Ok,
So, I have a SBC 355 Drag motor with a hydraulic camshaft,double row timing chain(less than 2 years old), locked out MSD distributor with bronze gear, 750 AED card. with no idling issues or known vacuum leaks. MSD 6al ignition and a blaster 2 coil.
Now for my issue!! When trying to set the timing, the more I Rev the motor the higher the timing goes. I have tried several different lights, changed out the MSD box, coil, and called MSD and they told me that there is nothing wrong with the electronics. The motor was freshened up a few years ago and probably has less that 75 runs on it since then. The timing will stay at what ever RPM I set it at but as I decrease or increase the RPM it either goes up or down. doesn't fluctuate and stays steady at each RPM.
What gives??? Any help will be greatly appreciated.

Distributor trigger or crank trigger ?? How many degrees does the timing move ??

Check your harmonic dampener...had an SFI [not naming the brand], that showed similar symptoms when the rigs began to separate.

Cam may be walking forward or backward.

I had one small block do it real bad years ago.

It’s Usually a roller cam that does it but any cam can do it.

If it has a stock timing cover look down behind the water pump and raise the rpm. Your looking for any movement of the cover. If you see that cover move that may be your problem.

quote:

Check your harmonic dampener...

Going one step further on that possibility, mark both the inner and outer rings along a straight edge. You then should be about to observe them with your timing light.

Are you 100% sure the mechanical advance is locked?

How much will it move? If its a few degrees it’s actually pretty common......

Just to add to what SCDIV1 said, was a cam button installed? I have seen the flimsy stock GM covers push out as the rpm increases..a lot!

Thank you guys for the feed back.
To answer some of your questions. It is a distributor pick-up and I am positive it is 100% locked out. The timing will move around 4 degrees total the higher i rev it. Not for sure if there was a cam button installed. I will certainly check everything that people have listed to try and pin-point this issue.
thanks again!!!

I have a flat tappet cam and a locked dist and a few timing lights. They will all show the timing move a few degrees if the engine is revved. I was always told that with a flat tappet cam the lobes are angled so the pressure of the lifter pulls the cam back into the block so a retainer or button isn't needed. This is very common and discussed many times and it always comes down to try other timing lights, and it never seems to matter as they all show the same.

Eman you are correct, I miss read the OPs hydraulic camshaft and hydraulic roller was in my head.

Eman/Deadon
So is this something I should be concerned with or just let it go???
What RPM would you recommend setting total timing at if this is common??

Try a cheap battery powered timing light on it.

Mine moves 2, 3 degrees with a 30 year old Sears Craftsman adjustable and none with a cheap chinese junk battery powered timing light.

What ignition box? The timing gets wacky on the red 7AL3 when they go bad....

Just saw SBF crank broken and was found to be bad dist that was locked found welded plate on top broken and moving

If you have too much end play in the distributor shaft, the shaft can walk up and down, which also allows timing to fluctuate. Depending what distributor you have, there's different specs for setting the end play. It's easy to do.

How many degrees is it moving?, a few degrees seems to be normal or it is on mine. The end play in the dist. can be a factor as can a loose rotor. Also the rotor top contact helps kep the dist. shaft steady. Also check for a worn button in the center of the dist. cap.

quote:

Originally posted by BigSexy:
Thank you guys for the feed back.
To answer some of your questions. It is a distributor pick-up and I am positive it is 100% locked out. The timing will move around 4 degrees total the higher i rev it. Not for sure if there was a cam button installed. I will certainly check everything that people have listed to try and pin-point this issue.
thanks again!!!

Leaving electronic issues out of the picture, timing can move from the following:

- too much distributor shaft end play
- worn distr. gear or cam gear therefore too much back lash, also check the roll pin holding the gear on the distr. shaft
- rotor loose or cap can move
- Assume the distr, has a mag pickup mounted on a plate, if either is loose
- cam torsional deflection
- too much cam end play (this issue can have a few causes such as a setup issue or assuming you have a timing chain with a stock stamped steel cover, the cover is flexing allowing too much cam movement.
- loose balancer
- faulty timing light
- rotor mech. advance not locked tight or the rotor mounting plate is loose to the shaft.

Probably a few more too...

I'd try a cheap one wire battery powered light. If that doesn't tell me anything different I'd check the depth of the distributor. But then again I run a System One oil filter so I'd have already been tipped off, if it were a depth issue taking the bronze gear out.

I thought it was common knowledge, the better the timing light multiple spark discharge, the more this occurs.

OP you just gotta eliminate each variable mentioned here.