Fuel economy of 7.4L (454) powered 3/4 ton suburban

[mwilliamshs]

A carb on a 5.0 should need less main jetting than same carb on a 7.4 but the 7.4 would need more idle fuel and more accelerator pump fuel, as you've observed. The bigger engine will pull more fuel on its larger vacuum pulses on the main circuit (so a smaller jet will work) but will need more fuel to idle (bigger jet and/or "looser" mixture screw) due to breathing more deeply at high vacuum (idle) and will likewise need more fuel to prevent stalling at quick throttle angle changes due to that higher volume of air being sucked in by bigger cylinders (so bigger acc pump squirter/cam/etc).

Very interesting project you have here. Looking forward to the diesel stuff!

15-16:1 AFRs can work quite well depending on valve type/seat condition. Worn valves burn easier due to smaller margins.

14FF in vans had 3.21 R&P somewhat commonly in my experience. I'm a van nerd.

[oil pan 4]

I may need to find a bigger accelerator jet. It still goes rather lean when I punch it, but at least now it stays within A/F meter's indicating range most of the time.

Looks like picking up a new set of 3.21 gears isn't going to happen as cheaply and easily as I thought. I tried to get some from the jeephut. They took my money and didn't send anything.
I found another place that claims to have them, justdifferentials dot com, for the low, low FML price of $650.
Well I guess I can justify it, I could pickup a set of 3.42 gears for around $400 to $450 at that point might as well pay the additional 200 or so and get what I want.
That greatly reduces the chance of me putting in an ARB air locker.

I am going to call them and place the order and make sure they actually have them.
For that price, it sounds like they are the only ones that carry them in stock and that they are aware of this fact.

I am not going to be able to get any fuel economy numbers from this gas powered suburban for a while. It has developed a pretty bad radiator leak. I will need to move the radiator from my diesel over before I can drive it much.

While carb tuning I got a plenty of time to listen to the engine run with the hood up and me with my head over the engine and what I thought was a rod knock or wrist pin knock sounds like its coming from under the valve cover. So I need to get some rocker arm oil deflectors and a valve cover gasket and pull it off, fire it up and hopefully all it needs is a rocker arm adjustment or maybe a new lifter.

[oil pan 4]

I got the 3.21 gears, they did have them and went ahead and picked up the master rebuild kit.

[mwilliamshs]

Originally Posted by oil pan 4

I got the 3.21 gears, they did have them and went ahead and picked up the master rebuild kit.

[kir_kenix]

I enjoy reading about your tuning efforts on that big piece of iron...but I keep thinking that a stand alone fuel injection system would be the ultimate solution here. I know the 454 is just a temporary place holder for your diesel, but I would really be interested in what a seasoned ecomodder could eek out of a msd or similar fuel injection set up. I'll bet you could post some very impressive numbers with a bit more tuning options and your new gears.

Got a time frame on the diesel/transmission transplant?

[oil pan 4]

It just depends on how much time I can put into it.
As you can see with the gear and ARB air locker fiasco I have the funds, just really don't like spending it.
With that gigantic trailer behind it and only being 2wd it would get stuck on wet grass very easy, or dig a hole going up a hill on a dirt/gravel road with an open diff.
I guess I should open the cover just to make sure some one didn't stick anything special in there, it would be kind of a waste to buy an ARB if there was some kind of posi in there.
All I know is it fore sure does not have a Detroit locker.

[cosmick]

One of these days I'll be showing how a '96-'00 Vortec 7400 in an '86 Camaro can see 30 MPG without drafting, going slow, ****ting the engine off, etc.

[oil pan 4]

I found a set rear disc brake conversion brackets for $120. Then use OE rotors, pads, lines and calipers from later year trucks for the actual stopping.
Eliminates 50lb+ of rotating mass.
How can I not?
Now just trying to find a pair of aluminum hubs that aren't astronomically expensive. But I can keep the steel hubs if that is not possible.

[drainoil]

Originally Posted by cosmick

One of these days I'll be showing how a '96-'00 Vortec 7400 in an '86 Camaro can see 30 MPG without drafting, going slow, ****ting the engine off, etc.

And laying down copious amounts of burnt rubber in non eco modder fashion

[oil pan 4]

Just think of it as a hybrid that burns rubber and gasoline.