Here is the deal... When I start my GS either cold or warm the motor will stop cranking sometimes just as it starts to fire up. It never did this with the old points and it started to happen after I installed the Pertronixs (spelling?) system with the "lobe sensor" (not the magnets). Part of the problem is that I never checked the timing before I put the pertronix system in and when I went to time it I noticed that there were two marks, the original "slot "and a painted line. The previous owner had the motor rebuilt and I do not know if the second mark is the new TDC. The car seems to run fine once it is started. Does it sound like my timing is too far advanced or retarded? Any advice on a fix? o No:
Sometimes you will get syatrer drag from the dreaded pertronix. My timing had to be adjusted when I put mine in. Advanced timing can also cause this, but if the car dosen't ping under load then it should be OK. When you say 2 marks are you in reference to the crankshaft dampner. If so, I don't see how there can br a new TDC.
Mike, Lots of guys will paint a second mark on their balancer to help set their total timing. If you don't have a dial back timing light, the second mark will correspond to 30* of timing.(the second mark will be 1 3/4" clockwise around the balancer from the original TDC mark. When you rev the motor, you watch the second mark. When it stops moving upward, your mechanical timing is all in, and then you can read the total timing right off the tab. If the second mark stops at 2* on the tab, your total timing is 32* You should also note the RPM where your timing is all in. 2500 or below is a good figure for a street car. If the initial timing is up around 18* or more, your starter may kick back when you try to start it, especially when hot. I hope you have better luck with the Pertronix than most. Some guys have no trouble, others have all kinds of weird problems.
It's funny you mention the kickback, Larry! I am working with a gentleman who was a GM mechanic in the '60s and '70s and we were just talking about broken GM starter casings and too much advance Friday afternoon.
I do get ping under load, I thought that may have been the gas, I was running 87 octane. Larry, I am only a novice when it comes to motor mechanics so bear with me. Should I still set the initial timing using the factory mark at the factory RPM (TDC @ 600RPM, with the vac. advance disconnected). I just went and looked at my motor again, The timing tab starts at "0" and goes 4,8,12. "+". There is a yellow line painted on the tab at the "10" location. I was mistaken when I said that there are two marks on the damper, there is only the factory line. I was going from memory because I set the timing last year and I just finally got frustrated with the kickback now. The kick back does seem worse when it is hot and the motor does seem to run hot (200-210 deg.) When the manual says to set the timing at TDC where would that be on the timing tab? When you say 18* or 32*, where are you reading this. Oh yea, my motor is the original '68 400 C.I. Again, bear with me, I only know enough to get me in trouble..:gt: I may end up seeing if a local Buick guru (Carman Fasso) can give my motor a good "power tune" because it seems to lack that Buick power that my '68 GS400 coupe had.
I'm sure Larry will be able to cover this in more detail: 600 rpm should be your idle speed in DRIVE, I should think. At least it is on my 455. 800 rpm should be your idle speed in PARK, unless I am greatly mistaken. Don't inch up to a tree, or put chocks under the front wheels to check your rpm in DRIVE. I have seen otherwise intelligent people nearly run themselves over doing this. Just get a dwellmeter/tachometer, and set your rpm in PARK. To double check, get a helper, and have him or her sit in the car with the brakes on in DRIVE, and you can check to see if it's at 600. It should be. I never check rpm in DRIVE, always in PARK, and the one time I DID check, it was exactly 600 in DRIVE after I set it to 800 in PARK. Old Harmonic balancers can "walk" on their rubber insulator and I wouldn't trust yours if it's the original. before I went nuts trying to tune the engine, I'd take a good hard look at the balancer and evaluate it's condition. If it seems that the rubber ring is cracked, pitted or otherwise deteriorated, I'd seriously consider replacing it before I got into tuning the engine in earnest. Sure, I'd set the rpm speed and timing, but I wouldn't take the timing light's word for initial timing; I'd use that as a baseline, drive it and see what's what. hard to start could be too much initial advance, and with an old balancer, it is possible that although you're right on 8* initial, it'sd just indicating 8*, and in fact you are much more advanced but have no way of telling. The outer ring of the balancer can and will move if the balancer is worn out, and if that happens, you can't rely on the timing light. if after timing, you still have knock and ping, and you are using less than highest octance gas, switch to the highest octane pump gas and asee what's what. It will not improve instantly, you may need a tankful or two. If it still persists, and at the factory timing, then it points another finger at your balancer being worn out, I should think. Knock and ping (detonation) can and will crack or hole a piston. Pinging can be present even if you can't hear it. Don't worry too much about valve recession, by the way, if anyone's mentioned it to you. Unleaded gas can cause problems with unhardened valve seats because the lead used to help lubricate them, pre-1973. Well, your Buick engine shouldn't have a problem. Higher quality alloy, you shouldn't need to worry about valve recession for 60 years or so. :laugh: ~edit that yellow line at +10* must have been put there by the previous owner. Stock distributor timing should be +8* if i recall, but a distributor modification can change that 'optimum' initial timing. My aftermarket HEI needs to be timed at +13* initial, but I didn't put a mark there, it's easy enough to remember. The previous owner didn't want to rely on memory, is my guess.
Mike TDC would be 0 on your timing tab. I agree with Chris, the previous owner put that yellow line there because that is where he timed the engine. Do you know if you have the original distributor in the car? Has anyone ever recurved it or changed the springs or weights? These are questions you need to know the answer to, before I can recommend where to set your timing. Stock distributors do not allow total mechanical advance until 4600 RPM. The stock distributor for a 68 400 would be 1111285. Stock timing would be TDC, 0 on the tab, and 30-34* total at 4600 RPM. If you moved the initial to 10*, you would have 40-44*, and ping, if not detonation, especially with 87 octane fuel. Another thing to look at is the advance stop bushing. You need a small mirror to see it. It is a small plastic bushing that fits over a pin in the distributor, and it limits total advance. They commonly deteriorate, and fall off. I'll post a picture to give you an idea where to look. Do you have a dial back timing light? If not, you should purchase one. Sears makes a really nice one, and it's only about 60.00 Without a light, you can only guess what your timing advance is doing. See if you can borrow one, and we'll go from there
Larry, I've been thinking about picking up a dial back light, do you know the brand/model of the Sears unit you mention?
David, It's a Craftsman Professional Timing Anylyzer, Part # 2194. I tested it against my 500.00 Snap-on Digital Timing light and it was within 1* Everyone should have a good timing light.
I will have to check to see but I do believe the distributor is original. The only thing that I know is that it was bored 30 over and a 455 cam was put in. I did not see anything unusual with the distrubutor when I put the pertronix system in last year. What is a dial back timing light? I know what a stock timing light is but what is a dial back? I will see where the current timing is set since I can't remember where I ended up setting it last year. :beer
I stopped into Sears this afternoon and they have this model here for $69.95 and a cheaper "non-professional" Craftsman for $49.95. At least the description fits, I'm not positive the # was 2194. I was out and about before your post. I didn't pick it up though. I'm off work this week, maybe I'll scout around a bit. It's described as an Advance Timing Light 0-60deg, is that what is meant by "dial back"? I've actually been thinking about a more expensive digital unit around $100. o No:
David and Mike, A dial back timing light has a dial and scale usually on the back end of the light. With a plain timing light, you attach the leads and shine the light on the balancer. You then see the timing mark and read the advance off the tab. With the dial back feature, you would move the dial until the balancer mark moves back to zero, then read your advance right off the back of the light. You can use the dial back feature to see your advance at any RPM. That is it's advantage. At higher RPM's, the mark would normally be beyond the tab and your sight. As you move the dial, it moves the timing mark back so you can see it. If you want to set your advance at say 32*, you would dial that amount onto the back of the light. When you shine the light at the balancer, you would see the timing mark well below the timing tab. As you increase the RPM's, the mark will begin to move upwards. At some RPM, the mark would stop and go no higher. At this point you simply move the distributor until the timing mark lines up with the 0 on the tab. You could then let the motor return to idle speed, and move the dial until the mark again lines up with the 0 to find what your new initial timing is. David, I'm sure the light you saw is the same one. It's a good one, and very accurate. Some lights can be off quite a bit. Sears has always been one of the best. I know for sure because I tested it against the top of the line Snap-on. I bought mine about 2 years ago on sale, so the price may have gone up. Here is a picture of the box.
Larry, thanks for the detailed explanation. The box has changed slightly, but it looks to be the same model.
Sears Craftsman David There was a test in one of the car mags a couple of years ago. Most of the timing lights were VERY inaccurate. Several degrees wrong. Sears Craftsman and Snap-on were the only 2 accurate. One's cheaper, you decide...:Brow: Jeff
