68 Charger Timing Question

[ikbrown]

Hello fellow B-body-ers!

New to the forum, not new to my mopar, and have a question...

Recently took my Charger on a roadtrip from Sac to Chico and back & close to all the way back we had a short and the car died. We traced the problem back to the fusible link wire and replaced that. Long story short, in diagnosing we removed the wiring harness that the fusible link is a part of (connects over to the alternator, distributor, horns, etc) and we had to take the distributor out to get it back in.

Timing is a bit off and my question is, with the engine modifications below where should we put the timing at? Previously we had it at top dead center, but our neighbor was saying w/ his Corvette w/ a larger cam (bigger than ours) he retarded the timing by 25% to run right. Anyway, here is the list of mods done to the engine to help out in the answer:

I have a 68 Charger w/ a rebuilt 383, high-lift / longer duration cam, increased carburetion (740cfm) carburetor, MSD ignition, and hooker headers/full 3" exhaust

If you need any additional information definitely let me know, and please excuse me if I sound like a noob, this is my first post to the site. I'll post a more formal introduction in the new member section soon!

Thanks for any help you can provide!!

 

[Photon440]

Hi, welcome to the forum.

To start, it's probable that your higher-than-stock lift and duration cam has dropped lower rpm cylinder pressures, so I would start with more advance, not less. Keep advancing it if you don't hear detonation, and read your spark plugs.

 

[ikbrown]

Hi, welcome to the forum.

To start, it's probable that your higher-than-stock lift and duration cam has dropped lower rpm cylinder pressures, so I would start with more advance, not less. Keep advancing it if you don't hear detonation, and read your spark plugs.

Thanks for the response Photon! So it would be a good idea to try ahead of top dead center vs. behind? What does read your spark plugs mean? I know the bout the firing order but not sure what you mean in this context. Thanks

 

[Gpuller]

Depending on your cam your initial timing might be 15-25 degrees. You'll have to limit the total timing to 35-38 degrees. That all depends on what distributor the car has.

 

[Meep-Meep]

As said above, larger than stock cams, especially if you have a 108 LSA cam, will often require huge amounts of timing to keep the engine happy. This is why for a street driver I like the 112 LSA cams, or depending on the specific grind, a 110 LSA can work well. You most likely have too low compression to support the cam you have installed and that just makes things worse.

And X2 Gpuller on the distributor fix.

 

[Photon440]

Thanks for the response Photon! So it would be a good idea to try ahead of top dead center vs. behind? What does read your spark plugs mean? I know the bout the firing order but not sure what you mean in this context. Thanks

Checking your spark plugs is a good way to see how the engine is running. After a hard pull, shut off the engine, coast to a stop and take a look. You can tell a few things about your timing and carb mixture. This page describes it much better:
http://www.4secondsflat.com/Spark_plug_reading.html

-=Photon440=-

 

[ikbrown]

Update to my post... I realize my Cam description may have not given the best of direction to help diagnose.

I looked at the shop's receipt I have for the engine rebuilt and the only thing it says for the cam is:

"Mild cam 260 degrees"

No mention of manufacturer or 108-112 LSA like Meep-Meep had brought up, but does this help at all?