The 305 in my '97 Sierra is going through more and more coolant. It's only a matter of time before the intake gaskets need to be replaced. Since it currently has 190k miles, I don't think it's worth getting that far without doing a rebuild. Since it's a 305, I don't think it's worth rebuilding at all. I definitely don't need yet another excuse to start accumulating parts, but I do want to have a plan.
My initial thought was to swap in a 383 short block, rebuild some Vortec heads I already have and upgrade to the MPFI spider in the intake. I was talking to a mechanic about this plan and he suggested an LS swap of some flavor. It would likely have at least as much power and almost certainly represent a huge upgrade in terms of efficiency.
My current 4L60 was rebuilt fairly recently and seems to be doing fine. I wouldn't expect it to struggle behind the 383, but I can't be certain. I can, however, be certain that it will only ever have four speeds. This truck sees so much time on the highway and towing, that I think it would really benefit from some extra gears and an LS swap seems like a great opportunity to get them.
I don't have a super clear idea of money or time investments for either of these options. Can someone with more experience chime in on which makes more sense? I'm fairly committed to keeping this truck, as it was my granddad's and seems to be a sweet spot between ease of use and ease of repair. That said, if it makes more sense to use another vehicle for my purposes, I don't want to go too far down an irrational path.
The 383 will (probably) be cheaper. A truck based LS will have more potential, especially if paired with the transmission its attached to. Might even out in the long run in increased fuel efficiency.
I'm sure a regular iron block 5.3 with trans will swap in rather easily. If you're keeping it stock then it probably won't cost you a whole lot and you'll get decent gas mileage too.
In reply to yupididit :
You mean even with the current 4L60? That's certainly a possibility.
In reply to white_fly :
Yeah I can't remember where I read but with the right swap mounts (can't remember the company name) the trans, driveshaft etc lines up as stock.
As others have said, apparently the swap is pretty darn easy. I have the 0411 ECU (but running the 5.7) in one of my GMT400s and it talks to all of the other bits on the truck easily with some EFILive tweaks; I assume it would do the same if it were running an LS instead.
Note that the Gen 1 and LS bellhousings are different; you would not be able to use your transmission with an LS.
You can also make some meaningful tweaks to the 4L60E's calibration with the LS 0411 ECU that might help it hold up with more juice in front of it. I also picked up nearly 2 mpg by the time I got it working the way I liked it. Even a stock LS drivetrain generally has a better transmission calibration than the GMT400 though, and of course a driver who isn't mechanically sympathetic could probably break a new 4L60 with a 305.
Building a mild Vortec 5.7 (or a 383) is pretty darn cheap, and both would outperform a stock 4.8 or 5.3 LS. Both will also be a big jump in usable performance over the 305. A typical build is not going to rev like an LS, but it seems to be easier to get the low end and midrange that you want in a truck with an automatic. I have no idea why this is, and is just personal experience based on a few warmed over trucks I have driven. Buying a known good LS and transmission will probably cost more, and buying an unknown engine and trans may mean you'll be buying rebuild parts anyway.
I did a complete 5.7 Vortec overhaul from the crank up, with pistons, mild overbore, Vortec heads modified for more lift, cam, valve springs and associated parts, Edelbrock MPFI intake, megasquirt, coil on plug ignition, etc for around $3000 a few years ago. I don't remember if that included the headers/exhaust, but I don't think it did. You could do the meaningful bits of that, skip the ignition system project, and use an 0411 ECU to save at least $1000, which is what I would do if I did it again. That was my first ever complete engine build, so I don't know that I am a good estimate on time. It took me around 6 months to pull all the parts together, get the block and crank work done, build Megasquirt, etc. I was definitely taking my time. That engine was in front of an NV3500, so no idea how an 4L60 would have done with it.
Probably, in the long run, it would be cheaper to sell your truck for parts, fly somewhere with no rust and pay top dollar for a Grampa fresh truck with 50k on it.
But thats not the point of the story here. I'd buy a crashed 6.0 truck or van and swap. You have all the parts you need then, other than the motor mount adapters. Building a wiring harness is possible, but takes forever, so I'd buy an aftermarket harness, too.
" Note that the Gen 1 and LS bellhousings are different; you would not be able to use your transmission with an LS. "
Is this completely accurate? I thought the story was that 1 bolt was off from the gen-1 trans bellhousing to the LS bellhousing interface. Meaning, besides leaving one bolt out, this is a bolt-together situation that is commonly done without problems.
This swap seems easier to do if the stock transmission is reused. What's the trans behind a 5.3 that might come with an LS that would be an efficiency upgrade, 6L80?
In reply to pres589 (djronnebaum) :
Typical 5.3 have 4l60e. I think the 6l80 came behind the 6.2 denali and escalade first.
In reply to pres589 (djronnebaum) :
It would be a really interesting thing to clear up if I'm wrong, because it would save the OP a lot of money. I just remember reading they were different when I was looking for a T56 for the Tahoe, so when an LT1 T56 popped up cheap I bought it and never really dug in any further.
The 6L80 would be the common upgrade, yes. I think the efficiency improvement is all around town though; top gear is similar from what I remember. I know some people who have exchanged 4L60s for 6L80s in trailblazer SSs, and the impression I got from the owners was that it was a barely measurable improvement in economy but a huge improvement in drivablility and fun factor. It's a small sample size of people, though.
My gut tells me that a 4L60E with enough torque in front of it or in a light enough vehicle works fine for typical driving, and the gains of the 6 speed matter a lot more with something like a 5.3 LS in a heavier application where it doesn't have the torque to deal with the gear spacing. My Tahoe and Silverado both feel perfectly adequate in most daily driving and usually feel like they can torque their way out of trouble. My parents' GMT800 5.3 Tahoe is always shifting 500+ rpm higher doing the same thing, and if you catch it in the wrong gear and need some juice, it has to downshift before you go anywhere. I feel like the GMT400s only need more gears if I'm towing or hauling heavy stuff (and both of mine have the longer 3.42 gears), where the GMT800 always feels like more gears would help it feel less gutless.
The SBC and LS bellhousings are pretty much the same, LS has an extra bolt at the top of the bellhousing that often isn't even used in swapped cars. You can physically bolt a TH400 up to an LS1 and you can bolt a 6L80e to a 350 with no issue. Crank, flywheel and flex plate spacing is where most of the issues arise when you mix and match transmissions with the LS engines. You have to be mindful of the flexplate and torque converter depths or you can easily break stuff.
There are crate 383's on Summit racing for just this sort of application. I'd go that route. Plug n play, warranty, etc. I think the 383 will have better torque down low compared to a stock 5.3.
The important thing is that the knowledge and any required parts to mate his existing 4L60 to an LS which makes a swap easier and cheaper to pull off.
The LS swap sounds like it wouldn't cost much more if at all using factory used EFI vs. aftermarket bits to fix the Vortec 5.7. That's just my guess though.
I've been struggling with a similar comparison for years. I'm really having a hard time getting over the sunk cost fallacy. I've got a Gen II LT1 from a '97 Firebird, that I bought before the LS engines were so ubiquitous and affordable. I stripped it to a bare block, then paid too much to have it bored .030" and clearanced for a stroker crank.
For what I put into it, I could have a complete ~150K mile engine and trans from a 4.8l or 5.3l GM truck.
On top of it, I want to ditch the Optispark, and have been way down the rabbit hole on 24x conversion with an 0411 ECM (really leaning toward Holley's LS ECM and harness), when it's all said and done, I'd have something unique-ish, powerful, and can say I did it, but I could have an LS in running and done in less time for way less money.
A new 350 long block with a roller cam and vortec heads is under $2,000 at jegs.
In reply to bigdaddylee82 :
Leave it as close to stock as possible. If you do an engine swap and later on have issues with it. Don't count on someone other than yourself being able to fix it.
Sure it may be simple to you but few mechanics are willing to do much outside of brake work or a water pump, maybe.
I had a S10 the 4.3 V6 was swapped for a 350 and even though it looked stone stock few places would even open the hood. Getting the A/C charged took more than 20 phone calls. I eventually wound up learning how to do it myself.
Since I made my living on the road I wound up selling the truck early rather than risk being stranded.
In reply to frenchyd :
Well, in my case that's of little concern. I'm never selling it, I've proclaimed I'll be buried in it when I croak, several times, and it's an extreme rarity I let anyone else work on it.
Watching this as it's definitely relevant
I'm personally a little tired of the "LS swap the world trend" and I'm sure that's coloring my opinion but I'd do the 383 swap. The 383 is more like a repair whereas the LS swap is more like a build. The LS is an excellent engine and I totally get the popularity but it's not like the 383 is bad and it'll bolt in. The exhaust and all the accessories will bolt right up. As engine swaps go the LS upgrade is a pretty simple one in this application but there's still going to be a bunch of details that'll need to be ironed out.
It's hard to deny the abundant supply of cheap 5.3s in the junkyard. A 383 would be choked down by the stock vortec induction. I bet a stock 5.3 could make more power for less money and return better MPG.
If I replace the 350 in my 88 c20, I'd be going for simple and cost effective, while still providing a power upgrade. The 350 Vortec roller cam long block that I mentioned, a bit more cam, the heads modified for more spring and lift, a carb intake and a Holly Sniper. Likely to be at least a 90 hp improvement over the TBI 350.
In reply to Floating Doc (Forum Supporter) :
I'm not sure you'd even need to mod the vortec heads for 90hp. I've read everywhere that they'll take .480 lift without any trimming and I've seen 3 different dyno sheets, one in an old Hot Rod mag, one on Richard Holdeners YouTube, and an episode of engine masters, where they all used cams with .480/230@.050, and all made 350hp or more, with an rpm performer intake and long tubes. TBI 350 only ever made 210 or so. They got bumped to 250 when they went to vortec heads but those were all mpefi, and not TBI.
If you are gonna "roll yer own," building a 383 for your existing parts will be cheaper. If your pockets are deep enough to even consider a crate 383, you will prolly be happyest with a LS swap.
The "low" prices for ls engines is very relative by the time you add up all the stuff needed. As mentioned, the bolt pattern is not the holdup on the trans., its the crank spacing.
ShawnG
UltimaDork
11/24/20 12:09 a.m.
Only in upside-down chevy world is 383 cubes better than 400.
Instead of using the 400 crank, use the whole engine.
An L29 Vortec would bolt in too but forget about fuel economy.
I'm not a hard core chebby guy, but I have heard a lot of guys that are comment about the cooling issues with the "odd man out" 400, and complaints about the siamesed cylinders. No personal experience, myself, just heard it mentioned. A lot.
