70newport

So after much consideration I took all of your advice and went with the mancini racing electronic ignition conversion distributor.

I was looking over specs sheet last night and it is telling me that for my 383 I should end up with a total timing of 56*.......

Everything I have ever read and set my timing by is to start at around 12* and have total advance finish at around 36*..... Looking back on old threads I still believe this to be correct. Can someone shed light on where im reading this wrong or If my world is about to change....

Top of page 7.

http://ep.yimg.com/ty/cdn/chucker54/...structions.pdf

Thanks,

Gary

Drag Pak

Total MECHANICAL will be set to 36 at stated rpm with the vacuum advance disconnected/plugged. Total with vacuum advance connected will be around 56.

I believe you need to go cruise the highway with a vacuum gauge connected to get your baseline vacuum vs rpm readings at cruise speed/rpm. Then do a driveway adjustment with a vacuum pump to set the timing at cruise rpm via the vacuum dashpot adjustment.

70newport

I am 100% open to being corrected but isn't 56 degrees total advance way too much? I have always aimed for 36 or so......

Drag Pak

Not with the vacuum advance connected cruising down the highway. Otherwise you are washing the cylinder walls with unburned fuel.
When you kick it. the vacuum drops and the timing goes to the total mechanical adjustment for best power.

70newport

Thanks for the assistance. This has now opened a new chapter in my engine research! Time to revisit something I thought I had a pretty good idea about!

Iowan

Drag pak, I appreciate you taking the time to explain how vacuum advanced timing works. It's a topic that needs to be addressed often here and I'm thankful for your input.

All my stuff is high hp low mpg combinations so I use mechanical advanced destibutors exclusively, so instructions well come!

70newport

I have had issues with my carb the last couple years where I only had manifold vacuum where I should have only had ported. ( Holley warranty was good to deal with) so the last 2 years I have ran purely mechanical also. New carb and new dizzy will hopefully be great!

Thanks again. Sorry for beating a dead horse.

Coronet 500

No dead horse, better to get it right than guess.

Drag Pak

I used to do that as well. Now it's 8 rows and 16 columns on a 12" screen.

Iowan

Are you talking about locked distributor and a programmable box, because I will be going that route in the future. Power management for a DOT tire class, I hope it works.

Drag Pak

BigStuff3 ECU, EFI

Iowan

Just using a computer for the timing is a big step from old school for me, we'll see.

70newport

So I finally got around to installing my new distributor and it sits as follows 10* initial w/o vacuum advance. 35* with mechanical advance at 2000 rpm.

With vacuum advance I'm at 24* initial timing at idle and total finishes at 49*

Seems to run the best there..... think that's a decent spot or what is everyone's thoughts?

I did set all of it on my driveway as I don't have a vacuum gauge in the car but my assumption is load shouldn't change advance.... please correct me if I'm wrong.

Thanks.

TVLynn

IT should not change at idle with the vacuum advance hooked up If it does you have hooked it up to full vacuum NOT ported

70newport

That's what I thought but have read a bunch lately that full/manifold vacuum should be used so you get that advance at idle..... this is the exact reason I have not used a vacuum advance for years.

RacerHog

For Argument sake....

Lynns point is correct.....

I your case... Dont run the Vacuum advance, It's fine without it, from what you have said.


You are good to go....

70newport

So I ran no vacuum advance for the last few years because I had issues with it and did not understand it. drive ability does seem better with it hooked up so I would like to run it but it sounds like the consensus here is that my timing is incorrect currently....... if anyone has the time to enlighten me that would be great.

70newport

I'm just throwing these in the mix for where I got my planning from to set my timing as I did.

thanks again everyone.

http://www.hotrod.com/articles/set-i...l-performance/

http://ep.yimg.com/ty/cdn/chucker54/...structions.pdf

RacerHog

If you set the Dist. up to run the advancement on the mechanical, and all in at 2000 rpm... You are good to go with out the vacuum advance....

You are correct on your assumption. Vacuum advance has been used in OEM application to enhance drive ability because car normally run less timing for Emission purposes and need timing to get things moving....

But if you re-curved the Dist. for performance.... You can discard the the OEM settings....


Kind of a crude way of putting it....

70newport

I did not re curve the distributor at all but it is all in for mechanical advance at 2000 RPM. Am I loosing Power by having the vacuum advance on? It seems all around better but I feel like im missing the boat on something here.

RacerHog

I see... Ok, we might need to sit down over a couple of "Pops" on this deal. lol
Understanding V.E. ( Volumetric Efficiency) might be what is lacking in this case? This subject can get soooooo, long winded that the basic principles can get lost in conversation, let alone On-Line.....lol

I guess I'm really not getting what your feeling or striving for?

If it's timing your not understanding, You might start by checking out How thing work.
http://auto.howstuffworks.com/ignition-system1.htm

All I can help with on line are just the common basic rule of thumb. Similar to what you have already read. The rest lies in the engine combination of if it needs more or less. That I think is the $1,000 question.

Hope this helps?