500, 472, 425, 368 Discussion, 68 472 Timing Question in Cadillac Engine Technical Discussion; My 68 472 is giving me fits setting the base timing properly. I put in the Crane electronic conversion kit, ...
My 68 472 is giving me fits setting the base timing properly. I put in the Crane electronic conversion kit, added dual exhaust, edelbrock 1406 carb, and a 1000 cca battery, new vacuum advance and all new hoses. (In case anybody asks). I have the Chilton 67-86 book and the 1968 cadillac shop manual. and I've set timings on cars like this for twenty years before I bought my 96 STS.
I thought timing was like riding a bike in that you never forget.
Anyway, here's what I do: I unplug the vacuum hose to the advance and plug with a golf tee. The car is at normal operating temperature. RPM is about 550 with the car in drive, parking brake on, (no vacuum goes there anyway, I just run PCV, Brake, Smog, Dist, and Tranny) and Wife in the Driver's seat with foot off the brake just in case. Timing light is on #1 cylinder (pass side) and connects to battery. Notch in pully lines up with the middle notch on tab =5 deg BTDC.
Here's what I get: car runs like crap.
Here's what I do: same as above, but gradually advance timing to what looks like approx 12 deg BTDC. Car idles smoother, sounds better, and I back the idle screw down because as I advance the timing, the RPM goes up.
Then: My mechanic says the timing is at 4 deg as measured by his Snap-On digital timing light, but my new yet low tech timing light is still showing 12 deg BTDC.
I get no indications that my timing gears are off. Car starts great even when hot. No hesitation at either mid range or high RPM and car is OK off the line.
So after this rather long dissertation, my question is this:
What is causing the discrepancy in timing readings between mine and my mechanics? and who's is correct.
I have heard that it is not uncommon for different timing lights to read differently. Dunno how to check this. Buy a case, and average the results?
I'm not familiar with how the Cadillac harmonic dampners are made, but I know with Chevies that the rubber ring connecting the center to the outside can slip, causing screwey timing readings. This is easy to check by looking through the #1 sparkplug hole, putting the engine at TDC, and seeing if the timing notch lines up with 0* on the pointer.
I sort of noticed the same thing over the years. Anyway, for vehicles of that vintage, I time them the old fashioned way. Advance the timing a bit and take it for a little ride. You want as much advance possible without pinging (or very little only under hard acceleration). This is the way the old timers did it (no pun intended). In fact some of the old school mechanics (not many left anymore) could set the timing perfectly on the first try just by listening to the engine at idle. No test drive, no timing lights. I wish I was that good.
Thanks guys. I set it pretty close by ear the first time, so I guess that makes me an old timer. I'll just mark it where it is and advance it a bit as needed. I'll borrow my neighbor's light and see if there's a difference. If not, I'll just follow the old maxim: If it ain't broke, don't fix it. Lord knows there is enough that is broke to keep me busy.
I still think I've got a problem with the timing because now that the weather has warmed up, she's overheating. After she runs for a while, she knocks and pings, but not before she gets warm.
Cooling system-wise, t-stat and water pump is good and I get good flow through the radiator. It hasn't boiled over, but the coolant overflow reaches max, and after a couple of days, the radiator is hella low.
Everything I read says that too much advance make the car run hot and ping. If I put the timing back to 5* she runs like a yugo.
Assuming my mechanic's timing read is right, I need a timing light. But if my light is right, then the cam is out of synch with the crank and I'll have to redo the timing chain. Does anybody else know how check valve timing?
Does anybody have experience with 8.8mm solid core wires affecting the strobe on an inductive timing light? Here's what the manual for my timing light says:
Some ignition systems and/or specialty spark plug wires (solid core wires, racing wires, offroad wires) radiate above normal Electro-Magnetic Interference (EMI) and Radio Frequency Interference (RFI) which can cause improper operation of testing equipment. Contact the manufacturers of these parts for instructions on how to use an inductive pickup with their systems.
Ape, I thought about that, but I've only been able to find new weights and springs for the HEI distributor. I have the old points distributor, but I put a Crane points eliminator on.
Besides, at 550 rpm, the mechanical advance shouldn't be kicking in, unless it doesn't unkick after it kicks in. I'll check it by seeing if the timing advances as RPM's go up with vac advance disconnected.
Ape, you may be right. I checked base timing today, and it wasn't as far off as it had been. I bet my advance springs are shot. I changed the timing to about 6-7* base, and if I get the mech advance doing what its supposed to do, I'll be ok. Now, I'm confident my valve timing is correct, just like the last 2 certified mechanics told me.
Automobile(s): '80 Fleetwood Coupe, 1994 and 1995 Mercedes 140 Coupe
Re: 68 472 Timing Question
Don't count on replacement springs to fix the problem. Try removing the rotor and working the mechanism back and fourth while spraying sone WD-40 or similar towards the shaft. Sometimes it takes a while to get everything free. In extreme cases the distributor has to come apart. Save your original springs. It could take a long time to get the curve that you want unless you have luck and/or test equipment.
Places like Summit or Jegs will have a recurve kit for a points dist. All the internal parts will interchange with Chevy points distributors.
Try cleaning up the weights first though, might not need the kit.
Weights did clean up nicely. I also got some gunk out of the springs. Reset the base timing at 6* and she runs much better than before at what was allegedly 6*. I think this is a done deal. With the timing where it should be and the mech and vacuum advance doing what they should be doing, all she needs is a good radiator and I can actually take her out of town.
Even at 6* BTDC at base timing, she was running a bit "Putt Putt" so I advanced the base to 10* with quite a noticeable difference. Something still seems "off" and I'm not 100% convinced the valve timing is optimal. If I disconnect the coil and bump her over to TDC on the #1 cylinder, isn't there a way I can look at the left bank of valve springs to see if the valve timing is right?
At Idle, my manifold vacuum is holding almost steady at 18, but if I put the base timing down to 5* it drops.
This puts me back at square one, so if anyone can tell me what to look at, I'd greatly appreciate it.