No, they are not at all as strong as a cummins.
Based on chevy cars and trucks I have driven, a decent straight 6 might compare to a two barrel 283 or 307. Your 454 has significantly more grunt than a straight 6.
CK5
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Are There Any Chevy Straight 6 Engines Out There 4 A 83 Suburban Half Ton Turbo400?
- Thread starter blackandgold51
- Start date
No, they are not at all as strong as a cummins.
Based on chevy cars and trucks I have driven, a decent straight 6 might compare to a two barrel 283 or 307. Your 454 has significantly more grunt than a straight 6.
You'd have to look at the truck brochures to be absolutely certain, but pretty sure the 305/350's produced more torque and HP than the sixes. The sixes produced theirs at a lower RPM IIRC, but peak was still less. Could be noticeable in a manual.
I read the thread. 23mpg was listed as his typical mileage with 25mpg being an outlier. I did notice that his truck has 3.42 gears, small tires, and a 700r4. This combination would certainly be pushing this truck towards the upper reaches of 6.2 economy. I'm not quite sure it supports your blanket statement that "the 6.2 will pull down 25mpg".
blackandgold51
1/2 ton status
Well if the 6.2 has a 700r4 behind it then maybe.
And I wonder why would t4m in the first place would put a 3 speed like a Turbo 400 behind the 6.2 if fuel economy was a concern. They should just made all 6.2 models with 700r4s
It is an ideal set-up for economy with a 6.2 with cruising rpm's falling right into the 1800-1900 "magic window" of economy. 25 mpg would have been more regular had I spent more time driving nothing but highway miles. It was consistent as could be in multiple ways. It was always slow, and the mileage never varied. The more highway cruising the closer to 25 mpg it wold get.
The statement "the 6.2 will pull down 25 mpg" is definitely dependent on what said 6.2 is bolted to. In my 81 Jimmy with a SM 465 and 40's the best my 6.2 managed was 16.3 mpg...tank after tank after tank on the way to Blazer Bash 2003, while revving at 2700 rpm the whole time. It's not like my C1500 is some 1 of 1 GM factory freak though. I'd love to see mileage numbers on a C10 with 6.2 and A-833 OD 4 speed, (pretty rare combo) or a swapped NV3500 in the same C10. I'm thinking with the manual trans it could see 27 mpg straight highway cruising...
Generally, I'd wager a stock height K10 with the 6.2 would get similar mileage. What kills mileage on a 6.2 is no different than any other engine. Aerodynamic drag, rolling resistance, weight, rpms.
The best my c10 250 six with a 465 got was 19 mpg, that turbo 400 will kill mileage just due to parasitic loss it takes to operate it. If you want mileage get a Kia.
I think it's a cool idea to be different. GM gas straight 6's can be torquey fun machines. Go big though. Get a 292 Chevy. A 302 GMC is another, but they are pretty rare birds any more now. Combine a 292 with a nv3500 to limit parasitic drag. Add a Clifford 4bbl intake with any one of the 4bbl tbi self learning efi systems and a Clifford split header. Run duals with your favorite mufflers you would be impressed with how they sound. It would be a fun ride with lots of low end grunt that could get decent fuel economy. Not 25 mpg, but better than a carb'd 454.
I'm a big fan of the 6. We had a club member that built a 302 GMC 6 for his 55 Nomad. Pulled hard with a 4 speed and you wouldn't have guessed it wasn't a small block by how it ran.
I'm a big fan of the 6. We had a club member that built a 302 GMC 6 for his 55 Nomad. Pulled hard with a 4 speed and you wouldn't have guessed it wasn't a small block by how it ran.
blackandgold51
1/2 ton status
That's what I've been thinking. A 6 straight that has enough power of a small block. Don't have to be big block
I've owned at three 250 straight sixes in various GM trucks--a 81 G-10 van with a TH350 & lock up converter and 3:08 gears,a '79 C-10 with a TH350,and a '75 2wd Blazer that had a 3 speed manual originally,I swapped in a 4 speed Saginaw from a '75 Vega,it had 4:10's ..
None of the above got over 16 mpg,the '81 van did a few times on a long trip to TN back when gas had no ethanol ,but it dropped to 12-15 mpg on todays fuel...and it was so under powered on long grades on the interstate it was hazardous,you'd bog down to 50 mph and even have it downshift into second gear sometimes and gain no speed..merging onto a highway was also a dangerous thing..
The two pickups did no better on fuel mileage,the '79 C-10 was probably the one that did the best on fuel having highway gears,but it too could bog down on hills unless you got it going 70+ mph before you hit the hill..that truck got a 305 after the 250 decided to lose the #6 piston's top ring lands,years of pinging ate the head off the piston,those integeral head straight sixes were noted for spark knock and loose wrist pins..I'd avoid any built after 1975 with that head design..the old style with the removeable intake & exhaust manifolds were much better..
That truck went much better with the 305 in it,and if anything it delivered the same mpg or close to it as the 250 six..
The 292 is a strong engine with good low end torque but its long stroke makes it a gas hog,and it wont like winding out in a truck with low gearing..friends that had one in square body trucks said 12-14 mpg was tops as far as mpg,and though that engine does pull well,you might not be maintaining 65 mph up hill if your towing something heavier than a tent trailer..
These engines can be made to scream though,if built right...a local dirt track champ used several 292's and beat many cars with big block chevy's ,one was in a Volvo PV544..
I do not think it is worth swapping in a straight six in hopes of getting better mpg,you wont--these trucks weigh 3+ tons and a small engine will be struggling to propel it all the time,and straight sixes were never mpg champs to begin with,maybe the dinky ones like a 194 or 230 cubic inch were better,but only in light vehicles like an old Nova..
I'd like to have a straight six just for reliability and ease of repair,but daily driving one does get irritating when you wish it had more guts to pass or maintain 65 mpg on interstates..
The 4.3 V6's do not have a stellar reputation,but they would probably do better than a straight six for power and mpg..the early ones with a 4 bbl were junk though,and a later one would require the wiring harness and computer to run..thats a ton of work,for what might be little to no improvement in mpg..
The 6.2--well,they may give a few more mpg than a gas engine,but you'll have to deal with glow plugs that might refuse to come out,diesel fuel is at least .50 more here than gasoline,so any "savings" are lost at the pump..and if it needs any injectors,the injector pump,etc,get ready to spend $500 ..they are about as powerful as a 250 straight six,and if I had a choice I'd prefer the straight six over a 6.2 that might break the crank or end up having the main bearing webs crack..
The straight sixes aren't bullet proof either--all 3 of mine had the masonite cam gear strip the teeth off and left me stranded on the interstate..they sell aluminum ones ,that is what I put back on--but to replace the timing gears you'll either have to pull the engine out--or take a lot of things off it like the fuel pump,distributor,lifters,valve cover,and take off the radiator & grill,and hope you can get the camshaft out...pulling the engine is faster and easier..
Keep in mind all of these engines are now practically extinct,and you'll have to do some searching to find one,and parts for it..up here they are getting very scarce,in "drop in and run it" condition..
I think the best way to get better mpg in a chevy pickup is to buy an S-10 with a 2.5 4 banger and a 5 speed...no work,it'll get you around OK,and you can still haul some stuff with it..
None of the above got over 16 mpg,the '81 van did a few times on a long trip to TN back when gas had no ethanol ,but it dropped to 12-15 mpg on todays fuel...and it was so under powered on long grades on the interstate it was hazardous,you'd bog down to 50 mph and even have it downshift into second gear sometimes and gain no speed..merging onto a highway was also a dangerous thing..
The two pickups did no better on fuel mileage,the '79 C-10 was probably the one that did the best on fuel having highway gears,but it too could bog down on hills unless you got it going 70+ mph before you hit the hill..that truck got a 305 after the 250 decided to lose the #6 piston's top ring lands,years of pinging ate the head off the piston,those integeral head straight sixes were noted for spark knock and loose wrist pins..I'd avoid any built after 1975 with that head design..the old style with the removeable intake & exhaust manifolds were much better..
That truck went much better with the 305 in it,and if anything it delivered the same mpg or close to it as the 250 six..
The 292 is a strong engine with good low end torque but its long stroke makes it a gas hog,and it wont like winding out in a truck with low gearing..friends that had one in square body trucks said 12-14 mpg was tops as far as mpg,and though that engine does pull well,you might not be maintaining 65 mph up hill if your towing something heavier than a tent trailer..
These engines can be made to scream though,if built right...a local dirt track champ used several 292's and beat many cars with big block chevy's ,one was in a Volvo PV544..
I do not think it is worth swapping in a straight six in hopes of getting better mpg,you wont--these trucks weigh 3+ tons and a small engine will be struggling to propel it all the time,and straight sixes were never mpg champs to begin with,maybe the dinky ones like a 194 or 230 cubic inch were better,but only in light vehicles like an old Nova..
I'd like to have a straight six just for reliability and ease of repair,but daily driving one does get irritating when you wish it had more guts to pass or maintain 65 mpg on interstates..
The 4.3 V6's do not have a stellar reputation,but they would probably do better than a straight six for power and mpg..the early ones with a 4 bbl were junk though,and a later one would require the wiring harness and computer to run..thats a ton of work,for what might be little to no improvement in mpg..
The 6.2--well,they may give a few more mpg than a gas engine,but you'll have to deal with glow plugs that might refuse to come out,diesel fuel is at least .50 more here than gasoline,so any "savings" are lost at the pump..and if it needs any injectors,the injector pump,etc,get ready to spend $500 ..they are about as powerful as a 250 straight six,and if I had a choice I'd prefer the straight six over a 6.2 that might break the crank or end up having the main bearing webs crack..
The straight sixes aren't bullet proof either--all 3 of mine had the masonite cam gear strip the teeth off and left me stranded on the interstate..they sell aluminum ones ,that is what I put back on--but to replace the timing gears you'll either have to pull the engine out--or take a lot of things off it like the fuel pump,distributor,lifters,valve cover,and take off the radiator & grill,and hope you can get the camshaft out...pulling the engine is faster and easier..
Keep in mind all of these engines are now practically extinct,and you'll have to do some searching to find one,and parts for it..up here they are getting very scarce,in "drop in and run it" condition..
I think the best way to get better mpg in a chevy pickup is to buy an S-10 with a 2.5 4 banger and a 5 speed...no work,it'll get you around OK,and you can still haul some stuff with it..
All things considered, MPG, torque, and good sound, I wouldn't think there really is a better cost effective option.
A wrecked 1st gen cummins can be had for a couple grand. Gives you all the drivetrain parts you need. Fab work for crossmembers and intercooler yes, driveshaft modifications, exhaust, some misc, and I think it could be done for 4-5K.
A 6.2 deeslow doesn't out torque a 454.
A 5.3 LS isn't going to get the economy or torque of a 12 valve, although it would probably be close with the right tuning, and would likely be more expensive considering the cost of a newer VVT motor.
Last I checked, 4BT's were more pricey than 6BT's.
There is no perfect answer to the questions @blackandgold51 poses...
Many times I also think "troll" reading his questions...
This ^^
Plus you hope that the motor itself and/or injector pump don't need a rebuild. Imo, diesels are the "in" thing now and 6bt is a bandwagon swap, you don't hear of anyone doing it "cheap".
I could see doing a 292 with mods and it would be neat but, again, not a budget build.
> I < would keep the 454 but if I just had to do some sort of swap I'd probably go with an INJECTED LS (not worth the effort for a carb'd version).
Keep in mind you can buy enough gas to feed a 454 for a long time with the same amount of cash you'd lay out to do an "experimental" engine swap in hopes of gaining maybe 5-10 mpg..
You might even find an S-10 like I mentioned for about the same money or less..
I do not mind paying more when you can have the ability to smoke the tires and go as fast as you need too,to merge onto a highway,or tow anything..but I do not go far or very often either...if I lived in a state where a trip to Walmart is 40 miles each way,then yeah,I wouldn't like the big block for just getting groceries..
You might even find an S-10 like I mentioned for about the same money or less..
I do not mind paying more when you can have the ability to smoke the tires and go as fast as you need too,to merge onto a highway,or tow anything..but I do not go far or very often either...if I lived in a state where a trip to Walmart is 40 miles each way,then yeah,I wouldn't like the big block for just getting groceries..
blackandgold51
1/2 ton status
Dont you call me a "troll" Cleetus Big Dummy*Fred Sanford's Voice*
So is it that you just like crapping on alternative ideas or you just have a crappy outlook on everything? Not everything is bad. Even if a 292 got 12-14 mpg that's probably still better than what a carb'd 454 of the 80's is going to pull. There are more options now to build something that has decent power and fuel economy. This might be a shock and all, but FI does wonders over carbs and mechanical indirect injected diesel in a 6.2.
Lets keep a couple of things in mind here. Straight 6's make torque. Gobs of it down low. They aren't high winding builders of horsepower. However if we look back in time to before the gas crunch era where GM made shitty attempts at using straight 6's for fuel economy (like the 250's you noted). Back before that time, you usually found a 6 teamed up with a manual tranny and deep axle gearing. No they didn't do 70 mph, they weren't built for that. It wasn't out of the ordinary to have a 6 with 4.10 or 4.56 gearing. That's how they made use of the 6's prodigious low end grunt.
Now lets bring it back to the current and use a combo of old and new tech to put together a decent running combo that isn't a danger to itself and keeps up with modern speeds. A 292 tied to a NV3500 with 4.10's and 31" tall tires (assuming a 2wd burb). The 4.10's are going to make use of the 292's torque but the OD gear allows it to get rolling at a normal highway speed without winding out the big 6 to an unreasonable RPM. Modernize the 292 with a decent Clifford Cam, electronic ignition and a computer controlled EFI system and I'd bet that the combination would get mid-teens or better on the highway and still have good power to keep up with traffic.
Worn out junk is going to suck fuel too. My 350 in my old 75 K5 was a suck ass dog on anything but flat ground or downhill with a tailwind. It might have got 10mpg on a good day with the q-jet fresh from a rebuild. On the hills if I couldn't carry momemtum into them I'd be rowing the shifter down to 1st doing 25-30 mph at the top. Same hill now with my 91 with the 5.3 I'm doing 60 easy. My main point here is just because the engine is big if it's worn out and running old tech don't mean it's not possible to improve upon it. Replacing an old worn out engine for anything else in the sole name of fuel economy isn't going to have huge return on the investment immediately.
It's a cool idea to discuss. If the guy wants to be different let him. It's not cookie cutter and common as anybodies belly button. And just for the sake of some 6 porn, here's a sweet little C20 I found at the Rocky Mountian Street Rod Nationals last year. Yes it's a 292...
Twin carbs with all the trimming...
You think an LS swap is more expensive than a cummins swap? I think you need to look into that a little further. I haven't done either swap, but LS engines are consistently for sale with complete wiring harnesses and computers for $500 and under by me. Obviously you need the computer flashed, new engine mounts, and a multitude of other small changes, but we aren't even approaching the complexity of a cummins swap. I'm not sure where you are getting your information. This thread is really starting to boggle my brain.
All I read was good realistic advice based on real world experiences in a thread that has people making claims of square bodies running 10 second quarter miles with straight six engines and dropping in 6.2s to get an instant 25mpg. Not everything in this thread is bad, but a lot is.
My replies were not meant to "crap on" anyone's ambition to try something different--I was just stating what my experience was with the many straight sixes I've owned over the years..
I am not dissing straight sixes at all,I feel they are some of the most rugged and reliable engines ever made...I feel its a shame they stopped making them in GM's in 1984,and that they didn't try putting EFI on them with a non-integral head here in the USA,like they did in Brazil..
I like straight sixes and have been keeping an eye out for one for sale cheap--one would be a good choice for a plow truck,or a daily driver you do not plan to use extensively on the highway on long trips or tow heavy loads...if I score a 250 six cheap and I had my 6.2 croak I'd swap a six into the '82 K2500 in a heart beat..
I bet it would be no worse on fuel than the diesel (I only get about 15 mph with it),and the HP and torque ratings and the rpms their maximum torque is produced at are almost identical..
A straight six with the TH400 in my diesel pickup would be a pretty un-killable combination..might not get great gas mileage but it'll last longer than the driver will probably..
A 5 speed behind a 292 would help with the mpg and I agree that engine is probably the most desireable GM straight six--however finding the correct motor mount frame brackets for the right side is getting quite difficult around here,there was so few sold around here..
I liked the 235 straight six in my '56 pickup,the 261 was its bigger brother,both had good low end torque..my truck got poor mpg due to a large one barrel carb and a 4:56 rear axle ratio,plus it was a heavy beast,weighed over 3 tons..but a lot of guys were very surprised to see a straight six when I opened the hood--they were expecting a small block...
I am not dissing straight sixes at all,I feel they are some of the most rugged and reliable engines ever made...I feel its a shame they stopped making them in GM's in 1984,and that they didn't try putting EFI on them with a non-integral head here in the USA,like they did in Brazil..
I like straight sixes and have been keeping an eye out for one for sale cheap--one would be a good choice for a plow truck,or a daily driver you do not plan to use extensively on the highway on long trips or tow heavy loads...if I score a 250 six cheap and I had my 6.2 croak I'd swap a six into the '82 K2500 in a heart beat..
I bet it would be no worse on fuel than the diesel (I only get about 15 mph with it),and the HP and torque ratings and the rpms their maximum torque is produced at are almost identical..
A straight six with the TH400 in my diesel pickup would be a pretty un-killable combination..might not get great gas mileage but it'll last longer than the driver will probably..
A 5 speed behind a 292 would help with the mpg and I agree that engine is probably the most desireable GM straight six--however finding the correct motor mount frame brackets for the right side is getting quite difficult around here,there was so few sold around here..
I liked the 235 straight six in my '56 pickup,the 261 was its bigger brother,both had good low end torque..my truck got poor mpg due to a large one barrel carb and a 4:56 rear axle ratio,plus it was a heavy beast,weighed over 3 tons..but a lot of guys were very surprised to see a straight six when I opened the hood--they were expecting a small block...
I helped a friend's son buy a c10 with a straight 6 in it. Dead stock. He put a header on it nice 2 barrel carb manifold. All the external tricks. That thing ran awesome. Got 17 to 19 mpg on the highway. It was also the only truck my dead bone stock 6.2 could stay with easily. In addition he rarely went more than 65 mileage dropped rapidly after 65. At 75 he was only getting 14.
Now my 6.2 burb. The best tank I ever saw in that was 24 mpg at about 60 mph. For 200 miles. Worst tank I got was about 13 towing 6500 lbs to Moab. Unloaded worst tank was 15 coming back from California, doing as close to 80 mph with a serious headwind.
My old 6.2 burb was a consistent 20 mpg on the highway. Dead stock. 700r4 3.73 gears and 30" tall tires.
Only truck it could actually beat was my buddies old straight 6 truck lol
Now my 6.2 burb. The best tank I ever saw in that was 24 mpg at about 60 mph. For 200 miles. Worst tank I got was about 13 towing 6500 lbs to Moab. Unloaded worst tank was 15 coming back from California, doing as close to 80 mph with a serious headwind.
My old 6.2 burb was a consistent 20 mpg on the highway. Dead stock. 700r4 3.73 gears and 30" tall tires.
Only truck it could actually beat was my buddies old straight 6 truck lol
A small turbo really wakes up a 292...note the ease of the 2nd gear chirps!...
8/23/10 Demo runs, It's just a little inline 6 - YouTube
8/23/10 Demo runs, It's just a little inline 6 - YouTube
Sounds like a Cummins, kinda ruins it for me.
Well it is a 12 valve.
