Timing retards on its own...

[redliner]

I have a very sturdy alum.timing cover on it I don't think it's flexin... The Billet MSD dist is new,as is the composite gear and MSD coil.The 6al is 25 years old tho

[treyrags]

Sometimes it is the light, also it is common with many electronic ignitions to see retard as rpm goes up.Its called slew rate or something like that.Basically it takes the electrnics a set amount of time to trigger the spark and as rpm goes up it falls behind.Many can be 1 or more degrees per 1000 rpm.

This ^ Like Joe said, set it where it runs best and don't worry about it.

[crazyman]

Alot of two stroke CDI's are set up to retard the timing with rpm. Don't worry.

[CREngines]

Which box are you using? The new digital 6al produces an immediate 4 degrees retard over the older boxes just swapping it out and a gradual two to three degrees with rpm. Just went through this with msd over a brand new box for the dyno. They are replacing it right now with a 6ALN (old 6al) because if i send a motor out the door with the ignition set off of the new digital box and it is installed in a vehicle with the old box the timing will advance 4 degrees. Needless to say that is bad for business. This is a noted problem with the new digital boxes from msd. they claim the old box loses 2deg at 10000, but this new stuff loses it alot faster. Also ensure that when the distributor was locked out the nut is tight so the reluctor ring carrier does not move independent of the shaft even a little bit.

I like my timing to stay where i set it.

[redliner]

Which box are you using? The new digital 6al produces an immediate 4 degrees retard over the older boxes just swapping it out and a gradual two to three degrees with rpm. Just went through this with msd over a brand new box for the dyno. They are replacing it right now with a 6ALN (old 6al) because if i send a motor out the door with the ignition set off of the new digital box and it is installed in a vehicle with the old box the timing will advance 4 degrees. Needless to say that is bad for business. This is a noted problem with the new digital boxes from msd. they claim the old box loses 2deg at 10000, but this new stuff loses it alot faster. Also ensure that when the distributor was locked out the nut is tight so the reluctor ring carrier does not move independent of the shaft even a little bit.

I like my timing to stay where i set it.

The 6al box is 25 years old.

[jsgarage]

The current Circle Track magazine also did some timing variance testing on three different high-dollar (to me anyway) Crane distributors: two ($1400-up) currently used in NASCAR racing and one cheaper ($400) street assembly. One had a digital brain box and used an optical pickup window that could be trimmed for individual cylinder timing adjustment. The timing spread on Keith Dorton's dyno was a max of 7 degrees (+1, -6) at various rpms and cylinders over 4000-8000 rpms for the worst. As the cost of the ignitions went up, the timing spread came down.... to a best of 4 degrees (+2, -2).
They also tested the effect of oversized distributor drive gears to remove some gear-lash; an .020-over gear was effective at removing only 1 degree of variance; tightening the hold-down clamp also changed timing by 1 degree. Makes for some interesting reading anyway. If this is state-of-the-art in big-buck-racing ignitions, I'd not worry much about your 3 degree spread.

[barnym17]

An interesting side note, this rarely happens with point triggered ignions.

[john@bmp]

If it bothers you, you can go to a digital 6 box, where you can put the timing wherever you want it. If you lose 3 degrees, just put 3 degrees more into that RPM range... Semantics I guess. Like Joe said, it really doesn't matter, but I'd love to know WHY it happens. Maybe electronics just can't keep up...

[dirtmod87]

I agree with Danta, I had a BBC i put together in a hurry on a friday night, had a few engines on the bench and i mistakenly put the wrong cam button in.. when i checked the timing on sat morning it would retard about 5 degrees at 4000rpms. Raced it that night. (Big block Dirt circle track car) timing would retard coming out of the corner and worked just like traction control, couldnt spin a tire . Set my fastest laps ever at my home track. Next week I fixed it and still wonder if there is something to be had for circle track guys looking for traction on a slippery track. just something to think about.. maybe us circle track guys should have the adjustable cam buttom for times it gets slippery, like a legal traction device

[rookie]

I third the Danta comment, i've seen rollers push the front cover out so bad the car would lay down about 100 ft out and no one could figure it out, watch your timing cover when you rev the engine if it bulges out, then you've found your culprit, if it's a consistent 3 degrees then as Joe said adjust accordingly.

[redliner]

Tis a very rigid alum. timing cover with a bolt threaded thru a boss on the waterpump to combat timing chain cover flex.There is a needle brg.cam button with the endplay on the cam set but would have t o look up the clearance don't recall....I must check the dist. etc. and if that is good I am n ot gonna worry about it and just run it where it runs best and call it a "topend retard" and call it a speed secret like Bigjoe says.....

[Small block guy]

I have a loose fit on the journals of the distributor housing and my block. Same issue. I think it makes the gear ride up or back and forth, just slightly. Short of bushing the block, I don't know of a fix???

[PFC1]

This is very normal for distributor ignitions. Put a crank trigger on it and you'll likely see 1 or less degrees of movement from idle to 5000 or more.

Bret

[redliner]

Thanks Small block guy and Bret! Maybe a crank trigger sometime but it runs purty good not tweaked yet but purty ok.

[Alan Roehrich]

You'll find that this can happen with electronic ignition systems, especially magnetic triggered systems.

Recently noticed this on a big block that had a 7AL-2 and an MSD distributor. We figured swapping to a crank trigger would solve it. It did not. The timing still dropped back, and still varied slightly.

What I ended up doing was repairing and rerouting the magnetic trigger cable. After that, the timing did not move.

I suggest using a shielded cable, routing it carefully to keep it away from anything that might upset the signal, and even grounding the shield on both ends.