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

[rmay635703]

Peak egt is most efficient only around WOT, below WOT leaner is usually more efficient.

Peak EGT is almost always around 15.5:1 (non ethanol gas) and 15:1 for ethanol blends

[oil pan 4]

Between 15.5 and 16.5:1 is usually the ratio I'm trying to get while cruising down the road.

I was considering adding an EGT gauge.
Sounds like a good reason to get one.

[oil pan 4]

To make the air fuel cruise adjustable on the fly I was considering an air bleed on a needle valve.

[oil pan 4]

The gasoline suburban is coming together. The engine is in and the headers I got almost for free that fit a 2nd Gen camaro do appear to fit.
That old 454 has been punched out and stroked out to about 488 cubic inches, or 8L.
The cast iron 1980s smog heads have been recycled into boat anchors hopefully and replaced with GM performance parts aluminum heads saving around 100lb.
The compression ratio is 11:1

It has a dual exhausted no catalytic converters. Being a 1984 3/4 ton it does not require any.
I'm thinking install catalytic converters, lose the stock style mufflers.
I don't want it to smell "racey".

[Piotrsko]

This going to be carbed or OBD2? I'm thinking that carbs are a bunch less efficient even with a custom tuned quadrejet

[oil pan 4]

Eldelbrock 800.
Since this isn't a daily driver no point in spending 5x as much on electronic fuel induction.
Plus I already exceeded new 2016 suburban fuel economy for highway and city mpg with the carb.

[slowmover]

A Q-Jet is great. Once warmed up (50-miles).

The 1987 TBI is better till that point. As a stand-alone it has aftermarket support going back twenty years in retrofit. HOWELL.

Q-Jet advantage past that is at WOT.

Dad had an ‘87 2500 V8-454. 3.54 years after TH400. Dead reliable thru 190k miles once a better radiator fitted. I added a Cloyes True Roller and Edelbrock water pump. Ran M1 5W-50. Brought consumption down. Today I’d run Rotella -T6. BALDWIN oil filter.

I was liking DENSO Iridium plugs before getting out of gasoline in 2007.

[oil pan 4]

Once I know the engine isn't consuming hardly any oil I will get expensive plugs. I'm running lower than normal tension oil rings so I may have to take care of an oil issue or 2.
Also have a carb warm up plate in case the eldelbrock rpm air gap dual plain intake manifold keeps the carb too cold in the winter.

[slowmover]

Was thinking about it as I drove this morning.

To get a VERY strong (consistent) vacuum signal to the QJet I was running , I used a MOROSO phenolic resin spread bore spacer (1/2”?) plus a chromed heat shield that extended well out from the carb. On MOPAR one is better off with the stock intake. None of that open plenum crap. A VERY long straight air column upwards from the divided 4way plenum floor. (I did change to in an infloor metered EGR Jet intake from 1972; takes away heat spike to lessen pre ignition).

The formula being, “cool fuel + warm air” (105F) it also took an electric fuel pump near the tank and careful routing of new oversized fuel line plus refelective insulation, to, again, maximize possibilities.

I used two fuel pressure regulators, a standard Holley before a CAGLE vacuum-reference regulator. Low vac Signal equaled an open pipe. The fuel not used was run back to the filler neck. Constant flow overall.

I used a later police-spec air cleaner housing with one closed snorkel (except under WOT) and one conventional snorkel plumber both to a full length exhaust manifold heat stove plus to clean air at the wheelwell housing. Only the normal closed snorkel saw underhood air not conditioned.

Atomization is a *****.

I wouldn’t do it that way again. It was successful but a PITA to put together. I had also changed the thermostat from 185F to 195F. Re-timed the motor to use premium fuel. Saw 16-18 consistently at 55-60/mph with an extra passenger (car became super sensitive to weight added). A friends dead stock ‘67 Imperial was a regular in the 16-mpg column at 65-mph. Outweighed my car by a few hundred pounds. (Higher cylinder pressure).

The other MOPAR advantage (extra care in engineering) was that the throttle was controlled by rods and cranks. Not a sloppy GM cable. Ones foot was actively engaged in nuances.

Dual exhaust with crossover and pipes that got smaller towards the rear of the car (longer than a Suburban). Heat retention = pressure. Velocity (thus scavenging). High performance manifolds off a TNT Model. (I don’t hold much hope of your Camaro headers lasting).

Today I’d use a 4-hole TBI and sweat the engine timing details. The total package of fuel delivery and ignition advance (from scratch). Mechanical, Vacuum, etc. starting g with advancing or retarding cam capability. This would be MUCH easier with FI and it’s consistency.

Altitude changes and dry air aren’t your friend in NM. Cold morning and hot afternoon aren’t either.

With 4.10 gears you have more safety than we did with 3.23 in re stoichiometric. I’d still want to err on the rich side.

Getting the slop out of the trans would be the priority. A very exact converter match.

Once on the road it’s the steering. Body bushings and tie rods must be brand new. Zero box slop. Keeping drive axle centered (panhard Rod).

Make the motor great, but don’t lean on it too hard. It’s the wrong approach versus steering & handling mods for reducing number, degree, and time on ANY inputs to change from steady-state, lane-centered.

A dash mount vacuum gauge, fuel flow meter & tach provide the feedback. Shift per vac drop.

[oil pan 4]

Oh I have headers so I will have to dream up a way to pull hot air to the thermostatic intake mixer.

I won't have a phenolic spacer but I will have that carb heater plate, it's about 1 inch thick.

Actually a vacuum reference fuel pressure regulator is actually a pretty good idea. Never thought about using one in a carb application.
At idle and driving down the road I only need like 3 to 20lb per hour of fuel, 1psi would be plenty of fuel pressure to keep the carb full. But at WOT it will need more like 250 pounds per hour or 40 gallons per hour.
That way the floats aren't trying to hold back 7psi at idle when gas just needs to be dripping into the bowls.

I have 3.21 gears to put in the rear.