V8 Swap vs. 4.3 Rebuild - Blazer Forum - Chevy Blazer Forums


Engine & Internal Chat about beefing up your Blazer's engine insides here.

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Old 01-25-2018, 08:34 PM
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Default V8 Swap vs. 4.3 Rebuild

I bought a nice little low-mileage 2000 Blazer 4x4 about a year and a half ago, so my daughter would have something to drive as she started college. I spent the first month fixing it up as much as I could with new upper and lower control arms, quality ball joints, poly bushing replacements for control arms and front sway bar, shocks all around, spark plugs and wires, cap and rotor, fuel filter, hood clunk fix, and probably even more that I can't remember at the moment. I love the vehicle; my daughter loves the vehicle.

Unfortunately, at only 130k miles and about a year after we got it, pretty much every gasket in the engine self-destructed, and it leaks coolant. Like, it REALLY leaks coolant. And some oil. And there's probably coolant getting into areas of the engine it really, really shouldn't be. Rather than just replace the gaskets, which is around a $1700 job for a shop, I wanted to just go all-out and either do a V8 swap or a performance build for the 4.3 V6, since our only real complaint is that it is pretty weak on power. The interior is in great shape, I just spent a lot of time and money rebuilding the front end, and it's a great vehicle other than the engine. Even if my daughter moves on from it, I will keep it for a mild offroading and camping trailer towing vehicle.

So, after several months of research on this and other forums, my head hurts. I've learned a lot, but it still feels like I am spinning my wheels on making a decision, so I am asking for some help. I would love to do a V8 swap, but with a new job and the fact that the engine is pending complete self-destruction I no longer have a lot of time to do it myself. I'm also not particularly talented at fabricating/welding, so any V8 swap option at this point would require me to be able to purchase all the pieces/parts, have the engine built and ready to go by an engine shop, and have the same or another shop do the actual swap. So, after all that preamble, here are my questions:

1. Can anyone point me towards a V8 swap option that would allow me to have the engine built separately by a knowledgeable shop, purchase most if not quite all required pieces and parts (mounts, harness, oil pan, radiator, headers, computer, etc.) in advance KNOWING they will work, while keeping all accessories (A/C especially), retaining a FI setup, and not requiring a lift kit?

2. If there is a good answer for question 1, does anybody know of a reputable shop in the Denver metro area that is capable of performing the swap in a timeframe of 30-45 calendar days?

If the answer is uncontrollable laughter, or a deep head-shaking sigh, then I will post up another question about how to proceed with a 4.3 performance build, but I'm really hoping somebody can help me rescue the V8 option.
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Old 01-27-2018, 04:28 AM
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Go to a local Cars & Coffee and ask around. There are motor heads everywhere, especially at the local Drag Strip. Go to "Corvettes Only" if it is still in Denver and talk to them about builders.

Last edited by 2004 Blazer; 01-27-2018 at 04:31 AM.
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Old 01-27-2018, 03:00 PM
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Check out jagsthatrun.com. They got tons of stuff for putting a V8 into an S10/Blazer. Lots of guys do that swap. I don't know much about the details, but I have heard you'll have to switch to an electric fan.
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Old 01-27-2018, 11:02 PM
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I've done a number of SBC into S-series swaps. No "kit" is going to be complete. You will still have to have the exhaust, cooling and wiring made The easiest swap into a 2000 would be a 96-02 Vortec 5.7 1st gen SBC from a 96-98 C/K, Tahoe, Suburban, or van. All your front accessories will bolt up as well as the fuel lines. The wiring mods are minimal the exhaust and cooling will take some DIY fabrication by you or the swapping shop. As a general rule paying someone to do a swap is costly. You'll definitely want to see other swaps they have done.
If it were my daughter I wouldn't recommend a swapped vehicle. They just aren't as problem free as a factory setup. Gm spends millions each year doing reliability testing before a vehicle goes into production. For a back and forth to school vehicle I'd fix or replace the existing engine. It's fast enough for her current needs.
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Old 01-29-2018, 01:03 PM
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Quote:
Originally Posted by Chance42 View Post
I bought a nice little low-mileage 2000 Blazer 4x4 about a year and a half ago, so my daughter would have something to drive as she started college. I spent the first month fixing it up as much as I could with new upper and lower control arms, quality ball joints, poly bushing replacements for control arms and front sway bar, shocks all around, spark plugs and wires, cap and rotor, fuel filter, hood clunk fix, and probably even more that I can't remember at the moment. I love the vehicle; my daughter loves the vehicle.

Unfortunately, at only 130k miles and about a year after we got it, pretty much every gasket in the engine self-destructed, and it leaks coolant. Like, it REALLY leaks coolant. And some oil. And there's probably coolant getting into areas of the engine it really, really shouldn't be. Rather than just replace the gaskets, which is around a $1700 job for a shop, I wanted to just go all-out and either do a V8 swap or a performance build for the 4.3 V6, since our only real complaint is that it is pretty weak on power. The interior is in great shape, I just spent a lot of time and money rebuilding the front end, and it's a great vehicle other than the engine. Even if my daughter moves on from it, I will keep it for a mild offroading and camping trailer towing vehicle.

So, after several months of research on this and other forums, my head hurts. I've learned a lot, but it still feels like I am spinning my wheels on making a decision, so I am asking for some help. I would love to do a V8 swap, but with a new job and the fact that the engine is pending complete self-destruction I no longer have a lot of time to do it myself. I'm also not particularly talented at fabricating/welding, so any V8 swap option at this point would require me to be able to purchase all the pieces/parts, have the engine built and ready to go by an engine shop, and have the same or another shop do the actual swap. So, after all that preamble, here are my questions:

1. Can anyone point me towards a V8 swap option that would allow me to have the engine built separately by a knowledgeable shop, purchase most if not quite all required pieces and parts (mounts, harness, oil pan, radiator, headers, computer, etc.) in advance KNOWING they will work, while keeping all accessories (A/C especially), retaining a FI setup, and not requiring a lift kit?

2. If there is a good answer for question 1, does anybody know of a reputable shop in the Denver metro area that is capable of performing the swap in a timeframe of 30-45 calendar days?

If the answer is uncontrollable laughter, or a deep head-shaking sigh, then I will post up another question about how to proceed with a 4.3 performance build, but I'm really hoping somebody can help me rescue the V8 option.
So you want to do this, but to a 4WD, right?
https://blazerforum.com/forum/builds...-blazer-94742/
Most would be exactly the same except for possibly the oil pan and headers. Should bolt right up to the trans that you have, but you might want to look into an upgrade for the trans. Nothing like this is a slam dunk guaranteed no problem swap.

Will cost tons of $$$$ if someone else does it for you with a rebuilt LS engine, especially in a short time frame. You could probably nearly buy a new SUV for the amount. Are you sure you want to do this?? Why not just pay someone to put in a $2000 GM Goodwrench V6 and get a 3 year 100K mile warranty.

Performance building a vortec V6 while retaining stock fuel injection will simply not work - injectors will not flow enough fuel to give much additional power, and it will not be in at an RPM where you can use it during normal driving with stock gears. Aftermarket fuel injection for Vortec V6 is pretty much made of unobtanium and is all custom stuff.

sorry

Last edited by Lesmyer; 01-29-2018 at 01:11 PM.
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Old 01-30-2018, 08:13 PM
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Thanks for the feedback everyone, it's really sounding like the V8 swap is probably not happening. Les, that link you posted is exactly what I was after except that I had a 4wd, I had been using that as my reference thread for quite awhile before my free time for the next year went *poof*.

As far as rebuilding/replacing the V6 with another, I looked at slapping in a crate replacement but I would really like to have something with a bit more oomph. I don't need much, honestly; even if I could get it to 240-250hp I would be really happy. I'm not trying to build a stoplight-to-stoplight burner or anything like that, I just want something that can make it up the mountains with a little less flogging, especially if I do some light towing (say, a medium-sized popup camper trailer).

Also, a lot of reading on issues other people are dealing with in regards to the 4.3L Vortec V6 has left me with the distinct impression that these engines come from the factory with some quality issues. Case in point would be my vehicle; all-around gasket failure at 130k miles, are you kidding me? I bought it used, but it came with a glovebox full of service receipts for all the regular maintenance you would expect a responsible person to have performed. I'm normally a Honda/Nissan/Toyota guy, and if that sort of thing happened to one of those engines after only 130k miles, especially if I'd been taking it in for regular scheduled maintenance, I would be pissed to the extreme, but people seem to just take it in stride with Chevy/GMC. I know there is a lot of negative confirmation bias because the people that post on the Internet are usually the ones who are having problems, you don't really hear from the people who aren't, but it seems to be a recurring theme with these engines. Should I expect a replacement crate engine to be any different than the original in this regard?

The other recurring theme seemed to be that if you tear these things down and have them rebuilt with quality aftermarket parts (such as the gaskets), and appropriate machining, balancing, etc., then they become much more reliable.

Again, thanks for the input, I think I am now looking at a V6 replacement/rebuild. I'll post up a new thread after I do some more research focused on the V6.
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Old 01-30-2018, 09:11 PM
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Buying a used vehicle, it's hard to know what you're getting, even with some service records. The longevity of a particular engine depends on a handful of variables. Lack of service, driving habits, isolated incidents, etc can lead to premature failure of an engine. Say someone has a waterpump fail, and overheats their engine. Now, that vehicle could be more likely to have a head gasket failure in the future. Say the head gasket fails, and fills the bottom end with coolant. It sits like that for a bit. then the head gasket gets replaced, and oil changed. Now it's more suseptable to bearing failure in the bottom end of the engine.

In my opinion the 4.3's are a well built, and reliable engine if properly taken care of. They are more or less a shortened 350- which is arguably GM's best engine overall(cue LS guys disagreeing)

With the new crate motor you are starting fresh, and control most of these variables.
I'm not certain if new crate engines already come with the upgraded intake manifold gaskets or not, but that may be a good thing to add to a crate motor to ensure long term reliability.


As far as getting 250 horse out of a 4.3: a mild cam, ls6 valve springs, roller rockers, high flow exhaust and intake (along with a proper tune) should put you right in that ballpark.
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Old 01-30-2018, 11:26 PM
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If you had it rebuilt at a quality machine shop, with the above modifications, they could increase the compression ratio with new oversized pistons (.010 -.030 ) and resurfaced heads to lower combustion chamber volume, resulting in even more power.
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Old 01-31-2018, 06:31 AM
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Quote:
Originally Posted by chevyriders View Post

As far as getting 250 horse out of a 4.3: a mild cam, ls6 valve springs, roller rockers, high flow exhaust and intake (along with a proper tune) should put you right in that ballpark.
Agreed, but I think "with a proper tune" should be in bold. A proper tune done on a dynamometer by an experienced operator. W/O it you'd be throwing money away.
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Old 02-03-2018, 10:48 AM
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Quote:
Originally Posted by Chance42 View Post
Thanks for the feedback everyone, it's really sounding like the V8 swap is probably not happening. Les, that link you posted is exactly what I was after except that I had a 4wd, I had been using that as my reference thread for quite awhile before my free time for the next year went *poof*.

As far as rebuilding/replacing the V6 with another, I looked at slapping in a crate replacement but I would really like to have something with a bit more oomph. I don't need much, honestly; even if I could get it to 240-250hp I would be really happy. I'm not trying to build a stoplight-to-stoplight burner or anything like that, I just want something that can make it up the mountains with a little less flogging, especially if I do some light towing (say, a medium-sized popup camper trailer).

Also, a lot of reading on issues other people are dealing with in regards to the 4.3L Vortec V6 has left me with the distinct impression that these engines come from the factory with some quality issues. Case in point would be my vehicle; all-around gasket failure at 130k miles, are you kidding me? I bought it used, but it came with a glovebox full of service receipts for all the regular maintenance you would expect a responsible person to have performed. I'm normally a Honda/Nissan/Toyota guy, and if that sort of thing happened to one of those engines after only 130k miles, especially if I'd been taking it in for regular scheduled maintenance, I would be pissed to the extreme, but people seem to just take it in stride with Chevy/GMC. I know there is a lot of negative confirmation bias because the people that post on the Internet are usually the ones who are having problems, you don't really hear from the people who aren't, but it seems to be a recurring theme with these engines. Should I expect a replacement crate engine to be any different than the original in this regard?

The other recurring theme seemed to be that if you tear these things down and have them rebuilt with quality aftermarket parts (such as the gaskets), and appropriate machining, balancing, etc., then they become much more reliable.

Again, thanks for the input, I think I am now looking at a V6 replacement/rebuild. I'll post up a new thread after I do some more research focused on the V6.
If you can find a marine V6 intake (that takes standard configuration type injectors where you can find bigger ones to support more HP) - then with an aftermarket camshaft, bigger injectors, and an expert tune for the PCM you can get maybe 250-300 hp with no other changes. Vortec heads are good, but depending on the lift of the cam may need clearancing to work with higher lift. Cam choice would be critical.
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