8ba with chev dist. timing info
 

Re: 8ba with chev dist. timing info
 

4* initial and 24* mechanical would give 28 total. Before you break something. try 4* initial and 16 mach all in by 2000. Give the vac about 88 for cruise. Better place to start. You can always add more.

Re: 8ba with chev dist. timing info
 

Re: 8ba with chev dist. timing info
 

Thats exactly where we set most of our conversions. The chevrolet distributor will usually be limited at about 24 degrees mechanical advance from the factory. Look under the cam and the numbers will tell the limits on the unit.. ex: A 728 cam is 28 degrees advance and a 738 would be 38 degrees. We use a brass bushing to limit the flatheads.
Let me know if ya need any help , glad to help.......:D

Re: 8ba with chev dist. timing info
 

Bubba what numbers do you think if i add vacuum advance?

Re: 8ba with chev dist. timing info
 

The vacuum issue is another story.
Typically vacuum is 12 degrees and mechanical is 12 degrees (distributor degrees) Problem is the mechanical is at lets say 3000 rpm=12 and 18 inches of vacuum is also 12 . Problem is you will never have 3000 rpm and 18 inchs of vacuum at the same time , especially under a load of any kind.
So they overlap each other .
You may have 6 degrees mechanical and 6 degrees vacuum advance making the total 12 (24 engine) etc.....
OR you could have 10 degrees vacuum and 2 degrees mechanical (low rpm) and still have the 12 .
The vacuum is typically good for 2-3 mpg on a standard vehicle .
Kinda hard to tune on a flathead .:eek:

Re: 8ba with chev dist. timing info
 

I am going to hook up my vacuum gage and go for a ride.

Re: 8ba with chev dist. timing info
 

My friend Richard (FLA) have been working on this same problem. Unfortunately a stocl low compression engine will require a much different curve than a 276 Hi compression long cam engine. His engine with an L-100 cam likes a max of 20 degrees at WOT. That's what we set the max mechanical advance at 2000 rpm. At present we're running 8 degrees vacuum. All this on regular gas. Right now Richard is making some recording equipment that will record the mechanical and vacuum advance under ALL driving conditions, thus we won't be guessing at the results. Unfortunately It won't apply to a mild or stock engine. The biggest problem is the apathy of some owners drivers, they don't experiment with changing the curves to find out what is best for their engine.

Re: 8ba with chev dist. timing info
 

Question ? is vac advance really nessesary on a flathead (chev distributor ) or just too much trouble.

Steve.

Re: 8ba with chev dist. timing info
 

Re: 8ba with chev dist. timing info
 

Good work and pretty good vacuum.
Dont forget to factor your rpm band in the deal as well.
And consider your gear ratio as a factor of cruise vacuum. Keep us posted and let me know if ya need any parts , springs, weights or distributor cams etc.....whats the number under the cam on the delco you now have .......??

Re: 8ba with chev dist. timing info
 

Under side of cam says 524

Re: 8ba with chev dist. timing info
 

Is the vacuum advance necessary. Absolutely not. The engine will run pretty good. Might burn more gas. But that's not the question. ill it run right. NO!

Re: 8ba with chev dist. timing info
 

The 524 is a 24 degree unit, thats the good one for the flathead.:)

Re: 8ba with chev dist. timing info
 

There is a nice article in "Street Rodder" about ignition timing and the new gas. Just remenber one size doesn't fit all