Need better gas mileage and performance

[Dingman]

87 3/4 ton 2wd 454 TBI th400 LWB.

I know LMC sales a TBI that is bigger and, But, damn near $800 bucks......Not

Will the TBI spacer help that much?

I wish I could put a full Exhaust on it without violating the Fed regulations.

Should have purchased a older truck I guess, but I love this truck. Brings back the memories from younger years.

Anything else we can do to these engines without too much cost and legally?

Been reading about all the performance add-ons, just don't know what is the best bang for the buck.

Later

[74 stepside]

Other than a good exhaust system and proper tune up, I think an overdrive trans is going to be very helpful and more pleasant to drive.

[Dingman]

I hear ya. is the 700R4 OD?

[74 stepside]

Yes but you would want one that is beefed up because of the 454 torque. A 4L80 is the newer overdrive trans that came behind big blocks. That would be ideal but pricey.

[Dingman]

Thanks for the info. I will look for a 4l80.

Anyone need a th400?? haha

[andrewmp6]

Its not really the Fed regulations its your state utah smog test everything from 1967 to brand new.Every other state that has smog test don't start testing tell the mid 80s even in cali.If it was me i would swap in a small block or diesel the small block will be the cheaper one but the diesel will give you the best mpg a truck can see.A 700r4 could work but like said it needs to be built up to handle a 454 the 4l80e is a better trans but will cost more to swap in.

[74 stepside]

In California 1975 and older is smog exempt. Not the 80s.

[INSIDIOUS '86]

A 700r4 with a boost valve and sonnax servo with a transgo shift kit will still take as much as a 4l80 but cost a third of that and go right in

This will be the best increase in mileage and performance. Next thing would be to have an engine with smaller cylinders and ditch the stock tbi and use a multipoint-MFI or newer more efficiant injection system
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[mud.man.rj]

That year (87) 454 only has about 245hp, with even 350hp if you did any mods the 700R4 will handle it easily, way, way cheaper than a 4l60 or 4l80 and basically does the same job. Could also try a stock appearing performance muffler that will flow better, also better air filter such as K/N and some roller rockers to take some stress off the valve train and help fuel mileage. The throttle body spacer works better for mid to top end better, not much low end and is more for performance than fuel ecomomy.

[mopar346]

I was thinking what mudman posted as I was reading down the thread, don't kid yourself that year 454 especially with the TBI aint that strong. Any well built 700R4 with all the updates will handle it fine and from what I under stand is a bolt in, you can even get an indicator to make the dash right. You will definitely pick up on mileage and on the big end, but I believe the 700 has the same 1st and 2nd gear as a 350 which is lower than a 400 so it will make the holeshot better as well.

I also didn't see anything on the gear and tire size, depending on the final ratio a swap might help mileage.

The best way would be to get rid of the TBI set up all together and go with a carb, but that might give you an issue come emission time.

[Zane M]

You could larger cat back exhaust, that would help.
You can also run duals, but you would have to have a dual cat set up.
I highly doubt you would get milage improvements by switching to a carb. For sake of argument that it would, the trade off would be the time spent each year getting it tuned just right to pass the tailpipe emissions.

[v30crewcab]

my buddy had a dually with a 454/th400, and a single wheel 454/4L80. the 4l80 one only got about 1/2 mpg better. wouldn't be worth my time to swap, but its up to you. Its just the nature of a bigblock to suck fuel!

[raws67]

So what are you getting for mileage? What are you using the truck for? The 700 has a lower 1st and 2nd gear than the th350. Also you can get a lockout converter for 4th gear on a 700 to increase mileage on the highway. Either way when its all said and done its still a big block 3/4 ton truck and your not going to get great mileage. The best and I mean the very best I ever got with my 454 dually was driving 55 on a flat highway and easing in to the throttle.

[mud.man.rj]

That's the thing with a Big block, still has Monster pistons and will never get great mileage no matter what you spend, but if well thought out dollar wise can be made better with some picking. Like mentioned, fully consider the "whole pkg" , as what I said as as mentioned gear ratio, tire size, even width amkas a difference, all personal chioce, i have a big block too and stayed with only a 35" tire (small for my stuff) but did go with a really wide tire to help hook up, have to compromise too to make it what you are happy driving. I am getting real world around 10mpg if I limp it, but I don't much so actually get around 5mpg having fun, which to me matters, no fun, well sell it. But you are daily driving so makes a diff. Lots of help and ideas here for sure.

[Firebirdjones]

Originally Posted by Dingman

87 3/4 ton 2wd 454 TBI th400 LWB.

I know LMC sales a TBI that is bigger and, But, damn near $800 bucks......Not

Will the TBI spacer help that much?

I wish I could put a full Exhaust on it without violating the Fed regulations.

Should have purchased a older truck I guess, but I love this truck. Brings back the memories from younger years.

Anything else we can do to these engines without too much cost and legally?

Been reading about all the performance add-ons, just don't know what is the best bang for the buck.

Later

There is literally dozens of things you can do that doesn't cost much. I find it best to first work with what you have and make it as efficient as possible before throwing money at it with expensive overdrives and fuel injection.

I have a 454/400 turbo/3.73 gears 79 1 ton pickup that is very respectable on mileage (14 highway and 12 city) Considering what it is, it's getting close to some of the newer SUV's that have fuel injection and overdrive with smaller engines. There is still a little more to be had as well. This stock 79 low compression 454 would push this 5500 lbs. truck to 14.70's as well so it was sporty for a big truck. Definately some mild performance there if you know how to extract it.

What kind of mileage are you getting and what are you looking for?

With just about any car I can find 3-4 mpg with tuning tricks and driving habbits along with other subtle things.

Things like wide tires kill mpg, improper air pressures, heavy wheels and tires. Next time you buy tires pay attention to the max air pressures and how much the tire weighs. A heavy wheel/tire combo takes more HP to turn it. Aluminum wheels are your friend, and some are heavier than others.

A proper tune on the engine. Not just your basic plugs and wires,,,but what kind of distributor curve are you running? Try to get all your advance in by about 2500 with roughly 38 degrees total. Then dial in an adjustable vacuum advance to add another 10-12 degrees, and hook that to manifold vacuum only. Just this alone will probably find 1-2 mpg.

Use a wideband to dial in the carb. Been using these for years on mine and customer vehicles. There is no other way to properly dial in a carb. Shoot for light throttle AFR's in the 14.7 range, and for extra mpg even tickling 15.0 doesn't hurt a thing. You'll have to play with power piston springs (quad) or power valves (holley) to dial in a nice curve depending on engine vacuum readings. I like to run a smaller front jet (as that's what you drive on most of the time) for a nice lean part throttle cruise AFR (better mpg) then drill the power valve orifice to add fuel under low vacuum conditions (moderate to heavy throttle) which makes up for the small front jets and use this along with the rear jets (or meter rods and hangers) to dial in WOT AFR at ~12.8 range.

You can look at other things for more power. The factory cast intakes on these engine of this area are subpar to say the least. You'll find 20-30 HP and TQ by swapping on a simple Edelbrock performer intake. A set of long tube headers (1 3/4" is large enough to keep it torquey) because we are moving a big boxy heavy truck, this will also add power under the curve where you need it. Finished with a decent dual exhaust system that has an X or H pipe.

You can start digging deeper with other tricks and really nit pick, like aluminum driveshaft for less rotational weight, using a clutch fan (should already have one) or eliminate that all together and go electric fans which is usually good for another 10-12 hp. Fresh air intake system for denser air makes more power and fuel mileage. Thinner oils throughout have proven to improve fuel mileage and I've seen big improvements on the dyno (although carrying it this far depends on the vehicle for me)
The transmission sucks gas with long drawn out sloppy smooth shifts, a shift kit makes them snappy, less slippage, and brings rpms down quicker. You can also play with the governor and the vacuum modulator to fine tune the shift spread and the part throttle shift points. Usually stacking the shifts closer helps on fuel mileage with lighter vehicles, but on a heavy vehicle (like a truck) it does more harm than good. I've found spreading out the shifts at part throttle helps to get the big boat moving easier and is less strain on the engine But this is something you have to play with since alot depends on gear ratios, tire sizes, weight of vehicle etc.....

Speaking of weight, that's a freeby. Anywhere you can find to remove weight that you don't need will help with MPG, braking, handling etc...This is where the aluminum driveshaft trick and aluminum wheels are a double wammy. You are taking weight out of the truck but it's also rotational weight that takes less HP to turn.

If you have an engine that uses oil, it's going to hurt mpg as it's deluting the fuel charge in the combustion chamber and hurting power. We can just go on and on here. It's a facinating subject and with rising fuel prices that aren't going to stop it really pays to make what you have as efficient as possible.

From there you can look into overdrives that should give you another 25-30% improvement in mileage. Personally for a truck like this (I use mine to tow a 10,000 lbs. trailer) a 700 was out of the question. It was either 4L80 for me or a gear vendor. I have since decided a gear vendor was a better choice for my needs (yet to be installed) because I can use it while pulling the trailer, and I can use it as a gear splitter (aka:6 speed) to help get those 10,000 lbs. loads moving easier from the stop lights. When not in use it acts like your basic 400 turbo. Price is a toss up. I had a 4L80 here (they run $1500+ for a ready to go unit) plus a lock up converter. Then you'll need a $6-$800 controller to run it, and still need a driveshaft made. In the end the Gear Vendor was about the same price when finished and I'll have a 6 speed trans when needed, plus it's rated to about 2500HP so it's not going to break or overheat while towing

Look at what you have first and maximize it before spending money on this stuff though, as it will start to get expensive in a hurry. I have an arsonal of cars here that are all respectable on mileage with alot of these tricks implied. It's the only way I can afford to keep driving them everyday

[THE "10" SILVERADO]

Having the right rear end gears will make a big difference.

[Firebirdjones]

Originally Posted by THE "10" SILVERADO

Having the right rear end gears will make a big difference.

Yep, depending on what you do with the truck and the tire size and how fast you want to run down the highway. Tailor that to the rpm and pick the gear from there, RPM's are key.

I run 3.73's with mine along with the stock (skinny) 9.5x16.5 tires that are about 29" tall.

If I keep the rpm's around 2800 I get 14 mpg with my 454/400 turbo pickup. that's about 67 mph or so and 65-70 is plenty fast for me. I find this gear a good compromise between MPG and the power needed to tow heavy loads and climb the hills around here. Very happy medium. The gear vendor will drop that about 30% and should give me another 2-3 mpg.

[spencer_41188]

when your talking performance not much is cheap

tbi is the best for fuel economy but not with a 3 speed auto

your best bet would be to find a newer truck with the nv4500 1996-2000 have better ratios and every gear is sencronised and all the power gets put to the ground insted of being lost threw the tq converter and the soft shifts

the exhaust cats coust quite a bit i would leave the factry one on and get a more free flowing muffler

efi with the cat will pass smog

a cold air intake like k&n only buy it once clean it a million times best way to go if you wana save money