I had checked timing a few weeks back and it was right at 35 as I expected. This is a 632 Chevy with a single dominator on alcohol. The distributor is a msd pro billet with locked out advance. At about 900 rpm it’s 35. Rev to 2000 it’s 32. I replaced the distributor thinking it had a problem and the new distributor does exactly the same it retards about 3 degrees when reved up.

Anyone experienced this with an msd pro billet locked out?

Should I just set timing to 38 to get 35 down track. There are no retard modules in place. The msd box is the red 7320??? Box with all of the regards disabled.

I never really looked at timing much. I just set it to 35 and didn’t look again.

Bob

I had this happen to me on a 598. Check the camshaft end play. If the cam can walks too much, the timing will vary as RPM's change. This only happens if you are using the pick up in the distributor to trigger the ignition. Mine seemed to settle when i held the RPM constant but when reving or changing RPM's up or down, the timing would move around. Was very difficult to diagnose. In my case my cam button was way to short and i had about 0.050" camshaft end play. I swapped to a crank trigger and the problem with the timing went away but then i had trouble with the rotor phasing moving around and had the occasional pop going down the track. Once i got the correct cam button and set the end play where it was supposed to be (i'm thinking 0.002" to 0.008") the problem went away.

I've heard of something similar happening if the wires to the pick up were swapped but that usually led to 10-15 degree reduction in timing as soon as the motor was brought up over about 1200 RPM's. Easy way to check is to swap wires in the distributor plug in and see if it corrects your problem.

This message has been edited. Last edited by: Triple Nickel,

The Internet forum crowd blames it on the box, on the timing light, on the pickup wire routing, yada, yada, yada. The fact is you’ve got slop/ movement in one/all the timing related components.

Ive run MSD Pro Billet distributors since they first came out and the timing on my engines has been rock steady whether locked out or running mechanical advance. I also used a dial back timing light all my cars for over 3 decades without issue as well I’ve checked this light against MSD’s one wire/battery operated light and found no difference in timing.

I would also start with checking cam movement.

I don’t remember how much it moved, but mine always moved a couple degrees with RPM while I was using the pickup in the distributor.

Never caused a problem and the car was consistent, but I eventually went to a crank trigger on everything.

Cam movement/end play/timing chain/belt or gear drive slop is what's going on more than likely.

Switch to a crank trigger, you won't be sorry.

As Ed indicated there is more than one reason for timing movements:

- End play on the distributor to much
- Camshaft end play too much, especially on roller cams
- Timing chain stretched
- MSD 7AL Red Box - these are noted for timing issues, if you have one, dump it. They fixed the issues with the black box.

If you want rock steady timing use a crank trigger.

As others have wrote, the older MSD 7230 Red Ignition Box (from 1995 – 2013) is known to have timing consistency issues. The newer (2013) MSD 7330 Black Ignition Box is the replacement.

Consider installing a crank trigger. This fixes any ignition trigger problems from cam walk or distributor.

The graph below is Grid data acquisition of RPM from Crank Trigger (Green) and Distributor Trigger (Purple). This is the same engine just switching trigger devices.

Chain slop. All my timing is in @ 3000. Spring configuration. one light/one heavy. (Non Locked)
Old school.... 632

Bang on the MSD box with the timing light on it... betcha the timing jumps.

We need to find the car that doesn't do this so we can all try our timing lights on it and see which light is the best. I don't think I've seen a car with a MSD box and distributor not do this. tried with many different lights.

Thanks for all the responses. The timing chain/set was new this season, the msd distributor is brand new a week ago. I just pulled the engine for end of season checks so I will check cam end play.

I have the same distributor in a sbc that will retard 10 degrees from idle-5000 rpm. Pertronix box and coil. Solid roller cam with .005” end play. Good luck finding a cure. I bump up initial idle timing to have the timing correct at 5500 or so. It’s sitting at 44 degrees at idle, 34 at 5500rpm. I may start looking at crank trigger timing as possible cure.

I had a SB Chev in the early 80’s that retarded 10 degrees from idle to 5000 rpm. Don’t recall what distributer was in it. An MSD 7 box probably. I also set the timing well over 40 degrees at idle. I could watch the stock sheet metal timing cover back up when I revved the engine. Just the opposite of what they usually do, push forward. I could find nothing obvious causing it. I had 3 engines at one time back then and don’t recall even what type cam was in it. Highly likely a roller lifter cam. I just raced it.....and won with it ! Lol

quote:

The timing chain/set was new this season...

That in and of itself does not guarantee a correct fit. Due to mfg. tolerances, tolerance stacking, line boring/honing, etc. Cloyes offers .005" and .010" undersize timing sets to address this very issue. I put a .005" under in a new Merlin III block.

That is why you do not set the timing at idle.
Chain stretch, cam walk, slop in distributor gear to cam, cam twist, oil pump loading, they all have an effect on timing. 3-4000 rpm puts a load on everything.
Crank trigger helps, but the slop is still there.

quote:

Originally posted by Eman:
We need to find the car that doesn't do this so we can all try our timing lights on it and see which light is the best. I don't think I've seen a car with a MSD box and distributor not do this. tried with many different lights.

Also, you shouldn't use a dial-type or adjustable timing light with an MSD ignition. Just a plain old basic light.

quote:

Originally posted by BD104X:

quote:

Originally posted by Eman:
We need to find the car that doesn't do this so we can all try our timing lights on it and see which light is the best. I don't think I've seen a car with a MSD box and distributor not do this. tried with many different lights.

Also, you shouldn't use a dial-type or adjustable timing light with an MSD ignition. Just a plain old basic light.

I’ve always heard that, but my old chrome Craftsman with the dial set to zero has never been wrong.

and neither has my now 34 year old Snap On Dial back timing light that I bought new in 1986.

That claim about dial back lights is amongst the many claims that are internet hearsay, rumor and myth.

quote:

That claim about dial back lights is amongst the many claims that are internet hearsay, rumor and myth.

While I'll agree about the myth part, I think the KISS principle applies here. Why do you lock out a distributor, why do you block off a power valve, to eliminate variables. There's potential of the dial to get nudged unknowingly and there is the potential the circuitry could go haywire (although in reality is rare in quality lights). You can guarantee both of the aforementioned situations have occurred at some point.

Also, I'll agree with Bad's theory on loading the system. I recall speaking with an MSD tech and he didn't like the fact I had a HVHP oil pump, validating an ignition company's concern regarding spark scatter due to oil pump and associated drive shaft.