Trouble

[Joe Flanagan]

Thank you, guys. I will look into those things. Right now I'm going to put a vacuum pump on my advance and see what it does. I just suspect that one thick wire that's in there. Then I'll take off the belt and check the damper. My engine runs very nicely except for the knock and stumble on acceleration. Does this fact rule out the timing gears being off? It idles beautifully and is very smooth once it gets past the stumble.

[Don Coatney]

The pictures of your timing gear appear to be correct.

When you say "thick" wire is this a stranded wire or a solid wire? This wire needs to be very flexable as it flexes as the point plate moves.

[Joe Flanagan]

That's the problem, Don. It's much thicker than the original and not very flexible. I'm thinking this could be affecting the way the plate moves and could be causing who knows what kind of trouble.

[james curl]

Pull your advance plat from the distributor. I have found that after sixty years the grease in the ball bearing has gotten very hard and restricts the movement of the plate to advance. I wash the old grease out with mineral spirits and re-lube with lubre plate assembly grease.

[Don G 1947]

I am reluctant to chime in because I don't know near as much as most of the guys who are commenting, but let me make a few comments. If the timing is changing I would check BOTH screws that secure the distributor. The one on the block and the one on the bottom side of the distributor. Also, it is possible that you have a lot of slop in the timing chain. To test this you can take off the distributor cap and turn the damper (by hand) until the pointer is over the timing marks. It doesn't make any difference which cylinder is where just as long as the pointer is over the marks. Note where the pointer is in relation to the marks (e.g. 2BTDC, 5ATDC). Then carefully turn the engine in the opposite direction and watch for the rotor to start to move. Just as it starts to move, note the new location of the timing mark. The number of degrees you have moved the crank is the number of degrees of slop you have in the the valve timing 5 degrees is great 15 degrees is of concern. One thing you need to consider when doing this is it is also adding in the slop between the distributor tang and oil pump. So if there is a lot of slop there then your reading will be compounded.

By the way, I do feel your pain. Just COMPLETELY rebuilt the engine and it ran PERFECT for 30 minutes. Then the compression dropped to 50 lbs and I couldn't hold any air in the cylinders when doing a leak down test. Everything coming out the breather. OOPS, back at the shop to replace all the brand new bearings, pistons, rings, and redo the machine work.

Good Luck!

Don

[Joe Flanagan]

First of all, I'd just like to thank everyone for their help. It's great to know that I can just come to the forum for advice. God only knows where I'd be without it.

Since my last post, I went out and did a couple of the things that were suggested. First, I put a vacuum pump on my distributor advance. Seems like it's defective. I tried a bunch of different attachments to pull a good vacuum on it and it wouldn't hold with any of them. I can't remember whether I bought a new vacuum advance when I rebuilt the engine or not. The mechanism will move the plates and hold them for about a second, but then the air starts leaking out of it and the plates slowly return to their original position. I disassembled it and looked inside the diaphragm as best I could to search for damage but everything seemed OK. The diaphragm material looks new. Maybe I did buy a new one, I don't know. I then replaced the other wire in the distributor with one of the proper diameter, much thinner with much more flexibility. I then managed to break my rotor, so I couldn't start the thing and see what it would do. I'll get a new one tomorrow. In the meantime, I checked the position of number 6 using the plug above the cylinder. At its highest point, the pointer is lined up with the TDC mark so I think I'm OK there.

What I don't understand in all this is how (if) improper functioning of the plates in the distributor can cause your timing to change. And if that is what is happening, could it advance my timing to the point where I'm getting a noise that sounds like a really fast rapping? As I said earlier, I retarded the timing this morning and it eliminated the noise as well as the stumble on acceleration. Maybe the engine wasn't warmed up enough yet to start making the noise. Maybe the noise is a result of bad timing. Maybe it's a bad wrist pin, which is where I'm putting my money, but I have to eliminate all this stuff before I dive into all that mess.

Only thing I didn't do was determine if the damper is moving on the crankshaft. Since the timing marks line up with number 6 at TDC, I assume it is not, since it would be too much of a coincidence, I think, for a shifting damper to happen to land on that spot just before I checked it out. I'll still check it, though.

Thanks again to all. I will keep you updated.

Edited June 27, 2010 by Joe Flanagan
More info

[Don Coatney]

I am reluctant to chime in

Dont be! You gave good advice! Continue to chime in as you see fit.

[Don Coatney]

The mechanism will move the plates and hold them for about a second, but then the air starts leaking out of it and the plates slowly return to their original position. I disassembled it

Joe;

How did you disassemble the vacuum pot? I have never attemped to do so.

[Joe Flanagan]

You can only disassemble it so far. There are a couple of screws that hold it on and you have to undo the tiny clip that holds the arm to the mechanism that actually moves. You remove the nut at the end, take out the spring, and you can't disassemble it any further than that. You can look inside the hole and see most of the diaphragm, though.

[Joe Flanagan]

This morning I conducted the test that was suggested by DonG 1947 (post #33 above). It looks like there is a lot of slack in my timing chain. I turned the crank by hand until I got to TDC. Then I reversed direction. When the rotor finally moved, the pointer was nearly off the timing marks. It looks like it gets about 10 to 15 degrees off TDC before the rotor will move. What do you guys say? New chain?

[Young Ed]

Joe did you not install a new timing chain and gears when you rebuilt the motor?

[Joe Flanagan]

To the best of my recollection, I did not. I'm pretty sure I used the original. The only thing I can plead in defense is ignorance and that's probably no defense at all.

[55 Fargo]

Hey Joe, looks like you are getting near the problem by process of elimination.

Heck Man, you gotta be stressed.

Joe, is there anybody in your area, that really know these engines, or engines for that matter, that could help you diagnose this trouble?

Sometimes a really experienced engine builder/mechanic, is worth there weaight in gold.

I am not telling you what to do, but sometimes 2 heads are better than 1, and especially when 1 is an experienced engine Man.........Fred

[Don Coatney]

Did you not replace the chain and gears when you built your engine?

How far can you turn the rotor in either direction before it stops?

[Joe Flanagan]

Don, do you mean turning the rotor inside the distributor by hand? If that's what you mean, it will go about 1/8 to 3/16 of an inch before stopping. Same in either direction.

[Don Coatney]

Don, do you mean turning the rotor inside the distributor by hand? If that's what you mean, it will go about 1/8 to 3/16 of an inch before stopping. Same in either direction.

That tells you how much "slop" is in the dustributor tang.

[Joe Flanagan]

Does 1/8 to 3/16 sound excessive?

[Joe Flanagan]

So here is my plan of attack. I first want to eliminate timing as a source of the knock in my engine. I've already replaced the two small wires in my distributor. I am replacing my advance mechanism, which failed the vacuum test. I will also replace my timing chain because like a doofus I used the original and I suspect there is too much slack in it. (It was eight years ago. I wasn't as smart then as I am now, heh heh). When those things are done, I'll run it and see what happens. If I still have the knock, I'm going straight to the wrist pins on 5 and 6 because that's where it sounds like it's coming from. Anybody have an opinion on that strategy?

[james curl]

When you say knock, do you mean a loud clicking simular to a loose valve only louder. I had to replace the wrist pins in number 5 and 6 after my 4600 trip where we cruised 65/75 for hours on end. I contribute my problem which also included broken top ring on both 5 and 6 to 10 degrees initial advance. After I replaced all of the piston pin bushings and reassembled the engine I checked vacuum at a steady 60, then 65, and finally at 70 mph and was surprised to see 14 to 16 inches at these speeds. At 14 inches of vacuum you ctill ould be getting between 14 to 18 degrees of advance at the crank and at 2.050 rpms you should have an additional 16 to 20 degrees of advance. At 2,,850 rpms you should have 18 to 22 degrees of advance at the crank. So if I use the 10 degrees initial and the lower of 14 degrees for vacuum and 18 at 2,850 you have 42 degrees of advance before TDC. If you went the high side then you would have 50 degrees before TDC which is a bit much.

[Joe Flanagan]

James, the sound is heavier than what a loose valve might sound like. It's a rapid knock that happens on acceleration only. Yesterday I retarded the timing and the sound went away, as did the stumbling on acceleration. But then the timing somehow changed itself back to TDC (or very near) and the sound was back.

I have to confess you lost me on the rest of your post.

[Cpt.Fred]

man, there should be a "print-complete-thread" button somewhere here.

this is another great read on this board, lots of stuff to learn!

joe, i'm almost certain your problem is the timing, if i may say so with my limited knowledge...

i had a similar problem when i rebuilt my opel engine 10 years ago.

the distributor shaft was worn and the chain too long, but the engine had a chain tensioner and i searched forever to find the problem.

my timing was jumping and "somehow changing itsself" like yours does,

when i get this correctly.

and: why should the noise goe away just by turning the dizzy if its source was mechanical?

i sure hope you'll find it soon and that it's not too bad.

where do you plan to buy your vac advance?

here's an old photo of my old "4-banger". sure loved that engine!

best from red-hot berlin! it's 35°C out there....

fred

[Joe Flanagan]

Fred,

I sure hope you're right. I believe that when I retarded the timing and eliminated the noise, it was the first time I started the car for the day. Maybe it didn't make the noise because the engine hadn't been warmed up sufficiently.

I have never heard spark knock, so I don't know what it sounds like or if it can be confused with a mechanical noise. It's definitely not "pinging." More like whacking.

I wound up ordering a vacuum advance from Andy Bernbaum. If you do the same, make sure you have your distributor number handy so they know which part you need.

That Opel engine looks like a very simple one to work on. It's not too different from the one that's in my 87 Toyota pickup. I love that engine, too.

[Cpt.Fred]

maybe you should try warming it up a little and then turn the distributor, see if the sound comes and goes?

i don't know spark knock on these engines either,

but on the opel it was ,like some wise guy from "top gear" once said, like barry white gargling with nails.

a real nasty, metallic, sharp knocking under the hood.

at the race this weekend i advanced my timing to get more punch,

when i retarded it afterwards i was a little too generous and when we rode home,

the engine didn't have power at all and sounded terrible.

i checked and i was before tdc, so i advanced a little and everything was fine.

it's amazing how the sound can change on these motors...

good luck!

[Joe Flanagan]

I wouldn't say the sound is like Barry White gargling with nails. It's more like Barry White hitting his head against something hard repeatedly and really fast.

[Cpt.Fred]

oh my...!