timing issue


#1

Hey guys I got a a 1991 Chevrolet suburban which I believe is 350 5.7 L engine and I seem to have a timing issue. It all started when I took the distributor cap off to check if it needed replacement, when I took it off one of bolts broke flush with the distributor and didn’t notice until I went to put it back on so I decided to just pull the cap back and when I did the second bolt did the same thing. Being stuck far from anything I tried wire ting the distributor cap down to see if it would run. Mind you not I am homeless and that wasy only option at that time.

When I started the engine it began spurting, choking and somewhat began to smoke so I quickly shut her down.

I’ve since then drilled out the broken bolts and retapped the holes and installed a new distributor cap and rotor button and started the engine and its sputtering like crazy and doing the same thing.

I next pulled off the cap and manually turn the engine and lined up the mark on the harmonic balancer to TDC and when I checked the distributor the rotor is about a inch or less from #1 plug and I’m on compression stroke because if I turn one more rotation the rotor is on the other side of #1.

I also noticed slack in the timing chain when turning the crank the rotor don’t move with it until the chain slack is gone.

I never moved the distributor and the engine ran fairly smooth until I started the engine with the rigged cap.

Any ideas what might have happened and why the distributor rotor has moved past #1 when on TDC?


#2

Not necessarily. What you describe is exactly what happens when you are “180 degrees out of time” The 4 stroke gas engine passes the timing mark TWICE in the time the distributor passes #1 ONCE. If you are turning the engine by hand, remove the front-most driver’s side spark plug, put your thumb in over the hole and turn the engine clockwise as you face it. If significant pressure doesn’t push your thumb away as the timing mark comes around, you aren’t at top dead center. Turn it one entire revolution and as the timing mark comes up on the pointer, pressure will come out. Stop when the mark lines up. Look at the distributor, is it pointing at #1 or is it pointing at #6? If it closer to #6 than #1, pull the distributor and re-align the rotor until it is pointed at #1. Install, and re-time.

Instructions are here:


#3


Yes I’m on compression stroke because when I do another 360 turn I’m near #6.

I’ve attached a picture and according to the timing mark on the balancer I’m at 0 BTCD as according to the sticker under the hood, but look closely the rotor is right around 45 degrees past #1 which is in the front right from the one my finger isn’t touching.

Basically I’m stumped on how the rotor moved that far off from trying to rig the cap down when the screws broke because before ever removing the cap in the first place the engine was running.

Anyways I’ve never messed with a distributor. To get the rotor back to #1 do I have to remove the whole distributor and reset it or is there another way?


#4

I’ve since then marked the distributor at #1 just to be sure I wasn’t turning the cap and its for sure past #1


#5

Reread what @Mustangman said carefully about compression on #1.


#6

I can’t get my finger in there and turn it and I have no helper so instead I’m going to use a piston stop tool and recheck it probably over the weekend.


#7

My initial thought goes something like this- it was running OK. You pulled cap to inspect, buggered it up and attempted to put it into the right spot with wire ties to get it back running. That caused it to run poorly, sputter and perhaps even backfire. The timing chain was already slack but still on time but when it ran poorly, it jumped time and is now off.

I would double check the timing just to be sure.

This leads me to believe something has gone wrong with the chain and tensioner set up. There will always be some “slack” if you reverse direction but it shouldn’t be huge amount.

Once you double check your observations, you could pull the dizzy to see if something got buggered up with it, causing the delay in rotation. After that, I’d consider pulling the chain cover to inspect…


#8

That will NOT help. You could be at top of the stroke as indicated by the stop but NOT on the compression stroke. Go to Wikipedia and read about 4 stroke engines.

I think TT is on the right track. IF you turned the engine backwards (counter clockwise) by hand and IF it has a boat-ton of miles like a typical 1991 truck, you may very well have skipped a tooth on the timing chain and now not only is your distributor out of time but you cam is also out of time.


#9

For some reason my phone wasn’t loading right when I first read that wiki page a few days ago but I understand it better now after relooking. So I guess I’ll just find a way to plug off #1 and use the starter to turn the engine until it spits it out then line up the balancer from there and recheck the distributor rotor spot. Would this work?


#10

I’m thinking when you switched distributor caps you placed then wires on wrong and you are off by one tower.


#12

I plugged off the hole and cranked the engine once and my plug popped pretty loud so that cylinder has got compression but beside the point. To make sure I’m on #1 I replugged #1 and it took server starts to pop out again then turns the crank by hand until the rotor hit the mark I made on the distributor and checked the mark on the balancer and sure enough its right around 1" give or take from lining I up to 0. If I turn it to line up then my rotor will be where I been saying about 45* past #1.

So now should I align the harmonic to 0 on then pull the distributor and reset it so the rotor lines up to #1 then try to start her?


#13

That’s what I was thinking. 1-8-4-3-6-5-7-2. The original small block Chevy firing order is permanently etched in my feeble mind.


#14

I aligned the new cap with the old one and switched one by one if looking from the front #1 begins right around 5 oclock. Also when I removed all the plugs I numbered them and rechecked and every wire went to the correct place.


#15

First, lets stop concentrating on the rotor and look at the reluctor. There is an eight pointed star shaped piece on the distributor shaft under the rotor. You will have to remove the rotor to get a good look. As the distributor shaft rotates, these points on the star go by a pickup commonly called an ignitor. On the side of the pick up facing the reluctor is a thin metal line.

Turn the engine toward TDC but as you approach TDC, look for the mark that indicates initial timing. I.e., if the engine is supposed to be set at 4 BTDC (4 degrees before TDC), then stop there. The line on the pickup should be aligned with a point on the reluctor (star) or very close. If it is not close, you have jumped timing.

Now this may not be completely true if the engine uses the computer for timing. If so, then there will be a cam position sensor instead of an ignitor and that should line way before TDC. I don’t have the details on this system.

BTW, the rotor I believe has a square peg and a round peg that go into corresponding holes in the mounting plate. This insures correct alignment of the rotor. I suppose that if you try hard enough, you might be able to mount the rotor 180 out.


#16

I took a look there is a blue dot on the reluctor and I’m guessing this should line up to the metal line “?” either way I’m having trouble locating the metal line.


#17

Can you post a picture?


#18

Yes I’ll get a picture later when I get back to it.

In the mean time I’m going to just assume the chain jumped and can timimg is off.

I’ve been searching on how to set the timing for the cam but so far I’m finding nothing on how to do this for a 350 SBC.


#19

If the distributor cap was not straight when you wired it down the rotor may have hit one of the spark plug wire posts causing the distributor housing to turn. Inspect the distributor housing at the hold down clamp for drag marks indicating the the distributor has moved.


#20

I would not assume that. But just FYI, there is a dimple on each timing gear near the teeth. You align the dimples as close together as possible, i.e., the dimple on the cam gear (large gear on top) is at the bottom and the dimple on the crankshaft gear is at the top. The engine is then at TDC on the compression stroke for #1 cylinder.


#21

Thanks for the info.

I finally got back to the truck and got a pic of the distributor as is this is all I’m seeing.

I’m not seeing that line you spoke of earlier, the only thing that I’m seeing is the blue dot that I mentioned. And I just noticed the green dot on the electronic part. Not sure if that means anything lol.

At this point in time I’m wondering if I should pull the dizzy out and drop it back in to where the rotor is pointed to #1. I’m concerned if cam timing is also off and I move the dizzy then start her I will possibly damage something internally if its not already done.