Timing and/or Carburetor Issues?

[justin85xx3]

Last week I was working on replacing my oil pressure sending unit and I bumped the distributor while I was wrenching it down in place. The distributor rotated on me slightly and I tried to set it back to where it was but after a test drive the car ran real sluggish and backfired. Before the oil pressure sending unit I also replaced the fuel sending unit in the gas tank (fuel gauge had stopped working too) and this was the first test drive since either were replaced.

 

Broke out the timing light and found that the initial timing has to be between 30-35 (using a digital timing light like this one), anything more or less and the car starts to bog down. I know that 30-35 is usually the total timing, but this is my initial timing at around 700-800 RPM at idle... All this, and no matter where I set the timing I can still hear it backfiring occassionally in the exhaust.

 

My father rebuilt the engine a few years ago and he put a mild RV cam in it and electronic ignition, but everything else is stock (350 with 2bl carb). The motor idles rough (it's always idled a little rough and as I'm a novice I just figured it was the cam. It would always die several times when first cranking up from a cold start and putting it in gear, but once it was warm it would do ok) but now when I put it in gear the engine stalls out even with the engine warm. I've also noticed a really strong exhaust odor lately, the kind that permeates into the skin and clothes prompting demands of an immediate shower from other members of the household once I come inside the house. 

 

Any ideas where I should even start here?

[Sam (Bones)]

did you disconnect the vaccum advance before checking the timing?

[justin85xx3]

did you disconnect the vaccum advance before checking the timing?

Yes I disconnected the hose from the distributer and plugged hose with a rubber vacuum cap.

[Sam (Bones)]

few things come to mind...your balancer outer ring may have slipped, you need to find true TDC and check your timing marks, also sounds like you maybe running on the lean side some

[Sam (Bones)]

and are you still running the points distributor?

[stangeba]

http://www.speedwaymotors.com/Tech/locating-top-dead-center.html

 

Like Sam mentioned,the outer ring may have slipped or spun on the rubber and now is no longer where it should be.

I looked on the interwebs and found several procedures but this one was, I thought, good.

 

I also remember someone using a coat hangar, stuck into the #1 spark plug hole then rotating the engine by hand till the piston hit the coat hangar and stopped the rotation, marked that spot on the dampener, reversed the direction till it stopped again, marking that spot, then using the center point of those two marks as TDC.

 

Not sure if that will work on your engine but it worked great on the engine he was working on.

 

If you do that and the TDC mark is already where it should be, a spun ring is not your problem.

 

I used a fancy timing light one time, it sure was different.

 

Anything else change since it ran great?

 

Bruce

 

[stangeba]

http://www.amazon.com/gp/product/B000EVU8J8

 

I found this in the (above link) review section: (What type HEI do you have?)

 

My wife purchased this Timing Light for me as a Christmas gift and it has some of the nicest features you could imagine. Only one problem though, it does not function with any vehicle that has an aftermarket MSD or Mallory ignition system installed. It functions sporadically when these type of ignition system are installed on your vehicle and the MSD website confirms this as well. Many timing lights have trouble reading the MSD's capacitive discharge multiple sparks. Dial back timing lights are not recommended either.

 

Very disappointing that I must send back this full featured Timing Light because it simply does not work with MSD (Multiple Spark Discharge) ignition systems.

[wallaby]

Those 2bbl carbs are nearly bullet-proof. It's pretty rare that one has a problem, but if your engine needs that much initial timing to run, either the balancer is wrong (as discussed above) or your carb is running way lean. With the noxious fumes out the tailpipe, I vote for the lean carb.

Try running the engine with the air cleaner off, and moving the throttle with your hand as you lean over the fender. Next you want to open the throttle with one hand as you cap your other hand over the top of the carb. The idea is to put a strong suction on the internals of the carb to pull through any debris that might be clogging things up. Take your hand off the top of the carb before the engine dies. A couple of pulls this way should do the trick, or its something more serious and requires the carb be taken apart.

 

Another possibility is bad gas. Is your gas fresh? Old gas just doesn't want to burn and can cause all kinds of grief. Just ask anyone who has stored a motorcycle or snowmobile or boat.... 

[Sam (Bones)]

Mark!!!!!!

 

it's great to see you!!!!! 

[justin85xx3]

Appreciate everyone's input so far. I put the monte aside for the past few months as I had to deal with real life, but I got back at it today and went over everything I could think of including your suggestions here. I got it idling really well and I set the fuel mixture on the carb just right but it still stalls immediately when I drop it in gear. I had it idling at around 900 rpm but also tried speeding it up to around 1100 and that did not help the stalling. I drained the fuel tank and replaced with fresh fuel, but that did not affect anything.

 

I did some more searching on the web and everyone mentions vacuum issues, so I checked all the vacuum lines and did a variety of tests and cannot pinpoint the issue. I tried sucking on the vacuum line that goes to the distributor and held the vacuum with my tongue and it holds vacuum just fine. 

 

I'm still at a loss. Figured I'd post some pics to see if anyone spots anything that I might be missing.

 

 

 

The arrow is where the vacuum line comes out of the carb and splits, one end goes to the distributor and the other to a vapor reservoir (??) beside the radiator. The yellow cap on the other vacuum port is for the line that normally goes to the air breather. I tested with that capped on/off and it didn't seem to make a difference on the stalling. 

 

[monte70car]

Try and remove the power booster vacuum line. The power brake booster could be leaking air cause it not to idle.

[Sam (Bones)]

on the drivers side valve cover, remove the line at the PCV that goes towards the front of the car. plug the "T" and see if that helps

[stangeba]

While reading this I also though of the power brake booster as a possible problem when you step on the brake.

Try this, apply the parking brake then, without stepping on the brake, shift to drive. See if it makes any difference.

Or unhook and plug the line as mentioned above.

Does it have a stock 350/400 trans?

If it has a newer over drive, could the converter lock up feature be stuck on?

Good luck,

Bruce

[wallaby]

Ok. Starting at the beginning, you said it ran sluggish and backfired. Did it backfire through the carb?

The pressure from a backfire can blow out gaskets or push off hoses and cause a vacuum leak. I still believe the engine is running lean and a vacuum leak could sure cause that.

Now looking at your pictures, it sure looks like you are missing one of the hold-down bolts on the base of the carb. Maybe it's just the photo but it looks like the carb is held to the intake with just 3 bolts and is missing the one in the right rear... in the back near your yellow vacuum plug.

 

You need all 4 hold-down bolts to keep the carb sealed against the engine. If that one bolt is indeed missing, your backfire probably blew out the gasket seal in that corner and now you have a sizeable vacuum leak. Maybe putting in a new base gasket and a bolt will fix your problem. I'm lazy, so I'd put in the bolt and tighten it down first and maybe your old gasket will continue to work.