hullinger

I've got a bone stock '73 Custom Cruiser that has a Q-jet from a same year 350. She runs way too lean and after opening up the carb I found the jets were 69 and metering rods were stamped 53C. I searched for an hour now and haven't been able to find what the stock jets and rods should be. Can someone shed some light on what I should be putting back inside the carb?

Chris

Fun71

The info I have goes up to '72 but it might be of help. It shows the same 69 jets but a richer 50B rod in '72.

Year & Application...Carb #......Main Jet.....Primary Rod................Secondary Rod

1970-350..............7040250...7031970.....7040701- "52C".........7033658- "AT"

1971- 350..............7041250...7031970.....7034849- "49B".........7038256- "AS"

1972-350.............. 7042250...7031969.....7034850- "50B".........7045778- "CG"




edit: I just realized this is in the Big Block section. Does the VC have a 455 in it? Here's the info for the '72 non-442, non-Toro 455. Same primary rods/jets on the 350 and 455 in 1972 it appears:

1972-455.............. 7042251...7031969.....7034850- "50B".........7045779- "CH"

hullinger

Kenneth,

Thanks! That's fantastic and yeah, she has a 455. I really appreciate your help.

Chris

455man

Google q jet tuning paper. There is a good PDF article and about halfway down it lists the jets and rods for qjets. It might help ya.

billmerbach

I've seem these papers on eBay called sun tech or something like that an olds guy has a whole cabinet of tuning sheets I can email him and see if he has one for a 455 of your year engine it gives a while engine tune up specs

turbobill

I have some accumulated data from tearing apart Q-Jets over the years.

One 455 Olds Q-Jet had 70 primary jets with 49B primary metering rods. Secondary side had a part # 31220 hangar with AU metering rods. I didn't note the year.

Another 455 Buick (1972) had 73 primary jets and 48B primary rods. Secondary side was an M hangar with CT secondary metering rods.

430 Buick (1969), 70/45B primary, K/AY secondary.

Couple of '74 Olds 455's, O/AX and L/CG on the secondary side. Didn't record the primaries.

If I recall, the power tip on the all the primary rods is .029" with the exception of a motorhome engine.. The two digit number on the rods is the cruise tip size. If you mix and match jets/rods, calculate metering area (area of the jet minus area of the rod).

hullinger

Thanks for all of your help as I really appreciate your time and info. What I'm finding and struggling with however is a whole lot of conflicting data on the factory specs for rods and jets.

The carb on my '73 Custom Cruiser was replaced with another Q-jet when I bought the car a few months ago. The engine is bone stock and had a bad light throttle, low RPM bog while the spark plugs showed a very lean condition. I pulled the carb and saw the jets were 69 and metering rods were 53C. I suspected the carb was set-up more for a 350 than the 455 that I have. So, I upjetted the carb to a 70 with no change in the bog. I changed the jets again to a 71 and now she is running and accelerating as smooth as silk but the spark plugs are still showing a lean condition. I think I need to richen up a bit more but don't want to overdo it and blow up my already lousy gas mileage.

So without the Q-Jet tuning papers listing a '73 Olds 455 I am really hoping for some advice on what I should do with the metering rods to really dial in the carb and get the air/fuel ratio right where it needs to be.

Chris

turbobill

Fuel mileage and a '73 Custom Cruiser are going to be mutually exclusive, especially in city/urban type driving. Even under perfect air/fuel ratio conditions, mileage isn't going to be great with a car like this.

Things working against you are a 5500 pound curb weight, low numerical axle ratio combined with a torque converter (lots of converter slippage) and the '73's also had EGR (mileage and driveability killer), low compression ratio and transmission controlled spark (no vacuum advance in first and second gears). Some of this stuff can be mitigated. Transmission controlled spark can be bypassed. EGR can be disconnected.

Other things can be done to help. Make sure your vacuum advance is working. This item can be a mileage/driveability killer if it isn't working. Make sure your mechanical advance is free and working. Set initial timing a couple degrees (or more) advanced from the factory emissions setting.

One of the biggest improvements I saw in cars like this in both mileage and power was a true free flowing dual exhaust system. Dual exhaust was optional, but seldom if ever ordered.

Try disconnecting the transmission controlled spark, EGR valve, and make sure the vacuum advance is working before jetting richer again. Also add 2 to 4 degrees of initial advance.

61reoldsman

check this page out ...www.route66hotrodhigh.com/PowerTuneQjet.html
Lots of good info for quadrajet tuning Olds specific.