ignition timing retards at revs

Thanks in advance

Does anyone have a solution or reason why ignition timing retards from the original seting when the motor is reved up to stage rpm not under load. Our system retards up to 1.5 deg however we dont have data logging on our timing system.

Hemi with rcd single mag drive
44amp mag and points box/coil
leahy cranktrigger pick up
system wired as per msd instructions

other than this the igntion system doesnt miss a beat

Thanks

Clarky

 

how much end float has the cam got ?

ash

 

set cam up at16th end float, however timing is taken from the crank trigger not via the mag.

thanks

 

Only thing that comes to mind is rod bearing, check it on # 6 cyl or any other cyl for that matter and see if it moves.

 

Cam flloat should be .000, maybe .002 at most. Aluminum block grows when hot anyways, so it will never be any tighter. If this is not the problem, it might be in the mag drive. Our mag drive (made by George Sitko) is rock solid at all rpms.

 

If you have a crank trigger it shouldn't matter if the cam is falling out of the front of the motor. It also shouldn't matter if George, Larry, Fred or Joey made the mag drive. It shouldn't move. The crank hub is triggering the ignition not the Mag through the camshaft. The crank hub is providing the signal to the pick-up and the crank hub is where you see the signal with a timing light.

Back to basics. You have unplugged the connector on the side of the mag and you did plug the crank trigger in to the connector like you are supposed to?

With the engine running with crank trigger the timing light on your mark should be so steady it should look like the engine is shut off and you are holding a Mag Lite on your timing mark.

Little things to consider. Pick-up gap to crank hub is correct. The pick up bracket bolts/nuts are tight so the pick-up isn't sliding around. Pick-up is properly grounded. Stick another points box on it if you have access to one. I can't assume you have an RCD crank hub/degree wheel set up, so I have to ask if you are sure the degree wheel isn't moving on the hub?

RG

 

This may sound stupid but.... the degree wheel isnt moving is it? loose hub ? loose degree ring? partially sheared crank key? or a loose crank trigger bracket? If the trigger has a switch and check that you are actually running off the crank trigger?

 

Thanks Randy, my next thing to try was a different points box.

Crank hub is rcd and like brand new and torqued to 400ft/lb, we strip and rebuild motor after every alcohol round in Western Australia, however will definately treat the motor to new key ways.

Thanks

 

Hello Mike

We check the phasing of the mag at the start of each meet, then change over to the crank trigger. The timing/crank trigger is checked before every run at idle and at launch rpm with a snap on timing light. We dont have any timers on the motor, nor do we vary timing timing during a run.

Thanks

 

Snap On ! Oh shoot! Try a light with no bells and whistles. NO KNOBS!

 

NO KNOBs or buttons on this one, have tried another local quality light and made no difference

Clarky

 

Mike

The motor has done this for a while, nothing has been changed component or set up wise. I honestly havent worried about it untill now as we have been developing the fuel and clutch systems, now that these are close I want that 1 deg back to stay in the mag. We have played around with the timing adding increments each meet. At the moment I believe we are running at our maximum safe timing point, tried and extra .6 deg and it wants to knock the little end of the rods around.

I have spoken with some other expereinced racers over here who see the same problem at stage with there timing, also one commented that the mag advances at certain points of the run(racepack logger). We are kinda under agreance that maybe what we are seeing isnt really happening.

I have organised a new points box and coil for the next round over here and will systamatically change parts out to see if a difference is made.

 

Mike

We run a whipple ontop of the motor that takes no load or power to turn. when I service the motor we do see some minimal damage to number 2 main that would sudjest the crank is wandering a little, nothing i am concerned about, i also see some scuffing from the rcd timing tab on the back of the degree wheel. We run the pick up for the rpm pickup for the motec data logger at 5 oclock and the crank trigger pick up at 8 oclock.

We run the fresh motor up today on the old points box/coil. Will pm you after the weekend with results

Thanks

Clarky

 

Maybe he's running a 8973 and not telling us!!! ha ha ...sorry...had to say it.

 

I have a INNAVATORS WEST balancer and a MSD crank trigger... My timing retards as I take up the RPM'S ...The higher I take it, the more it retards...I start out slow and take it up higher... I have tried everything' and still haven't found the problem

 

Have you checked the cam backlash?