic. With the low end torque, running less stall should feel like you are more connected to the pedal. When you talk about bumping up against an obstacle, if the torque is there, lower stall would seem to work better.

It'd be interesting to hear experiences from rock guys. It seems to me that low end torque, coupled to a low stall converter, would allow more gradual application of power, instead of off/on with a higher RPM/stall setup, leading to spinning tires.
 
Lower gears help in all of these scenarios except non-towing MPG.
 
So I ended up dragging home a '85 K20 with a 454 as a donor motor. Spent a grand on a truck that drove up on the trailer, when everyone seemed to want at least that much just for a 454 long block. I'll probably regret this soon, lol.

Has a 14bolt SF in it, and some kind of a 4 speed manual with an aluminum cased transfer case in it. Based on the appearance that a couple meth heads chewed out the opening in the trans tunnel with the two teeth they have left, someone swapped it in. Fingers crossed that it's a 32 spline SM465, so that I'll hopefully be able to get more than $100 out of it, lol. I need to verify gear ratios, but this may well be the route to lower gearing and an axle upgrade at the same time...at least in the rear.
 
if true 85 trans parts its 32 spline and hydro clutch . would be a 208 tcase unless newer and then a 241 and thats a keeper .
 
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Definitely looks like a towing engine.
 
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