442Harv

I was wondering if the chain jumped only about one tooth, would you still have a high compression reading? Or how far before it would cause compression problems?

Sugar Bear

It would definitely lower the compression. How much? I'll guess at least 30%. If it jumped there is also the potential for a bent valve(s). Best to do either a compression test or a leak down test after the new chain is installed but before the front cover is installed.

Hope this helps.

66SportCoupe

If a timing chain jumped in a stock oldsmobile gen 2 V8 you should not have any bent valves. It is NOT an interference engine.

joe_padavano

I've never seen an Olds chain "jump". Usually when the cam gear teeth become nibs, the chain just comes off completely.

oldcutlass

I've never seen a timing chain jump just one tooth... I have seen them slip halfway around the sprocket.

joe_padavano

Yeah, it's when the cam "gear" becomes a "pulley"

442Harv

Why I was asking,is because. It is not running good. It is a 68 400, the timing mark shows way off, but when he gave it a compression test all cylinders where 175-180. When we checked to top dead center and look at the rotor, it looks real close, so I figured if it is off, it can't be much, but enought to make it run bad. He redid the hole engine years ago, but I don't think it has more than 5K on it since rebuild. He does not have much time to work on it, and when we do, the neighbor complains about gas fumes, bothering him, so we have to take the car down the street, or do something when he is not home. Makes it hard to spend much time with it.

joe_padavano

Who is "he" who redid the motor? Have you verified TDC on the balancer? It's more likely that the balancer has slipped than the chain is off by a whole tooth. And if the engine was rebuilt, I'm assuming the timing set was new and used all-metal gears, so it isn't going to "jump" a tooth. Is it possible that the timing set is an adjustable one that was installed incorrectly? Has it always run like this since the rebuilt, or is this a recent problem?

442Harv

He, is him and me. We put the cam in straight up. This car ran great for years, ran in the low 14s, never a problem. He has been keeping it at his mother inlaws garage, did not drive for about 3 months ,The last time he went over to drive it, and change the oil is when it starting running bad. I also thought the damper slipped, but does not look like it, but that should not make it run bad, just not read timing right,right?

joe_padavano

So it was an all-metal timing set with about 5000 miles on it? That's not the problem. Get a piston stop and verify TDC on the balancer.

442Harv

Yes it had new chain and gears.

joe_padavano

So that isn't the cause.

fleming442

Bad gas- use Seafoam as a stabilizer.
You can run it out or drain it, but it's got to go.

442Harv

It's not gas. The timing marks shows it is about 70 degree advanced, but runs bad,

matt69olds

make sure the advance weights in the distributor are free to move. And I assume you are checking the timing with the vacuum advance disconnected and plugged?

olds 307 and 403

Is it possible the distributor wasn't completely tightened down? Even the floppy chain out of box Cloyes Street Roller didn't skip with about the same mileage. Try retarding it, if the advance weights check out and TDC is in the right place. When a timing chain skips it cranks almost almost like no plugs are in the motor. I had it happen on a high mile Olds 307.

442Harv

Just a little more, info about his problem. Motor was complete rebuild, but years ago. He has not driven the car much. Has it stored at his mother in laws house. Car was running good last time running. Went to drive it one day, and change oil, been setting about 2 months. He said car ran bad, brought it home, started checking it out. Checked the timing, was way high. like 70 degrees. Thought his timing light went bad, but also has a timing tape on it. I take my light, which is a set back one, same reading. Vac disconnected and plugged, weights move. So he tunes it up, not much better. He has Protonic in it. We checked the dampener,looks good. Found top dead center, checked timing mark, and location of rotor, looks good. We advanced it as far as we can till vac can hits fire wall, and it runs better, but not like it use to. That's about all we have done so far, like I said he does not have time, and when he does the neighbor is home and complains about the gas smell into his garage. Car has always been gassy, lot of cam in the car. Just trying to get info help, before taking anything apart. Thanks for all input

joe_padavano

The engine won't run with the timing at 70 degrees BTDC, so clearly the damper has slipped or the timing light was connected to the wrong cylinder.

Sugar Bear

Firing order correct? Timing light connected to front cylinder on left/driver's side ignition cable?

OLDSter Ralph

Whats Protonic ?

fleming442

I think he means Petronix pickup in the distributor

442Harv

Yes, sorry for the spelling.

olds 307 and 403

My 8 to 1 350 started up and ran after swapping the distributor and it ran shitty. I checked the timing with my dial back, 72 degrees! It ran badly, just like he mentioned, it is possible. I am surprised this high compression 400 didn't ping with that much timing.

442Harv

Yes, I know it will not run with 70degrees advance, and probably not turn over. That is why I'm asking where the problem may be. I also think if the damper slipped, that would not caused the engine to run bad, just show wrong timing, or is my thinking wrong?

fleming442

Start by confirming TDC. It doesn't take that long

442Harv

We have