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

[oil pan 4]

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?

[oil pan 4]

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.

[cosmick]

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

[oil pan 4]

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.

[oil pan 4]

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.

[silverHX]

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.

[kir_kenix]

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*.

[silverHX]

Originally Posted by kir_kenix

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.

[oil pan 4]

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

[cosmick]

Originally Posted by silverHX

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.

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.