Ignition timing on 67 426 HEMI

Posted By: az426john

Ignition timing on 67 426 HEMI - 06/01/11 03:52 PM

I set the timing on my 67 HEMI using the vacuum gage method (max vacuum - 1 inch) and ended up with 25 degrees initial and 40 degrees total checked with a dial back timing light.

Idle is 800 RPM in neutral.

The distributor was rebuilt professionally to stock specs.

The car starts and runs fine with no pinging or dieseling at shut off so all seems fine.

The engine is 30 over with a therotical 9.46 compression. I am running a 24-278-4 Comp cam with 227 Intake and exhaust duration @ 0.050. I am using Arizona 91 octane junk gas.

The total timing seems a little advanced to me.

Thoughts???

Thanks for your help in advance.

Posted By: 69hemibeep

Re: Ignition timing on 67 426 HEMI - 06/01/11 04:07 PM

That does seem high. Mine is stock 10.25 and stock solid cam. I started at 36 total and had to back it off from there until it was happy, I'm not sure where it is total now I need to check and this is with the same crappy gas. You might have a nice combo with your compression ratio and cam for this fuel but 40 seem high

Posted By: mickm

Re: Ignition timing on 67 426 HEMI - 06/01/11 04:15 PM

i think it is too high, but as the second posted noted, your combination may like it. most hemi's seem happy in the 34-36 range.

i would simply back it down to 34 and see what it feels like, and work it up a degree or two at a time. if you can't tell any difference you can just decide where to stop. of course a track would be the best way to find out what it likes best.

Posted By: Dodgem

Re: Ignition timing on 67 426 HEMI - 06/01/11 04:22 PM

But did you check your harmonic to see if it is in fact 0 at 0 and many timing lights can be off 4 to 6 deg??
If it runs good and don't ping don't worry be happy!!!

Posted By: az426john

Re: Ignition timing on 67 426 HEMI - 06/01/11 05:20 PM

Dodgem,

I did check the Harmonic Balancer for correctness when the motor was rebuilt and the timing marks are pretty much on except for whatever slop there is in the timing chain.

Now the timing light may be a different matter, but I did check it against a non-dial back timing light that I have and they both show approximately (within about 2 degrees) the same results.

Posted By: RapidRobert

Re: Ignition timing on 67 426 HEMI - 06/01/11 07:58 PM

Quote:

I set the timing on my 67 HEMI using the vacuum gage method (max vacuum - 1 inch) and ended up with 25 degrees initial and 40 degrees total. The total timing seems a little advanced to me. Thoughts???

Yes you set the initial properly but the total (initial+ slots & vac adv disconnected/plugged) cannot be finalized until you have the initial # in hand which means you need to shorten the slots and the tried & true totals that MP lists (35-sb 36-38-bb /6-32) are surprisingly dead on and you then play w the springs to adj the curve then plug in/adj the vac can. Not sure what it is for a Hemi as I never have owned one, have never worked one one and probably wont (in this lifetime) but I know it's not 40

Posted By: 52savoy

Re: Ignition timing on 67 426 HEMI - 06/03/11 05:05 AM

Quote:

Quote:

I set the timing on my 67 HEMI using the vacuum gage method (max vacuum - 1 inch) and ended up with 25 degrees initial and 40 degrees total. The total timing seems a little advanced to me. Thoughts???

Yes you set the initial properly but the total (initial+ slots & vac adv disconnected/plugged) cannot be finalized until you have the initial # in hand which means you need to shorten the slots and the tried & true totals that MP lists (35-sb 36-38-bb /6-32) are surprisingly dead on and you then play w the springs to adj the curve then plug in/adj the vac can. Not sure what it is for a Hemi as I never have owned one, have never worked one one and probably wont (in this lifetime) but I know it's not 40

I went that rout on my '68 Hemi maybe 15 years ago because when I rebuilt the motor the dist. timing was stuck around 50 degrees total. After checking everything, I soldered and filed the weight slots to get the timing back down plus played with the springs but then the car started hard and didn't idle. I took the the distributor back apart and cleaned out all the solder. When I started the car up the timing was right on...

To day I haven't figured that one out.

I put a Pertronix in it shortly after and it helped clean up the idle plus no more points to keep up on.