Here is the problem. Fuel is getting into my oil and it is leaking from the base and top of my carb. The guys in tech/general engine said my carb is not functioning correctly. Its a stock Q-jet. What could be causing this to happen? Would a rebuild kit take care of my problem? Just hoping to get some insight here. Just broke in my cam and don't really want to start my car up again with the fuel issue.

 

The most common problem with the Q-Jet is the spun-in aluminum plugs in the bottom of the fuel bowl casting, leaking. They develop dissimilar-metal electrolysis between the aluminum plugs and the chinesium fuel bowl casting, which eats away the chinesium that the carb is made of; and sooner or later, they ALL leak.

Take off the throttle plate, and look at the bottom of the fuel bowl. Near the front of the carb there are 2 "tower" looking structures. Each has 2 such plugs on it. They are small, less than ¼" in diameter.

When you rebuild the carb as you need to do, after soaking it in carb cleaner and before re-assembling it, wire-brush the whole area all around those, to bare clean metal, and epoxy over them real good with JB Weld. Put it in the oven on "warm" for a couple of hours to harden, before putting it back together.

There are 2 MUCH LARGER plugs under the secondaries. Those rarely cause trouble, because they're sealed by a gasket.

 

Sofakingdom is dead on with the well plug issue and there's a link to a photo of the plugs (and some good rebuild info) in the following thread started by Nate86:

https://www.thirdgen.org/forums/carb...qjet-need.html

If you're leaking from the top and base you've probably also got a float/needle/seat problem. This is also addressed in a rebuild. Get a $20 kit, a can of carb cleaner and let us know if you have any issues as you go along.

 

Thanks guys. I picked up a rebuild kit and carb cleaner yesterday. Going to start later today. You can bet if I have a question I will let you guys know

 

Make sure you count turns to seat the lean stop screw (holds the mixture control solenoid in), the rich stop screw (if you remove it, you can leave it in) and the idle mixture screws. This will allow you to put them back in at the original settings, maybe saving some time measuring things.

 

Yup wrote that down. At first I couldn't figure out that the lean stop screw held in the mixture control solenoid My first time ever rebuilding a carb. But I just wanted to make sure this stuff is carbon build up before I scrape it off.


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Also is the little wire piece in this pic the needle? I didn't see one on my carb when I was taking it apart.

 

Looks like someone may have epoxied your plugs prior, were your idle mixture screws exposed? Still a good idea to scrape what you can off and hit them.

The needle is the silver piece. It fits into the brass seat. The wire is the clip that connects the needle to the float arm. There should be a little diagram in the kit as to how the clip should connect.

 

The stuff you point out is epoxy; somebody totally wasted their time and effort putting it there. Those are the 2 large plugs I mentioned that don't need it.

The needle is the skinny part with the rubber point in the bag. It's the moving part of a valve. The brass part is the seat, it's the stationary half. The float works the needle: when the bowl is full, the float pushes the needle closed on the seat to shut off the flow of fuel from the pump; when the level drops, it opens. The piece of wire is just a clip to hold the needle to the float. When you put the clip onto the float, DO NOT put it through the little holes; it needs to hang freely from the semi-circular part in between the arms.

The tall structures just to the right of the useless epoxy in the pic, are where the epoxy SHOULD HAVE been put. The one that's toward the top of the pic looks like it's been leaking. Wire brush all that metal there until it's perfectly clean; then clean with lacquer thinner; then epoxy over the plugs and bake it on "warm" in your oven for an hour or 2.

 

Yeah, I see now where they may have tried to epoxy the taller plugs but the plugs are exposed.

Also noticed you've got an after market inlet installed (or is it just painted blue?). Do you have a stock mechanical pump installed and is it using the hard line from the pump, behind the water pump to the carb? Is there a filter installed in the line or under that inlet?

 

Yeah its an aftermarket inlet. I am using the stock style mechanical pump. Put a new one in during the cam swap. I replaced the stock fuel line with a braided line that has an inline fuel filter. My edelbrock intake was a lot taller than stock so the stock line wouldn't reach the carb haha.

Im going to pick some JB weld tonight, clean those plugs up and cover them up. Then put everything back together tommorow.

 

Ok I epoxied the plugs and got everything nice and clean. I have started puting everything back together. I looked at the rebuild kit instructions, and im pretty sure I have the wire attached to the float correctly. Just want to make sure so here is a pic. Kinda blurry but the wire just sits on the brass float arm right?

 

The wire should clip onto the needle prety good; and the other end should just kind of hang onto the float. You can see a little circular kind of place on the float: that's where it goes. NOT through the holes.

How did your epoxy job on the plugs turn out?

 

That looks super clean. When you opened it up were the four tubes (air bleed and emulsifier) still attached to the air horn?

 

Alright im pretty sure I got the wire set up right. When I was disasembling my carb I did not see the wire so maybe that was causing my problems. The epoxy job turned out good. I used JB weld and put it in the oven for a little bit.

Yeah the 4 tubes were still attached to the airhorn when I removed it.

 

The old wire should have been clipped pretty well to the old needle, if not it could have hung up the needle causing your problems. I usually find at least one or more of those tubes loose.

Go ahead and check your TPS spring. Make sure when you depress the TPS plunger that the spring is strong enough to keep the TPS body from moving down into the bore. I've seen this problem a few times. Probably from varnish building up within the TPS assembly. I've added a second spring on a few to fix this.

 

When I press down on the tps plunger the body does move a little bit into the bore. Should it move at all? I don't think the rebuild kit came with any new springs.

 

The spring should keep it from moving..much. I assume that over time the plunger's picking up some varnish that makes it a little harder to depress, overcoming the spring tension. If it's only moving a hair (1/8" or so), it's OK. If not, you can hit the hardware store for a second spring about the same size as the TPS spring, then intertwine them or replace it altogether with a slightly stronger spring.

I've had them move so much in the bore that they wouldn't send a WOT signal to the ecm.

 

Yeah it was only going down an 1/8 or so. I put the carb back on the car today and it fired right up after a couple of cranks No leaks too Sounds sweet with the new cam. Just need to set the valve lash again and figure out the timing. I have an old set of valve covers that I can cut the tops off to set the lash with the car running. Not sure what to set the timing at but im just glad my car is running again

 

Set your timing to 4 degrees advanced with four wire connector off. Put a light on it and make sure it's advancing correctly.

If you get a chance to pick up a dwell meter, hook it up and see where you're at. A voltage meter to check your TPS setting is good insurance too. In the meantime, if you've set everything back where it was you're probably close. If the converter lock up's working you know the ECM is happy.

 

I got the engine at 8 degrees advance right now. Still seems sluggish and lacks power when I get on the gas. I will mess with the timing more tommorow.

Can I get a dwell meter from any auto part store like autozone? Ive got a volt meter so I will look up how to check the tps.

 

You can get a dwell meter for around $25 or so. It comes in handy if you're ever diagnosing carb/sensor problems. Keep in mind though, that the computer only controls primary metering. IAB adjustment using the dwell meter won't find any power you may be missing.

8 degrees may be fine for you. Just make sure you're getting timing advance with throttle. With ESC wire connected the engine should be around 24+/- degrees and additional throttle should kick it up more. You kind of have to estimate without the extended timing marks but you're ensuring that it advances, not necessarily how much.

There's some attachments in that thread started by Nate86 that outline ccc-qjet adjustments to include IAB and TPS.

 

I picked up a dwell meter last night. Also I am getting timing advance when I use the throttle. Ive got class later tonight so I will probably read up on using the dwell meter and then test things out tommorow.

 

You'll find a funky green spade type connector near the passenger side firewall. It's the positive lead for the dwell meter. Hook it up on the six cylinder scale and with the engine warm you should see a ranging dwell reading indicating the duty cycle of the MC solenoid. If everything is operating correctly the dwell should constantly swing back and forth about +/- 10 degrees or so. Adjust it so it averages around 50%. Need help let me know.

By the way, have you swapped your secondary rods/hangers for something a little richer, yet?

 

Just tested the dwell. It was bouncing around from 22-28 on the 6 cylinder scale. So I want to adjust the IAB valve screw till I get to 30?

Right now I have DR rods and a B hanger. Should I swap them out?

 

Yeah, adjust the IAB to get it to hover around 30 degrees, with trans in drive (doesn't really make much difference). Opening out the IAB leans the mixture and dwell should drop to richen in response.

Rods and hanger should be good.

 

Oh yeah, properly ranging dwell is a good sign that all of your sensors, etc. are operating correctly. You must have done a good job rebuilding the carb.

You'll also be able to use the dwell meter in the future as a diagnostic tool for all types of sensor/carb issues from vacuum leaks to sensor checks. Hang on to it.

 

Ok I got the dwell to hove around 30 degrees Which wires on the tps sensor do I probe to check the voltage?

 

Middle and Lower. You can pop back the tab on the wire side of the connector and slide a safety pin/needle/etc. in there. Then reconnect it and check your voltage. Should be around 0.40 volts at idle. If you're not off too much it may not be worth opening up the access to the small screw.

If you do have to drill out the cover, be careful. It's easy to damage the screw or airhorn.

 

Im supposed to check it with the engine off, key turned to run position right? I checked it like that with the probes in the middle and lower and only got a reading of .02 volts and .08 when I moved the throttle to WOT. That doesn't look right, maybe im doing it wrong?

 

If you've backprobed the three wire electrical connector with a needle/etc. do a continuity check between your probe and the metal tangs inside the plug so you know you're good. Then plug it back in and try again. Should be able to get a good reading with ignition on/engine off. Was the M/C solenoid clicking? Should be (at least for a few seconds).

If you were getting good vacuum advance it indicates that the TPS is functioning correctly so you're probably suffering from operator error.

 

Took the car for a test drive today to see the affects of changing the dwell. Boy did that help out From a stop it pulls nicely to 6k rpm. It accelerates a lot better now. Guess I just need to mess with it to untap more power.


Also here is a soundclip

http://videos.streetfire.net/video/9...d100eafed6.htm

 

If the dwell is off the ecm loses some of it's ability to adjust primary mixture. Your dwell was a little low so it was limited on the amount it could richen the mixture. This can affect driveability at low throttle openings and throttle transitions between primaries and secondaries. Something as simple as changing to a better air cleaner can affect the mixture and require a dwell adjustment.

Sounds like my camaro but a lot better looking. What's that crazy looking line going to your carb inlet? Still running the mech pump in it's stock location?

 

That line is my fuel line The fuel pump is still in the stock location. I had to put a new fuel line in because after I installed my Edelbrock Q-jet manifold the stock line was too short and couldn't reach the carb haha.

The car is running good. Idles pretty smooth. Ive been driving it around town with no problems. Went out on the highway today but there were a lot of cops out so I kept it under the limit Pulls nice up to 6k rpm in first. 2nd gear pulled up to 6.5k rpm and still wanted to go but I let off. What rpm's can I safely take it to without breaking something? Can't wait to take it to the track

 

That depends on your definition of safe and the components and condition of your valvetrain, etc.

Keep in mind that the stock tach could be off a good bit. It may be reading higher than actual rpms. You may be able to use your dwell meter as a check for your guage tach.