distributor/timing 67 427 tri power

[Mark F.]

Ok. This is one has me stumped. I replaced the intake manifold gaskets on my 67 427 tri power due to a leaky old gasket. I put everything back together. I marked the distributor before removing it and did not rotate the engine at all after I removed the distributor. After it was all back together, I went to start it up and had back firing etc. Clearly the distributor was off. So I proceeded to remove the left side valve cover and go about the process as I normally would. Got #1 at TDC on the compression stroke, set the distributor back in, routed the plus wires in the proper firing order and it started right up. However, when I put a timing light on it the balancer mark was about an inch advanced of the timing mark plate. If I dialed the distributor back to retard the mark on the balancer to align with the marks on the timing plate the RPM would drop and the engine would not run as smooth. So, thinking i just got the distributor in off just one tooth, I drove it to my shop where I keep it thinking I'll just drop the distributor back a tooth later that week when I have time. I went thru the process again, watching #1 intake valve, get TDC on the combustion stroke, turn the bump the engine so the mark on the balancer is 0-12 degrees advanced, drop in the distributor, identify #1 and attached all the plugs wires in the firing order. When I went to start the engine it wouldn't start. It did have some minor firing ( no back firing) but clearly something was off. I repeated the process just to make sure I didn't miss something, same results. I've done this process now 3 times and still the engine acts the same way. If I rotate the distributor either direction it doesn't even attempt to fire.
I know that this is not rocket science. However, I've never done this on a 67 427 tri power. Is there something I am missing??

[Danny P.]

Re: distributor/timing 67 427 tri power

Mark , this is my old school way I do it , a starter push button switch helps if working alone , no need to remove valve cover to find # 1 , I pull the # 1 plug bump until compression comes up feel it with your finger and then align to TDC at 0 timing tab, then make a mark on Dist. housing where # 1 wire on the Dist.Cap then point the rotor just before the mark and make sure vacuum advance unit is where you wanted to be and make sure dist. Shaft line up with oil pump shaft then drop the Dist. Hold down Dist. housing and bump starter until it drop down into place , to confirm it at # 1 keep bumping the starter until compression come up again and align TDC 0 mark on tab and rotor should be pointing at #1 mark On dist. housing if it does install cap then it should start and setup timing at the spec. Should be at 12 degrees other members may have other ways this works for me . Danny

[Mark F.]

Re: distributor/timing 67 427 tri power

Thanks Danny!. I have not been using a remote start button. So, I'll get one of those and try your method. I'm REALLY getting tired of taking the valve cover off and on so I'll do the finger route. The one thing I wasn't doing is dropping the distributor in and then bumping the motor until it drops all the way in due to the oil pump shaft alignment.... then bump the engine again on the compression stroke to 0 degrees and see if the rotor is point at #1. Instead I was using a long screw driver to adjust the oil pump shaft. I think your method might be more accurate. I should mention my distributor is not the points type. Thanks again and let you know how things work out.

[Duke W.]

Re: distributor/timing 67 427 tri power

The common mistake you made was to remove the distributor with the crank at whatever position it was when last shut down. Yeah I know you "marked" the orientation of the distributor, but clearly something is amiss.

My recommendation prior to removing the distriibutor is to ALWAYS rotate the crank to place the balancer notch at the initial timing point on the timing tab BTDC #1, NOT TDC, as most people say.

At the above indexing and IF the distributor was properly assembled and installed, the rotating and stationary pole piece tips should line up, and the cap window plane should should be approximately normal to engine centerline.

The way out of your dilemma is to go back to basics. Start beyindexing the crankshaft as I described above. Remove the distributor. Verify that the dimple on the drive gear is pointing the same direction as the rotor tip. Also verify that the #1 plug wire is indexed in the cap terminal immediately next to the right (pass. side) cap widow edge.

To reinstall hold the distributor above the hole with the cap window and rotor tip straight ahead. As you drop the distributor in the rotor will turn CW as the gears engage, but it probably won't seat due the shaft flat not engaging the slot in the oil pump drive shaft. You'll have to tweak it. (I use a Home Depot paint mixing stick) Be patient, it may take several tries.

Once seated turn the distributor housing so that the pole pieces line up. This is called static timing the engine, and initial timing should be very close to where you set the balancer notch on the timing tab.

Start the engine and when warmed up enough to idle stably below 900 (the centrifugal start point) check and set timing with a light, VAC hose disconnected and plugged, of course.

Screwed up distributor assembly (dimple) and installation (wire indexing) are common and result in less than optimum operation. None of the service manuals say anything about proper dimple indexing. I figured it out back in 1965, but a lot of guys including professional mechanics still don't understand the issue.

The above procedure has never failed me or anyone I helped sort out situations like yours.

Duke

[Mark F.]

Re: distributor/timing 67 427 tri power

Hi Duke, Thanks for the instruction. Just a few quick questions: (1). What do you mean the "dimple" on the drive gear is pointed in the same direction as the rotor tip? By "drive gear" do you mean that there is a dimple in worm gear on the bottom of the distributor that engages with the cam?
(2). You say to make sure the #1 plug wire is "indexed" in the cap terminal immediately to the right of the cap window. I am not sure what you mean by "indexed". Are you saying the #1 plug wire should be connected to the terminal post immediately to the right of cap window?

(3). You say : "once seated turn the distributor so that the "pole pieces" line up" What are the "pole pieces"? Do you mean the pin at the bottom of the distributor shaft lines up with oil pump fitting? I am not sure what you mean by "pole pieces".

Thanks!

[Duke W.]

Re: distributor/timing 67 427 tri power

Hi Duke, Thanks for the instruction. Just a few quick questions: (1). What do you mean the "dimple" on the drive gear is pointed in the same direction as the rotor tip? By "drive gear" do you mean that there is a dimple in worm gear on the bottom of the distributor that engages with the cam?
(2). You say to make sure the #1 plug wire is "indexed" in the cap terminal immediately to the right of the cap window. I am not sure what you mean by "indexed". Are you saying the #1 plug wire should be connected to the terminal post immediately to the right of cap window?

(3). You say : "once seated turn the distributor so that the "pole pieces" line up" What are the "pole pieces"? Do you mean the pin at the bottom of the distributor shaft lines up with oil pump fitting? I am not sure what you mean by "pole pieces".

Thanks!

1. The distributor drive gear has 13 teeth and it can be installed with the dimple pointing same direction as the rotor tip or 180 degrees opposite. This affects the clocking on the distributor housing at a give initial timing. On small blocks it doesn't allow enough initial timing on SHP engines before the VAC hits the manifold and too much a tooth off before the VAC hits the plug wire support. The dimple is below the teeth of the distributor gear at the base of the shaft. It might actually work okay on a big block, but all big blocks originally had the dimple pointing the same direction as the rotor tip. I know that works. Why mess with success?

2. The #1 wire MUST be installed on the cap terminal that is immediately next to the right (passenger side) of the cap window edge. Your service manual should have an illustration.

3. The stationary and rotating pole pieces of the mag pulse TI distributor each have eight projections. As they pass each other this signals the TI amp to turn off the main power transistor that causes the coil field to collapse inducing high voltage in the secondary circuit to fire the plug. It's the equivalent of the points opening on the conventional single point distributor.

To static time a single point distributor you rotate it until the points just open. An ohmmeter will get you within one degree and I can eyeball within a couple of degrees.

Duke