I am having trouble getting my engine to run right after putting the top end back on. I need some quick help with this, as I need to get the car running in the next few days. It's a 1985 LG4. Here's the problem:

I've blocked all the vacuum ports on the carburetor, and the EGR valve thing, so I'm pretty sure I don't have a vacuum leak. The car will fire up, but it sounds lumpy...like it's not running on all 8 cylinders. There's some black smoke coming out the pipes too, which would indicate unburnt fuel. After a few seconds, the engine will bog down and die, but it'll start up straight away if I crank it. Trying to keep the car alive by holding the throttle partially open results in a backfire through the carb and an encore of whispy white smoke emerging it. I discovered that while the car is running, if I pinch the fuel line, or manually open the choke butterfly, the engine revs pick up a bit and seem to run stronger.

I have not set the timing with a timing light, but if the car starts and runs I can only assume that the timing can't be far enough off to stall the car. I haven't adjusted the mixture settings since I took the carb off, so I don't see that they're wrong. Here are my questions :

1. Why would the car just stall? Even if it weren't running on all cylinders, if it runs at all it should stay running.

2. Could not having the inline fuel filter installed somehow "over-fuel" the carb, causing it to run rich? Incidentally, I do have an inline filter installed further down the fuel line, I just wondered if the GM filter caused problems if it weren't there.

3. On the distributor there are the usual 3 plugs on the driver side(tach, batt and the other one), but an additional 4-wire plug coming from the passenger side also...would that be something to do with the electronic timing advance?

4. Would something simple like a lack of spark on one or two of the cylinders cause black smoke from the pipes, and the engine to stall?

Many thanks,

Si

 

I'm open to any suggestions, obvious or not. I am going to start by checking each ignition lead for a spark. Any suggestions as to what to try if they are all sparking?

 

It could very well be your timing.

My friend felt the need to mess with his timing on his newly built 350 and got his eyebrows singed from the carb backfiring. It caused from not enough advance (retarded. The timing, not my friend ).

His has the XE274 cam with an MSD Digital 6 box.

We just finished it Friday night, and he couldn't keep his hands off of it after I and another guy set it up for him.

I guess that'll learn him.

 

I'd say one of 3 things (or a combo of them?)

A) Timing is off
B) Carb needs a tune-up
C) Carb may need a rebuild

 

first thing you need to do is reduce the banner in your sig so people don't have to scrool over to read your thread. are you sure the valves are right? i'd guess not and you already know your timing isn't right, and pretty close isn't good enough. move the distributor a bit ,or have someone do while the engine is cranking.

 

Could bad adj. valves cause running rich/lean and more/less vacuum too?

 

Si,

Add my name to the list of those suggesting setting the timing ASAP.

Also, I haven't been near any yards lately, but should be going this weekend. I'll see if I can round up the parts of that bolt kit.

 

Thanks for the replies guys

Is it that big then? Apologies, I just got a new computer and the resolution is mega-high. I'll get right on it.

As far as I know the valve lash is set right, I followed Vader's directions. I'd prefer to set them with the engine running, but obviously I can't so I'll check them all again tomorrow. As for the timing, I know pretty close isn't good enough when running a car, but I wouldn't have thought the engine would stall if the timing was "pretty close", I thought it would just run badly. Am I wrong about that?

Vader...no hurry on those bolts, although could you add the throttle cable bracket to the cart too please or at least post a picture of it so I can make one!

 

the 4 wire plug is your electronic spark timing, the car should run without that plugged in, you need to have it unplugged to properly set the timing, are you sure that you have the spark plug wires on the right cylinders? double check that.

 

Yea, double checked and triple checked that one.

I have that connector unplugged already, because I thought it was the spark timing.

 

ok first off why did you have the top end off? what did you do, are you sure nothing got in and contaminated the carb?

 

Because I was replacing the head gaskets and valve stem seals, along with various other odd jobs on the engine. I'm sure the carb is not contaminated, it was in a container most of the time it was off the car, and I cleaned it out and replaced the top gasket before I fitted it to the car.

 

i'm thinking either you moved an adjustment in the carb or something.

my car did that at one time because i somehow had little metal chips inside the carb, replaced it and that solved the problem.

you can get a q-jet remanufactured by holley at autozone for around 150 i believe

 

Not in this country you can't....

I could probably pick up a replacement carb if I had to, but I want to make absolutely sure that is my problem first.

 

just a FYI, when i put my motor together i had the distributer dropped in a tooth off. The motor started but ran like garbage, much like yours is. I put the timing light on it only to see that i had 60* of advance at idle. So don't think it won't run if the timing isn't right.

Eric

 

there is no such thing as having the distributor a tooth off, only thing that affects is the rotor relation to the cap, which is solved by turning the cap.

 

fine then, the distributer was dropped in such a way that it was impossible for me to position the cap in relation to the rotor and have correct timing. Repositioning the distributer on a different tooth allowed me to gain the correct relationship between rotor and cap. Always gotta be difficult....

Eric

 

what happened? I would really like to know how it is comming along. this may have nothing to do with your problem but, I know when my brother inlaw put his motor in he had a simalar problem he kept getting real crazy and asking me why it was not running right and why it would shut of ect. I kept telling him his timming was off. he just asking me over and over (like I should know what he did) well I got fed up went over with my timming light and set it. it ran fine alittle rich but, the right timming has his car running now.

 

zupmanz28 sorry, didnt mean it like that, your right about the positioning, but if you could not turn the cap in such a way then it was more off, i'm just trying to help

 

I'm with Zup, it sounds like your rotor isn't pointing at #1 when it is at TDC, it'll run, it'll backfire, it'll sound like crap, it'll belch smoke and it'll shake like it has the DT's. If the oil pump shaft wasn't in quite the right position when you put the dist in it may have made the rotor turn to just in front or behind the #1 terminal.

 

Well guys, the timing was off a little, but the main problem was the valve lash, as ede mentioned. It was set too tight and I had very little compression. Runs like a top now, but I need a throttle cable bracket / TV cable bracket to be able to move the car now. If anyone has these brackets, I would be very interested in buying them and paying the shipping costs.

Many thanks for all the help

 

no problemo man, i was just being difficult

Eric