Brians1

Guys....need some help. I have been searching high and low across the net, every site you can think of and I can't get a straight answer. Where does my vacuum advance vacuum hose connect to on my factory Rochester Q-Jet (M4ME)? Can someone post a pic showing where theirs is hooked up to ???

CA-Legal-Vette

Easy answer, it doesn't. The 81 distributor doesn't have a vacuum advance, it's done electronically by the computer. Also, the carb should be an E4ME.

Are you sure that it isn't an 80?

Brians1

Ca-Legal-vette thanks for the reply.
Yes I am positive it is a 1981 and it did come with and has an HEI distributor with vacuum advance. I have been in several sites, even called a few parts places to make sure they showed direct factory replacement distributor has vacuum advance. Yes my 81 also has the first year if CCC as well. I'm really just hoping someone with and 81 would be kind enough to take a picture or two and post it for me so u can do a state and compare and get my Q-jet hooked up accurately. (Also my smoke pump system has been disconnected and removed )
So some if my vacuum lines will be plugged up

c6silver

If your car is an 81 there is no vacuum advance, it's all done by the CCC system, unless someone swapped back to a non CCC carb and distributor. Plug a scan tool into the ALDL and see if you get any data or trouble codes.

Brians1

c6Silver...well you bring up a good point. I bought the 81 from the owner and at the time the Factory Q-Jet was in the shop getting rebuilt. Part of my deal with the purchase was getting the Q-Jet back from rebuild. There was an Edelbrock 1406 on it which I took off to place the Factory Q-Jet back on. Would the usage of the Edelbrock 1406 at the time warrant the need for him to place a Vacuum advance HEI Distributor on the vehicle vs. using what sounds like the NON Vacuum Advance Original?

Also you mentioned a scan tool plugged into the ALDL...is this where I have to watch the "blinks" and cross reference back to the list (i have teh Haynes manual) to see what code its throwing..or is tehre an eaiser way to get teh code from more modern readers off teh shelf?

Really apprechiate the help here as well guys...I want tio get my vette runing again and I'm sure with your help ill be there soon.

c6silver

Yes, the computer would set a code and light the service engine soon light without the right CCC carb on it, and an older style vacuum advance distributor would HAVE to be put on. The bigger question is what intake manifold is on the car, because Edelbrock carbs are square flange like a Holley, not spreadbore like a Q jet...the 1406 won't bolt to a factory intake without a hokey adapter plate.

A scan tool can be purchased at Autozone for around 100 bucks and no, you don't have to count flashes on the bulb...the bulb may be burned out or (in the case of less than honest sellers, removed) so that it LOOKS LIKE there are no trouble codes set .

c6silver

I think your course of action depends on what your goals are. You can leave the vacuum advance distributor in the car and put a pre-81 Q jet on it (get a vacuum diagram for an 80 Vette for reference in this case), or if you want the car the way GM designed/built it, you need a CCC Q jet and distributor. What are the smog laws (emissions testing) in your state ? Is the catalytic converter still on the car ? Is the wiring harness for the CCC system still there and intact ? Do you want the car original or functional ? Will you be doing some hot rodding in the future ?

Brians1

c6silver... Thank you. Yes the Edelbrock 1406 had an ugly adapter plate (that was also leaking fuel thru it..)...I have removed it, I got the original bolt set for the Q-jet and bolted that back on (the carb shop supplied a new proper gasket for the Q-jet as well). so sounds like I need to get an OEM Distributor (maybe at Autozone or the like..suggestion on Brand, etc??)..and also get the scan tool and see whats going on it it. I am also chaning out teh plugs and going to reset the timing....I have seen All suggestions lead to 12 BTDC as what is optimal. again all conversations around this vacuum advance tying into the timing being set accuratly. this is def "fun" trying to revert back to a blind change someone made...but with your help im getting there

c6silver

First, is the Q jet a CCC Q jet or pre CCC ? Lets start there. If it's CCC, then just go to the junkyard and get a large cap HEI CCC distributor from a Chevy and replace the cap, rotor and HEI module. I would use GM/DELCO parts for the cap and rotor (and plug wires) and an ACCELL or MSD HEI module (don't forget the dielectric grease under the module). Start at 6 degrees initial with the timing spade connector disconnected. (You need a shop manual for working on CCC cars).

SIXFOOTER

Your getting pretty good info here.
I'll add mu .02, as stated the 81 did not come with a vac advance dizzy, it is HEI, just has an electronic advance controlled by the CCC.
Some, if not all 81's came with an Edlebrock 2101, pretty good intake. Changing to a 1406 would not have required changing to a vac advance dizzy.
Your cheapest and possibly best rout might see about snagging the factory dizzy from one of the 81 guys in here that has removed it. Its easy to rebuild and is every bit as reliable as any other factory HEI unit.
If your other CCC components are all in place and function, that will get you running in pretty short order.
Other things to look for and think about:
Is the O2 sensor in place and plugged in?
Is the electrical connector on the transmission? The TH350C has an electrical lock up converter also controlled by the CCC
There should be a sensor mounted on the drivers side firewall with a vac hose or 2 on it, it is needed to measure ambient Baro pressure and manifold vac to feed to the CCC.
To tune it you will need access to a dwell meter, it gets connected to the green single wire connector that should be part of the engine wire harness on the passenger side of the motor along with the metering valve connector and the choke heater power.
All that stuff is required to get the CCC system fully functional and operating in closed loop.

Brians1

c6silver...great follwoup Q's....to answer..for now I want the car to run. In Feb/March I plan on getting a new top end (most likely an edelbrock 2022 or the like)..but as the car sits is right now:
In FL..no more Emmissions testing
Smong pump removed and exhaust ares capped off
I have the original Chevy Intake Manofold on it still.

Brians1

Sixfooter Thank you as well...man I have some homework to do you and c6silver have already given me a ton of great info...I believe I will start with replacing to a Non Vacuum Advance Distributor and get it runing from there. Then set timing...and now sounds like investigate the Trans connections (Vacuum and Electrical)...AND I have to get a Scan tool...Wife is gonna love it when I tell her all of this..if I tell her... LOL.

I will keep you posted via this thread on how my investigation and changes go to get her runnning again.

c6silver

You can do better than the 2022. That intake won't fit under your stock hood. Go buy an aluminum head TPI Vette engine and replace the cam with the ZZ4 crate engine cam, new valve springs, maybe some 1.6 rockers (watch piston to valve clearance) and port the stock aluminum carb intake. Have the CCC carb re-jetted for this combo. Should be about 345 hp. If you have someone like Lingenfelter's port the heads, maybe 380 hp. I would talk to Chris Petris at Corvette Clinic before you do anything else. If you don't want to mess with porting your stock intake, get one off a 305 chevy at the junkyard (just make sure it's aluminum, or look for an aluminum L82 intake for sale, and port that). Or for truly big fun, build a 406 with good heads, same intake and carb tricks, stay conservative on the cam, and really turn that sucker loose.

c6silver

I would ditch the TH350c for a 2004R in a heartbeat, and swap in some real rear gears like 3.54s . Converter lockup will stay the same (controlled by CCC) and you'll have overdrive for fuel mileage and lower rpm highway cruising, which means less wear and tear on the engine per mile driven by virtue of less rpm per mile.

Brians1

c6silver...you mentioned O2 sensors as well so I took a peak at cost and fitment via autozone...this diagram look accurate?... 4 total sensors ??? I was a ford guy but turned chevy (sold my 67 Mustng to get the vette) and I didnt have any O2 sensors on that....I know some newer vehicles have 4 or 2...just want to make sure I buy corerct quantity since i am not familiar with teh car just yet.

** BTW can you tell how much work I am getting done today (lol...been on this forum all morning and Multi tasking)...thanks again - Really Appreciate the info !!! **

c6silver

I would also add the dual snorkel L82 air cleaner setup (the whole thing) and a K&N filter. Check out Hypertech's chip for your car too.

If none of these options give you enough power, swap in a Big Block with a factory Q jet iron intake from an LS4 or LS5 Vette and put the CCC stuff on it (carb and distributor). It bolts to the same mounts and the same trans so no issues there, use coolant hoses and front brackets from a Big Block car. You'll need headers or big block exhaust manifolds and some exhaust work, but that would be the ultimate.

c6silver

Just 1 O2 sensor until the mid 90s.

Brians1

Ok that sounds better as I didnt think the 81 had the "Smarts" yet for that many sensors...I do have the original Dual Snorkel and duct work ...lots of oprtions for me...Once I get it running again my wife will have new confidence in an upgrade for power (the ultimate goal of course).

Brians1

c6Silver/Sixfooter...I guess i have maybe a silly question...since we all identified i have a vacuum advance and clearly dont need it...can I just remove that componet from the distributor and will it function as a Non vacuum advance..or is that just nto an option?

c6silver

NOT an option. It needs to have the systems inside of it to allow timing to be computer controlled, it's NOT just a matter of vacuum vs non-vacuum advance...it sounds to me like you really have no idea what's going on with this car and it's systems...PLEASE buy a FACTORY GM shop manual for your 81 Corvette. It's THE BEST tool you'll ever buy for your car. Chilton's and Hayes manuals are just a crutch that can get you by in a pinch if you have the basic working knowledge of these systems...the GM manual will spell it all out and break it down WAY further than a generic manual can.