Brake and Carb Help...........

[coptertom]

Hey Guys,

After four months in the garage I finally got my 81 back to my hanger.......Just had ingition wires, plugs, true dual (left cats off), hooker headers, new S/S brake lines, calipers, rotors, power brake booster, master cyl, rebuilt carb (stock) and to top it off.............a new paint job!

Just have a couple of questions that maybe you guys can help with.

First: Brakes...........they certainly work a lot better than they did. I notice however that when I put the vette into gear and take my foot off of the brake...........the vette just sits there. You have to give it gas to get it to move (almost as though the pads are snug to the rotors. The mechanic mentioned that the emergency brake was not working and that the pads on the emergency brake needed to be repaired.

Would that have anything to do with the brakes feeling as though they were tight? Or is it just that since I have a whole new brake system, that the brakes just need to be broken in.

Second: I had the carb rebuilt and new wires and plugs. The carb seems to be loading up with gas and the check engine light came on. When I disconnected the electrical sensor on the carb (stock), the check engine light went off and the vette seemed to run smoother. It still loaded up, but not as much as when it was connected.

Any ideas? I know that I am asking a lot with out much info to go on...........but hopefully it is a start to try and figure out what is wrong.

 

[Sensei]

Hook the electrical connector up on the carb and check the trouble code. Then you can fix the problem. Just disconnecting the wire will not work! God bless, Sensei

P.S. Who rebuilt the carb?

 

[coptertom]

Thanks for the reply Sensei. It is good to know that this forum is here to help...........Today I am going to gunk the engine then I will check the trouble codes. I am guessing that the trouble codes will be in the shop manual. The carb was rebuilt at a carb shop down here that is known for doing good work. The shop however does not specialize in vette's. I am thinking that a carb is a carb and hence they are pretty much all the same. Hope that I was not wrong. I also made sure that when the headers were installed, that they reinstalled the Ox senser. I sure would like to get my vette up and running good. It has been sitting in my garage for a good five years.

Does anyone have any suggestions re the brakes? The vette stop fine..........just that the brakes seems to be snug as a bug.

Thanks Guys

 

[Sensei]

The carb is an E4ME, which is an electronic Quadrajet. It is not Vette specific and was used on several GM vehicles from '81 through about '85 I think, particularly on trucks ('81 was the only year they put it on a Vette). It is a great carb but it does have a few peculiarities, Many shops will not work on them. They are the most technically complex and advanced carbs ever made to my knowlege.

As for your brakes, I know I had to loosen my e-brake because it was dragging, then it did not hold any more. Jack up the rear end and see how things turn as you adjust the cable tension. Maybe someone with more knowlege on this subject will chime in. God bless, Sensei

 

[Carver81]

Replacing the carb

Sensei and others...

So what is involved in replacing the stock carb on an L81? I just had mine tuned up and am told it needs to be rebuilt or replaced. Because of the 3C computer controlled engine management system, I am of the opinion I can't just take off the Rochester Q-Jet and replace it with another carb...there are electronics to think about. Is this correct?

Carver81

 

[SIXFOOTER]

Carver, changing the carb for annother of the same type is no more or less complicated than any other carb. If your wanting to swap it for something else, you would need to also replace the distributor for one with a vac advance unit on it and you would need to modify the TCC lockup circuit.
Personally, I would get the one you have fixed, it is a Very good carb and capable of running a 350 hp engine with little or no mods (secondary jets maybe).

Coptertom.
Make sure your O2 sensor was hooked back up when the duals were put on. If they were full length headers you will need to mount the sensor in the collector, and change it to a Heated type of sensor since its so far from the head.

 

[coptertom]

Hey guys I am looking for some assistance on making all the correct connections to my
E4ME Quadrajet carb. I want to make sure that all the vacuum hoses/lines are properly hooked up. Would any of you possibly have a diagram or photos of your connections. It might help me in trying to figure out what to do to get the vette running smooth.

Sixfooter Sir,
I made sure that they hooked up the O2 sensor when they put the duals on. As far as I can see, they hooked up a two wire O2 sensor, just behind the header on the exhust pipe. I am not sure if it is a heated type or not. Thanks!

 

[Carver81]

Fixes for the carb?

Hey SIXFOOTER,

Do you have any tips, things-to-watch-out-for, or suggestions to make sure I get a good job done on getting the carb fixed? (Other than getting a knowledgeable mechanic!!)

I too would prefer to go the route of getting the carb fixed. Funny thing I do have to mention is that when I had the engine steam cleaned (for the first time in its life) the car has actually never run better. It's like it just wanted someone to take care of it better!

Carver81

 

[SIXFOOTER]

Hey guys I am looking for some assistance on making all the correct connections to my
E4ME Quadrajet carb. I want to make sure that all the vacuum hoses/lines are properly hooked up. Would any of you possibly have a diagram or photos of your connections. It might help me in trying to figure out what to do to get the vette running smooth.

Sixfooter Sir,
I made sure that they hooked up the O2 sensor when they put the duals on. As far as I can see, they hooked up a two wire O2 sensor, just behind the header on the exhust pipe. I am not sure if it is a heated type or not. Thanks!

Here you go

 

[SIXFOOTER]

Carver, the best advice I can give you is do some research and find a Good Reputable shop or do it yourself. The GM service manual has a pretty good description on the adjustments. Lars the the resident carb guy, unfortunately he doesn't do these carbs. I'll be doing mine soon as I get the engine where I can fire it up, about 2 more weeks and I'll do a writeup on it if no one else posts good stuff before then.

 

[coptertom]

Hey Carver,

Thanks for the pics...........It doesn't get any better than this! It just goes to show just how good this forum really is.

 

[Carver81]

SIXFOOTER posted the pics

Hey Tom T. SIXFOOTER posted the pics and you are absolutely right they are fantiastic. Thanks so much folks for all your help.

 

[TMPJoe]

Hey Tom T. SIXFOOTER posted the pics and you are absolutely right they are fantiastic. Thanks so much folks for all your help.

yeah they do have a rebuilt one at Ecklers but its $499!!!

try seeing if they have a kit for it?

 

[big2bird]

yeah they do have a rebuilt one at Ecklers but its $499!!!

try seeing if they have a kit for it?

NEVER buy a rebuilt carb. Rebuild yours. Get the kit and do it. NAPA has the M/C solenoids and TPI sensor. You need a couple special tools, and you can do it in a day.

Guys, Engine parts are engine parts. Why go to a vette vendor?

 

[GerryLP]

....a new paint job!

Just have a couple of questions that maybe you guys can help with.

First: Brakes...........they certainly work a lot better than they did. I notice however that when I put the vette into gear and take my foot off of the brake...........the vette just sits there. You have to give it gas to get it to move (almost as though the pads are snug to the rotors. The mechanic mentioned that the emergency brake was not working and that the pads on the emergency brake needed to be repaired....

Second: I had the carb rebuilt and new wires and plugs. The carb seems to be loading up with gas and the check engine light came on. When I disconnected the electrical sensor on the carb (stock), the check engine light went off and the vette seemed to run smoother. It still loaded up, but not as much as when it was connected.

Any ideas? I know that I am asking a lot with out much info to go on...........but hopefully it is a start to try and figure out what is wrong.

Tom,

If they told you that the rear emergency brakes are no working, then perhaps he should have fixed them. But for now, it seems that the pads may be too tight (perhaps even bare shoe pads) against the rear rotor inner drums. You can loose the emergency cable adjusting nut at the point where it pulls both sides of the emergency brake (it should be visible just above the transaxle shaft) OR loosen the adjusting wheel on the pads through the slot at bottom of inner splash guard. The slot usually is covered by a rubber plug.

On the carb issue, when a E4ME carb is rebuilt, they should base-line it with the idle mixture screws at 3 and 1/3 turns out (from bottoming), the air valve should be set at 1.75" , and the throttle position solenoid should be at the position where it is between 0.5 and 0.6 volts when the throttle is at curb idle. The problem is that some shops often do not set them at the basic setting. And I can understand that it could be considered academic for the shop to set the throttle position solenoid , since they would have have to guess where the curb idle would be set at, and the throttle position solenoid is not difficult to to adjust either. However, the air valve requires a special gage (it is a "j" shaped rod) that has the correct dimension to transfer to the air valve adjustment screw (I have one).

I will post the tool part numbers later on tonight once I return home from work.

 

[hdkeno]

Last year i had my mechanic (who used to work on c3-c4 vettes back in the day at a chevrolet dealership) rebuild my carb with the aforementioned carb kit from napa which was about $75 or so best that i can recall,I had a bad tps sensor and the base gasket was leaking (dry rot) so he did the rebuild,and the carb is like new ever since.

No hesitation,rough idle stalling etc.

So i agree have yours reboilt if you can find someone that is knowledgeable on these carbs.

Ken

 

[big2bird]

Tom,

If they told you that the rear emergency brakes are no working, then perhaps he should have fixed them. But for now, it seems that the pads may be too tight (perhaps even bare shoe pads) against the rear rotor inner drums. You can loose the emergency cable adjusting nut at the point where it pulls both sides of the emergency brake (it should be visible just above the transaxle shaft) OR loosen the adjusting wheel on the pads through the slot at bottom of inner splash guard. The slot usually is covered by a rubber plug. I thought the adjusting slot was in the outboard side of the hub.

On the carb issue, when a E4ME carb is rebuilt, they should base-line it with the idle mixture screws at 3 and 1/3 turns out (from bottoming), the air valve should be set at 1.75" , and the throttle position solenoid should be at the position where it is between 0.5 and 0.6 volts when the throttle is at curb idle. The problem is that some shops often do not set them at the basic setting. And I can understand that it could be considered academic for the shop to set the throttle position solenoid , since they would have have to guess where the curb idle would be set at, and the throttle position solenoid is not difficult to to adjust either. However, the air valve requires a special gage (it is a "j" shaped rod) that has the correct dimension to transfer to the air valve adjustment screw (I have one).
What is a throttle position solenoid?
I will post the tool part numbers later on tonight once I return home from work.

 

[GerryLP]

I thought the adjusting slot was in the outboard side of the hub.

You know, You are right.:ugh On common cars it is on the inboard splash guard. For the vette, it is through the hole on the axle hub flange. Sorry!:confused

What is a throttle position solenoid?

The throttle position solenoid is the one that receives input from the computer and adjusts the throttle for best road conditions...















....just kidding...

I meant the throttle position sensor.

 

[GerryLP]

Tom,

I will post the tool part numbers later on tonight once I return home from work.

Tom,

The GM CCC Carb gauge kit is from Thexton, and it is part number 370. Not as commonly found everywhere, but if you take your time, you'll find it on eBay, or some other web location. Also Thexton 362 has the TPS tool in it.

It comes with the TPS screw tool, the float ruler, and the air valve preset tool. It also comes with pretty good instructions.

The shop manual has more complete instructions as well, but basically, once you set the basic setting on the carb, fine tune the air valve by using a Dwell meter's test lead attached to the green test connector on the L81 carb harness. Make sure you connect the black lead after starting the engine and disconnect it before shutting-off the engine (In between, I place the black lead clamping on a rubber hose to be safe). You sue the 6 cylinder scale. The engine has to be fully warm, and then you try to get the moving needle (it should waiver back and forth in small amounts) as close to 30 as possible.

Just read the instructions on the shop manual. It is hard to be concise in this web setting without writing a novel...

 

[coptertom]

Thanks guys..............I just purchased a new S/S ebrake from Muskegon Brake (good prices and quick ship out), and took the vette to the brake shop to have it installed. This should take care of the brake issues, since the Entire brake system will be new!

I have a carb guy that works on muscle cars coming out to the hanger tomarrow to take a look at the carb issues. I am going to show him all of the posting that you guys have sent. I am sure that all your help (Sensei, Carver81, SIXFOOTER,TMPJoe, big2bird, GerryLP and Ken aka/hdkeno), will help get this tired vette up and running smoothly!

I will keep you posted.

Thanks from the eye in the sky!