1971 CEC solenoid and vacuum

[Patrick H.]

Greetings All!

As many of you know, I have a 1971 350/270 4 speed. Regarding this, I have a question on the subtleties of the CEC solenoid operation:

Presently, when the key is on, it will engage and the idle will rise in both 3rd and 4th gear, just as it is supposed to. My question is, When is it supposed to allow vacuum to bypass it and therefore get to the distributor vacuum advance?

When the car is at rest, whether running or not, there is no vacuum going past the solenoid. Is there ever a time that vacuum gets past, or is that what happens when it activates, the plunger extends and the idle rises?

As I understand it, vacuum is NOT supposed to get past the solenoid in 1st and 2nd gears, but is in 3rd and 4th. Correct? I am getting some bogging upon first applying the accelerator off the line, and by 2500 RPM or more the engine takes off. I am wondering whether the solenoid may have something to do with this. And yes, I have bypassed the solenoid and put the vacuum line directly to the distributor as a test. This seems to help somewhat, but my idle then raises to 1300 RPM from the previous 800RPM range, and I'm not sure if this "nullifies" the test. Or, is my mixture just too rich?

Thanks for any and all assistance you might be able to provide.

Patrick Hulst

[Bill Clupper]

Re: 1971 CEC solenoid and vacuum

The operation of your solenoid is correct. the "bog" is likely attributable to one of the following: A: General tuneup-points, plugs, wires, etc B: Carb accellerator pump not at 100% efficiency C: Ignition timing (initial) set too low D: If the "bog" comes when you open the carb fully, the problem could be in the spring tension that holds the secondary air valves closed on a Quadrajet. These are adjustable, The tension is determined py the position of a slotted shaft located on the passengers side, near the shaft for the air valves. It is held firmly in place by a very small allen bolt mounted vertically directly under the slotted shaft. check the spring tension in your secondary air valves with the engine off. Open the carb throttle fully and push on the air valves. You should feel some resistance from the spring. If little or none is found, you may have your culprit.

[Bill Clupper]

Re: 1971 CEC solenoid and vacuum

The operation of your solenoid is correct. the "bog" is likely attributable to one of the following: A: General tuneup-points, plugs, wires, etc B: Carb accellerator pump not at 100% efficiency C: Ignition timing (initial) set too low D: If the "bog" comes when you open the carb fully, the problem could be in the spring tension that holds the secondary air valves closed on a Quadrajet. These are adjustable, The tension is determined py the position of a slotted shaft located on the passengers side, near the shaft for the air valves. It is held firmly in place by a very small allen bolt mounted vertically directly under the slotted shaft. check the spring tension in your secondary air valves with the engine off. Open the carb throttle fully and push on the air valves. You should feel some resistance from the spring. If little or none is found, you may have your culprit.

[Jack H.]

Re: 1971 CEC solenoid and vacuum

Agree, problem is likely NOT the fault of CEC. CEC solenoid fires under the following conditions if your car's switches/relays are functional:

(1) For 15-30 seconds upon initial start regardless of engine temp. (2) So long as engine temp (sensor in RH head) see below normal

operating temp. (3) Whenever enging temp sensor sees higher than normal operating

temp (summer grid lock traffic). (4) When manual tranny car is in high gear (3rd/4th) -- autos also

in reverse gear.

When CEC solenoid fires, it boosts curb idle (setting by twisting solenoid plunger screw) and boost varies with engine but is typically 150 RPM. This action also connects the distributor vac advance to carb vac source. So, solenoid at rest = no vac advance, solenoid fired/engaged = higher curb idle + vac advance.

Your car shouldn't 'dog' in low gear without distributor advance. Proof is comparing performance on initial start/cold engine to warm engine operation. However, a few other variables enter the picture here -- choke adjust, pull-off adjust of your 213 Q-Jet.

Might want to check that you don't have a sticky heat riser valve causing partial restriction of RH exhaust bank. Also should look for vac leaks and verify the action of your primary shooter as well as primary mixture setting. Last, don't overlook the obvious -- are carb screws torqued to spec along with intake mounting bolts....

If secondaries aren't opening (they do lock closed when carb and engine are cold), you'll know it because it'll be impossible to climb above, say, 4000 RPM with engine running lean and missing.

[Jack H.]

Re: 1971 CEC solenoid and vacuum

Agree, problem is likely NOT the fault of CEC. CEC solenoid fires under the following conditions if your car's switches/relays are functional:

(1) For 15-30 seconds upon initial start regardless of engine temp. (2) So long as engine temp (sensor in RH head) see below normal

operating temp. (3) Whenever enging temp sensor sees higher than normal operating

temp (summer grid lock traffic). (4) When manual tranny car is in high gear (3rd/4th) -- autos also

in reverse gear.

When CEC solenoid fires, it boosts curb idle (setting by twisting solenoid plunger screw) and boost varies with engine but is typically 150 RPM. This action also connects the distributor vac advance to carb vac source. So, solenoid at rest = no vac advance, solenoid fired/engaged = higher curb idle + vac advance.

Your car shouldn't 'dog' in low gear without distributor advance. Proof is comparing performance on initial start/cold engine to warm engine operation. However, a few other variables enter the picture here -- choke adjust, pull-off adjust of your 213 Q-Jet.

Might want to check that you don't have a sticky heat riser valve causing partial restriction of RH exhaust bank. Also should look for vac leaks and verify the action of your primary shooter as well as primary mixture setting. Last, don't overlook the obvious -- are carb screws torqued to spec along with intake mounting bolts....

If secondaries aren't opening (they do lock closed when carb and engine are cold), you'll know it because it'll be impossible to climb above, say, 4000 RPM with engine running lean and missing.

[Patrick H.]

1971 CEC solenoid and vacuum: Jack & Clup

Jack and Clup,

The operations you describe seem pretty much as I believed them to be. I was mostly unsure as to when the distributor was to actually "see" vacuum.

In addition,

1. It seems to "dog" when warm. And yes, I know that secondaries do not open when the car is cold and therefore it will have sub-par performance. My car was driven for 20 miles on Saturday before I reached the autocross and had a chance for several first gear starts to find out how bad it dogged.

2. The choke pull-off and primary shooter seem to be working just fine. There are no vacuum leaks that I can find, and the several screws holding the air horn to the main body are all secure. As for choke operation and idle mixture I make no guarantees, other than to say that the choke is fully open when the car is warmed up.

3. My points, wires, cap, etc are 3 years old, and about 6000 miles on them. The plugs I just installed 2 weeks ago. The only thing related to ignition that I haven't checked is the timing. As the bog (and black smoke) only comes with full pedal acceleration from a slow speed (relative to the gear) and not with light or part throttle acceleration, I actually figured the carb to be more of the culprit. I just want to make sure that the solenoid is not. In the 3 years I've had the solenoid on the car it has never seemed a problem, but if you've read my comments in months past, my carb is an expensive doorstop.

I'll check out the spring that Clup noted, as I have adjusted this on other carbs before, but not this one. I also plan to have the choke and idle mixture examined.

By the way, I noticed the bog when coming off the line on each of my runs this past Saturday during our club's NCCC autocross. Did anyone else know that a (relatively) stock 1971 L-48 with bad old tires can be faster than C4's and even ZR-1's? Even faster than guys who do this all summer long? What a blast!

Patrick

[Patrick H.]

1971 CEC solenoid and vacuum: Jack & Clup

Jack and Clup,

The operations you describe seem pretty much as I believed them to be. I was mostly unsure as to when the distributor was to actually "see" vacuum.

In addition,

1. It seems to "dog" when warm. And yes, I know that secondaries do not open when the car is cold and therefore it will have sub-par performance. My car was driven for 20 miles on Saturday before I reached the autocross and had a chance for several first gear starts to find out how bad it dogged.

2. The choke pull-off and primary shooter seem to be working just fine. There are no vacuum leaks that I can find, and the several screws holding the air horn to the main body are all secure. As for choke operation and idle mixture I make no guarantees, other than to say that the choke is fully open when the car is warmed up.

3. My points, wires, cap, etc are 3 years old, and about 6000 miles on them. The plugs I just installed 2 weeks ago. The only thing related to ignition that I haven't checked is the timing. As the bog (and black smoke) only comes with full pedal acceleration from a slow speed (relative to the gear) and not with light or part throttle acceleration, I actually figured the carb to be more of the culprit. I just want to make sure that the solenoid is not. In the 3 years I've had the solenoid on the car it has never seemed a problem, but if you've read my comments in months past, my carb is an expensive doorstop.

I'll check out the spring that Clup noted, as I have adjusted this on other carbs before, but not this one. I also plan to have the choke and idle mixture examined.

By the way, I noticed the bog when coming off the line on each of my runs this past Saturday during our club's NCCC autocross. Did anyone else know that a (relatively) stock 1971 L-48 with bad old tires can be faster than C4's and even ZR-1's? Even faster than guys who do this all summer long? What a blast!

Patrick

[Patrick H.]

Re: 1971 CEC solenoid and vacuum

Clup,

I checked my secondary air valve operation as you mentioned. The resistance wasn't exactly firm, but they definitely didn't flop open, either. I have increased the resistance slightly and will see if this helps.

Any other thoughts?

Patrick

[Patrick H.]

Re: 1971 CEC solenoid and vacuum

Clup,

I checked my secondary air valve operation as you mentioned. The resistance wasn't exactly firm, but they definitely didn't flop open, either. I have increased the resistance slightly and will see if this helps.

Any other thoughts?

Patrick

[Jack H.]

Re: 1971 CEC solenoid and vacuum: Jack & Clup

Sounds like you're doing a good sleuthing job of due diligence, Pat!

The 'black smoke' comment is new/key. Says you're running rich. Let's kick somethings around....

The CEC solenoid works because there's a vent passage from the internal vac valve through the solenoid adjuster threads to engine compartment atmosphere. To prevent airborne 'gunk' (a real hi tech term) from being sucked into your carb/intake when the solenoid's in it's non-fired mode and carb vac is vented, there's a built-in filter on the end of the CEC solenoid.

I've noticed it takes progressively longer to idle down to non-fired curb idle RPM setting as time goes by and the filter on the CEC solenoid begins to clog. Could it be that your CEC is pretty gunked up, some gunk is working it's way through the air path into the carb? SB able to remove the solenoid, soak the CEC solenoid's filter and blow 'er clean with reverse air....

Next area to play with is the fuel/emissions stuff. Tank is sealed vs. vented. Hoses feed carbon cannister with replaceable cloth filter. Meant to re-capture tank vent fumes. Though there's no restrictor in the tank fill, it was NOT meant to FULLY fill the tank, cause raw gas to overflow and waterlog the charcoal cannister. Might be an angle or two here (fresh cloth filter on cannister, back off on 'top up', check hose integrity).....

Last, if all else fails, is to go see someone like Jerry Luck for a dyno tuned/tested 213 carb. Also, consider playing with the primary jets/rods in what you've got. Try one jet size down with the current primary rods and see if that gets you relief (jets are cheap, easy to come by at United-Delco/Chevy). Can tell you for absolute, my 'Lil Red does NOT dog/blow black smoke hot or cold WOT off the line....

[Jack H.]

Re: 1971 CEC solenoid and vacuum: Jack & Clup

Sounds like you're doing a good sleuthing job of due diligence, Pat!

The 'black smoke' comment is new/key. Says you're running rich. Let's kick somethings around....

The CEC solenoid works because there's a vent passage from the internal vac valve through the solenoid adjuster threads to engine compartment atmosphere. To prevent airborne 'gunk' (a real hi tech term) from being sucked into your carb/intake when the solenoid's in it's non-fired mode and carb vac is vented, there's a built-in filter on the end of the CEC solenoid.

I've noticed it takes progressively longer to idle down to non-fired curb idle RPM setting as time goes by and the filter on the CEC solenoid begins to clog. Could it be that your CEC is pretty gunked up, some gunk is working it's way through the air path into the carb? SB able to remove the solenoid, soak the CEC solenoid's filter and blow 'er clean with reverse air....

Next area to play with is the fuel/emissions stuff. Tank is sealed vs. vented. Hoses feed carbon cannister with replaceable cloth filter. Meant to re-capture tank vent fumes. Though there's no restrictor in the tank fill, it was NOT meant to FULLY fill the tank, cause raw gas to overflow and waterlog the charcoal cannister. Might be an angle or two here (fresh cloth filter on cannister, back off on 'top up', check hose integrity).....

Last, if all else fails, is to go see someone like Jerry Luck for a dyno tuned/tested 213 carb. Also, consider playing with the primary jets/rods in what you've got. Try one jet size down with the current primary rods and see if that gets you relief (jets are cheap, easy to come by at United-Delco/Chevy). Can tell you for absolute, my 'Lil Red does NOT dog/blow black smoke hot or cold WOT off the line....

[Paul Young]

Re: 1971 CEC solenoid and vacuum

Patrick,

Another thought would be to check your vaccum advance. It can be easily done with a hand vaccum pump. Good hunting. By the way could your better times come from being the more daring driver? Paul

[Paul Young]

Re: 1971 CEC solenoid and vacuum

Patrick,

Another thought would be to check your vaccum advance. It can be easily done with a hand vaccum pump. Good hunting. By the way could your better times come from being the more daring driver? Paul

[Jack H.]

Re: 1971 CEC solenoid and vacuum

Easier to bypass the CEC with a hose, use a timing light and watch 'er fly! '71 SB base had 15 deg max advance, so it'll all stay on the balancer scale (static + dynamic)....

[Jack H.]

Re: 1971 CEC solenoid and vacuum

Easier to bypass the CEC with a hose, use a timing light and watch 'er fly! '71 SB base had 15 deg max advance, so it'll all stay on the balancer scale (static + dynamic)....