NightHawk84

I own an 84 TA LG4 4bbl. I'm switching out the 305 for a 92 L98 350, and I'm keeping the 84's Rodchester Q-jet. I know I need to rejet it, and I know what I need, but no one seems to have the parts... here's the situation:

1) I called Champion. They said they have the Q-jet (part # 3-638) for the police interceptor version 350. This is all good, but it's a ~$400 carb, and I was told all the parts from this Q-jet will fit into my current one. The only problem is, they don't sell jets, rods and hangers for carbs... only complete rebuilt ones. They said Edlebrock bought the machinery from GM and to try them....

2) I called Edlebrock. They said they make a Q-jet, but it is a non-electric one called "M4M", and that mine is called "M4ME". The tech guy didn't know if the M4M jets, rods, and hangers would fit or work in my M4ME, but they do sell the parts for the M4M.

So I am asking... will Edlebrock's M4M Q-jet rods, hangers, and jets fit in my 84's Q-jet??? If not...

3) Who sells rods (DA), hangers ("B"), and jets (What is a good sized jet for this application?) for an 84 Rodchester Q-jet??? Would a dealer have them?

I've tried NAPA, Pepboys, Advance...ect. Any help would be much appreciated. After all, I'd rather spend $40 on jets, rods and hangers and $100 to get them insatlled, than $400 on a new carb.

howardhughes

why do you think you need to rejet it?i know q-jets like the back off my hand i believe they're the best carburetor ever made.there's way of reducing the air flow to the secondarys to give more fuel.there's also a thing i made up called knifing the q-jet.it was later stolen from me.guess i shoulda pantented it.if your interested in anything i've said.and you have some knowledge about the quadrajet,i.e.take apart and put together.let me know i might be able to help you good luck

Momar

Could you explain this knifing?

Ben

howardhughes

sure it's like port and polishing heads only you do it with a carburetor.

Momar

How would one go about doing this, and is it worth much of a gain?

Ben

five7kid

iTrader: (14)

Typically, the only tuning you need to do are adjustments and secondary rods/hanger. Here's one possibility for the parts http://www.carbs.net/rodshang.asp , they do carry the DA's and B.

The secondary jets are not replaceable. You just change the rods and hanger to change the secondary mixture.

Someone in the recent past talked about a "L69 kit", that includes primary jets & metering rods. Supposed to allow the computer to provide a richer mixture for healthier engines. Not sure who has that available, you might try a search of this forum (or the motor swap forum, not sure which I saw it on).

Momar

I already have the metering rods and hanger for mine. I was just curious. I am going to be putting mine on a 350 that hopefully will end up with decent power. As far as the primaries, I didnt think you needed to jet them either because you can adjust your fuel flow and mixture and soforth and the computer takes it from there? What good would this kit do? Maybe quicker response? If the primaries were richened though would we have to find a different combination for the secondaries to match it?

Ben

howardhughes

it's a little lengthy.when i have more time later today i'll go into it.the ones i've done the people were happy.

five7kid

iTrader: (14)

The computer does control the mixture in closed loop, but as I understand it, with a larger and/or healthier engine than the LG4, it is possible for it to be lean even with maximum solenoid dwell. The kit gives a richer potential, and also, as you say, better trottle response.

The secondaries pretty much overwhelm the primaries at WOT, so even if the primaries are slightly richer, you probably won't have to redo the secondaries.

I don't have any problems with the primaries on my setup, even though the cam is much, much larger than the LG4, and flow capacity of the engine has been similarly increased. Part of that may be due to the fact that I drive at 5800' elevation.

Momar

Ok, since my car is not running yet, I havnt got the chance to try to tune my quadrajet yet, but from reading on the boards, I got the idea that you could adjust your richness/leanness until you got it into the range that the computer could compensate for? I do remember one guy saying that he had changed his jets on one of these I think though. I think it would be interesting to see what kind of a difference it makes.

Ben

Auggie

Well, I have a stock Q-Jet on my 355 and also on my brothers 406 and neither of them have any mods done to the pri. side of the carb. Both carbs are computer controlled. I have been useing an Air/Fuel Monitor gauge from K&N for years. Both of these carbs have been modified to 750cfm and new metering rods and hangers installed. The way I go about this is to install a strong spring on the sec. lockout arm so the sec's won't open. I find a nice lonley road and do a couple WOT runs and check the fuel monitor and both carbs run around 13:1 air/fuel ratio on the pri's only. Then I remove the spring and repeat the process on the sec's. I have used these A/F monitors during dyno pulls to verify their readings and I got to tell you there right on. Just my .02.

Auggie

Momar

How much do these gauges cost and how do you wire them up?

Ben

Momar

To modify them to 750 all you have to do is grind and slot that tab right? What are the specs on your 355 and what rods and hanger are you running?

Ben

NightHawk84

Thanks for the info all... I'll try Carbs Unlimited five7.... thanks for that. I'll let you all know how it goes.... thanks again.

Auggie

Well Ben, the spec's on my 355 are as follows:
C/R = 10.3 to 1
Manley Flat top Foraged Pistons
305 60cc mod heads
Cam Dynamics cam
222* @ .050 Int & exh
Int Lobe Center = 107*
Exh Lobe Centers = 113*
Lobe Sep. Angle = 110* (idles a little rough)
3* Adv.
Valve lift = .467
750 Q-Jet (computer controlled)
SLP 1 5/8" headers (no cat)
NOS/150hp
I don't know about sloting, but I do grind off the tab and install a set type screw above it which allows me to control the amount the sec. air valves open.
The hanger I settled on is the letter (I). The metering rods I use are CE .041" Edelbrock #1951. These are slighty rich but when I push the button I feel better when all the LED's light up on the A/F monitor. Before I installed the NO2 kit I used (AU .053) metering rods. You can buy A/F Monitors from Summit for around $30 (Pg. 154).
They use 12v and an oxygen sensor. I removed the 02 sensor for my computer and used it for the A/F gauge and installed the new one for the computer.



Auggie

Momar

What are those heads you are running? Do you have the casting number, or are they aftermarket? I have a set of 305 heads that have been ported and gasket matched, and I was considering using them but have been told that they will still only flow about as much as a stock 350 head if I have the 1.94 and 1.6 intake valves installed so I have been looking for a set of used aftermarket heads for a decent price. Do you have any track times or dyno numbers with that setup?

Ben

Auggie

Well, who ever told you that was right. They are also thin castings. I used them because I had them. Track times are as follows.
With the NOS = 12.62/111.92

Without the NO2 = 14.28/98.78

Auggie