Hi to all. I have an ongoing condition with my camaro. I suspect is either something on my engine set up, since i have tried several carbs with little change in condition. I have an overbore GM ZZ3 short block (355) with flat pistion (CR 10.5), and topped with a Trickflow Twisted Wedge ALimun heads(62cc) and an edelbrock performed intake. The camshat is the the GM ZZ3 (221:208, 112) and I am using Crane Gold Roller Rocker arms (1.6 Ratio). The engine in completely mechanical (no ECM, no EMISIONS). It has a factory Mechanical q-jet from the 70. For the ingnition, I am using mallory unitle comp 9000 serios (vacum advance) along with the Mallory Hyfire VI electronic module. The engine runs fine, idle nicely, no type of smoke at Tail pipes, and not backfires, just smells! However, my problem is that I have this strong gas odor at the pipe. Is like there is some unburned fuel pasing thru. The smell is noticiable. I have tuned and retuned countless of time my Q-ject. I am sure that my factory plugs are not leaking. I cannot lean out my mixture any more. I have tried other carbs with similar or worts results. One car I got from JET performance had the worst emission ordor. It literally desintegrated the internals of the Catalytic Converter. Here is my opinion: 1) The problem could be in the Ignition timing. Since I am using Roller Rocker arms of 1.6 ratio, the valve train geometry is compromised and setting the distributor timing at zero is not the best posible adjusment. Should I advance or retard the ignition? 2) Having a High compresion ration could somehow be responsible to this odors. I know I am close to the solution, but some pointer could always help. Thanks!!!

your cam and valve train timing (and 1.6 rockers), are not directly related to your distributor.

what timing are you running? base, and full?
0* timing is definately not right, just want to make sure you're not running that. Cam is 221/208? that right? I'd say start with 14* initial, 36* full, and no vacuum advance for now, to tune it.


Now, you say you're sure you don't have leaking well plugs, so:

what primary rods in the carb?
what primary jets?
secondary rods? hanger?

is the smell at idle? only ? or all the time?

is your choke setup right?

Thanks for you post. currently my timings is set at Zero. I will follow you advice an play with 12 & 14 Degree advance.

The carburator I have if from and 1970 350. I will port the info of the carb later on (I have to look for it).

The carls smells all the time. If I WOT I will get a black smoke (the one from unberned fuel) otherwise no smoke whatsoever at the Tail pipe.

Thanks for the feedback!

ok yea, first off, boost the timing hardcore. F-bird will probably chime in, as I have very little experience with anything aside from a stock cam.

but i'd guess 14* would be an ok starting point. you may have to shorten mechanical/vacuum advance, depending on the dist, we'll see how difficult that is. but yea, wayyyy more timing for sure.

then we'll see what rods/jets you have

THanks, I have to keep an eye on my dyslexia, Man, what I wrote/posted before was in code!

I should know what jet, needle and hanger I have by the end of this week!

thanks!

Here is the info about the caburator.

rod : 50 MM

Jet 74MM

According to the Edelbrock Performer RPM Q-jet Manual, on the Calibration Reference Chart, this carb should be Base.


I will dismantle the carburator, orverhauled, set the timing in 12 Degree, and keep you posted.

Thanks

Know what the secondary rods are? (those are EASY to check.)

Technically, those are 50M (perhaps, or just 50), and means it's got .050" as the dimension worth mentioning. The 74 is also .074" opening.
not that that really helps...

I think that's a pretty lean setting for a fairly beefy motor. Generally they say .030" difference is about right. So for 74 jets, 44 rods. A fatter rod will be leaner at times when vacuum is high enough to pull the primary piston down, idle, off idle, cruise, but not high throttle. I don't think those need changing now.

I don't think you need to fully rebuild the carb (unless you think it's old and could use it), but here's a good starting point.

-Bump up timing
-check float level (might be too high)
-once timing is higher, the car will want to idle higher, so you can turn down your curb idle, until the car is at the "right" rpm. (whatever you like, say 750RPM).
-reset your mixture screws to highest vacuum

I think that should probably cure it, with that little timing, you probably had the curb idle cranked pretty far open to get it to idle, so it would have been a bit rich, and may have had a slight bog as well....

This condition persist in all my three mechanicall Q-jets. A couple of years ago I really wanted to learn the q_jet, so I went to my local Junk Yard and bougth a couple. I will never forget how many they them pile over a 55 GAL drum.. It was a painfull site.

I really dont think is the carburetor internals. This one was rebuilt last year, and I only use the car on the weekends ( my weekend warrior ride).


But to cover all bases, I will take it out, clean it, and rebuilt. THem I will adjust the timing. I want to make sure does epoxy sealing are still good.

I will keep ypu posted on how it turns out.

Thanks

yea, they're dime a dozen in JY's, i've got a stash, along with extra parts as well

I think you may be wasting your time re-rebuilding it. But hey, your time is free, and I guess you're not freezing your hands down there while trying to do it eh?

Let me know how it works out.

You are rigth, I lived in michigan for a while. working on the car was a real pain...

Now, in the tropics, since I live near one of our former bases, the rainfores it rigth there, with all its Jurasic Period insects. Man, work at night, and next thing you know, you are been ambush by them.

I agree with you, it might be waste of time to rebuilt the carb. But for my camaro, I do strange things. I will adjust the timing first, see how it behaves. I might have to recalibrate it.

Right know I am rebuilding the body of the car. I had some rust in the floor. I dismantle the whole interior, cutted out the rusted area, and later I will weld some sheet metal. Its going to be a long restoration.. I will enjoy every bit

Thanks, I keep you posted on the timming impact.