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

In addition to the little 7.4L engine it has a 3 speed automatic transmission and 4.10 fuel economy gears.
What, 4.10 gears are great for economy compared to optional 5.13 gears.
I don't know what it gets for gas milage but I am going to find out.
I have been told anything from 10 highway to 8 city to half that.
Its got 140,000 miles on it, that means its burned at least 14,000 gallons of gas. Soon it wont be burning any gas.

Well the bad news is the numerically lowest gear ratio I can locate for the full float GM 14 bolt 10.5 inch axle are 3.42:1 gears. The same gears my half ton suburbans 8.5 inch 10 bolt semi float rear has.
I wanted to pick up some 3.23s, but that's not happening.
Edit: It is happening. NitroGear makes 3.21 gears, the numerically lowest ratio known to have ever been produced for 14 bolt full float. But they are $600. NitroGear is the only producer for 3.21 gears, they are aware of this and have priced this gear set accordingly.

The 454 and 3 speed are only going to be in there till I can pull my 4 year old diesel engine out of my rusted out half ton and repair, update and improve its 700R4 transmission and move it all over. The current 700R4 shattered its torque converter lockup, a 27 spline lockup converter on an obsolete 27 spline input shaft and I cant even find a replacement lock up torque converter because everyone has gone to 30 spline which GM started using in 1985.
Edit: I have found some 27 spline options but they are limited to say the least.
I have almost infinite options available for 30 spline torque converters, (almost) nothing for 27 spline. But swapping to a 30 spline input shaft and drum will fix that.

This 3/4 ton suburban has a few important improvements over the half ton. Mainly the 3/4 ton frame, full float heavy duty axle, bigger brakes, class 4 hitch, working trailer brake controller, 40 gallon road warrior fuel tank and its not rusted out.

Its running really painfully rich, I have an edelbrock performer carb on the way and I am going to take the wide band O2 sensor meter out of my Camaro and dust off my advanced edelbrock carburetor tuning kit and get that thing running the correct A/F ratio.

I filled up the 40 gallon fuel tank from about 1/2 tank, took 20 gallons, so it looks like the gauge reads correctly.
Then I am going to weigh it tomorrow and drive it around for a few days and see what it gets for MPG, I am sure the as is FE will be disastrous. I am not sure what day the new carb is getting here let alone when I will be able to put it on and tune it.

This should be interesting!

My brother wound up with a fast C30 Crewcab dually several years back through an interesting series of events. The owner blew up the original 454 in the truck around the same time his 396 powered drag car was wrecked so he plopped the built 396 into the truck. Then he traded the truck for my brother's barely broken in 4-wheeler.

That thing was a beast! It would light up all 4 rear tires! It never broke into the double digits on fuel economy, though. It was a wallet killer at '90's gas prices!

Oil Pan,

What a project! What year of suburban, and 2wd/4wd?

In the short term, some 235/85R16 tires would provide some good “rubber gearing” to go along with your 3.42. The only other option I know would be an axle swap for a D60/D61 rear axle with a 3.07:1, but that may be more work than you want to want to for just a 11% reduction.

For the long term solution, are you set on keeping the automatic transmission? I had headache after headache on my 4l60 (which is basically just a 700R4) behind my 350 in my 1991 Chevy K2500, until I finally swapped it over to a NV4500 stick shift. That was without a doubt the single best fuel saving mod I have ever done on a vehicle.

If you want to keep it an auto, you could always try to find an Allison 1000 from a 2001-2007 Chevy 2500HD/3500 with either the 8.1L Vortec or 6.6 Duramax. Those are 5 or 6 speed (6 speed= double overdrive) depending on the year and built like a tank. I would think you could get one out of a wrecked 8.1 gasser reasonably cheap. They make stand alone TCMs to control them, as they are popular for cummins swaps.

I have dreams of a future ¾ ton diesel suburban project, so I will be watching with interest. Oh, and we want pictures!

Remember to run the flame thrower exhausts on low.

200-4R converters work for 27-spline 700R-4s, even RockAuto.com sells reman Dacco converters for the 200-4R, use an '86 Monte Carlo SS version for a high-ish stall, pick some version that bolted to the disastrous Olds 5.7L diesel for a low stall.
3.21:1 gears exist, but can't be had new anymore, for the 10.5" axle. Cheaper to swap a D70 with 3.07:1 from an '89 Cummins, or a 3.08:1 Ford 10.25", both are full-floaters.
The 454 is a lame 7.9:1, but swapping the '96-'00 heads bumps that up to 9.0:1, which is good for those at higher elevation.
I suggest a B&M TorkMaster 2000 converter for the TH400, it will reduce slip at cruise from 200 RPM down to 50 RPM.
Weiand makes an intake manifold specifically for the "peanut-port" heads, but if you want to keep the EGR then Edelbrock is still the only choice.
The absolute best MPG cam for a 454 is Comp's HighEnergy 252. Hedman makes the cheapest headers, but the Doug Thorley's are legal.
For tires, BFG makes a LT255/85R16E you might consider.
Be sure you have the GM 5" airdam that matches your front bumper, then lower the 'burb as far as practical.

Although my big hauler is a completely different make/ model etc, it's still a heavy low mpg beast nonetheless. I don't have the $$ to do much as this time for mpg improvements but I will be watching your thread for inspiration :)

And cosmick, I see you are UAW. My father was a member for almost 40 years.

Really interested what you can eek out of the 454 before doing the diesel swap. If you can pull down 12 or 13 on the highway that would be a major victory in my eyes...what with the weight, gearing, and lack of OD.

What year is the "new" suburban?

Had a 02 1/2 ton 4x4, got 18ish on long HWY trips with a 5.3, 15 on E10 was normal, 12.5 on E85. With E85 prices I'd tune the Elebrock to run that. almost $1 cheaper a gallon around here, well $0.80 a gallon cheaper. is close to $1. I have rods and seat kit in the garage left over from putting a 600cfm on a 350V8 S-10 if you need them doubt I'll ever use them, cover shipping and it's yours.

3:42s in a 3/4 ton Suburban with a big block / diesel? Good luck with the 700R4. Those transmissions aren't bad, but with that much weight, that much torque, and that little gear, whatever trans you put in it is going to have to be well built and well cooled.

a 6.2L diesel only makes a truly lame 240 ft/lbs TQ, no more than an equally lame 305 gasser. The 6.2 feels torquier to drive than the 305, but that's only because the torque comes on quicker and stronger off idle.
A 700R-4 does need to be "built" to survive a 6.2, but even stock 305s break the best of stock 700R-4s, however, the 700R-4 isn't inherently weak, most of the guts are as strong as TH400 guts. The aftermarket has addressed the rest.
Cruise RPM for a 700R-4, 3.07:1 gears, and 33" tires is fine for a 454, the 6.2 probably can't pull it, however.
If you want MPG with a 454, then swap it into an '84-'90 Trans Am. The math says 25 MPG is possible. If I had money I'd do just that, first trying to pass emissions, then trying for 30 MPG.
The Viper V10 started as 488 cubic inches, they gave it a 0.50:1 sixth with a 3.07:1 rear and 26.2" tires. Only a bit of researching uncovered the '87 GM G-body was able to pull similar RPM with similar drag from only 262 cubes. It was a 200-4R with 0.673913:1 OD, a 2.2857:1 rear, and 25.5" tires. So if a 262 can pull that, a 454 should pull much less RPM. Probably need a divorced NP205 to get enough launch ratio with an even taller rear gear, even if swapping a 2.97:1 first, a la Mustang Cobra, in place of the Viper's 2.66:1.
This may all seem a bit off topic, but I think it worth considering what's possible, drag permitting. Or lack thereof.

I have set of 2nd gen Camaro headers on the way. I think they will fit.
The price was right. Might run side pipes, no mufflers or anything.
I just want to play with it a little before I pull it and drop in the diesel.

I don't have a 6.2.
I have a 6.5L block, with 6.2L heads then that is twin turboed and intercooled.
Then while the diesel engine is out I am putting a waste gate on and I may put a the bigger new injector pump on along with new injectors. The injector pump has a lot of miles on it and I believe the injectors leak a little.

The Th400 has 3 major design flaws as far as I am concerned, it has no over drive and no torque converter lock up. There are after market options to put a locking torque converter on a TH400 but, but its still missing a gear.
Then the first gear in a TH400 is about 2.5:1 where a TH700 has a 3.1:1 first gear.

Cooling the TH700 wont be a problem. I have 3 transmission coolers and 1 factory installed transmission fluid heater. As long as the torque converter lockup is working the 3 cooler are tremendous over kill. When lockup is engaged not towing anything I think it actually needs the factory transmission heater.
I have only seen it get real hot with no converter lockup while towing another car on my trailer.
I weighed the 3/4 ton suburban, with a full 40 gallon fuel tank it weighed under 5600lb. So the weight difference between the half ton and 3/4 appears to be nearly nothing, or about as little as a full versus low tank of fuel.

I am having a transmission shop near Lubbock rebuild the transmission. They are going to put in a 30 spline 5 planetary gear set, high pressure high volume hydraulic pump and upgraded higher count clutch packs and most importantly a working 30 spline lockup converter.
Sad thing is they want almost the same amount of $ to build that bullet proof 700R4 as my local transmission shop wants to do a stock rebuild. I have been told my local shop is a rip off this appears to be true.

When towing something heavy my plan is to put the shifter in 3 making it like a TH400 since they share the same 3rd gear ratio of 1:1. And because my 700R4 is an 1984 the torque converter lockup will lockup in 3rd gear. Later 700R4 transmissions will not lockup in 3rd gear unless you modify them.
Plus I added a torque converter lockup control switch. I can turn the lockup off, run it like normal or turn it on when ever I want.

The half ton suburban was getting right about 21mpg towing my small trailer on the interstate at 70mph until it lost its torque converter lockup.

Oh its 2wd. Its a C2500 (GMC). I found that with 4wd you spend more time working on it or around than actually using it.
Plus it seems like no one wants old 2wd suburbans so they are cheap.
It appears the only way to get a 2wd 3/4 ton suburban with full float axle, towing package with trailer brakes, 40 gallon fuel tank, class 4 hitch, heavy duty axle was to get one that had a 454 gas engine and TH400. Which is fine because I already have the engine I want.

My specification was to find a 2wd. Had to be 2wd, I did not want 4x4 at all.
With what I am going to tow with it I really should have a 3/4 ton and full float axle, I already am pushing the limit of what standard 15 inch tires on 5 lug wheels can carry. I found that late 90s and 2000s jeeps use 16 inch 5 on 5 wheels but then the 16 inch load range D tires exceed what the rest of the vehicle should be carrying.

I will be adjusting the rubber gearing. The half ton had 31 inch load range C tires. The 3/4 ton has 32 inch tall 10 ply tires on 16 inch wheels.

The 6 speed allison transmissions I can find are around $2200, that doesn't include freight shipping. Then the standalone controllers appear to be at least another $1500. Then I would need a custom drive shaft. That trans with a controller shipped to me I am looking at about $4000, plus whatever a custom drive shaft costs.
I can get the TH700R4 rebuilt and bullet proofed with a new torque converter for about $1400 to $1500.
If I could pick up a used 6 speed Allison locally for cheap, yeah I might do it.
The 5 speed Allison has the same top gear ratio as the 700R4, so that wont help fuel economy.

I don't want to do an NV4500 swap because my engines internals were balanced by a machine shop in Virginia beach. Swapping from a flex plate to fly wheel would mess with my engine balance.

I was wondering if 3.21 is a type-o, but looks like I was looking for the wrong ratio. I found parts referencing that they work with "3.21, 3.42, 3.73 and 4.10" gear carriers.
Kind of like trying to find 4.11 gears, when they never made them, but always had 4.10 gears.
So thank you, I am use to 10 bolt stuff which has 3.23 gears.
I will look for 3.21 gears if I cant find any I will go with 3.42 gears.
I don't have to have new gears, I could go for a used set.

All 700R-4s can lock up in 2nd, 3rd, and 4th, if you wire the pressure switches correctly. Forget the manual switch, just wire in a vacuum switch for engage / WOT disengage, and a brake switch so you don't stall your engine or hurt your lockup in a panic stop, when you'll forget a manual unlock.
Any torque converter the average guy can easily afford isn't built to hold WOT while locked up. There are $900 race converters that can, but neither a mild 454 nor any diesel can run a 4400-stall converter.
Too many guys with manual switches are either too bold or too cautious about when to use lockup.
The biggest problem with lockup in 2 / 3 is getting it to unlock for shifts, plus seldom are you cruising at an RPM less than the converter's stall speed except in OD.
Stock stalls start around 1400 for the 700, and around 1200 for the TH350 / TH400, but as I referenced earlier, a GM 1200 will slip more at cruise than a good aftermarket 2000.

Having balanced more than a few engines, I can say that if it was done correctly, your last statement is a false assumption.
You might also consider the 4L80E, with a '92-'93 diesel GM controller from a salvage yard. This is the cheap way to control any electronic OD 4-speed auto. $20 for the box, $85 for the reprogramming.

Actually, in my salvage yard Saturdays, I have found 4.09:1, 4.10:1, and 4.11:1 gears in GM 10.5s. Some genuine GM, some aftermarket, but all exist. And really, it doesn't matter that greatly which you end up with, even if you have a 4X4 with a front axle 0.02:1 off.
The 3.21:1s are most likely found in C20 C6Ps, but sometimes in C30s. They only came behind 454s, they were mid-'70s to mid-'80s, and were used behind SM465s and TH400s.
This info comes from GM's heritage center.
I've been seeking a set of 3.21s myself, no luck in the last year. The tooth count is 45:14

I only added the manual switch after my torque converter lockup turned to dust for trouble shooting.
I wont run the lockup in 2nd gear. I didn't think it was a good idea.

I drove this 7.4L powered suburban as is for 55 miles and it averaged 6.5mpg. I cant say for sure that's its driving around town fuel economy, but the trend is pretty clear. I filled it up and its not leaving the yard again until the edelbrock carb goes on there for tuning or unless I have my very large trailer on it. I also picked up a used edelbrock oval port BBC intake manifold, since I don't want to use a spread bore to square bore adaptor.

What's your initial timing set at? Computer-controlled advance, or vacuum + centrifugal? Does it have a QJ with sealed idle mixture screws, or are the screws accessible? If accessible, have you adjusted for best idle vacuum? You want as much initial as it'll take without becoming hard to start hot or cold. No less than 6 degrees initial, even if computer-controlled. Probably no more than 14 degrees if non-computer.
If vacuum advance, use manifold vacuum. If computer controlled rather than vac / centrif, then there may be some wire to unplug. Typically tan with black stripe.
The QJ has more potential for better MPG than the Edelbrock carb, while the engine is stock, you just need to find and fix the leaks, both fuel and vacuum.
Once you convert to the Edelbrock parts, then get a non-computer HEI.

I have no idea what the time is, I was just driving it as is like the average joe.
It has a electronic HEI with vacuum and mechanical advance.
I was thinking I would set it for 12 to 8 degrees of initial advance and then I would have to look up what the total advance the 454 like to run it.
I don't think I am not going to mess with the timing until after I put the new intake manifold and carb on there. I will go out and check the timing after dark, but I don't plan on driving it any more as is if I can help it.

What is easier to change out metering rods on, the edelbrock 1405 or a Q-jet?

5 parts showed up today. My free aprox half used up set of 3 year old 265/85R16 tires from my friend, those will replace the dry rotted, pealing 235/75R16 tires on the back. and fedex delivered my made in merica Edelbrock 7561 fuel economy intake manifold.
I have to drive the super gas hog today :( , need to take it down to the tire shop to get the tires put on the back and take a Camaro wheel down there too, the Camaro has been sitting so long one of the tires tread separated just from sitting.
All I need is the edelbrock 1405 carb and the weld in oxygen sensor bung so I can install my AEM wide band O2 meter and get tuning that A/F ratio.

The 7561 is an RPM AirGap, probably the worst thing for MPG short of a single-plane. The younger guys call it a fail.

That was a joke.
So how is the dual plain edelbrock so much worse than the OE cast iron intake?
I know the ports are a little mismatched but that doesn't appear to effect anything aside from top end hosepower which I don't really care that much about.
The worse thing I could do for fuel economy is leave it as is.

I am getting everything on. I pulled the edelbrock apart to change jets and needed to be cleaned really bad (have a great picture for the ethanol can do no wrong crowd). Then found the metering rods are all gone from my tuning kit. Its been over 4 years since I messed with it, so have no idea where they are or why I would have put them any where else besides the tuning kit.
I already know a factory 1405 carbs jetting will also run painfully rich here just like the Q-jet so I am doing the next best thing and putting smaller primary and secondary jets and keeping the metering rod the same since I don't have any other ones.
Also putting the smallest accelerator nozzle I can get on there for now.
The OEM jet size is .1'' up front and .95" in the rear.
Pretty much my only option with what is left of my kit is to put .98'' up front and .92'' or .95'' in the rear. I think I will try the smaller .92 jet in the secondaries.

Based on the jets that are missing from my tuning kit I believe I have installed .89'' in the secondaries and .95'' primaries but have no idea what metering rod in my Camaro.

set timing to zero. Not a 454 expert or anything but my 350 tbi has a way lower knock count when i data log it with the base timing set to zero.

I think he is going to need some advance...fuel doesn't ignite/burn the instant it ignites. He is probably on the right path somewhere 6-10* before tdc...maybe more/less depending on what grade gasoline he is planning to run.

I have a feeling that you set your 5.7 back to "factory" specs (assuming computer controlled ignition since you are data-logging it)...and not actual tdc/0*.

I set base timing to zero by disconnecting the electronic spark advance, (brown wire under dash for me) factory specs. I had it at 12* and have played with it a bunch only to find it just simply runs better at zero. some people claim 4* advance is perfect. My engine is a 94 tbi all stock, except for ultimate tbi mods, tbi spacer and intake + exhaust. 328k miles on it and still runs like a champ, i feed it mobil1 every 3k.

I was just going to use 86 octane for sure as long as that motor is in the C2500.

And your cranking compression is likely 40+ psi more than any stock 7.9:1 454, especially if you're at lower elevation and the 454 is at higher elev. The LO5 TBI 350 starts over 9.1:1, with a much earlier intake valve closing point, and higher-velocity intake ports.

Yeah stock C/R is a Briggs and Stratton inspired 8:1 (rounded up).

I got the edelbrock 1405 carb on there with the smaller jetting appears to be really close to what it actually needs. I have not moved the wide band O2 over yet.
Set timing 4 degrees before tdc. It runs so much better.

Glad to hear that you are moving in the right direction. Wide-band will really allow you to zero all the way into that perfect 'zone' for your set up, at your current elevation.

I'm really enjoying your progress, but I must admit I am ultimately much more excited about your diesel swap. I've followed your 6.2/6.5 Frankenstein, dual turbo adventure for a couple years now...and I'm excited about the new platform. You don't know how many time's I've looked at Suburban's on Craigslist itching to follow you down that path (except with a manual).

Good luck and have fun.

The diesel and remade 700R4 will replace the 454/TH400 in this C2500 eventually.
The diesel will get its mild steel cross over pipe replaced with 2 inch 316alloy stainless and waste gate with side exit screamer pipe. It has to have a waste gate because when I go back down to sea level it will hit over 20psi and that's too much.
Then since the body on this C2500 I will install all the high voltage accessories I wanted to put on my old suburban but never did because I knew it would be a pita to move it all over.

What other accessories can you go electric with? I know you are rocking an electric water pump, fuel pump, fans, air compressors, etc. Electric power steering would be awesome if you could get it to work reliably...it would really, really suck to have to park that tank with the gear ratios supplied with the stock gear box. If you get that far you might as well ditch the alternator and go completely beltless.

I just called a guy from Craigslist about a mint '89 Suburban (gasser unfortunately). I doubt he'll come down far enough for me to bite, but we will see how it goes. Incidentally, any tips besides crossing your fingers on identifying a good 6.2 block while it is installed? Besides looking to see if it's been aftermarket turbo'd, looking for one of those mythical "high nickel" early years, etc? Seems to be a lot of people dumping older diesels lately at ridiculously low prices...but I hate to grab a doner vehicle with a junk block.

I may go back to a belt driven water pump.

How to find a good 6.2L block. Stay away from the 660 casting if you can. See the engine run if you can.
I have horrible luck with used engines so I just rebuild them.
The high Ni blocks are cool but don't get hung up on finding one.
I think the best 6.2 block are the ones machined during the years that GM made both 6.2 and 6.5 at the same factory. They fixed the 660 casting design flaw in this casting and the blocks were cast so they could be bored to 6.2 or 6.5L. When bored to 6.2 the cylinders are stupid thick. These blocks are as desirable if not more than the high Ni blocks.
Also go with small valve heads. The small valve heads rarely crack.

Problem with going beltless is the water pump, that's a constant 5 amp electrical draw. A belt driven coolant pump makes an alt delete much more possible.

Problem with some kind of on/off power steering is the hydroboost brake system. I say get a gasser (like I did) keep the vacuum brake booster and you can run on the highway with the P/S unhooked or on a clutch. I would like to come up with some kind of way to clutch the P/S.
Then replace the vacuum pump with an oil pump drive out of a military HMMWV.
The cam vacuum pump adds an additional 500 watt load at cruise RPM.
You can replace the always turning, almost always unneeded vacuum pump with an electric vacuum pump that can almost always stay off.

Also run a J-code intake manifold. I tested all three, C then J then F and went back to J.
I also installed a peninsular upper plenum, its made for an F code intake but with a little adaptor plate I made it fit.

If you are going to tow, get a 3/4 ton and stay with 2wd if you can stand it.
As far as I can tell there is minimal weight difference between 1/2 ton and 3/4 ton.
It looks like 4x4 half ton with a 350 will weigh more than a 2wd 3/4 ton with a 454.

I also noticed that the 454 suburbans are in pretty good condition. Have lower miles than SBC and diesel counterparts. For example the suburban I bought has 140k miles that's less than 5k per year average. Another one I looked at had just over 100k and there were a few survivor 3/4 ton 454 powered suburbans with under 50k.
All the 350s and diesels normally have way over 200k miles and people want way too much for them. For some reason 2wd 454 powered suburbans are not that desirable.

"The cam vacuum pump adds an additional 500 watt load at cruise RPM.
You can replace the always turning, almost always unneeded vacuum pump with an electric vacuum pump that can almost always stay off."

I remember somebody running the pump and crunching the numbers a while back (may have even been you) and I'm still amazed by the 500 watt load.

I am going to have to go 4wd unfortunately...I just live too far in the sticks to even consider 2wd right now on this type of rig. Every time it rains or snows/thaws we need 4wd to make it out of my 3/4-1mile drive way/lane (huge hill for around here...no incentive for the county to drop gravel since I'm the only house on the lane).

However, I really only need to be able to pull 10-12,000 lbs with this rig. Anything more than that and I will bust out one of the trucks. So I could conceivable run 3.42's or higher instead of the 4.10's or 4.56's like a lot of guys are running.

I appreciate the information you have provided on 6.2's, and I'll keep it on mind while stalking craigslist. There are 3 trucks and 2 Suburban's within 100 miles of me that I plan on looking at this next week when I get home...crossing my fingers I can snag a good one.

Yes I tested it.
3.42 are the most highway gear you are going to be able to find for full float 14 bolt.
I would love to find a 3.21 ring gear but no one makes them any more.
EDIT: NitroGear makes them.

I may have located a source for GM 10.5'' full float 3.21 gears, at "thejeephut dot com".
(EDIT: the jeep hut does not have any 3.21 gears)
Says they are "discontinued" so I believe that means once they are gone, they are history, unless someone else does a production run.
Total for me looks like $307. I could easily save $300 in fuel swapping from the OE 4.10 gears to 3.42-3.21 in this pig.
The 3.21 gears and an ARB air locker and I will be all set.

Everywhere else I have looked might have the FF 10.5'' 14 bolt 3.21 gears listed but shows "not available" or has a price of "$0.00". Kind of makes sense that a jeep place would have them. I don't think GM full float 10.5 inch rears are popular with jeep guys. I think they like to stick with Dana or ford 9''.

The current half ton diesel setup is 31'' tires, 3.42 (10bolt) rear. The 3/4 ton suburban will have 32 inch tires and it looks like I will have the 3.21 gears now.
To counteract the taller gears and taller tires at low/start/stop speeds and keep from going from a tow monster to a towing turd I have a few alterations to make to the 6.5L/TH700R4 before it takes the place of the gasoline 7.4L/TH400.
1 More fuel. At the very least turn up my injector pump, maybe get one that can fire more fuel through the injectors.
2 Replace the torque converter, since the one on the TH700R4 is shot. The original OEMs diesel converter should be 900rpm stall. The one I found is 1200rpm built for diesels that go 4x4ing and/or tow.
3 Activate the VGT on the holset.
4 At higher speeds while towing revert the TH700R4 back to TH400 mode by putting it in 3rd gear.

In other news the rod and jet tuning kit came in, then a few hours later while I was at work another package with some additional smaller jets not included in that big kit arrived.

I moved my AEM wideband O2 over into the suburban.
From my initial setting the idle was a tad too lean, needed about 1/8 of a turn rich to make it idle between the 16 to 18 range.

Gentile acceleration is lean, between 15 and 16 to one. That could burn a valve.
Moderate acceleration is around 15.
Flooring it meters fuel in at fuel at a rate of between 13 and 14 to one.
Cruise is around 16:1. I am pretty sure that is in the valve burn range.

I think I will start off by seeing what the next size smaller metering rod will do (will let in slightly more fuel during acceleration).

Edit: when I took the motor apart I pulled the exhaust valves and they showed no signs of burning.

My Madmax tune looks like its going to be something like, 0.042'' accelerator pump jets (about 30% bigger than standard) running max stroke, 0.104'' secondaries (9% larger than standard and the largest standard metering jet), 0.95 primary jets (5% smaller than standard) with 7047 metering rods (standard).
I think the 0.95 primary jet will allow me to just replace metering rods to change normal driving charaistics.

The small accelerator pump nozzle was too small. Caused the engine to sputter. Tried the standard nozzle, also too small.

Now this carb is normally used on small block engines, ranging from 5L to about 6.6L.

I run the same carb in my Camaro and its jetting is totally different than this.
The primary, secondary and accelerator jets are all smaller.
The factory setup 1405 carb will run stupid rich all the time on a 5L at this elevation.

The same carb on a 454 will run kind of lean when you don't want it to, but then will run a little rich at cruse. Getting it to run a little lean at cruise is the trick and I think I got it.
I am sure its not going to be happy cold starting.

Edit: when I took the motor apart I pulled the exhaust valves and they showed no signs of burning.