25mpg 71 C10. Need Your Help!

[The Big Green]

This is a good thread. A buddy and I are wanting a reliable engine in our '67's. The only difference is I lay body. Any ideas if the pans on the 6.2 hang below the front crossmember on these trucks? I know the LS are ok on a bagged truck.
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[shortbed70]

If your going to go with 6.2 step up to a 6.5turbo and you'll be good just know that these parts are pricey and I have rebuilt a ton of them. They don't make alot of power but the torque output is good. Good parts in them too mahle pistons,roller cams and chevy stuff bolts right to it.
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[don t. - 72gmc]

Originally Posted by crazy longhorn

2nd that.....but I havent seen 20 yet(too many toes in the throttle) ? 2002 silverado/2wd extended, with a 4.8. The last tank on the hyway was 18mpg(cruising 75 mph, with the AC on). This truck is new to me, so I dont know if thats good or bad....but its sure better than the carburated stuff I was running crazyL

I've got a SWB 07 Sierra, 4.8 w/4x4, minimal options, 48k miles, bought new. With the AC on, cruise set at 75, best = 19 mpg. Usually avg 15-17.

FWIW.....don t. ....

[The Youngen]

Originally Posted by shortbed70

If your going to go with 6.2 step up to a 6.5turbo and you'll be good just know that these parts are pricey and I have rebuilt a ton of them. They don't make alot of power but the torque output is good. Good parts in them too mahle pistons,roller cams and chevy stuff bolts right to it.
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Only problem i have with the 6.5 turbo is that my 95 2 door tahoe on straight highway trips cruise control set and everything, best i get is 18. Besides a fuel module issue, the 6.5 has held up to around 160k. Also, it actually has more power than ill need. We tow and plow with it. Id rather have more mpgs and less ft/lb / hp.

[weaintscared]

Originally Posted by The Youngen

Only problem i have with the 6.5 turbo is that my 95 2 door tahoe on straight highway trips cruise control set and everything, best i get is 18. Besides a fuel module issue, the 6.5 has held up to around 160k. Also, it actually has more power than ill need. We tow and plow with it. Id rather have more mpgs and less ft/lb / hp.

I'll never see that many mpg
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[Hottrucks]

I throw this out there and you can flame if you want but here goes

I have a 472 caddy in my C 10 with a th 400...mileage with my foot out of it around town is 19 to 20..highway mileage sucks because of the RPM...rear gears are 3:73...so think about that.....good torque with the right gears will result in good mile but like was said before its has to be a complete set up...don't look for a big motor to get mpg if its twisted to tight or lugs all the time?

[1LoC10]

get a 4.8 and bolt up one of them TCI 6X behind it

[slotdad]

what did you use for exhaust manifolds/headers? I have a caddy 500 begging to go into my 69 c-30

[weaintscared]

Well I just might get a few Mpg from what y'all are saying I'm going to run a BBC but I did buy a T56 6 speed to go behind it

look at my build & let me no what u think
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[67_C-30]

A 6.2 powered 1/2 ton will absolutely get 25 mpg or more with an OD trans. I had an '84 K10 with a 6.2/700R4/3.08's and it got around 27 on the highway. Now, I will say I'd recommend a lower rearend gear only because 4th was useless in town. I kept it in Drive in town and put it in OD on the highway. It would be worth a few mpg to have a peppier truck IMO.

You can put the 6.5TD on it and add about 70HP and around 150 ft lbs TQ but you will see a slight decrease in mileage (despite popular belief). I've seen pretty much no change with the Banks set-up. They claim a gain in mpg, but I haven't really seen it - But - I haven't seen a decrease like I have with 6.5TD set-up. The Banks set-up does have a very slight lag down low whereas the 6.5TD set-up pretty much has a instant power. The difference is that the Banks is non wastegated and the 6.5TD has a wastegate. The wastegate allows pretty much instant spool, but costs some mpg. The Banks set-up does make a little better mid to upper range power. Both really wake a 6.2 and still offer good ecomony.

[N2TRUX]

As much as I love the LS motors, they are NOT a viable choice if your asking for more than 20+ mpg. I have owned several of them in many different configurations, and they will NOT get more than 20 mpg.

I frequently hear claims of 20+ mpg from owners of LS conversions. I would have to see it to believe it, and honestly I don't. If my daily drivers that came from the factory can't get that kind of mileage, why would a conversion in an old brick shaped truck get better.

[rob32472]

with price difference of the two fuels would it be more cost effective in the long run to go with an ls gas powered engine? The ease of installation alone is worth something... just my two cents

[67_C-30]

Originally Posted by rob32472

with price difference of the two fuels would it be more cost effective in the long run to go with an ls gas powered engine? The ease of installation alone is worth something... just my two cents

That's a good point and a valid question. The 6.2 is actually an easier swap than a LS engine, so that's not a factor, at least with the 6.2. Another factor is that low mileage military takeout 6.2's are available for $300 - $400, and the LS engines, electronics, electric fuel pump, etc. are significantly higher. It would take a lot of miles to "pay" for the LS set-up i would think. I get asked all the time how I am affording diesel in my Blazer, but the truth is even ith it being higher per gallon, I still cannot come close to it with a full size gas powered truck. I have my doubts that a LS powered 67-72 will get as many mpg as a 6.2 powered truck. I am basing that off the fact that LS powered newer trucks don't get near as good as 6.2 powered trucks from the early to mid 90's. The LS powered trucks are gonna be a lot more fun though!

[mrein3]

First of all, you aren't going to get close to 25 mpg around town. No way. If you can find one, the 84 K10 67_C-30 is talking about got up there in the 20s on the highway but I doubt it did that in town.

How many miles are you going to be driving around town per year?

I put together a quick spread sheet. I made some assumptions.

Assume you pay $3.65 for gas and $4.00 for diesel fuel.
Also assume you some how get 25 with a diesel verses the standard 13 for the average 350 powered, carburated truck.
In 12000 miles or one year that 25 mpg truck will save $1449.23 over the standard 350 gas powered vehicle.

Now back in the real world where you can expect to get 18 on a really good day in that diesel verses that 13 you can already get with a good tune up with what you got, you're only going to be saving $702.56 in fuel costs per year - provided you drive 12000 miles per year.

If you drive less, say 6000 miles per year you can cut those "savings" numbers in half. In other words you're talking a whole lot of pain, suffering, and money spent for little to no savings in fuel cost.

Plus if you go diesel you have to deal with gelling fuel, heaters, and all the other fun stuff that comes from driving a diesel in the winter.

If it were me I'd keep what you got running in top shape and just drive it.

[steelhorse]

How about a gm 4.2 from a Canyon or Colorado with matching stick.

[67_C-30]

Originally Posted by mrein3

First of all, you aren't going to get close to 25 mpg around town. No way. If you can find one, the 84 K10 67_C-30 is talking about got up there in the 20s on the highway but I doubt it did that in town.

How many miles are you going to be driving around town per year?

I put together a quick spread sheet. I made some assumptions.

Assume you pay $3.65 for gas and $4.00 for diesel fuel.
Also assume you some how get 25 with a diesel verses the standard 13 for the average 350 powered, carburated truck.
In 12000 miles or one year that 25 mpg truck will save $1449.23 over the standard 350 gas powered vehicle.

Now back in the real world where you can expect to get 18 on a really good day in that diesel verses that 13 you can already get with a good tune up with what you got, you're only going to be saving $702.56 in fuel costs per year - provided you drive 12000 miles per year.

If you drive less, say 6000 miles per year you can cut those "savings" numbers in half. In other words you're talking a whole lot of pain, suffering, and money spent for little to no savings in fuel cost.

Plus if you go diesel you have to deal with gelling fuel, heaters, and all the other fun stuff that comes from driving a diesel in the winter.

If it were me I'd keep what you got running in top shape and just drive it.

6.2's consistantly get more than 20 mpg in town. I get more than 20 mpg in town with my military Blazer with 6.2/TH400/3.08's and I'm running 33X12.50R15's. In a 2wd truck (as light as the 67-72's are compared to the '80's trucks) with an OD trans I have no doubt the 6.2 get real close to 25 mpg. These engines do around 16 mpg in a M1008 1 1/4 ton trucks with 4.56 gears and TH400 trans. They are very economical engines that are known for fuel mileage, and it is what they were designed for. For comparison's sake, here's a guy that built a '77 Vette years ago and is getting more than 40 mpg with a 700R4 and 2.73 gears. http://ecomodder.com/forum/showthrea...-avg-1128.html



All that being said - I probably wouldn't put a 6.2 in 1/2 ton 67-72 truck unless I was building strictly a commuter, which is case I would just try to find a nice 80's 1/2 ton with a 6.2/700R4. I put the 6.2 with turbo in my 1 ton for decent pulling power with a lot more ecomony than a BBC. I have ran these engines for years and got great service out of them and enjoyed supurb mileage. They aren't the fastest thing on the road, but they get the job done, and best they are dirt cheap.

[Ackattack]

I think even a 5.9L Cummins will get you close.

I talked to a guy with a 1 ton dually (don't know if it was 2wd or 4wd) quad cab and he said he got 22mpg. I assume it was a manual, but in a much lighter truck like ours and optimized for economy I think even the 6 cylinder cummins could do it.

My first thought was the 4banger cummins which was already mentioned.

On another note, I had a 2005 crew cab z71 pickup with the 5.3L, 3.42 gears, and ~32" tall tires and I got 22mpg out of it. Granted that was in WA where the speed limit is 60 most places, but still, that truck weighed ~5800lbs. I think a LS can get you pretty darn close, again, if it is set up correctly. [I also got 33mpg in my LS1 corvette, but it weighed a tad less than 3k lbs and had a 6 speed manual]

And finally, while we're on it, you could get a 1.9L VW TDI engine. I have no idea if you could even get a rwd tranny hooked up to it, and it WOULD be a turd in a truck, but it would get more than 25. (51mpg in my jetta )

[5150.4.67]

My dad has had a few 6.2s. Rarely saw greater then 20 mpg, even with O.D. and 308's...... only got worse after he put a turbo on it. And talk about slow off the line.....That being said, it was the highest mileage capable diesel he's owned.

I love diesels for towing/hauling, but other than that, are a bit of a nuisance when speaking of the older technology diesels, in my opinion.
They cost more to service, the fuel cost is generally greater (at least here in Cali), they make a significant amount of noise, and usually are quite heavy (typically twice the weight).

I have a little Acura TSX with a 4 cylinder, and I average 26. And that car weighs half as much.

My $.02? I think 25mpg in a heavy truck is a pipe dream.

[mrein3]

Originally Posted by 5150.4.67

My dad has had a few 6.2s. Rarely saw greater then 20 mpg, even with O.D. and 308's...... only got worse after he put a turbo on it. And talk about slow off the line.....That being said, it was the highest mileage capable diesel he's owned.

I love diesels for towing/hauling, but other than that, are a bit of a nuisance when speaking of the older technology diesels, in my opinion.
They cost more to service, the fuel cost is generally greater (at least here in Cali), they make a significant amount of noise, and usually are quite heavy (typically twice the weight).

I have a little Acura TSX with a 4 cylinder, and I average 26. And that car weighs half as much.

My $.02? I think 25mpg in a heavy truck is a pipe dream.

This is what I was trying to say. 25 is a pipe dream and if you are running a diesel, they stink, are a pain in the winter, are noisy, heavy, all of which eats into your "savings".

[Boog]

Hey Youngen. This guy is doing just what you are contemplating. Says he is finishing up his swap to a 6.2 with manual OD trans. You should send a PM to 1968chevyc10
http://67-72chevytrucks.com/vboard/member.php?u=66496

[djw32]

Be very careful when purchasing a 6.2L diesel from someone on craigslist. The 6.2L is notorious for having head issues. Find someone in your area fixing the heads, the cost to repair one is crazy high. I thought about throwing a 6.2 in my 70 c-10, but I decide I would rather have an ls in there.

[67_C-30]

I'm not trying to start a pissing match, but the OP said:

Originally Posted by The Youngen

Sorry, didnt mean 25 town, 25 highway since my driving is split so like 21 around town?

This is very doable with a 6.2. I've done it time and time again with heavier, squarebody trucks. The 6.2 (650 lbs) is not a whole lot heavier than a stock SBC (575 lbs) and is actually a little lighter than an iron headed BBC (685 lbs) with a factory intake.

Now, I still say I'd buy something else as a DD and keep it a gas V8, but a healthy 6.2 would achieve the numbers he's asking about.

[Ulf]

Originally Posted by 67_C-30

I'm not trying to start a pissing match, but the OP said:



This is very doable with a 6.2. I've done it time and time again with heavier, squarebody trucks. The 6.2 (650 lbs) is not a whole lot heavier than a stock SBC (575 lbs) and is actually a little lighter than an iron headed BBC (685 lbs) with a factory intake.

Now, I still say I'd buy something else as a DD and keep it a gas V8, but a healthy 6.2 would achieve the numbers he's asking about.

In Scandinavia Merc diesels are popular. Om 617 survives turbocharging, Om 603 is another godd engeinr if you choose the TD version. Om 605 is godd for about 400 hp with turbo and the best bet is a OM 606 24 v, Turbo that can be forced to delver around 6oo hp if u let Mynää in Finland tune the pump.

[palallin]

I got very close with my '67: 327/Quadrojet (well tuned), 4-sp Saginaw car tranny, 3:08 rear gears. I got 21.x on the highway and never did approach the top speed.

[joeydurango]

I figure eight years later, the PO either got what he wanted, decided to drive it as is, or sold the truck...