Timing & dist question->SB 360

[DMZ73]

Sorry for the dumb question in advance.

Setting  the timing in my 73 challenger 360 to 12-13 deg.
Seems to run great without the vacuum advance hooked up.
As soon as we hook that up, the car goes to crap.
try to open the throttle and it backfires thru the headers.
Take off the vacuum advance and all is well.
Popped the dist cap off, and notice that the rotor weights are not anchored down (not screwed down.
Wondered if that had anything to do with the situation.
please enlighten me.

Good Vacuum

Seems retarded backfiring out of headers
Runs fine without vacuum
12-13 advance initial timing
Is it 12-14 full timing? 
Loose part within the distributor (screw)? 

Thanks,
Dan
 

[Bullitt-]

Not sure about the loose parts your talking about but the vacuum advance problem you describe has to be your using the wrong port....you want metered vacuum which has no vac at idle...What carburetor are you using?
  Initial timing of 12-14 sounds good...total timing w/o vacuum advance 36@ around 3000rpm...max timing with vacuum advance upward of 50

[Chryco Psycho]

I generally leave the vacuum disconnnected anyway

[Oldschool]

I generally leave the vacuum disconnnected anyway

  

[CUDA JAS]

Not sure about the loose parts your talking about but the vacuum advance problem you describe has to be your using the wrong port....you want metered vacuum which has no vac at idle...What carburetor are you using?
  Initial timing of 12-14 sounds good...total timing w/o vacuum advance 36@ around 3000rpm...max timing with vacuum advance upward of 50

Not to confuse the OP, but others will suggest hookign the vac adv to manifold vac, whick does affect idle.  I have had good luck with this, as it smoothed out my rough idle (lumpy cam). 

My suggestion would be to make sure your carb is set propley (running on the idel circuits, etc).  Make sure your timing is set correclty with out vac adv (which it sound like it is)  Alos make sure your dist is in good working order (post some pics of the loose parts if you can).  Once you have that all sorted out, you can try the vac advince again, it hooked up to manifold vac it should increase the idle, which woudl necessitate a small carb adjustment.

If you have the same symptoms, you can back out the vac advance a little (allan wrench into the vac port) and see if that helps.

Also, what cam are you running, I know my 360 likes a little more initial (mine is at 18 I think).

Jason

[moper]

I'd first suggest making sure the firing order is correct, especially in regard to 5 and 7. Then make sure the distributor is ok. One of the weights (if its a factory stock part) will just kind of flip around down in there... Unless both the weights move, the centrifical advance wont advance. So you have one med weight spring, and one very stiff one that has about 1/8" of free play before it starts having any real affect. The vacuum advance will work properly when connected to ported vacuum and on a street car only helps. It does not negatively affect idle or full throttle. Also, the level of vacuum required to start the vacuum advance moving can be ajdusted with a 3/32 allen wrench. Sounds like yours might not have enough preload. But check the firing order and stuff too.

[DMZ73]

Here are the pics with an explanation


I looked on my stock 360 dist, the screw is tightened to the rotor, not allowing the weights to shift freely.
Just dont know what position it needs to be locked down at. I guess I'll try to lock it down the same way the stock 360 dist is for starters.
The timing is set without vac advance. It runs great without the vac advance.

Thanks again!

Dan

Dan

[CUDA JAS]

Hmmm...I think that screw attaches and locks down the pick up...it should be set to the specifed distance from the reluctor using a feeler guage.  Once set it should not move. If it does move, the timing will fluctuate.

jason

[Talkwrench]

It would be interesting to see what your total advance is [no vac]. I have just set mine to 12.5 initial and it is 33 total, is all in by 2800 RPM.
Was originally 10 and 30 total.  Car does go a little better, but I think its a little harder to start. I adjusted the excl pump [edel 600]  for a quicker squirt and now it starting to feel like a V8    I will try to get 36 total and see what happens...

[Chryco Psycho]

the screw in the pix hold the pick up in place , you should have a gap of .008 between the pick up & the reluctor

[CUDA JAS]

DMZ73 - which part is moving / loose in the dist? 

If it is the big round ribbed piece that fits over the main shaft you have a different issue.  That piece is held tight to the shaft by a roll pin.  If that piece rotates on the shaft you will never get your timing right!

Jason

[Aussie Challenger]

 As Chryco said tighten that screw, if loose, when vac advance connected the plate will move the gap and effect the timing greatly, it is a wonder that it will run and you haven't damaged the reluctor and pick-up.

[DMZ73]

I tightened it down based on the gap set from the previous dist from the reluctor to the pick  up.
It does run really well right now, without the vac advance. When I hook up the vac advance from the carb to the dist (left port of edelbrock carb) , it goes WAY lumpy. (probably more tuning?) It is set between 12-14 deg. without vcac advance. Otherwise, it runs great through RPM range.
I just need someone to give her a once over with me- preferably someone who has done this before. I am sure it is a stupid mistake.
Sounds AWESOME!! no more popping through the headers or carb!

Dan

[DMZ73]

Like I said, it was a stupid mistake. 
I tightened the reluctor, switched the vacuum ports, and BAM!
Runs incredible!!!! 

Thanks guys!

Dan

[Bullitt-]