[1980 TA]

I was driving yesterday and had a clear, flat stretch of road and wanted to test my panic braking. I set the car down hard and it died, I coasted to the side of the road and it wouldn't start. It had done this to me two weeks prior and it started but had little power but I was able to limp it home. Once there I found that the distributor had slipped retarding timing. Reset it and it was good to go.

This time it wouldn't start and had to be towed home. Once at home I finally got it started but had to max out the timing to do so. It will not idle down. If I back off the timing it will die. If I try to idle it below 1500 it will die. If I turn on the AC it dies real quick.

I did get to drive it around the block today and it ran great above 2K, but would die if I got below that. The AFR was showing where it always had in this range.

At 2K I have 10 inches of vaccuum which is way low. At idle before the problems, I had 15 to 18.

The carb is an Edelbrock and I rechecked the float settings. They were close to the factory specs, but resetting them made no change.

Adjusting the idle screws makes no change.

I thought maybe the hard stop flooded the car, but it has never had the gas smell which I figured it would have had it flooded.

I have plugged every vaccuum accessory and that made no difference. I won't guaranteed that there is no vaccuum leak, but everything was in place when the problem came up and have been triple checked or unhooked and the port plugged.

I noticed when I had the carb apart that there was some setiment of some sort in the bowls. I wonder if something on the idle circuit got plugged.

I had noticed in the past few weeks it occassionally would surge while cruising at low loads which I believe should have been the idle circuit.

There are a bunch of great motor/carb guys on this board and I am hoping someone can come up with some ideas as I am at a loss at this point.

If I had a spare carb, I would swap to see if it is in fact the carb, but that is where I am leaning at this point.

[getmygoat]

Sounds like you have a vacuum leak.

Dollars to donuts your booster is toast.

[1980 TA]

I had thought of that, but shouldn't my vaccuum get higher when I pull the line for the booster and plug it at the carb?

I checked the manifold to head bolts and they are tight. I sprayed carb cleaner around the base of the carb and it made no change. I had always heard that if there was a leak here, the cleaner would temporarily seal it rasing vaccuum and or idle speed.

I did put a bottle of carb cleaner in the tank. This seemed to help some. I was able to get it to idle at 1100. It still wouldn't pull over 7 inches at idle. I lowered the step up springs and it would at least move under its own power.

I am still running a ton of advance, but it would even restart hot, although it was a little tough.

[1980 TA]

I checked the booster again. I pulled the line feeding the booster and no change. I plugged the line and the car lost vaccuum. There was a difference making me believe the booster may be bad, especially since heavy braking seems to be the common link.

With the booster port plugged, the car ran pretty rich.

I was still low on vaccuum but the longer the car ran, the more the vaccuum started coming back.

I had over the past few months had to jet richer to get good driveability making me think that the booster was slowly going.

How much affect does primary jet size have on idle characteristics, if any? Do the jets affect the idle circuit?

I hope so as that might explain why it is running so rich now and the idle screw have no affect.

I was really hoping that plugging the brake port would immediately fix the problem although it seems like a step in the right direction.

If I can get the motor back in tune, I'll address the booster. I am not too disapointed as I had been looking at a hydra boost set up for a while and this would give me the reason to do it.

[Tim Corcoran]

If the booster is not leaking, removing the line to the booster and plugging it will have no effect. If it runs different with the booster line off and plugged that it does with it hooked up then you have a leak in the booster. There are shops that will rebuild your booster.

Tim C

[1980 TA]

I jetted it a little leaner with no change in vaccuum. I plugged every vaccuum line but the PCV, no change.

I really think something is wrong with the carb but I can't figure out why hard braking would mess something else.

But I have a harder time thinking that hard braking could cause anything else to break.

[Geoff]

The E carbs are a very simple carb, with an excellent float system, with little that can go wrong. Although highly unlikely, possibly the floats got bent with the panic stop. They have a lot of leverage against the float needle. I would check it anyway, easy to do, no gaskets required. Float level should be 7/16".

You said you 'occasionally' got surging at low loads. That could be an air leak [ booster? ] causing leanness, OR, fuel pump pressure erratic causing occasional flooding, unlikely.
I would disconnect & plug all vacuum lines, including the PCV. If you run vacuum advance connected to manifold vacuum, leave it CONNECTED. If ported vac adv, DISCONNECT. See if you can adjust your idle. If ok, reconnect the PCV; should get a slight rpm increase, necessitating readjusting idle speed slightly & the idle mixture screws. If you get a BIG rpm increase, the PCV is probably stuck open or manifold vacuum too weak for it to operate. Reconnecting ported vac adv, if used, should have no effect on idle; if it does, then the throttles blades are open too far at idle [big cam? ]. Reconnect the rest of the vacuum lines & note any change; there should be none. The above assumes that the float level is correct & carb is ball park adjusted.

[1980 TA]

I put on a new fuel filter and PCV today. No change. I put on a new Edelbrock 600 CFM carb (750 originally). Once I got it started I was able to at least drive it. The AFR was showing max rich at low engine speed. Once the car got going, it actually ran fairly well, just not much vaccuum although it got better the longer I drove it.

For the most part the AFR was very rich throughout all situations which struck me as odd as the carb was much smaller than what it replaced. At least with the smaller carb the AFR would come off of max rich.

[1980 TA]

I took the intake off to replace the gaskets as I figured I had a major vaccuum leak and this was about all that was left. When I turned it over there is a crack in the exhaust crossover all the way across from front to back and along the sides. Could this be the source of the exhaust leak? It is an EGR intake if that matters. The crack is over three inches long.

[1980 TA]

The new intake did not fix the problem, although I am happy to have one without a crack in it.

I pulled the distributor and found that the mechanical advance could not move. I could not get it to move with a hammer. It was rusted solid. When I started to disassemble the distributor to try and fix it it was missing a tanged washer on the bottom as well.

The shaft also had a lot of resistance to spinning so I ordered a new distributor and it will be here tomorrow.

Just to make sure, on replacing a distributor, you turn the motor over by hand until you feel air coming out of the #1 cylinder and then keep going until the timing mark is lined up, correct? This should be top dead center, right?

I know it is a simple question, but I want to make sure. This is how I staged the motor for the new distributor.

[kyle_blake]

yes correct.
finger.
look down and hopefully the line has not gone past the ZERO mark

Do not try and move it back with a strong arm, you could loosen the bolt.

Just bump it over again until it happens again and falls before TDC.

then use strong arm to move it forward so it's all aligned up.

[Malky]

You have a lot of weird stuff going on here.

Do you have an EGR valve? If so, a valve stuck open could explain some of your problems, especially no idle.

Fixing the distributor will definitely get the car running better but I don't see how it can be related to your cut-out under braking.

[1980 TA]

No EGR. I replaced the distributor with a new one today and it fired right up. Timing was in the right ballpark and everything looked good there. The engine still would pull very little vaccuum and began backfiring through the carb.

From what I have read, this sounds like a valve problem. Does anyone else have any other ideas?

[1980 TA]

I advanced the distributor and it idled smooth at 1250 but still only pulled 7 - 10 inches of vaccuum. I was able to drive it around the block and it didn't drive bad considering there is something wrong. The AFR is fine at idle, and then dances around a bit while driving. I know it is a little lean on the primary side given the smaller carb and I haven't jetted up yet.

It backfired out the carb twice while I drove it but I don't know if that was because it was lean or not. When I let off the throttle with it in gear the vaccuum will jump to 15 to17.

I am going to do a compression check next as I can't think of nothing else to check.

I tried a can of sea foam as I figured it couldn't hurt at this point. It seemd to smooth things out but no change in vaccuum.

Here is what I know to this point.

The carb is new

The intake is new and sealed properly

The distributor is new and installed as it should with the motor at TDC

Vaccuum is too low

The motor only runs with a high amount of initial advance

The motor turns slow when warm but will start. This seems consistent to me with a motor running a lot of advance.

The motor actually runs smooth at higher rpms. A vibration I had before is no longer noticeable.

The motor doesn't make any odd sounds.

The problem started when I slammed on the brakes and the motor died.

Come on guys, there are a bunch of knowledgable folks here and someone has to have some thoughts.

[1980 TA]

I found a timing chain test on line that said to watch for rotor movement while turing the motor the opposite direction. According to the article one should see movement in rotor in 3 to 5 degrees.

Doing this I checked mine twice and got 14 degrees of movement on the first test and 18 degrees on the second test.

Am I safe to asume that the timing chain is stretched and casuing the problems?

In further reading on stretched timing chains, I found that this will cause low cylinder pressure in all cylinders which I believe should lead to the consistent, steady low vaccuum reading I am getting.

[kyle_blake]

I believe the higher Hg of vacuum you are seeing on your gauge when you let off the gas while driving is an EXPECTED normal CONDITION.

At least if your mesuring manifold vacuum...

I've seen this condition in several vechicles I've travelled in over the years.

You've got the new carb and install it but then you find out your distributor is rusted ?

I don't believe a stretched timing chain causes the inability to have your car idle correctly between 600rpm-850rpm.

I dunno I'm probably venturing a little to far, some mechanics here can verify that better then me.

When you say backfire, you mean carb spits fuel back up right?

Or is it a much louder noise?

You mentioned valve's...earlier.

I had a couple lobes on my old Hyd. camshaft's lobes grind down.

I didn't have the starting problems you have but when I revved it up past 1500 rpm, you bet you could hear the pat, pat , pat back threw the carb.

Just some ideas.

I guess the hard braking moved something to failure. Hmmm

[getmygoat]

Originally Posted by 1980 TA

I found a timing chain test on line that said to watch for rotor movement while turing the motor the opposite direction. According to the article one should see movement in rotor in 3 to 5 degrees.

Doing this I checked mine twice and got 14 degrees of movement on the first test and 18 degrees on the second test.

Am I safe to asume that the timing chain is stretched and casuing the problems?

In further reading on stretched timing chains, I found that this will cause low cylinder pressure in all cylinders which I believe should lead to the consistent, steady low vaccuum reading I am getting.

Funny because as I was reading your previous post with current symptoms - I was also thinking timing chain.

You've tried running it with every possible vacuum port plugged simultaneously, right?

Maybe the sloppy timing chain jumped a tooth under the severe deceleration?

Another option might be the severe decereration caused oil starvation on the valve train and caused cam and/or lifter(s) failure(s).

[1980 TA]

I've tried running it with every vaccuum line plugged and no change there. I am pretty confident that it is not a vaccuum accessory problem.

I pulled a valve cover and did some quick checks that would point to a lifter/valve problem and everything passed.

I found some old posts on this board where one of the members recommends no more than 10 degrees of crank movement before the rotor turns for grocery getters. This confirmed my findings of a bad timing chain.

The fact that it runs better at higher rpms makes me believe that the timing is retarted even though the timing light says everything is in order.

I called around town to some garages and got to the guy everyone in town recommended. His first thought was bad timing chain as well. He did refer me to a 30+ year GM mechanic that also taught classes on internal engines and I am waiting for him to call back.

[getmygoat]

I'd suggest doing it yourself... For the cost of having it done you could drop in a new motor.

[72 Street Bird]

Sounds very much like the timing chain is stretched. The chain has most likely jumped a tooth each time you had trouble restarting it causing the valve timing to be off farther each time.
If you have the capability to do it yourself I would. My friend spent between $400 and $600 to have his replaced when he was out of town and his jumped.