385 timing without vacumn advance

[mdross1]

Any of you running vacumn advance? What about you that do not.Those that do not what do you run for total advance.My 460 with Aluminum heads,Edelbrock Performer RPM,Lunati 235 @ .050,Dan Davici 1000cfm with no vacumn ports.Looking for ideas!

[Tom Wells]

mdross1,

Hmmmm.....

Without going on a hunt for the exact figures, here's what my memory says: 12 degrees initial (maybe it's 11?) and 20 degrees centrifugal (maybe it's 21?) for a total of 32 degrees, all in by about 2500 rpm.

This is on the 521 with a hydraulic roller cam and EFI. The distributor is an MSD and has no vacuum port. The computer does not control the spark timing - it is entirely controlled in the distributor.

On my next engine, a 557 similarly set up but with a 950 cfm Holley I plan to use about the same advance figures. The biggest difference is that because I had to use a Motorcraft Duraspark distributor due to hood height problems, I will be using the vacuum advance also, limited to about ten extra degrees at part throttle. The extra goes away when the throttle is opened significantly.

I have a Holley 950 cfm carburetor with no spark port and no vacuum port for the PCV so I have ordered another base plate for it that does provide those ports. Perhaps you could get another base plate for your carburetor to add them too?

Tom

[Silverback51]

My 460 is set up the same as Tom's. 32 total advance all in at 2500 RPM's with 20 degrees centrifucal. It's a small cap MSD unit.

[Randy Rosenberg]

Mine is about the same as well, however I'm using vacuum adv as well, to get better hiway mileage.

[oleyellar]

My motor is happy 10-14 at idle and between 36 and no more than 38 degrees total advance. I run a modified Ford Duraspark distributor, removed the vacuum advance and welded the advance slot to limit the advance.. There are some really good posts on the 460Ford.com website about setting them up.... There is a vendor over there that explains exactly how it's done. He sells units he modifies for $50 bucks. I don't think I have ever checked my timing at idle since. Just run the motor up set total to 38 and lock it down.
http://www.reincarnation-automotive....ons_index.html
Paste this and go look, this guy knows 460 motors.

John

[bobcowan]

I used to have an excellent article that discusses this, but now I can't find it. Maybe some one else can find it.

Base timing is predominantly determined by the cam shaft. Bigger cams need more base timing. I'm using a cam with .248* intake duration at .050" (.304 advertised). I use 18* as base timing. The article recommended a range in that area.

The second factor is engine vacuume. When you're in that area, use a manifold vacuum gauge. Set base timing where vacuum is the highest.

SBF's do best with total timing somewhere around 36*-38*. BBF's do best with a little bit less, like 32-34*. You want it all in by 2,500-3,000.

Vacuume advance should put 8-10* additional timing when vacuum is high - idle, low thottle cruising. But that's something you'll have to play with until it feels right. You don't want detonation when you tip in the throttle to climb a small hill.

For a street car, I bleieve in keeping timing very conservative. You might pick up 10hp with an additional 4* of mechanical advance. But what happens on a hot day? Or if you get a tank full of mediocre gas? Now you have detonation that will break the pistons. For peace of mnd and longevity, keep it conservative.

[Randy Rosenberg]

Here's a good article about ignition tuning: http://automotiveu.com/tuningperformance.htm

The guy who wrote this tuned my 460.

[mdross1]

Thanks for all the input.Just to get a feel for the new carb,will run without any vacumn advance,PCV will have to be to the atmosphere with a new breather.