Timing Advance

[pgermond]

What's up with my timing? If I set it at 36 as recommended by SA I get backfire when blipping the throttle at idle and it cuts out at 5300 rpm. I set it at 45-47 (by mistake) and it runs perfect up to 6000 rpm when the rev limiter kicks in. My neighbors came over (unsolicited) and said it sound much better.... my wife even noticed the difference on our drive Sunday.

Pro-Billet, with red bushing and red springs. Any thoughts?

[TurnpikeBoy]

Only one..........Holy Chit.

Did the timing marker/timing reference point move?

[souzape]

Phil- I've seen this before. When the distributor shaft gets spinning real fast it sets up a reverse-induction polar moment down the distributor shaft which causes a disruption of the vortex flow into the primary side of the carburettor and hall effect signal on the air cleaner hold down nut. This in turn can cause a laminar separation in the intake ports and result the sparking plugs mis-firing due to exceedingly lean mixtures in the burner cans at engine speeds above 4350 RPM.
You probably need to get your beast on a good engine analyzer where they can watch it run under load.

Phil S.

[pgermond]

TurnpikeBoy - that was my first thought as well

Phil S. - That was my second thought - not the "reverse-induction polar moment".... or, "a laminar separation in the intake ports and result the sparking plugs mis-firing due to exceedingly lean mixtures in the burner cans",....... but getting it on a dyno. Thanks for the laugh.... only an aviator could say all that with a straight face

[souzape]

Phil- see you in Sparks...sure it will be running fine by then.

Phil S.

[Justin Upchurch]

Bittentoo had a problem that sounds like yours, he even has a T-shirt to prove it His problem turned out to be the coil. PM him for the details.

Justin

[Brent]

First things first, check the pointer and the balancer. Bring the motor to TDC and check the pointer. 6-8 degrees on that balancer is only about 3/8".

Do you have an adjustable timing light?
If not find someone that has one. It will have a dial on the light that allows you to set the ammount of timing you want on the light and then use the TDC mark on the balancer. It is a lot easier than trying to find those small timing marks. You can start the motor and turn the dial on the light until the TDC mark aligns with the pointer and you will see what the timing is at.

If you hold the motor at 2000 rpm does the timing bounce around or sit still?

Do you have a vac secondary carb or mech secondary?

[JeepSnake]

Agree with Brent - pointer could be installed wrong, could be the wrong pointer altogether, pointer could be bent, balancer could have mark in wrong position, could have more than one mark, outer ring could be separated, etc. etc.

I'd verify TDC with a piston stop, then start checking to see if the balancer & pointer marks line up, and go from there.

Cy & I have personally "fixed" at least 5 engines that I can think of that had nothing wrong with them except extremely retarded distributor timing. There's any combination of causes, but it is VERY common.

[pgermond]

Thanks guys, I appreciate the comments. Pointer, marks, everything is where it's supposed to be. The timing doesn't bounce around and I have vacuum secondaries. It's running great, so until I get it on a dyno I don't think I'll worry about it...... just really bizarre

[souzape]

Phil- if everything is stable (timing marks not jumping around, etc.) you might double check just to make sure you are using the correct #1 cylinder spark plug lead for your timing light. Stranger things have happened (like using the front plug wire on the opposite side of the engine).

Phil S.

[bittentoo]

Justin is right, I had a similar problem. I had to continually advance my timing just so the engine would start, much less run decently. It was running rich and backfiring out the pipes. My initial timing started out at 15*, then I had to bump it to 20* then a few months later 30*.

At that point I said that's it, I have to find out what is going on.

Pulled the dist. out and checked the gear, a little wear but not bad but I replaced the gear anyway, but no help.
Replaced the MSD pickup in the dist. even though it ohmed out good, no help.
Grounded a sparkplug against the header, nice blue spark.

Figured it was the timing chain going south so I pulled the front of the engine off, timing chain looked great.

OK, must be carb, replaced at least a half dozen power valves, new gaskets and tried rejetting, no help, infact it was getting worse, now I was up to 35* just to start the engine. I didn't dare drive it with so much total timing in it. I learned that lesson.

Checked for TDC, that was fine and the balancer wasn't an issue as it is an ATI dampener wirh no rubber insert.

Broke out the dial indicator and redegreed the cam just to make sure I didn't get it a tooth off when I had it apart, cam is where it should be.

I have been working on this POS for over a month now a was completely stumped. Out of desperation I replaced my coil with an old one I had laying around, and Bingo! It was fixed!

What I found out was, a coil can spark just fine on the header at atmosphere, but at 6 or 7 atmospheres of cylinder pressure and if it is weak it takes more initial timing to ignite and burn the fuel in the cylinder.

If you haven't done a rear wheel dyno, by all means do one. They are neat and take the video camera! The Houston group did one while my car was down but I went a few weeks later and did better thay I expected (most are disapointed). The cleveland went 422@6500 rpms and 390 torque. Not bad for a all iron motor with a flat tappet cam!

Anyway, check the obvious stuff first, but don't fight it too long before trying a different coil. Good luck.

[eliminator]

They are called a dial back timing light, you dial in the total advance and it reads it at the zero degree mark.

Yea, run that on the chassis dyno like Kelly said and you will be cussing Unique when you pull your rear end to replace the broken bolts.

All you guy's going to the chassis dyno better find a better place to strap the rear end down other than the lower control arms of the IRS.

[pgermond]

I have an appointment for a dyno tune on Monday. $450 + parts , or maybe .... we'll see. I'll post the outcome.

[pgermond]

An update -

My son came in to town unexpectedly over Easter, so I canceled my dyno. However, in the mean time things have really come together and the car is running as good, or maybe better than it ever has. A carb spacer on the intake manifold, adjusted the float levels, eliminated the choke, set the timing, and replaced the 160 t/stat with a 195.

If I was racing I would probably still pursue the dyno, however, for now I have noooo complaints.

Thanks again for all the input!

[bittentoo]

Good for you, Phil!

[Brent]

Very good news.

Now drive it to homecoming. (-;

[Rocky]

I have had some of the same Gremlins as you. I have a 390FE with 428 Cobra Jet heads, Edelbrock intake and a 750 Holley 2 pump w/ no choke. What kind of spacer did you use, and what did you set your float levels to?
I have my engine out fixing a rear main leak. I went through my Carb and found my Primary Power valve was a Dummy plug. I should have listened to Maurice Weaver when he told me not to trust a New Holley.
Any info will be appreciated

Tom

[pgermond]

Tom,

I have two spacers - 1/2" and 1/4".... currently using the 1/4". I set the floats at the bottom edge of the sight hole. A problem I didn't have was vacum leaks, but one should always check the vacum port on the front of the base of the carb to insure it is capped off.