engine timing problem

[Timothy B.]

I have a friend with a 1967,327/350HP car and he installed a Petronics 3 ignition, we are having a timing problem.

The distributor timing curve was set by me with a 524 weight base instead of the original 530 base and I installed the black springs which gave approx 24* centrifugal advance at 2600RPM (my distributor machine). When I did this two years ago the electronic switch was a Mallory which seemed to work fine and the engine ran strong. This Mallory had three wires, positive, negitive to coil and ground.

At the drags in June the shutter wheel (part of this Mallory switch) came apart and the engine quit when he was getting ready to run again. He states the car ran fine before that. After installing the Petronics 3, the timing seems to be all over the place and engine misses. I removed the distributor to find the contact plate ground wire missing which I assumed is the problem after talking to Petronics on the phone and installed another spare contact plate with a new ground wire like it's supposed to be.

Yesterday, I installed the distributor again and the timing seems better but still jumps around and the car will not even run with the vacuum advance unplugged. Either the Petronics has been damaged or something else is wrong. The way the timing jumps around it almost seems like the chain is loose or balancer slipping. The engine runs but it's not right and will not idle below 900 with any kind of stable idle. The car has a comp cams 284 duration (seat to seat) as it was described to me and that's all I can tell you about the engine. It ran great before this happened at the drags..

I am stumped, and have turned the gear 180*, seems the same. Moved the distributor one tooth clockwise and counterclockwise and same thing.. ALL SUGGESTIONS ARE APPRECIATED..

[Jim T.]

Re: engine timing problem

Are you providing full 12 volts constantly to the ignition bypassing the ballast resister?

[Patrick H.]

Re: engine timing problem

I run a Pertronix on my 71 and like it; just wanted to state that I'm not anti-Pertronix.

However, if it were me, I'd swap in points and see if the problem goes away. I think you're just guessing until then.

[Timothy B.]

Re: engine timing problem

There is full 12 volts to coil + as the instructions say, no ballast resistor. I am thinking about installing a spare points distributor to see if the problem goes away.

When I called Petronics the tech really could not tell me where the switch activates and fires the coil. He stated a magnetic field is broken by the points cam and I told him it's a old weight base cam he said it did not matter that it will work.

I am also going to check all the engine grounds but I think they are good enough. At this point, I really don't know what to think unless the balancer is slipping and playing tricks on me. The car just does not run right.. No smiley face after this one!!!

[Robert C.]

Re: engine timing problem

Tim,

Quick question. Have you hooked a vacuum gauge up to this car. I'm trying to figure out a problem on a'67 with an "unknown" camshaft. I can't get steady idle vacuum. One guy I spoke with said a long overlap cam will produce a vacuum gauge fluctuations at idle. I called Comp Cams and they told me they'd only expect to see a slight flutter of the needle with long overlap cams. Since your friends engine is modified, if you get a chance, I'd be interested in seeing what it does, since it sounds like it's modified !

Thanks in advance, Bob

[Timothy B.]

Re: engine timing problem

Bob,

I had a vacuum guage on the engine a few years ago when I first curved the distributor, the vacuum reading was approx 10" but not a bad fluctuation. The car was idling steady at 8-850- RPM, this is with a Mallory switch with a plastic shutter wheel. It's a bad design as it is attached with a screw through the weight base where the rotor screws would go but they are smaller with a nut on top of the rotor. That's how it broke, he relates the nut came off and the shutter wheel got destroyed.

The breakerless on my 67 is attached the same way but the allen head screw threads into the weight base holes and tightened which secures the shutter wheel, then on top the rotor is attached with lock washers and nuts to the remaining threads that stick through the rotor holes. .

I had him clean the fuse block connection over the weekend and now I need to check the voltage at the coil + terminal, this Petronix needs 12 volts to run properly. I have not had a chance to work on the car this week because of other priorities. The car runs terrible..

You may want to check for a operating vacuum advance that is fully deployed at idle and also run 12* initial advance. Idle timing will be 27-28* and that may help some. Be careful total WOT (inital + centrifugal)advance does not exceed 38*.

[Robert C.]

Re: engine timing problem

Thanks Tim,

After finding 2 more leaks (minor), I'm at 10 inches, which may be ok for this cam.

Bob