The Stovebolt Site Forums The Shop Area Engine Shop Timing issue

Hello all!

I have a 51 3100 with a 216, which I believe is a 48 216. I have been dealing with the well known stumbling/hesitating under acceleration. I’ve done just about everything that is usually done with the exception of replacing the dizzy. The odd issue I am having is when setting the timing on the bb, my bb bounces around consistently when the engine is missing. Anyone experienced this before?

I have accomplished the following: ignition system replacement(points, condenser, plugs, wires, cap, rotor) carb has been replaced, valves have been adjusted, ran with valve cover off and all valves operating properly... and proba Lt more that I missed.

I pulled the dizzy out and I specked it and there seems to be a lot of up and down play on the gears. The vacuum advance works properly from what I can tell. The dizzy moves under acceleration.

I have dual straight pipes and a 12v conversion.

Have you removed the breaker plate and inspected the centrifugal advance system? It sounds like you've got some broken or missing springs on the advance weights. You should be able to turn the rotor a few degrees clockwise against spring pressure, and it should return to the same place every time you do that. The angle of the gears on the distributor and the camshaft keeps the gear pushed one direction while the engine is running (up, I believe) so vertical play isn't an issue unless it's really excessive.
Jerry

Couple of things to tinker with here. The wear between the gear and the bottom of the distributor body shaft can only really be corrected by removing the gear, removing the guts, and shimming under the shaft itself. Installing shims between the gear and the distributor body shaft, common with the V8 distributors, actually moves the breaker plate pretty high, sometimes way too high, from the distributor lobes. So what you might try is loosening the clamp and pushing down on the distributor body which my help take up some of the slack.

What number is your distributor? The reason I ask is that the early distributors did not have the spring and Bakelite pad arrangement as part of the grease cup. As far as I know this was a later addition to help with shaft stability as it wore. If your shaft is really worn, and does not have the spring arrangement, a wobble might be what is causing the fluctuation. There are no bushings in these distributors.

You might also consider pulling the distributor out, take it apart as far as you can, and give it a through degreasing and inspection of the advance weights. Pay particular attention to the springs and whether the pins are tight, the springs are both in place, and the weights are free and working. Lube the weights with some light oil, grease the springs and pivot points with grease (I like the red or blue stuff myself), then put it back together and reinstall, making sure you press the body down tight before tightening the clamp. Recheck the point gap and install. Get the motor running and put a dwell meter on it and make sure the dwell is within specification. Then check the timing and see if it is still fluctuating.

I've come up with a way to press a hardened sleeve over the distributor shaft that's fitted to a Torrington needle bearing in the housing just under the centrifugal advance that totally eliminates the wobble and dwell change caused by shaft and housing wear. It's a fairly simple modification that only requires a little bit of machining.
Jerry

That is very clever! Would you be able to post photos? I would love to see how it’s done. The excess vertical movement can really play havoc with the timing

The bearing doesn't control vertical movement, although a thrust washer or a flat needle bearing could be added at the top during the machining process pretty easily. This one is a Torrington needle bearing pressed into a counterbore in the top of the housing that will control lateral movement of the shaft. I lube the upper bearing by inserting a grease fitting in place of the cup, spring and disc. In the process of "blueprinting" the distributor, I also use a dial indicator through the hole for the wiring connector to check the lift of each cam lobe once the lateral play of the shaft is removed, and use a diamond dust needle file to match up the lobes. It's pretty impressive how much error there is in cam lift from lobe to lobe.
Jerry

Sorry for the late reply fellas, I had some shoulder surgery today. So I was convinced to install langdons HEI kit, so I put one on order. I’ll pull my old one apart and rebuild it once I’m able to move again. I tried buying a dwell meter and they are extremely hard to find. I bought a multimeter type and it doesn’t work as advertised..

Ebay, plenty of them on eBay.

Bought two dwell meters off eBay this year. Shipping was almost more than the units themselves.

This is why I miss sears

My dwell meter has about 50 blades, and it's marked in thousandths. AKA "feeler gauge". The batteries have never run down, also!
Jerry

Yeah that’s what I was use... but is wanted to learn more about measuring dwell an dwell angles... I just don’t like spending money on Chinese machines that don’t work.

"Dwell" is simply an average of the voltage available at the points or the downstream side of the coil primary when the points are open, and closed. The term "dwell" is a contraction of the number of degrees of distributor rotation the points "dwell together" (points closed). At that time the voltage that can be measured at the points will be zero, since one side of the points is grounded. When the points are open, there will be a voltage equal to the battery voltage or the charging system. Let's do a little math ;

Battery voltage: 12.6V (running on battery power only)
Total available degrees of dwell: 60 (360 divided by 6)
Specified dwell angle: 32
32 divided by 60 = points are closed 53% of the time
12.6 X .53 = 6.66V
12.6 - 6.66 = 5.94V

When the engine is running with 32 degrees of dwell, an analog voltmeter (NOT DIGITAL) from the above example will read 5.94 volts, as the points will be open 47% of the time. If you have an analog voltmeter, you've also got a dwell meter. Digital meters react too fast to the changes in voltage, and the numbers on the readout will just be random gibberish.
Jerry

Update! I installed Langdons HEI kit and my bouncing timing mark issue is solved. I’ll chock that up to a worn distributor. The engine seems to be running great now, although I cannot drive it right now due to my shoulder surgery... I’m still healing.

While parked and engine running I get a whining/squealing noise from the exhaust when decelerating still...

Anyone have any ideas?