I have been checking my plugs and they all indicate the mixture is lean (light gray to white). I have plugged all the vacuum leaks. The car seem to run well. I have set the idle mixture to maximum vacuum-20.5 inches. There does not appear to be any issues based on the vacuum gauge. Idle and revved readings are steady with no needle jumping and the needle jumps to about 25 inches after releasing the throttle to settle back at the idle reading.
so I suspect it's the stock 1973 quadrajet which I bought online to replace the original. It functions fine but the guy told me all of their carburators are calibrated to the stock configuration. The thing is, my 455 is a 73 block and intake, no emissions, but I have E-heads and headers. The pistons are aftermarket 30 over shallow dish. The rest of the motor is stock-not the higher hp w30 455. What I believe the case is the flow through my engine is greater than what the carb is setup for causing a lean condition. What size metering rods and jets came stock on a 1970 455? The shops around here charge a small fortune for setting up an O2 sensor, so I really do not want or need to optimize my motor to achieve maximum power. I just don't want to run too lean.

 

Calibrated to a "stock" configuration is merely a starting point for sure.
Are you experiencing any drivability issues? Tip-in, bog etc?
How does the secondary side feel?
Verify WOT is WOT from depressing the pedal not by actuating the throttle while under the hood.
What do the tailpipes look like?

Are you asking about the primary rods/jets or secondary rods or all of the above?
Many many different configurations for a 70 QJ.

The best thing to do IF you are having drivability problems and have exhausted all external adjustments is to remove the air horn and see what the primary rods n jets are.
Also, look at the secondary rods and cam alfa letter designations. This will give you a starting point to order parts.

If you decide to play with these items only make one change at a time.
Purchase a few different rods & jets.

Give Cliff Ruggles a call. He will be able to provide parts and pointers. He will want to know what's already in there before you call.
Have a cup of coffee and a pen & paper ready before you call. Around noon week days is best to get a hold of him.

https://cliffshighperformance.com/

 

This thread has some information. The accuracy of the chart has been questioned, but its a place to start. Grain of salt, they say.

https://classicoldsmobile.com/forums...stions-149436/

I have a similar set up. I have experimented with jets and rods I ended up two jets sizes from the stock #70 jet to #72 jet. I don't recall the rod number. I went as far to #76 jet and its too much in my opinion. I used no science in this quest, just butt dyno and visual plug checks. Some will say its a waste of time until you can get a wide band on it. I had fun hope you do to.

 

Good points. The primary side is what I am interested in. I am not into the secondaries that often to cause a lean burn indicator on the plugs. The company I bought the carb from only said it was calibrated for a stock 73 olds 455. There is currently no tip in bog in fact it is very responsive. I would like to richen it a bit since it runs lean.

 

Uncle Tony would agree with how you did it.

 

I took apart the original 1973 carb 7043251 that came with the motor . I kept it because the accelerator pump tower was broken. The Jets on that one are #70 and the metering rods are 59P. Can't really use that as a reference since the motor came off a jet boat (The vin id indicate the motor came out of a 73 car). I just wanted to see how difficult it was to get to the jets. I am assuming the carb should be taken off the car in case you drop something down the hole.

 

Yes it would be prudent to take off the carb, to avoid the risk of dropping the pesky small parts. I like to use a small tray, like an old baking sheet. Not the one the wife bakes with.

 

I second this , also one should look at his forum as well.. I used his 44 primary rod to richen up a bit knocked 10F Deg off heat and runs great now kept stock 70 primary. Jet

https://cliffshighperformance.com/simplemachinesforum/

 

Conventional wisdom lately has been to jet the carb one or two steps richer when using ethanol laced fuel.
These carbs were originally calibrated for straight gasoline. Ethanol laced fuel has less heat content per gallon than straight gas.
Usually, a change of one or two sizes richer in jets will make up for the ethanol gas.

 

Ntoice how the carb jet/rod kept getting leaner as years went by due to emissions

https://oldsjunction.classicoldsmobi...sfaq/ofcrb.htm


FYI last two digits in jet /rod spec # are size

 

The fuel with less hydrocarbons like Phantom said leans out the mixture and so does a free flowing exhaust. Changing the primary fuel rods will solve your primary lean condition.

 

The Q-Jet I ran on my car had APT screw, that makes it MUCH easier.

You need to find the lean limit. The way I did it (and the way explained in the Q-Jet tuning manual) is to drive the car at a steady highway speed, and pay attention to how it runs. Then either turn the APT screw out a little at a time, or go one step leaner on the metering rod. Drive the car again on the same road, ideally under the same weather conditions. Keep leaning it out until you feel a lean miss, it kinda feels like a fish nibbling on a hook. That’s your lean limit, go a couple steps richer.

once that’s done, you can play around with different spring rates on the power piston, secondary metering rods, etc.

Widebands are great tuning tools, but people managed just fine for decades without them.

I ran my Q-Jet with the part throttle cruise for years set the way I described. I bought a LM-1 wideband from a friend and put it on, imagine my surprise to find part throttle cruise at 15.5-15.7. That’s far leaner than I would have ever considered, I’m guessing that played a huge part in why I could knock down 17mpg pretty easily.

Give the engine what it wants, not what you think it needs.

 

I don't know if mine has that screw adjustment. I think that was on the next generation

 

Early APT was in the throttle body. Centered between idle mixture screws. Could be still capped off yet. It takes a little work sometimes to free them up, but when you get them out give Cliff R a call and he has a replacement that makes adjustments much easier.

 

The tuning process is the same, it’s just more difficult with the older carbs.