Rebuilt QJet from Cliff not running right

I just installed the 76 Q Jet Cliff Ruggles rebuilt for me last year for my 455. I fired it up and it was racing pretty fast, around 2000RPM, then it would slowly die. After doing this a couple times, I got it to run for about 5 minutes idling at around 1200RPM, but then it slowed down and died.
I tried adjusting the cold idle and warm idle ajustment screws, but they did nothing. Now it's dying as soon as I start it up. If I keep the throttle open holding it around 2500 rpm the engine will run, but it feels like it just wants conk out. As soon as I let go of the throttle, it dies.

My previous carb was an Edlebrock performer 750cfm using a 1" spacer. Timing was set to 13 deg initial advance, and it idled around 800rpm.
The engine is .030 over and had a TA212 cam, 76 heads with stage 1 springs and 10:1 pistons.

Here are a couple pictures. The only vacuum hoses I have connected are the timing advance and PCV, which is how I had the Edelbrock set up. Cliff shipped back the rear vacuum diaphram loose, so I didn't reinstall it.

I'm sure it's something I did or screwed up, I'm just not sure how to troubleshoot it.








Thanks for the help!

 

Did you call Cliff, I'm sure he would help too.

3rd picture looks like you have two gaskets under the carb? What intake is that?

2nd picture indicates choke is on, and fast idle is engaged. Will the choke release and the front flap open?

 

i think were trying to adjust the hot idle with the fast idle set and you set the low idle so low it wont run thinking it wasnt making a difference.

 

Didn't get a chance to call Cliff yet, it was getting late here.
I have two of the 1/4" gaskets from Cliff under the carb. Was trying to get 1/2" space in there. I can try removing one and see if that changes anything. I'll start there and see what happens.

both idle screws are back to their original position now. I tried each one seperately at different times.

The pictures were taken before I fired it up. The choke is releasing and the front flap opens like normal.

Intake is Edelbrock Performer.

 

You need to use the edelbrock adaptor plate when using a spreadbore carb on the squarebore intake. Says in the edelbrock info regarding the performer intake that not using that plate will cause a huge vaccuum leak.

 

Indeed, it sounds like a massive vacuum leak. Also verify that you aren't opening the EGR valve, if it's still on there. A high idle can bring that on, if the thermal vacuum valve is stuck open. Also, those gaskets can be flipped 180 degrees around the front to rear axis. That's another source of a vacuum leak. Done that one myself.

 

This is a spreadbore intake. I hade to use an adapter when I had the squarebore Performer carb on it because the intake is spreadbore.

 

Did you plug the small vaccuum port on the rear base of the carb? It's very easy to miss, but will cause alot of problems if it's not used or capped. It's the size of the advance ports but at the very bottom on the back.

 

Guys,

The Performer is a spreadbore intake, the Qjet will work fine with no plates or adaptors. Just make sure ALL vacuum ports are plugged.

Listen, FIRST make sure all vac ports are plugged, then check the needle and seat for trash. Sounds like you have some trash stuck in it and its flooding, hence the high idle then dieing out. Just take off the top plate of the carb, remove the float and pull the needle out. Best to take the carb off the car.

Easy way to tell if you have trash in the needle and seat is if the carb emits a smokey mist when you shut it off. That is excess fuel in the intake evaporating. Very simple. If you find trash in the needle and seat, it will be best to go ahead and change the spark plugs once its fixed. It takes VERY little raw gas to foul a spark plug. Dont change the plugs and you will chase your tail trying to figure out whats wrong with the carb and timing when its the plugs the whole time.

Here is the Performer info from the Edelbrock site.

 

Oh, and that carb sure is purty. Sure looks better than my scroungy qjet.:3gears:

 

Thanks Jim, I didn't notice any mist after I shut if off, but I'll check again tomorrow. If that is the case, how do I clean the trash out? I've never done any carb work myself, so this is all new to me.

 

I went to my local Borders at lunch today and their automotive section left a lot to be desired. Only 2 Shelves for cars and 1/2 shelf to How To books. So I went and ordered Cliffs Book from Amazon, I'll just have to wait longer to go through it.

 

This will help in the meantime.

http://www.oldcarmanualproject.com/manuals/Carbs/Rochester/QJet/HTML/MCarbRoch1973_4M_0001.htm

Devon

 

Run the engine to get some heat into it if you can. When you shut it off, if the carb smokes there is raw fuel sitting in the intake manifold and it is evaporating causing the mist.

An easy way to tell if you have a vac leak is to do this. While the engine is running, slowly cover the top of the carb with your hand. If the idle speeds up, you have a vac leak.

To clean the needle and seat, pull the carb off the engine then send it to me.

OR,

Remove the carb from the engine. Take a very small punch and push the pin back holding the accellator pump rod in place. Remove the rod and disconnect choke linkage etc. Remove the screws holding the top plate on and lift the top plate off the carb carefully. Next remove the gasket and the primary metering rods. Then lift the float out and the needle should come out with the float. Look down into the seat area and you will prolly see a small piece of trash sitting on the seat. This will keep the needle from shutting off fuel flow when the float is up and the fuel bowl is full.

Reverse everything to put it back together making sure to seat the plug that holds the primary metering rods in place. Dont overtighten the top plate and be careful pushing the pin back in place that holds the accel pump arm.

Its not as complicated as it sounds trust me.

Or again, send it to me and I will do it for you and send it back.

Another thing you might try is to remove the fuel inlet line from the front of the carb, and the fuel filter if it has one and blow some compressed air into the fuel inlet. Not too much pressure tho. This may blow the trash out without going into the carb. Put a rag over the top of the carb in case any fuel blows out too. I dont want fuel going all over the bottom of your hood.

Hope this helps.

 

Jim,
Thank you very much for both the explaination and offer. I did some more fiddling this afternoon, and right now I'm pretty sure it's a vacuum leak at the gasket(s). I got the car to run with some adjustments and now it's idling at around 700rpm, although the idle isn't as smooth as I would like it.

I sprayed some starter fliud at the base gasket while it was running and it sped up. This was something I remembered from a long time ago, but I'm not sure it it still has merrit.

Since I was trying to get 1/2" space between the carb and manifold I used two of the 1/4" base gaskets. One I got from Cliff, which is the blue one, and the other was from T/A Perf, the black one. The black one had some patterns molded in it, so I matched them up to the base of the carb. I think this setup is what is causing the leak.

So now what I think I need to do is find a 1/2" spacer to use, problem is I've never seen one listed anywhere. I've only seen 1" spacers, and the 1/4" base gaskets, which I why I picked the gaskets.

 

You can get 1/2" spacers. Post for one in the parts wanted section on the board here. I'm sure someone will have one.

When the engine is running, cup your hand over the primaries and if the idle speeds up you have a vac leak. Very easy to check.

 

Keep in mind you have to set the idle mixture screws on the bottom of the carb... Set them to get highest vacuum using a gause with the car in gear and wheels blocked.

 

Hopefully the new spacer works out for you. It sucks to have to tinker with these things but it sounds like you aren't in too bad of a spot considering what other possible problems it could have been. Keep us updated on what the spacer does for you.