CK5 - The Full-Size GM Off Road Community

Thinking about dropping a 454 into my 70 Suburban. I'll be using it a lot for towing and some wheeling. How do you all like your big blocks? Am I looking at breaking about 7MPG on the interstate??? /forums/images/icons/smile.gif

I have a 454 in my 78 it gets about 9 mpg towing or not. I have 3.73 gears and run 33s on it. I love it!!

I have a 77 3/4 ton 2 wd suburban, with highway gearing in the rear, and it pulls 13 MPG regardless of speed, towing, loaded, or empty and more importantly, you don't lose any speed going up long mountainous hills. I'd never trade it for a small block. I've beaten ricers while hauling a loaded car hauler behind me, and absolutely love the sound of a bigblock roaring through glaspacks in the I-10 Deck tunnel.

do it. do it now.

-Rich

Do you guys have any idea if you've got to change the motor mount towers to get the big block in the truck?

Go for it! My dad used to have a '76 C20 with a 454 and it got 7MPG no matter what. Whether it was empty driving around town, or had the camper and a boat behind it doing 70 down the highway, it always got 7MPG. I have a 402 BB in my '72 Chevelle and theres nothing like the torque, I have 2.73:1 gears and can light em up for 30 feet from a dead stop /forums/images/icons/shocked.gif Now that I'm done ranting you probably wont need big block mount towers, I've only done 1 small to big block swap where I needed big block motor mounts.

Outstanding! To tell you the truth, I'm tempted to drop the 454 in my Camaro, but need it in the Suburban for towing. Maybe when I win the lottery!

My big Block (http://community.webshots.com/photo/27430197/27430622FNZLjfydvv)

That's how I like my big block. I went from an inline 6 to a small block. When I went from the small block to the big block I didn't have to change the motor mounts or the motor mount brackets (on the frame). My uncle uses his BB dually to tow a 30' trailer to the track. I was following behind him once and I was having trouble keeping up with him. You gotta love that torque on demand.

Well, I took the big jump and got the block. Now its time to build it and drop her in!

Sweet! choose your Cam wisely... the biggest gain in power your engine will see will come from your initial cam selection. some better-than-stock heads will help, but having a good bumpstick is what'll bring the bastard to life.

-Rich

Since I tow with my Suburban, I wouldnt do anythign but a 454 in it. Wouldnt even think of a small block. Heck, even if I didnt tow I wouldnt do anything but a big block. And gas mileage is not much worse since the motor is not in a constant struggle.

Ken H.
'85 Suburban - 3/4 ton - Detroit rear - 4.10 - 454 - 400 trans - 33 muds

I actually get better mileage in my suburban with the 454 then my friend does in his with the little 350.... the gearing is pretty close to the same, but I get 13, and he gets 8. the reasoning for this, is the 454 creates more torque initialy then the 350 ever does, making it so I don't have tu burry my foot in the accelerator to make my truck move. he has to almost floor it to make his leave a stoplight ( part of his problem is he's running 31x10.50's on a 2wd, where it was meant to run littler tires... 235/75-15's) where I can out accelerate him at an off idle speed ( even when I was running 33's under it)

-Rich

wow better miileage with a big block? i didn't know that was possible. /forums/images/icons/shocked.gif /forums/images/icons/cool.gif

all you gotta do is get your carb dialed in right, have a better-then-stock cam in it, and enjoy. like all BBC's, mine gets 12-13 regardless of uphill, downhill, loaded, empty, hauling a trailer, or racing people on the freeway at 95 MPH. if I keep it at high speeds for a long time, I notice it dropping down to 10, but it stays in that general range of mileage

-Rich

cool, what about EFI? could the same be said about a tbi or mpfi 454?

Adding fuel injection will bring up the mileage and power of just about any motor, plus response, everything.

A big block will get better mileage sometimes because it is not working as hard as a small would be pulling a load or just lugging around a big Suburban.

I like having big blocks in both my Blazer and Burban. wouldnt go any other way.

Ken H.

I finally got that big 468 put in the beast. Put a TH400 behind it along with a NP241 transfer case. Got rid of the 305/350/203 piece of junk that was in there. The power is great- Now for the axle upgrades!!!

Anybody out there got any 70 Suburban parts? I need a good set of barn doors for mine.

I have a mildly built 454 (http://community.webshots.com/photo/28203132/28421383GWCftbMbdy) in my Suburban (dropped it in last year to replace the 350). Tows pretty good. Still havent gotten accurate figures on gas mileage yet.

I also have a stock 454 in my 81 Crew cab w/4.10 gears and 35's. It gets about 7 mpg towing or not. Not much on acceleration, but it always gets the job done.

The built 396 in my other Crew Cab will break loose the 40" tires on pavement. Gets no better than about 5 mpg though on the highway.

I like my mildly built 454 in my K30. Got enough power to do this and that, but the 5 to 7 mpg really takes the thrill out of going to the gas station quite a bit. /forums/images/graemlins/frown.gif

BTW, where in Kans-Ass are you? I'm in central part, 35 miles west of Salina.

I think this has been asked before but I have yet to see a clear answer. If you install a TBI 454 into a previously TBI 350 truck (Burban in my case), will the original puter still work, will I need a completely new one, or will I just need a new chip (Is a chip cheap or easy to install?)? My dad gave me a 454 2 bolt short block and I want to build it into a thumper. /forums/images/graemlins/thumb.gif. Maybe its just me but I think the size of Sub's and K30's neccessitates BIG BLOCKS!!! /forums/images/graemlins/eek.gif

How about gearing-transmission-lift-tire combos with some of these subs that run over 10 mpg? I'm looking at adding a 454 to my crewcab instead of the 6.2TD for the broad torque range and greater output but I too am not very excited about mid single digit milage when running empty. I'm also not very encouraged by the report on the stock 454 with 4.10's and 35s being kind of a dog. That's not far off from what I'm going to have......
I've considered a gearvendors overdrive but am not too happy with $2400.00 up front just to get better milage. $2400 buys me a lot of gas, and I don't have to do it all at once. Of course splitting gears in the TH400 might be nice with Wally on the trailer.

My dear old Dad gets 200km per saddle tank in his '79 C20 w/454 (bone stock, with 11' camper) /forums/images/graemlins/blush.gif

So 10km per US gallon, and that's what - 6mpg?! /forums/images/graemlins/eek.gif

My '88 crewcab dually gets 6 MPGs. It has a FI 454, turbo 400/205, and is lifted 10" and runs 42" Swampers with 5.13 gears. This is with a 9.5' Lance cabover camper. When I bought it new in 1988, with the stock 7.50-16 tires and 4.10 gears the best it ever got was 9 MPGs. I am very skeptical about any big block equipped 4x4 doing over 10 MPGs...

</font><blockquote><font class="small">In reply to:</font><hr />
How about gearing-transmission-lift-tire combos with some of these subs that run over 10 mpg

[/ QUOTE ] I had a 93 4wd 3/4 w/454TBI 4L80E 4.10s and 32 tires.It got 13-14 MPG with hi oct gas ON THE HIGHWAY. My 79 K5 with 454TBI, 4L80E 4.10s and 35s gets the same thing. In town they get about 10 mpg.

</font><blockquote><font class="small">In reply to:</font><hr />
If you install a TBI 454 into a previously TBI 350 truck (Burban in my case), will the original puter still work, will I need a completely new one, or will I just need a new chip (Is a chip cheap or easy to install?

[/ QUOTE ]
You will need a new computer OR a new chip - the chip pulls out and can be replaced very easy if you can get to your computer. You will also need a different throttle body - (more CFM and bigger injectors). The rest of the system is pretty much identical.

1978 K1500 Suburban: 396 BBC, EDlebrock intake, Carter AFB 650, Open chambered heads, TRW forged pistons, Pink connecting rods, forged crank, Cloys-Double true roller timing chain, Edlebrock RPM cam and lifters, Competition Cams "Magnum" roller tip rocker arms, Hooker headers, dual Flowmasters - It is much more fun to drive than a 350
Aluminum battery box - Optima battery, Factory Tach
TH400 rebuilt w/Hughes Torque convertor (oversized stator bearing and brazed fins)/NP205/10b with Warn Premiums/12b w/ Auburn Gear LS and Mosher Axles,
3.73's with 35's
Gets 9-10 mpg combined driving.

Boy, what I would give to be able to get 10 mpg with my 454. /forums/images/graemlins/frown.gif

I've got a '92 dually, xtra cab 4x4 with the 454 and the 5 speed. I run 31" tires and have 3.73 gears. Without the AC running it gets better than 13 on the highway and about 11 in town. I am thinking of going to 4.11's for a little better pulling power.

</font><blockquote><font class="small">In reply to:</font><hr />
ThatK30guy Lamented gas mileage
Boy, what I would give to be able to get 10 mpg with my 454.


[/ QUOTE ]

I pull 13 MPG in town, out of town, uphill, downhill, full, empty, towing, doign burnouts, in reverse, or idling for hours on end with the 454 in my 77 C20 sub. I attribute my gas mileage to a Comp cams Xtreme engergy 11-234-3 cam... not only does it produce mad power over a stock cam, they also have started advertising it for its gas mileage improving quantities. it has a good strong smooth idle, ( I've had it idling down to 400 RPM before, with no problems at all) and it gives nice snappy throttle response. the 454 project I'm building up now, is getting the same bumpstick put in it, as well as a performer manifold to shave some weight, and add some power.

to give some comparisons, my 77 C20 pickup with a 350/Sm465 got 12 MPG the way I usually drove it, and 16 when I grannied it, my friends 76 C10 suburban 350/400 gets 8 MPG, my 73 K20 350/350 gets 7, and my 77 C20 suburban only got 10 when I had a 350 in it. ( that lasted only 2 weeks tho.. )

its your call, but chances are, your gas mileage will either stay the same, or vary by perhaps 1 MPG either way. the ass-dyno will feel an immense difference tho, with slam you to the back of your seat acceleration... or at least mine does.

Sounds possible, but when I take in consideration of another guy I know from out of town, whom has a K30 set up the same as mine (454,400,205,60,14,4.10,33's), with me running a carb and 35's, him running a Holley Pro-Jection, he claims to get 18 mpg!!! /forums/images/graemlins/eek.gif /forums/images/graemlins/eek.gif /forums/images/graemlins/eek.gif /forums/images/graemlins/angryfire.gif

18! No way! /forums/images/graemlins/shocked.gif

there's a guy on my old 73-87 chevy truck mailing list who claims to get 18 MPG on his 78 crewcab dually 1 ton. its only 2wd, which shaves the wegiht of the front axle and T case out, but &lt;shrug&gt;

-Rich

I would not argue that under cartain conditions that it would not happen. But over all?

I know, thats what I told him. I'm still skeptical about those numbers anyways. /forums/images/graemlins/tongue.gif

Gee, 18 mpg? I cant figure whats up with my Utility truck. It has a 454 and TH400, factory 1-ton, but I robbed the Dana 60 front for something else. It's a heavy truck, but it's fuel injected and all stock, and it uses the same amount of gas as does the Big Crew Cab with 40" tires and a built 396 with a Holley 750.

Even with new plugs and wires, it seems like the '87 throttle body injected Utility truck gets about 5-6 mpg even on the highway with no load and 235/75R16 tires.

Wow! thats really bad. /forums/images/graemlins/eek.gif

I agree! That sucks just like my carbed '85. /forums/images/graemlins/angryfire.gif /forums/images/graemlins/tongue.gif

Stephen, I built an 88 3/4 ton sub 4x4 with a 513 Cad engine, US Gear aux trans behind the BOP T400 &amp; Np208 running a 4.56 geared D60 and 14BFF on 33" tires. Consistantly got 8-9mpg towing a 5500# trailer. Would always pull 12-13 running empty. Nothing like splitting those gears in the mountains. Have witnessed 2 Gear Vender failures while towing trailers. I found the US Gear to be virtually bulletproof. Carb jetting, adjustable MSD remote timing control and keeping RPM's low really helped in fuel mileage. I cammed for maximum torque @ 3000 and usually cruised around 2300-2500. Ran it for 4 years with not a problem. Have many times wished I had never sold the truck but wanted to "down size".