I've been having problems with the 72 and I think I may be onto something. This is a bone stock 1972 Buick 350, and when I bought it ran excellent. Then it started to hesitate and die when I came to a stop. I tried most of the obvious things, checking for vacuum leaks, got the carb rebuilt, tried and tried to set the timing but the problem progressively got worse. Now it will start, but it backfires and is fouling the plugs generally running like crap. I finally went and got a rebuilt distributor and installed it. It ended up not solving the problem. I did notice that the only way I could get the car to start and run relatively decent was to retard the timing. Knowing that I should be advancing the timing something else must be going on. So I believe what may be the real problem is that the timing chain has slipped a tooth or two. Done so far: - New (Rebuilt) distributor, cap rotor, points and condenser (30 on dwell) - Found the compression stroke, set the timing mark on "0" (harmonic balancer/block marker) - Installed the new Distributor with the cap pointing at #1 cylinder - Started the engine and it running really rough, slightly turned the distributor counter clock wise to add advance to the timing and the engine ran worse. - Then I turned the distributor clock wise (Retard the timing) and the engine ran better, but still not as it should. I understand that I should be about 4 Degrees BTDC (4 degrees advanced) for my initial timing. When I set it at that the engine wont even idle. If I retard the timing about 6 to 8 degrees the engine will idle, but still backfire and hesitate when put into drive. Are all of these symptoms indicating the engine has skipped a timing gear tooth, possibly two? I did another test by watching the distributor cap as I rotated the crankshaft using a socket, and I did have what I consider quite a bit of play on the cap when reversing direction on the crankshaft. The cap did not move until the crank rotated about 1/8th of a turn. This could indicate quite a bit if slack on the timing chain. Do the wise ones on the forum think its time for me to pull off the front end of the engine and check the timing marks, look for plastic shrapnel and replace the timing set? Your thoughts would be greatly appreciated.
miles on the motor ? how do the plugs look ? running rich , gas smell ? maybe a stuck float ? probably not with a rebuild . 2bbl or 4bbl ? with the cap off does the rotor turn smooth ? and if you try and turn the rotor by hand it will want to lift n shift a little - that may just be because of the beveled teeth on the gear - but it should not have any back n forth movement ( play ) in the shaft . there is some timing and tune up info in here somewhere and someone will chime in with some solid ideas .
Sure sounds like the timing chain has slipped to me. Had exactly the same symptoms in my neighbor's Cad and that's what it was.
Do you have a timing light with dial to see how much timing you . what do you have vacuum advance connected to. Ported or manifold.
Plugs are new but covered with black soot, running real rich (I believe due to the timing issues), Yes to the gas smell. Not a stuck float, just had the carb rebuilt by the person everyone recommends here on the forum (Can't remember his name) 4bbl quadrajet. The new distributor is firmly in place, compared to the original dist, it's a great improvement. Very little if no play at all. I don't know how many miles are actually on the engine. It is the original engine that came with the car. Numbers match.
Bring the engine to #1 TDC compression stroke. Pop the distributor cap off and see if rotor is pointed directly at #1 electrode. If so, the timing chain is ok., If not, well, you know what to do.
I hope you still have the original distributor and that you did not have to give it in for a core. The original 1972 350 distributor was part number 1112109, and it had between 12 and 16* of mechanical advance in it. That means that if you time it to an initial timing of 4* BTDC, the most the total advance at wide open throttle could be is 20* The Buick V8 wants 30-34* for best wide open throttle performance, so in a word, you are cheating yourself out of a lot of power. That distributor is one of the good ones because you can advance the initial timing and total timing and the engine will LOVE it, even a stock engine. It reminds me of a fellow Buick guy I saw at our local cruise night with an all original 1972 GS350. He complained to me that the car was a slug. I checked the distributor, and yes, it was a 1112109, and yes, it was timed to 4* intitial. He lived near Jason (Buick64203), so I told him to see Jason and ask him to set the total timing to 32*. The next time I saw Jason, he told me after he timed the car, it left rubber for the first time ever. The guy was so thrilled to have a Buick with some balls. The rebuilt distributor you got could be from any year Buick. Some had as much as 30-34* of mechanical advance. Your stock 4* BTDC initial timing no longer applies since you no longer have the original distributor installed. I hope you kept the original. If not, go back, give them the core charge and get it back. I'm not saying your problem is not the timing chain. It could be. The nylon teeth on the cam gear are known for coming off, and the chain could have skipped a tooth or two. It's possible. You can remove the distributor cap and move the crank with a breaker bar and socket on the balancer bolt. Move the crank one way, then the other. Watch the rotor. It should move as you move the crank. If there is a lot of slop in the chain, you'll see it.
I still have the original Distributor, I will look at the remanf one and see if it has the part number you listed above. Thanks for the tip, that's an important one. To answer the other question about TDC on #1 cylinder, that is what I did before I took out the old distributor. The cap on the old distributor was pointing half way between the #1 and #8 spark plug terminal. That was my first clue it may have jumped a tooth...
Sounds to me it jumped. If you want to know for sure pull the fuel pump and use a camera to look inside, you should see damaged teeth. Dumping the oil should reveal fragments too. Personally i would not keep running it, good chance you could bend some valves if it jumps again while running.
Yeah, that's what I am thinking too. The good thing I have not driven the car much since it started acting up. Sounds like a good fall project. Is there any good write up's or videos showing the replacement process? I'm just thinking if it would be better to pull off the grill, radiator, fan assembly, and while I'm doing it replace the water pump and possibly oil pump gears. Any other tips for the project like "watch out for the timing cover bolts breaking" kind of stuff. I will be doing quite a bit of forum searching for more info. This car is my baby and I want to do it right.
u may find a tooth or two had worn/broken off the plastic cam drive gear. replace that gear with a metal one & add a new chain. crank gear s/b okay.
Pull the grill? Don't even go there, unless you plan to replace the camshaft. You can get it all by leaning over the pointy nose. I will admit that I have yet to replace the bumper and grille after I re-Buicked my Skylark from Chevrolet power. It's a lot of room for the engine hoist and to lean in for other work. I'll be putting them on next weekend if I don't have to work. And it really does sound like a timing chain replacement is in order.
If your just pulling the cover to replace the chain and gears, theres no need to remove the grille or radiator.
Protect the radiator if you do not remove it.... Nothing worse than a rad leak after you fix something else...
The reason I wanted to remove the radiator and grill is that I'm 6'6" and leaning over or laying on the fenders gets real old after a while. Also I think I will be able to get more leverage with the front end removed. I plan on repainting the front of the engine once I am done with the timing set replacement. I show the car and always look for a chance to clean up an area if I'm in there doing work. Also I don't want to scratch the paint on the fenders.
Todd, Did you ever check the part number on that rebuilt distributor you bought? Don't forget to prime the oil pump once you button everything up.
HAH! I'm 5'-9" and I'm tired of leaning over the radiator and grill! Anyway, it does seem like it is a timing chain problem. I've seen timing chains/gears fail in as little as 9 months/a few thousand miles. That happened back in the '80s when there was a union strike at some plant, and I used a McQuay-Norris timing chain set. It was pretty embarrassing to tell the customer that these thing failed in less than a year. Everybody was scrambling for parts. I had personally replaced that timing chain and gears the first time. Not cool! These components should last a long time with proper maintenance.
