Eratic timing mark??
Thread Starter
Race Director
Joined: Oct 2005
Posts: 12,470
Likes: 1,548
From: Camp Verde AZ
C1 of Year Finalist (performance mods) 2019
2017 C1 of Year Finalist
Eratic timing mark??
My timing mark at idle seems to jump around a bit too much (+/- about 3 degrees from where it should be), even with PLEASE READ:
the EFI set at 10 degrees timing mode, so no RPM advance is possible and a new distributor,
so no, my distributor isn't worn out,a nd I am not getting variable timing from a centrifigual advance mechanism.
This sorta leaves my timing chain as teh only culprit, it is woern out and sloppy?
Thanks,
Doug
the EFI set at 10 degrees timing mode, so no RPM advance is possible and a new distributor,
so no, my distributor isn't worn out,a nd I am not getting variable timing from a centrifigual advance mechanism.
This sorta leaves my timing chain as teh only culprit, it is woern out and sloppy?
Thanks,
Doug
Drifting
Joined: Apr 2004
Posts: 1,303
Likes: 36
From: Allen Park Mi
that would do it...
i was getting +/- 8 degrees before I put a new chain on... you'll also notice it if you get the motor well above max centrifugal advance and let off the throttle... it will usually show more advance also... but i'm not sure it warrants a timing chain swap unless you are going into the motor for some other reason.
a few degrees at idle isn't going to do much and as long as it is steady in the upper rpm range you should be fine...
A
i was getting +/- 8 degrees before I put a new chain on... you'll also notice it if you get the motor well above max centrifugal advance and let off the throttle... it will usually show more advance also... but i'm not sure it warrants a timing chain swap unless you are going into the motor for some other reason.
a few degrees at idle isn't going to do much and as long as it is steady in the upper rpm range you should be fine...
A
Melting Slicks
Joined: Sep 2003
Posts: 3,050
Likes: 2
From: Orange Ct
I think there is away to check the timing chain slop buy rotating the engine manualy one way untill the rotor moves. Then rotate it the opposit diection and see how many degrees before the rotor moves. I don't remember what a good number was.
Thread Starter
Race Director
Joined: Oct 2005
Posts: 12,470
Likes: 1,548
From: Camp Verde AZ
C1 of Year Finalist (performance mods) 2019
2017 C1 of Year Finalist
Speaking of going into teh motor for otehr reasons....
Are the newer ZZ cams, or other modern GM cams interchangable into the old SB?
Just considering options, I see these high lift, short duration roller cams on factory/crate engines, and wanted to explore that possibility as well as the old standby mech lifter cams.
Not really looking to increase my top end, but some more torque in the 2500-5000 RPM range would be nice
.
Doug
Are the newer ZZ cams, or other modern GM cams interchangable into the old SB?
Just considering options, I see these high lift, short duration roller cams on factory/crate engines, and wanted to explore that possibility as well as the old standby mech lifter cams.
Not really looking to increase my top end, but some more torque in the 2500-5000 RPM range would be nice
.
Doug
Le Mans Master
Joined: May 2006
Posts: 7,708
Likes: 266
From: indy indiana
i dont see how it could be the chain. its under constant tension when running so shouldnt be jumpy.If it where streached.it would simply read more retarded,wouldnt it? Sounds more like sloppiness in the distributor.
Limping across the line
Joined: Oct 2002
Posts: 5,299
Likes: 109
From: Peoria Az
Doug does your distributor have a vacumm adv dashpot?
Also is the cap and rotor new with the dist also?
Remember the driven gear is a helical cut gear and end play will cause the shaft to rise and fall,climbing and falling down the curve of the gear.
Also is the cap and rotor new with the dist also?
Remember the driven gear is a helical cut gear and end play will cause the shaft to rise and fall,climbing and falling down the curve of the gear.
