Justifying a 4bt swap?

[RickTheEngineer]

Hello everyone. Just a question about a potential M1009 build.

Being a blazer, those frames aren't super strong. But, here is the thing. Allegedly, the 6.2 was rated at 165hp and 330 ftlbs of torque, which probably none of us are getting especially these days. Fully dressed, a 6.2 diesel is around 725lbs. Now, a 4bt is around that weight, but the numbers for a stock engine is notably below the figures that 6.2 had to offer back in the day. Now, of course one could build it up to 200hp fairly easily. However, reliability is probably going to be compromised, even if you make all the right upgrades (aftermarket piston rings, head studs, etc.). As for a 6bt, in its stock configuration, it will already be more than enough, and will not have any strain on the engine. If anything, it will experience even less abuse since it would not be wise to push it on a blazer. For those that want to box their frames, I have heard from many folks out there (some being GM mechanics from the squarebody days) that they have seen blazers with a 6bt on a stock frame BUT with a beefy crossmember, and they seem to hold up well. (Obviously D60/14B swap and whatnot). But seeing as how my M1009 will see some light/moderate off road use (no towing) I am not sure if this would be a good idea. What are your thoughts? What is the best way to go if one were to perform a swap like this? I even thought about the Isuzu 4HK but those are 1000lb engines, which puts you right back at 6bt status.

TLDR, 6bt stock, or built 4bt, and why?

 

[richingalveston]

6.5 navastar or gep or even a p400 would be an easier swap. the 6.5 stock would be about same as a built 4bt. same weight. P400 a little heavier.

a built 4bt will rattle a blazer to pieces. 6bt's can also cause a lot of vibration problems. They are not a smooth as the v8 diesels I have a 6bt in my motor home and love the motor but it also vibrates real bad at idle.

Rich

 

[glaser06]

6.5 navastar or gep or even a p400 would be an easier swap. the 6.5 stock would be about same as a built 4bt. same weight. P400 a little heavier.

a built 4bt will rattle a blazer to pieces. 6bt's can also cause a lot of vibration problems. They are not a smooth as the v8 diesels I have a 6bt in my motor home and love the motor but it also vibrates real bad at idle.

Rich

X2 on all this. 4bt sounds good until you ride in a vehicle that has one.

Sent from my SM-G930T using Tapatalk

 

[RickTheEngineer]

I constantly hear mixed opinions about the 6.5. Enough for me to be really skeptical about it. Some say the power was decent, some say it is a joke. Some day that it is reliable as ever, some say that cracked blocks and burning oil are a staple. I am sure that a lot of that is relative, but still, more mixed reviews than what I saw for cummins products. Also, I am no stranger to a 4 cyl diesel engine. I used to have an Isuzu c223 engine in a truck, and I did think it would rattle a filling out. But overall, I didn't care too much. As for a 5.9 12V, well, from what I understand, rattles aren't too bad, its the volume of that engine that gets old, but my 6.2 is really loud too, so I am not sure on that either.

 

[richingalveston]

you have to get to the navastar or gep 6.5 motors to get good blocks and reliability. The gm blocks yes had problems. not to hard to get a rebuilt navastar ready to drop in and it will cost you less than the 4bt swap.

a properly tuned 6.5 will be half as loud as the same 5.9 The 6.5 is still loud but everything is when you have a stock cucv with no insulation.

 

[red]

6bt is overkill for a blazer and makes for alot of front end weight.

Can build a 6.2/6.5 to make good power reliably. 400-480ft/lbs torque. Smooth operation, truck is designed for that engine, etc.

4bt Cummins or the Isuzu 4bd1t/4bd2t are great swap choices. Easy to crank them up reliably to 400+ft/lbs torque. 4bt rattles like crazy and should use hydraulic motor mounts because of that. The 4bd1t/2t don't rattle as much but weigh more because they are sleeved engines.

 

[red]

The main problem with the 6.2/6.5 is that they really don't like getting over 215F coolant temps and GM kinda screwed up their cooling systems. On the 6.5 the factoy turbos are phenominal at building heat and choking the exhaust flow. With the electronics GM put the PMD right in the intake valley, which has temps high enough to start melting the solder inside the PMD and start loosing connections.

 

[RickTheEngineer]

Hmmm sounds like an interesting detail. I definitely think that a 6.5 swap will be objectively easier. Were those all mechanical engines? I wonder what the reliability is of the two compared to one another

 

[RickTheEngineer]

Here is the thing I do not get about the 6bt. A lot of folks online say that its just too heavy to put in a K5. And it feels that way, but here is the thing. I actually work for a diesel company specializing in generators and we used to deal with the 6bt actually. From my documents, it says that a 6bt should clock in at 950 lbs. Now the thing is that a 6.2 diesel clocks in at 750 lbs. So that is only a 200lb difference. What I just don't understand is if everyone is scrambling to reinforce the frames of their trucks so a K5 or 1/2 ton can take the abuse of 6bt, what is the difference between that and having a big snow plow in front of your truck with the 6.2? Do you think a 6bt is a legitimate swap idea? (Assuming d60/14 bolt swap and strong crossmember?)

 

[glaser06]

I know Wikipedia isn't the best source for this but their dry weight for a 6BT (5.9L 12 valve) is 1100 lbs. I know these motors are considerably heavier than a big block chevy motor.....

 

[RickTheEngineer]

That is what I had read too... Although when we weighed ours it was like 950 with oil in there. Hmm, alright lets say its like 1050lbs, give or take. Thats about a 300 lb difference between that and a 6.2. The two batteries weigh about 60lbs each, so thats a total of 120ish lb. If you relocate them to the rear of the truck, that means youre gaining 160lb up front, and if we want to be conservative, lets say 200lb. Thats like a person sitting over the axle. I know that that's just weight we are talking and not all the gobs or torque it makes, but considering it should theoretically never get much more than daily driving abuse, I can't imagine it'll mess much up. That's my opinion, but I have been wrong before of course. Maybe add a leaf up front too as a bonus?

 

[glaser06]

I'd guess a little lower on the weight of the batteries, I can install mine 1 handed into the truck. Maybe 35lbs each? Even still just 200 lbs on the front axle is a lot more weight (for tires, ball joints, steering components, etc.) Not saying it can't be done, just that it will accelerate wear on everything up front. Not sure about the 1009s but my 1028A1 has 3 leaf front springs which are pretty heavy duty (I got into a discussion somewhere on here on spring rates of the stock springs....I can look it up if ya like).

The 6.5 can be run all mechanical, or you can run a remote PMD (out of the intake valley)to keep the electronic injection pump alive. They are very reliable motors when done like this. Not powerhouses by today's standards but good for 400,000+ miles if you start with a good block (6500 Optimizer would be my choice or a Navistar). Plus everything else is plug and play on our trucks for it, tranny bolt pattern, accessories, etc. There's even a guy here who is fabricating cooling system upgrade kits to eliminate hotspots within the motor for those of us in hot climates and heavy haulers.

Again, everyone has their own tastes, budget and skills. I looked into a 4bt for a good long while before deciding to turbo my 6.2L instead. Eventually, I think I'll swap to a 6.5 but not anytime soon.

 

[richingalveston]

it is not just the weight of the motor, it is the horsepower and torque that the old frames cannot handle.
most people who do this make major changes to the frame.

there is a build somewhere on this site where they put the 6bt plus an intercooler. it can be done and has been done

I do recall new front springs were needed for the weight

The build I saw installed a 5 speed tranny. Not sure what you would need to do in order to use auto tranny.

 

[RickTheEngineer]

My batteries are 58 lbs a piece, and a lot of them are around 60 lbs, especially deep cycle stuff. I am sure specs can be found online for those, since I think it can vary a bit. And that is true, about the torque situation. I was honestly planning on getting a bone stock 6bt and leaving it as is with some kind of auto trans behind it. I know there are some good ones out there for a build like this. I guess as long as you treat it like a daily, not hit it hard, and just enjoy the ease of climbing hills, it shouldnt be too bad, considering that a built 350 can do that all day. I guess what it comes down to is what it will be used for and how it will be used. Also yes, front springs would have to be beefed up a little.

 

[WillWagner]

Unless you re gear, you will loose road speed, 4B 2500-2700 rpm unless you jack the RPM. What does the 6.2/6.5 turn?

 

[scottladdy]

Unless you re gear, you will loose road speed, 4B 2500-2700 rpm unless you jack the RPM. What does the 6.2/6.5 turn?

3600 and 3400 red lines respectively. However, you want to try to match your gearing with the engines "sweet spot" which is not always max RPM. For the Detroit's that is mid 2K +/-. I don't know what the 4BT's sweet spot is but assume it is lower than red line.

The fact remains, a lower peaking engine will require "higher" gears to be drive-able in a similar fashion.

 

[red]

Hmmm sounds like an interesting detail. I definitely think that a 6.5 swap will be objectively easier. Were those all mechanical engines? I wonder what the reliability is of the two compared to one another

6.2, 6.5, 4bt, 4bd1t/2t, 6bt are all available with mechanical injection. Reliably the 4bd1t/2t and both Cummins engines are capable of 500k+ miles before rebuild. The Isuzu engines are sleeved, rest of the engines listed are not. 6.2/6.5 I know people with more than 400k on their engines with the GM blocks but that is not the norm (the newer blocks are better than the GM ones). That being said, the 6.2/6.5 is much cheaper to keep running or to replace than the others.

Another thing to think about with the engine weight in a k5 is that the 6.2/6.5 was a very heavy engine for them. The chassis was built for the small block gas engines and the front suspension had to be upgraded to handle the 6.2/6.5 weight.

 

[RickTheEngineer]

Here is a question not too many people are asking... what is the best trans to use? I know that you can always use a NV4500, but what about automatics? I know an Allison 1000 can take the torque all day, but will that match up to a np205 tcase? Would that even fit under a k5 without having to do custom body tub work?

 

[Barrman]

I went through this thought process a year and a half ago when I started the Cowdog truck build. GEP 6500, 4BT or 6BT?

4BT was just too much money for the same basic performance as a 6.5 with a turbo and actually less road speed. But, in theory longer engine life.

6BT would be great. However, reinforcing the frame, different cross member, different front and rear axles to handle the weight and power, different springs, no 6BT reliable automatic transmission out there that I can afford. All led me to consider a 6BT into a square body as a $10,000 swap when all the parts and time is added up.

6500 isn't cheap, but as pointed out above. They do work and fit pretty easy.

 

[red]

Here is a question not too many people are asking... what is the best trans to use? I know that you can always use a NV4500, but what about automatics? I know an Allison 1000 can take the torque all day, but will that match up to a np205 tcase? Would that even fit under a k5 without having to do custom body tub work?

Allison requires either a 1" body lift (minimum) or the transmission tunnel being reworked and the np205 can be adapted to it. Trans absorbs more power than other models. Cost and a much more expensive stand alone computer are big factors. Unless you're cranking up the power above 500ft/lbs torque it's just overkill.

4L80E is a proven option. Can be run as a manual valve body or with a stand alone computer. Pretty simple and very durable transmission that works for the power levels discussed here with a long life span.