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Should I Or Should I Not Keep The 454 Carbureted And Put In A 350 In A 83 Suburban C20 Dually?

Yea, still the carc paint the military used.
Chemical Agent Resistant Coating.
At least the base green color is original.
Not sure about the camo spots.
Was like this when i got it.
Rust free though.
 
But you also gotta look at the money spent swapping the engine.
Would take a long time to pay back for a 2 mpg savings.
Yes, a junkyard swap is even going to cost plenty.
Never happens fast, easy, or cheap.
 
Stinky said:
A 454 will get better mileage than a 350...that is a good one!

You are getting 8 mpg now, I assume. I assume because your post, as mentioned, is lacking in facts. A 350 will easily get 25% better mileage (10).

But, your 454 mileage will not drop off much, if at all while towing. Depending on what is hooked to your bumper, a 350 could get 8, and be a real dog.

How much do you tow? That trailer that is pictured could be towed w.my 2.4 Nissan, and a 4.3, and a 305. A 350 would be overkill.

So, what mpg are you getting now?
What do you tow?
What is ur axle ratio?....my guess is that you could use some gears.
What is ur RPM @ 60 mph?
Click to expand...
It's got a turbo400 and the Rpm is high at 55mph.

Nd that trailer isn't the only thing tow, I sometimes tow heavy than that(my 1999 Crown Victoria is down now so the suburban the substitute, which the crown Victoria tows the light stuff with a tow hitch which the crown Victoria does have a truck like chassis known as body on frame).

Soon will be towing a couple of vehicles or maybe more since I might start doing car transports with Big Red. Nothing too heavy like a f350 though
 
K5wrench said:
But you also gotta look at the money spent swapping the engine.
Would take a long time to pay back for a 2 mpg savings.
Yes, a junkyard swap is even going to cost plenty.
Never happens fast, easy, or cheap.
Click to expand...
Right. Might as well keep the 454 and be easy on throttle(which i am)
 
K5wrench said:
Yea, still the carc paint the military used.
Chemical Agent Resistant Coating.
At least the base green color is original.
Not sure about the camo spots.
Was like this when i got it.
Rust free though.
Click to expand...
Carc.....wonder where I can get that paint from.....I like thecolor of my suburban but not for long. I rather substance with some style over flashy.
 
blackandgold51 said:
I got a 1983 Suburban C20 Dually(I'll send pictures in other post of it) Converted that has a 454 Carbureted wit a Turbo400, along with longtube headers and dual exuast.

I'm worried bout fuel mileage which I wonder about putting in a 350. Although today I took out the big air filter which was taller than a regular filter which been causing a problem with fuel mileage.

One thing I worry is that if I put in a 350 will it still come close to pulling heavy loads like the 454
Click to expand...
Tall air filter will not make it worse, should make it better,
blackandgold51 said:
It's got a turbo400 and the Rpm is high at 55mph.

Nd that trailer isn't the only thing tow, I sometimes tow heavy than that(my 1999 Crown Victoria is down now so the suburban the substitute, which the crown Victoria tows the light stuff with a tow hitch which the crown Victoria does have a truck like chassis known as body on frame).

Soon will be towing a couple of vehicles or maybe more since I might start doing car transports with Big Red. Nothing too heavy like a f350 though
Click to expand...
The th400 is a big factor in the low mpg.
A 700r4 can be much better and should be fine with a stock 454.
And you need to tune your 454 right.
As mentioned above the mileage doesn't drop as much when towing.
I was towing with my 350 a car trailer with a blazer on it, I was getting 5mpg and down to 25mph on big hills. 10 mpg with no trailer.

454 gets 8mpg towing same load and should get 10 without towing.
That's carb and carb.
No experience with fuel injection trucks yet.
I will soon I am putting a tbi 454 where a tbi350 was
 
imiceman44 said:
Tall air filter will not make it worse, should make it better,

The th400 is a big factor in the low mpg.
A 700r4 can be much better and should be fine with a stock 454.
And you need to tune your 454 right.
As mentioned above the mileage doesn't drop as much when towing.
I was towing with my 350 a car trailer with a blazer on it, I was getting 5mpg and down to 25mph on big hills. 10 mpg with no trailer.

454 gets 8mpg towing same load and should get 10 without towing.
That's carb and carb.
No experience with fuel injection trucks yet.
I will soon I am putting a tbi 454 where a tbi350 was
Click to expand...
5mpg in a 350 and 10 mpg without trailer? Crap.

Maybe I should stick with the 350.

I though it was the other way around of a small block engine being the in-the-middle engine which , if you want some power with decent fuel mileage get the 350. While 454 makes less mpg but slot of power and the 454 more of a performance engine.
 
imiceman44 said:
Tall air filter will not make it worse, should make it better,

The th400 is a big factor in the low mpg.
A 700r4 can be much better and should be fine with a stock 454.
And you need to tune your 454 hi right.
As mentioned above the mileage doesn't drop as much when towing.
I was towing with my 350 a car trailer with a blazer on it, I was getting 5mpg and down to 25mph on big hills. 10 mpg with no trailer.

454 gets 8mpg towing same load and should get 10 without towing.
That's carb and carb.
No experience with fuel injection trucks yet.
I will soon I am putting a tbi 454 where a tbi350 was
Click to expand...
I might get a 700r4 but it has to be a heavy duty one. Not the original ones. I heard the ones built is better and last longer as turbo400.


Does there has to be any modifications to the vehicle to install a built 700r4?
 
blackandgold51 said:
I might get a 700r4 but it has to be a heavy duty one. Not the original ones. I heard the ones built is better and last longer as turbo400.


Does there has to be any modifications to the vehicle to install a built 700r4?
Click to expand...
blackandgold51 said:
5mpg in a 350 and 10 mpg without trailer? Crap.

Maybe I should stick with the 350.

I though it was the other way around of a small block engine being the in-the-middle engine which , if you want some power with decent fuel mileage get the 350. While 454 makes less mpg but slot of power and the 454 more of a performance engine.
Click to expand...
It's true up to a point.
When you exceed the comfort zone on a 350, mpgs start plummeting quickly. Towing a small boat or a small utility trailer mileage only dips to 8mpg .
 
blackandgold51 said:
I might get a 700r4 but it has to be a heavy duty one. Not the original ones. I heard the ones built is better and last longer as turbo400.


Does there has to be any modifications to the vehicle to install a built 700r4?
Click to expand...
The 700r4 will need a torque converter lock up controller.
 
I'd stay with the TH400 towing...put larger tires in the rear or add a gear vendors overdrive to raise the gearing to reduce highway rpms..
You can buy lots of gas for what you'd spend on putting a 700R4 in it ,which will likely not last long towing..
 
diesel4me said:
I'd stay with the TH400 towing...put larger tires in the rear or add a gear vendors overdrive to raise the gearing to reduce highway rpms..
You can buy lots of gas for what you'd spend on putting a 700R4 in it ,which will likely not last long towing..
Click to expand...
I don't know about that.
I have towed plenty with the 700r4.
Used the right way it will live a long time
 
diesel4me said:
I'd stay with the TH400 towing...put larger tires in the rear or add a gear vendors overdrive to raise the gearing to reduce highway rpms..
You can buy lots of gas for what you'd spend on putting a 700R4 in it ,which will likely not last long towing..
Click to expand...
Gear Vendor?
 
Gearvender is an aftermarket over drive unit that bolts onto the rear output of your transmission.
They are nearly 3 grand.
 
imiceman44 said:
Tall air filter will not make it worse, should make it better,

The th400 is a big factor in the low mpg.
A 700r4 can be much better and should be fine with a stock 454.
And you need to tune your 454 right.
As mentioned above the mileage doesn't drop as much when towing.
I was towing with my 350 a car trailer with a blazer on it, I was getting 5mpg and down to 25mph on big hills. 10 mpg with no trailer.

454 gets 8mpg towing same load and should get 10 without towing.
That's carb and carb.
No experience with fuel injection trucks yet.
I will soon I am putting a tbi 454 where a tbi350 was
Click to expand...

I might put on a TBI on the 454 with vortec heads(can you if possible tell me how to put on heads which will be my first time).

Or might keep it carb and just put on heads
 
Just keep it as is and enjoy it. I used to have a 77 C30 crewcab dually with the 454, th400, and 4.10 gears. It got 7mpg weather or not if I was towing. It did a great job pulling a trailer with my ~6500-7000 lb k5 on it. Don't make a big project out of it. Just don't use it as your daily if you are worried about gas mileage.
 
Update. The 454 is not really bad on fuel mileage in stop and go city, yesterday evening around 5 or 6pm i put in 9.98 of fuel which the needle went off right in the middle of the "empty" sign line and went up over the "2nd line" on the fuel gauge one line from the empty line. Drove it smooth (which i usually do and not like a maniac" and the fuel lasted which the fuel meter went a little inch on top of the last line until i added some fuel today around noon. Again stop and go traffic mainly 35mph
 
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