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Carburetors Carb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.

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Old 01-24-2011, 01:29 PM   #1
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Edelbrock 1406 - Setting timing, strong gas or exhaust smell

Forgive me, I'm sure these questions have been asked numerous times, but I didn't have luck finding specific answers when searching.

I have a '82 Trans Am with the LG4. When I purchased it, it had an Edelbrock intake and 1406 on it. To my knowledge, the rest is stock other than a cheapo air cleaner on top of the carb. I've been fighting a very strong fuel smell, even at idle. I'd adjusted the carb numerous times but still no luck. However, I'd never checked the timing. After checking, I'm not sure what it was at, but I couldn't even see the mark, it was seriously advanced. The first time I set the timing, I didn't help matters since I thought the timing mark was a little white dot, not the engraved line. So I was setting my timing using some speck rather than the real line. After talking to Edelbrock's Tech-line, they recommended setting the timing to 10*. The sticker under the hood says 6* at 500 RPM in Drive. Unfortunately, I'm usually working alone so I can't set it with the car in drive. I need to talk my wife into sitting in the car while I set it I suppose, but she hates coming near it because of the smell, lol. This isn't my picture, but this is what my timing mark looks like:

Click the image to open in full size.

Reading this from the article on the site:

If you still can't read what's on your timing mark: Assuming you are standing in front of your car, facing the engine, the "valley" of the biggest of the v-shaped notches should be zero degrees.

The Vs are upside down when you look at them from the front of the car.

The next peak (pointing towards you) to the left of the big V is 4* advanced, one more peak to the left is 6* and so on in 2* increments.

Accordingly, the one and only peak to the right of the big V is 2* retarded.


If I understand that correctly, that corresponds to the marks on the pic, right? Does 10* at idle sound right, and correspond to about 6* in Drive? If that pic is right, I don't have a 10* mark, so I just set it so the engraved line is about the same distance from 8* as 6* is. Does that sound right?

Afterwards, I've adjusted the carb by unplugging the vaccuum line coming from the distributor (which I have plugged into the passenger's side port, which does not have full vaccuum at idle,) moving my cap that's normally on the driver's side (full vaccuum) port over to the passenger side, then hooking up a vaccuum guage to the driver's side port. I've adjusted the two idle screws back and forth many times, and it now pulls right at 20 hg. It actually slightly jumps between 20 and 20.5 hg. Some of the posts I've read on the boards say you should then move over to the passenger port and adjust again, but as it doesn't have any vaccuum at idle, I get no reading to adjust by. That's should be correct, and the whole idea between the two ports, right?

Does all of this sound correct? Any other options to make sure it's tuned just right and to get rid of the smell? Since doing this, the gas smell has gotten MUCH better, and really is more of an exhaust smell. I would just like to get rid of it as much as possible as I hope to do new interior soon and don't want the smell to get into the new stuff. I can actually still smell it on my clothes as I sit here typing this.

I've also put new plugs and wires in/on, but probably haven't driven 10 miles since then honestly, so I'm not sure if I can read the plugs that soon or not. I've also taken it to an exhaust shop to put on the lift just to make sure there's no holes or leaks in the exhaust.

ANY advice is welcome, and sorry for all the (probably repetitive) questions!
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Old 01-24-2011, 09:22 PM   #2
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Re: Edelbrock 1406 - Setting timing, strong gas or exhaust smell

You've got the carb tuning right - with that vacuum guage method - tune to get the highset vacuum possible. Then adjust idle back down if needed with the idle set screw on the linkage.

You're right with the timing as well - as far as the tabs go - each 'valley' is 1 degree, each 'hill' is 1 degree - but the first notch is wider (longer), and so the first 'hill' is 4 degrees like you've got shown. 10* won't show (no notch for 10) - so you kinda have to guess.

But - regardless of notches - where to 'get it right' is the point where your car 'likes it best' - if that makes sense. Really doesn't matter to anyone (but the car) where exactly that is. It just helps when trying to set it to have a place to reference.

Forget the "in drive" part - doesn't matter right now. Besides, it's dangerous - if your life insuranxce is paid up, the wife might just run you down, collect the cash, and cry it was an accident! Just set the timing where the car likes it, and adjust the idle screw on the linkage a bit here and there to bring the idle back up/down after you get the timing set good. Slightly rich is better than lean - not burning gas as efficiently, but lean can mean bad things (like holes burned in pistons).

So, set the carb screws where you get the most vacuum with car running. Then play with the timing - I carry my timing gun with me, and go for a ride. Punch it really hard - if you get spark knock at WOT, then timing needs to probably come down a hair - adjust, drive more and try again.

If you want to get better throttle response after that, then order a timing tape (Mr. Gasket makes them, get from Summit). Like $8, it's a roll of tape that adheres to your balancer - it tells you what timing is when you are looking at the 0 mark on the tab. So, if your timing is set to 8 degrees advanced - the line for 8 degrees will show AT THE ZERO point on your tab. You have to measure the diameter of your harmonic balancer and order the right size (think mine was 6 in, think there's also a 6.75in). It allows you to see timing at higher RPM's - thus you can see what folks refer to as total timing (the timing at WOT). But you really don't have to go to WOT - at about 3000rpms the timing usually maxes out. You want a total timing of about 32 - 36 degrees BTDC at 3000 RPM's. So then, you can adjust the timing up some to get closer to that total timing at 3000 RPM's. But keep in mind, you don't want to have any spark knock either, so you can't always adjust the timing to get up to 36* at 3000RPM's.

It's because the weights and the vacuum advances the timing at higher RPM's - different weights and springs allow more or less timing to be added at higher RPM's. Stock distributors don't really come with the right weights and/or springs to advance the timing enough to get toi that theoretical 36* at 3000 RPM's.

That's where I'm at. I have my base timing set at 11* BTDC, but my total at 3000RPM's will only get to about 28* - I need different springs and/or weights in my distributor to get a better timing curve at 3000+ RPM's (to get more timing to come up faster). But if I set my base timing higher, I get spark knock, which is bad.

Hope any of that makes sense.

Basically, set carb to get most vacuum, set timimg where the car likes it, and re-adjust carb again (idle screw). You should be able to get most of the richness tuned out so that it doesn't smell so bad of gas that it runs everyone out of the neighborhood. Usually, if you increase timing, then your idle goes high, and you have to adjust idle down some.

It's a proposition of adjust this, tweak that, readjust this, tweak that again, check this, readjust that, tweak again - until you find a sweet spot where car is happy and no one has watery eyes.

Oh - and fuel pressure - do you have a guage? Get one and install close to the carb - on the 1406, you want no more than 5.5psi - think I'm set at 5psi. If it's over 5.5, you'll need to maybe get a regulator and bring it down some.
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Old 01-24-2011, 10:22 PM   #3
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Re: Edelbrock 1406 - Setting timing, strong gas or exhaust smell

Thanks a lot for the reply! A lot of good info in there! I thought I had to have the procedure for the carb right, but I just wanted some verification.

You mention that you have to get it where the car "likes it." I get that that's probably going to be very subjective, but how exactly do you tell? It seems like it's idling nice and smooth, so the only other thing I have to really go off is the smell I suppose. You also say that slightly rich is better than slightly lean. How exactly can you tell? Sure, it's idling smooth, but I could increase the timing, making the RPM go up, then just bring the RPM's back down with the idle screw right? Then it would still probably idle smooth but be richer or leaner than before. What are the signs to look for?

Forgive my ignorance again, but what exactly does spark knock sound like? I've always heard of it, but not sure I've ever heard it. Is it more of a knocking, or metallic 'pinging'? Is it something you'll definitely notice, or are there varying degrees of it?

How do I know what RPM's to shoot for? Go for what's on the sticker under the hood? Or is it pretty much subjective as well?

I'm sorry, I forgot to mention that I'd tested the fuel pressure as well, and it was in the 5-5.5 range.

Finally, IF everything is tuned right, shouldn't pretty much all the smell go away? Obviously, if I stand in the exhaust is one thing, but to just be around the car and then smell it on my clothes once I come in? IF everything is tuned right and the smell is still there, what could that mean? Just an old car? Cats need replacing? Can they go bad? Anything like that?

One other thing, my timing gun is a Harbor Freight cheapo. There's no dial or numbers or anything, just a weak light. This still should be fine to set the base timing at idle though, yes?

Again, thanks a lot for the response and advice. I really appreciate your time!
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Old 01-25-2011, 01:48 PM   #4
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Re: Edelbrock 1406 - Setting timing, strong gas or exhaust smell

Yes, "where the car likes it" is quite subjective, and can vary alot really. But it's a starting point. Like you said, you can bump up the timing, and lower the idle at idle screw, and not really notice a difference at an idle - but you might notice other changes. For instance - when I did mine, I had low vacuum - not enough for brakes (a slightly lumpy cam). But I noticed that if I increased timing, and lowered idle with screw, I could get same 'good running car' with greater vacuum (now enough for the brakes). So - to a degree, adjusting the timing up and readjusting idle down will increase vacuum. If the vacuum is increasing, there may be better (or worse) fuel efficiency as well (ie more or less of that gas smell). I never thought about the gas smell at the time, I was concerned with my vacuum and brakes - so I didn't notice - but you get the idea.

Rich vs. lean - rich will make your eyes water when your face is in the exhaust, and you'll smell unburnt gas. Now naturally you don't want it that rich.

If it helps, I think my screws on my Edelbrock are set at a point about 2.5 turns out - if you screwed both all the way in, and then turned them out 2.5 turns, that's about where I'm at. Also, note that changing the screw may take a minute or 2 before you actually notice the change in idle or exhaust - should only be a few (like 5) seconds when watching the vacuum guage.

On the spark knock - yes to the pinging. If you've ever heard a car that supposed to have super but was running on regular, then you know the sound. Like I said, you want to punch it hard, and listen for that knock - if you have it, chances are (from my experience) that you need to back the timing down a degree or 2 and try again.

On the RPM's - Not too many folks that I've ever seen with an aftermarket carb ever have an idle below about 800. Mine is set at about 900 or so - my car just seems to like it there a bit better - when I went lower, sometimes it wants to idle too low, and higher than 1000 just seems like too much to me.

On the smell - my car runs rich as well - but it kinda prefers that, so I don't mind. It's not eye-burning gas smelling rich, but it is rich. I have to be really warmed up well (like water temp above 190) in order to not have a 'soot' spot on the driveway under each tail pipe - but all carb cars will usually run that rich when cold (because of the choke).

It's kinda difficult - OEM the factory carb and distributor worked together electronically, and could adjust each other based on ECM inputs - there wasn't a need to have timing set higher than maybe 4 degrees because the cc-distributor could advance itself at any time, and could advance itself higher than an aftermarket standard vacuum advanced distributor. But now, you don't have those fancy gadgets, and you have to find a happy medium with mechanical and vacuum advancing on the timing, which usually means setting the timing up higher. 10* BTDC seems to be a good starting point for most to get the car running and start tweaking. But given that your factory timing tab doesn't even show that mark, it's all weird (in your mind).

Check into that timing tape - it helps alot. Another trick - grab some white fingernail polish - by hand turn the motor so that the timing line on your balancer is sitting at 6* BTDC on the tab - then paint a thin line on your CLEAN balancer where the 0* mark is on the tab and let it dry. That new line you painted, will be 6* PLUS whatever you read on the timing tab. So, if the white line you made is at 4*, then you know your timing is REALLY at 10* - make sense?

I think I lied earlier also, I think my timing NOW is set at closer to 14 now rather than 11 - it was 11 before, but after I got the timing tape and started to try and get a higher total timing (at 3000 rpms), I adjusted my base timing up more I think - it's been awhile.

If you can't get the bad smell tuned out - I'm not really sure. It means your running too rich. Maybe there's dirt inside the carb on a needle valve or something, blocking air flow or something. Maybe the choke is improperly adjusted - is the butterfly all the way straight up/down when the car is warm?

Check Edelbrock's site - there's a ton of info there on choke adjustment, setting idle, tuning, etc. They are great with their instructional sheets - sometimes too good (you can get lost in the particulars). There's also some of these in a sticky on the carb section here, and some videos as well from Edelbrock. No need for any new jets or rods or pumps - you don't need that much fine tuning now.

Speaking of pumps - which hole in the linkage is your accelerator pump attached? Might try another one just to see how it changes things. There should be 3 holes to try. The upper hole is going to start the plunger farther down, thus should add more fuel I'm guessing, and lower hole opposite I guess - might try changing that.

Yes, a cat can go bad - but usually when it does it gets blocked (unburnt fuel collects into a carbon buildup inside that the exhaust gases can't flow through), and thus it gets clogged and the car doesn't want to have any power on take-off - so I wouldn't think that's your problem.

Your timing light should be fine - no need for any fancy junk until you try tuning a race car, and even then they did it with exactly what you have in the old days. I've got the same gun myself.

And I should also note - I'm in no way any expert on any of this. Sounds like to me you know as much as I do, you're just having a hard time getting there (as I did). It takes time and patience - especially when you are like me, and overthink everything, and although you have the knowledge, you kep reminding yourself you don't know what you're doing. I just kept playing (and I'm still playing) with different settings. Little bits at a time - tiny adjustments and then run her to see. I always made the mistake of adjusting too far too fast.

Just keep playing with it, you'll get there. See if you can hook up with an old timer at a local Joe Blow shop close by to help. Pick an old, dirty place where there's more grease on the guys T-shirt than on the cars - that's where $50 and a 12pack can buy alot of help from someone that knows carbs and what it should smell like, taste like, feel like. There's a pretty big car following in Greenville I believe - might hunt around for some of the "classic" guys (old 60's and 70's rods), and see if they know anyone around good with carbs. Do a google search for "chevy club greenville sc" or something like that and see what comes up.

Hope I didn't make it worse by gabbing. Just telling you what I know, which given your knowledge seems to be more of a reassuring note than anything else. Check out the Edelbrock instructions, watch the videos, play a tad more, and see about the old greasy guy if all that fails.

Good Luck! Maybe we'll see each other at F-Body Gathering in Atlanta one of these years!
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350 Carb 10:1 Dometops Mild Cam
Hedmann Headers Hi-Flo Cat/Aerochamber Muffler
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Old 01-25-2011, 01:48 PM
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