scooter500

iTrader: (1)

What hangers & rods work well for higher MPG?

The carb is set to factory settings.

It's running good using a "G" hanger and "CH" rods right now.

Response is good/smooth, just wondering how to tweek for better/best fuel economy.

Thanks -

five7kid

iTrader: (14)

Rods & hanger don't influence MPG. If you're employing them, you're gulping gas.

scooter500

iTrader: (1)

Don't some gulp a little slower though?

scooter500

iTrader: (1)

ok, what hanger(s) & rod(s) would help open up faster, if I wanted to get ready for the track?

Damon

What he means is that secondary rods and hangers don't affect fuel economy since the secondary side of the carb isn't feeding any fuel into the motor until you open it up- beyond about 1/2 throttle or so when the throttle linkage begins to open the secondies.

Don't know the specs on your motor, but if you've got a set of CH rods in it now I think you'll like the improvement that a set of DR (305 HO rods) gives you. Your G hanger is fine.

scooter500

iTrader: (1)

thanks - got that down for an option someday.

reason for asking was remarks in Roe/Ruggles books made me wonder if there was in fact a more lean set-up for hangers/rods (lean set-up not specifically talked to in books). I see the big point: using secondaries = more fuel = lower MPG.

five7kid

iTrader: (14)

Any leaner than CH, you might as well tie the secondaries shut.

scooter500

iTrader: (1)

lol I could not figure it out from the books. stick w/ the G hanger as well?

jordo2114

sorry to steal this thread if i am but mine bogs if u punch it and will almost stall out until i let out i think this means i am lean i have stock hanger and rods i think the hanger has an I or an H lol but how do i tell what the rods are and what should i switch to thanx

FlippindaBird

iTrader: (10)

sidebar...

what rods came stock on a 1987 LG4???

different from other years??

jordo2114

mines an 86 lg4 i found the rods were CH and the hanger must be an I

Fast355

iTrader: (2)

My stock 1983 305 had DRs on a F hanger from the factory.

FlippindaBird

iTrader: (10)

ok new question, i have never actually pulled mine yet, its probably real lean though... but how would i know what rods and hanger it had??? is it printed on them??

chesterfield

DDs on an I hanger.

scooter500

iTrader: (1)

yes, I can tell you about the stamps into the metal. Hangers are stamped right on top w/ letters ranging from B to V & rods are stamped w/ 2 letters.

What I don't know is if a G hanger is considered lean, and if not what's a better choice for a commute to work, and overall if hangers and rods are matched (presume they are but don't know principles) - hopefully we'll get some schooling here shortly

chesterfield

http://home.earthlink.net/~quadrajet...ow_ratings.htm

I love Quadrajets. I just love 'em.

Fast355

iTrader: (2)

My Cadillac 307 vin 9 had DDs on a K! Knowing they wouldn't cut it on the stock 180 HP 307, much less the 300 hp 403 that was going in its place, I swapped to a DA rod on a G hanger and all was great, even on the stock 307.

http://www.hioutput.com/tech/qjetrod.html

Keep in mind that the stock opening under the secondary rods is .1360 on all Q-Jets and is not easily changeable. The smaller the end of the tip (90* airvalve opening #) the richer the WOT A/F ratio will be. You can have several tapers using the same power tip size. The difference here is small but substantial. The difference in taper along with the hanger is how you adjust the mid-range air fuel ratio. The small end of the taper is how you adjust the high rpm air/fuel ratio. Also keep in mind something like my stock 307 is only going to slighly open the secondary air valves and only going to pull so much air/fuel into the engine. A stock base 305/307 may only pull 30% of the air valves opening where a built up 400 may pull 70%+.

Sonix

iTrader: (1)

DD's are FAT!!! (lean!)

A bog going into the secondaries is usually caused by a misadjusted air valve. Set the tension right.

If you go to a different letter hanger (that basically tells when it STARTS to raise the secondary rods), that'll make it go rich SOONER. HOW RICH is defined by the rods.

It's a tuning tool. We can't sit here and tell you what you need, try a bunch and see what runs best.

Fast355

iTrader: (2)

Exactly.

DDs are the LEANEST factory Q-Jet rod made. They came in most of the 140ish HP cars like the factory 307s, LG4 305s, and 4.3s. I know for a fact that my Cadillac could not get out of its own way with the DD rods and the 1/2 blocked secondary air valve.

All rods start out with very similar closed (0* air valve opening) sizes. As the air valves open the rods then taper toward the smaller power tip end. The power tip end size varies depending on the rod. The overall taper of the rod also differs depending which rod you have. You can have two drastically different rods with the same power tip size.

You can also fine tweak the A/F ratio by the hangers. B-V where B is richest by pulling the rods out the soonest and V is the leanest with the latest openings. DRs on a F/G are a good place to start for most builds.

Years ago Hot Rod magazine built a Junkyard jewel engine running a Q-Jet carb. They took a mid 70s 350 and put 083 TPI heads and a mild comp cam in it. The engine made 320 FWHP using a DR rods on a T hanger (13:1 A/F ratio) and 32* total advance @ 3,600 RPM. Proof you don't have to go huge on the rods to make good power.\

http://www.corvetteclub.org.uk/files...une_a_qjet.pdf

scooter500

iTrader: (1)

Thanks everyone, the tips and links are great! I might try a K or similar hanger if I happen to see one ... on the way to trying to create the ... lol ... commuter dream car!

Guro 305

So what's the best combo for power?

Sonix

iTrader: (1)

the one that keeps you in the right AF ratio across your power band.
It's a tuning TOOL, we can't tell you which one to get for your engine. That's like asking what the right belt size is.

Guro 305

Not really. You could simply say I don't know and that would suffice or you could also give different examples for different setups.

For example, mine is a 305 with just headers and a 2.5" exhaust all around with a high flow cat. So what would be a good setup to use to maximize what I got?

Sonix

iTrader: (1)

I could rattle off examples until i'm blue in the face, and it wouldn't do you any good at all.
I don't know your altitude.
I don't know your driving style
I don't know your engines modifications
I don't know how many miles are on the engine
I don't know which headers you have, or if you have single or dual exhaust
I don't know which rods/hangers you have available to you

So since I know so very little, i'll give a complete wild guess, and satisfy your thirst for tangible information.
Use a K hanger and DR rods, stock for an L69. How's that?

Fast355

iTrader: (2)

Funny how the L69 used the K hanger. The LE9 Van/Truck engines used the same DR rods on a F hanger, atleast my stock 1983 Q-Jet did. 17083226.

scooter500

iTrader: (1)

Cliff Ruggle's book lists 3 combos for power, depending on engine, etc. set-up.

I'm going to try different hangers for fuel economy. Cheap experiment.

Guro 305

a) Read my location. Thats no more then 12ft above sea level tops.
b) Ok, I like to DRIVE my car. I like power and acceleration. I don't however go 60 down a residential and more then 90 on the highway.
c) Yes you do, I told you only headers with a highflow cat and the exhaust is 2.5" all around.
d) approx. 154,000
e) Headers are from Summit. Y-pipe is also from Summit. High flow cat' is from Magnaflow. Stock 2.5" setup from the cat back.
f) That, I will have to check and get back with you on.

Fast355

iTrader: (2)

Even if he had all that information, it is ultimately not going to matter. EVERY engine is different in regards to tuning. They can be similar, but to get where you want to go, its going to take some experimentation. The rod that is best for power can also be best for fuel economy because ideally you should not be even close to tipping in the secondary side if you are trying to get good gas mileage. 95% of your fuel delivery is controlled by the primary side of the carb. You should start your tuning here and get the primary side optimized before you start on the secondary. Keep in mind on the CCC Q-Jet you only have one size of metering rod, but you can change the jets. If you change the jets keep in mind that the CCC Q-Jet rods are like the 80s M tipped truck rods in that the power tip is larger diameter than the normal power tips, resulting in less fuel flow for the same size jets. Its not really a problem but rather a detail. I would start with the stock jetting and disable the secondary side of the carb. With the secondary side disabled and the Mixture control solenoid unplugged you are going to want to find an area clear of traffic where it is safe to do some WOT runs. You are going to want to time the runs over "X" distance. Typically the CCC Q-Jet primary side is set very lean, even with the mixture control solenoid disconnected WOT is lean. I have seen stockish LG4s as leans as 14:1 @ WOT. I would shot for about 12.5:1 @ WOT on the primary side. This is generally where you will find that your car runs the quickest. Once you get the jetting right, you will want to adjust the idle mixture screws and IAB Rich/Lean stops to achieve the desired mixture control solenoid dwell so that the ECM can control your part throttle fuel delivery to keep your emissions low and your fuel economy high. Once you get the primary side dialed in, you can start to work on the secondary side. First properly set the air valve, I like to use 7/8-1 turn on the spring. I find this works best for most lower rpm applications where a tight torque converter and numberically low gears are used (your stock LG4 car). If you go too loose the car will have a nasty tendency to bog during the transition to the secondaries and even when the transmission makes an upshift @ WOT. Make for sure your vacuum break only takes about 1-1.5 seconds to release or a sluggish transition to the secondaries will result. Now you can start working with the secondary metering rods. Time out your acceleration runs, using various metering rods. DRs are typically a good place to start. They have a nice tapper and power tip to them for a 200-300 hp street engine. You can also alter where he enrichement happens in relation to engine load/rpm by changing the hanger. The hanger really is just to fine tweak the secondary a/f ratio. At 90* air door opening, all hangers are equal, but at the lower openings, they vary widely. If you find the engine leans out as the secondaries come into effect, drop to a lower letter hanger. If you find it goes to rich as the secondaries kick in, go to a higher letered hanger. Hangers go B-V, IIRC.

Sonix

iTrader: (1)

Thank you Fast! I was just trying to make the point there.
I don't have a magic calculator that I can put in all that information, and spit out a recommended setup for you ( although that would be nice...)
You need to tune it yourself.

Guro 305

Yeah but come on. At least Fast lent a little more sense of direction.

That's all I was looking for anyway.

Sonix

iTrader: (1)

My bad. I'm just getting lazy
https://webdisk.ucalgary.ca/~jmknopp/public_html/
Read the top three files (the .doc files). They are excellent q-jet tuning articles.
If in doubt, use Fast355's advice though, his was specific to cc-jets, where my articles are specific to non-cc (well, Lars' articles, but i'm hosting them so...)
Many of the concepts are good for both carb styles.

Guro 305

Yup yup. CC all the way!