Timing question

[sheetsofsound]

My travails with a recently resurrected car continue...

Timing. As I move the timing toward 2 degrees BTDC at idle, there begins a loud, intermittent knocking sound. When I say loud, I mean it sounds like a piston is trying to move sideways through the block. Scary. As I retard the timing toward, say, 16 degrees BTDC the knocking disappears, unless I rev the car hard at idle, at which point it will knock once as the RPM's rise. At @ 12 to 16 degrees BTDC, it will idle, but driving under load the car sounds like tractor and there is no power. The timing retards smoothly when revving at idle. Vacuum at idle is @18.

This all seems very... well... retarded.

Why can I not get the car to 2 degrees BTDC? And what IS that loud knock?

Just to make things interesting... I have two cars and both cars are doing similar things, so I am thinking it is something that I have changed on both cars. The only thing I have changed on both cars are the spark plug wires. The measured resistance on the wires is 1000 ohms, well below the 5000 ohms that Mildred recommends, but higher than 0 ohms that solid wire would provide. One car has the stock AC Delco distributor, and the other has a Crane/Allison set up using the Lucas distributor. Do both these ignition set ups require the 5000 ohm cables in order to work properly? The cables I put in were Beck/Arntley at @$40 per set. My next choice of cables from the local auto parts store is @$85 per set, but there is no guarantee that the resistance will be higher. When I ask for electrical resistance info, the helpful reply is, "Yeah, these are the recommended ones for your car. Dunno." What brand have others used successfully?

And finally - Are my efforts to become less retarded actually being stopped by spark plug wires, or could it be something else? Beer, perhaps? Should I start drinking <i>before</i> noon? Wait... what time is it?

[Workshop Help]

First things first...and it appears we have several things to go over first.

Terminology - BTDC means the ignition spark is being triggered before the piston reaches the top of it's throw. On a TR7 timing marker plate, (which is labelled, by the way), the BTDC area is on the lower part of the plate. ATDC means the ignition is being triggered after the piston reaches the top of it's throw. The ATDC area on the timing plate is on the top part of the plate.

Please clean off your timing marker plate with brake cleaner or whatever stout solution you have so you can actually and clearly see the marks engraved on the plate. Thank you!

Next is the matter of whether the timing marks are in fact a true representation of the engine being at where it's supposed to be.

This is determined by following the steps outlined in the Factory Workshop Manual.
A. After removing the valve cover, rotate the engine to bring #1 piston to top dead center when both valves are closed and the notch on the camshaft flange and the camshaft front bearing cap are aligned.
B. The distributor rotor must now be pointing at the rear intake manifold bolt. If not, remove the distributor to rotate the shaft so it does align with the aforementioned bolt.

Illustrations of this can be found in Section 12.10.14 of the Factory Workshop Manual.

At this point, the timing marks on the front engine pulley should be lining up with the timing marker plate for an initial engine start up. Further refinement to the desired ignition setting can now be achieved with your timing light.

Please perform the above steps. The loud knocking can possibly be attributed to a mal-timed engine.

Please report back on your progress. Your personal pit crew is standing by in eager anticipation.

Mildred Hargis

[sheetsofsound]

Timing marker plate is as clean as a dinner plate. Unfortunately before I could get to the garage with the stout solution it was, I must confess, consumed by yours truly. I cleaned the marker plate with a tiny wire brush instead. So clean it shines.

Timing mark on the pulley is at '0'; notch on the camshaft flange and front bearing cap are aligned; the distributor is pointing at the rear intake manifold bolt. I had already done this, but had not removed the valve cover, instead peering under the oil cap with a light and a small mirror. I have now taken off the valve cover and all looks as it should.

Anything else before I return the valve cover to its rightful place?

[Workshop Help]

Engine vacuum at 18". All the marks line up. You've got ignition fire. You've got gas in the cylinders. The engine runs.

But, the engine knocks and lacks adequate power with the timing being shifted all over the place with no real happy spot being found.

Folks, is it time for our hero to perform a compression test? I think it is. Oh, and is there oil in the crankcase?

Mildred Hargis

[Hasbeen]

How old is your petrol?

My 15 horsepower John Deere ride on mower refuses to run on petrol more than 12 weeks old. It knocks like a 1950s diesel, develops no power, & emits clouds of white/grey smoke, if asked to do so.

While I have never found a 4 pot so sensitive, & have run 7s on aging fuel at times, it was never more than 6 months or so old. If yours has been sitting for a long time, that might be a problem.

Incidentally, is there any water in the carb float bowls, or in line filter. If the thing is getting an occasional gulp of water, it could misbehave in protest.

Hasbeen

[sheetsofsound]

The petrol is new; I drained the tank completely and refilled it a month ago. The carbs I rebuilt, so no danger of water there.

Oil is where it should be and has almost no miles on it - still a beautiful clear brown. (Almost the colour of my favourite stout solution. What time is it?) Compression test will have to wait, as my superhero costume is at the cleaners until Tuesday. (I have to work at my straight job, in other words.)

[sheetsofsound]

Compression test hasn't happened yet as I got sidetracked. Tried starting her up (its Tuesday) and she wouldn't go. Fiddled with the Allison/Crane optical pickup in the dizzy and got her to go. Noticed a few things:
1) Vacuum is down to 14~16.
2) Terrible shaking continues; misfire?
3) Timing can now be set to 2 degrees BTDC with very intermittent very loud knocking.

Happy about the timing, but unhappy about the change in vacuum, I pulled the plugs to get ready for compression testing. Plugs 1 and 2 are a golden tan colour - nice! Plug 4 is black. Plug 3 looks just like when I put it back in - clean. Seems my misfire is happening there? Could the misfire be the cause of my loud knocking?

Compression test will happen after I make dinner for the ravenous horde that resides with me.

[Workshop Help]

Substitute that misfiring cylinder spark plug cable with a good spare and see if the knocking subsides. Clean the spark plug gap with a few swipes of sand paper.

The compression test is important.

Remember, the vacuum gauge needle MUST be rock steady and not dancing around.

Mildred Hargis

[sheetsofsound]

Subbed in a new cable to no avail - still knocking.

Compression test as follows:
Cylinder #1 - 142 psi
Cylinder #2 - 140 psi
Cylinder #3 - 150 psi
Cylinder #4 - 135 psi

Vacuum gage is rock steady at 15.

I am wondering about the vacuum hoses, as I have not replaced them. They look alright, but they are a bit stiff. Perhaps there is a small leak that manifests when under load? That doesn't help explain the misfire, but maybe explains the chugging?

Random, probably unrelated detail: Could the bypass valves be part of the problem somehow? When I rebuilt the carbs, I replaced the diaphragms in the bypass valves and I'm not sure I set them properly, as the adjustment procedure didn't work on my car as described because of the misfire.

[saabfast]

If plug 3 is not doing anything also try switching that for an old plug. I have had plugs fresh out of the box not work on more than one occaision (all NGK's which seem to have gone downhill now made in France!).

Alan
Saab 9000 Stg 1 (now passed to son for his family car)
Saab 9000 2.3 FPT Auto (now gone that others might live)
Saab 9000 2.3 LPT Auto (sold on, wish I had it back)
Saab 9-5 2.3 Vector Auto Estate
'81 TR7 DHC

[DNK]

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">...(all NGK's which seem to have gone downhill now made in France!).<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

<font size="6">Sacrebleu</font id="size6">

Don
Stick a Wedge In It
80 TR7 V8 Kick in the pants

[sheetsofsound]

Sacrebleu, indeed. Turns out not to be the plug.

So I changed the plug and wire which made no difference. Just for laughs, I put the timing light on each wire in turn to see if I got a consistent flash. Cylinders 1, 2, and 4 all show a steady pulse from the timing light; cylinder 3 shows intermittent flashes that seem to run counterpoint to the loud knocking.

From my timing light test, I am assuming that somehow cylinder 3 is not getting an steady electrical pulse from the ignition. Working backwards, its not the plug, its not the wire; next is the distributor cap.

It looks brand new. The connection to the spark plug wire is shiny and clean, the wire is tight in the socket. Inside the cap, the contact is clean with no evident oxidation. (I had cleaned it before I tried to start her up.)

The rotor looks fine as well.

Next is the Allison/Crane optical pick up. It is obviously sending a clear pulse to the other 3 cylinders, and without understanding how the trigger sends an electrical pulse all that well, I assume it is sending an adequate signal otherwise I would have problems on all 4 cylinders instead of just one.

I checked the shutter and all four of the slots for letting light through look the same, with nothing to obviously stop the transmission of light.

Tracing the electrical connection back further leads to the watchamacallit that is attached to the coil.

Obviously, the ship carrying my knowledge of ignition systems runs aground here. Are there four different circuits in there, leaving me wondering if circuit 3 is faulty? So my watchamacallit has failed? If there aren't 4 circuits in there, then the signal is not being distributed properly, which leads back to the distributor.

If the coil and the ballast resister had failed, I am guessing that it would be obvious on all four cylinders. Am I wrong about this?

Is there a more obvious reason why I'm not getting a steady electrical signal on cylinder 3?

As I said, I don't know how the Allison/Crane system works exactly, but if the same circuit is used to fire all 4 cylinders, then it is the distribution of the spark that is at fault, which leads back to.. the distributor.

I feel like I'm chasing my tail.

Edit: I checked the connection from the top of the distributor to the inside and found the problem, I think. There was some intermittent resistance on cylinder 3. There were some very small spots of oxidization that my aging eyes missed, probably because of the colour. (Time for glasses, I guess.) I tried to clean them up, but I still got sketchy readings with the ohmmeter. Tomorrow I shall attempt to get my hands on a new Lucas cap and see if that solves things. This has taken a long time, but at least now there's hope.

[Hasbeen]

It does sound as if your problem is with your distributor cap, leads or plug. I have another look at them. Can you switch No 3 & 4 plug lead & recheck. they should be long enough, & that would narrow down the problem. Swap plugs too perhaps if it's not the lead. If something duplicates the problem in different cylinder, you've found your problem.

I have heard of funny things with disy caps, So it could easily be that. Can you borrow one. A trip to a good tuner, with testing gear preferably with a dyno would probably be worth the money, if you can find one.

Has this disy operated properly previously? We once had a funny one.

In the Ford factory competition prepared GT HO Falcon I was to drive at Bathurst in 69, [see video of what happened to that in the "Man of Leisure" thread in general chat], we had a lack of acceleration out of corners.

After practice we took it to a mates dyno in Orange a town about 40 miles from Bathurst. The thing felt fine driving over. He connected all his exotic test gear to it, & ran it up on the dyno. The first we found was no sparks at all on one cylinder. The plug lead was routed wrongly, & had burnt through on the exhaust manifold, somewhere out of sight.

Beauty, we had found the problem. But no, it was worse, one cylinders ignition was 30 degrees retarded. That took some head scratching, but we found one lobe on the disy cam was machined 15 degrees wrong. Turning at half engine speed, gave 30 degrees retarded spark.

Over all we picked up 68 BHP. We were pretty excited, I had been only 0.9 seconds of fastest time in practice.

If that disy is new to you, it could have something as crazy. If one pot was advanced that much, it would cause a hell of a knock.

[sheetsofsound]

I have switched leads and plugs a couple of times now with all this, so I'm pretty confident that the dizzy cap is the culprit. I have since measured the resistance from the plug to the inside of the cap and found cylinder 3 to be quite different from 1, 2, and 4. It will probably take me a couple of days to get my mitts on a new cap, but it is only $15 and, at that rate, a good gamble.

Sounds like quite an adventure with the Falcon. 30 degrees? Jeez, I hope that isn't my trouble.

[saabfast]

I have also had the problem before with one cylinder missing due to tracking in the dizzy cap, although the tracking could not be seen. Sometimes a wipe and spray with WD40 will make it better for a short while.

Alan
Saab 9000 Stg 1 (now passed to son for his family car)
Saab 9000 2.3 FPT Auto (now gone that others might live)
Saab 9000 2.3 LPT Auto (sold on, wish I had it back)
Saab 9-5 2.3 Vector Auto Estate
'81 TR7 DHC