You are probably right. Timing and carburation go hand in hand. Another thing I discovered on my build ( as one may have suspected) was that the lack of vacuum signal to the carb required some modifications to it as well to get a good running engine. Keep tweaking and you'll get it to where you want it.

If were talking a Q-jet here then get Cliff Ruggles' book on the q-jet and follow one of his "recipes" for a larger cam.



I do not disagree with your claim that a dyno session is valuable and worth the money. Problem is that some of us do not live in an area that dynos are as plentiful as circle k's. So we have to devise other methods to measure our results. I use driveability and 0 to 60 timings. It's what I got at my disposal.
The nearest dyno is a dynajet 176 miles to my south. At 19 MPG, at best, that would cost me $75 just to get there and back. best case scenario, and 5 1/2 hours of driving. Then it cost $125 per hour of use. Which sounds like a pretty good price, once I get there that is.

So the methods I use to measure my results are all going to subject to human error and/or anecdotal.
Even if I did get to the dyno it may be just a "happy" dyno and provide me with little usable information unless I used that dyno only on repeated occasions for a comparison basis of previous runs on my engine only. Not comparable with any other engine/tranny/ rear end ratio combos. Since it's unlikely I would make the trek for repeated dyno sessions it's not real likely that I'll even use one any time soon.
There are some tune and time sessions scheduled at a track 100 miles to my north this spring that I may attend since I can have all day to tweak. That may be more useful than anything I can do on my own. But of course that info is subject to track conditions, weather and my own reaction time and technique.

 

Bill,

I guess I was summarizing and trying to generally reach a truce, so the discussion could continue on topic. I wasn't trying to put words in your mouth or misrepresent anything that you or others were saying. To be perfectly honest, as this post went on and the comments devolved from the issue to something else, I didn't read all that you wrote as your comments weren't directed at me (maybe they were, as I said at some point I stopped reading). I didn't butt in to your back and forth with 69427.

What I saw happening was that one recommendation, not by you, was just to set the timing all in at 36 (the same starting point I use), but then stop there. It didn't fit with the OP's low idle vacuum that requires more initial timing. Another comment, also not by you, was set the timing all-in and plug in the vacuum can and drive the car. That doesn't fit with the OPs very first statement that the advance can had no effect. What I thought I was seeing was just set the all-in and nothing more needed. Well, I don't agree with that.

In any event, I will try to watch my wording in the future.

 

Also lets note he has a mild 350 with 9.6 to 1 and only 9 inches of vac .. Car most likely runs like a lawn mower ... I suggest 36 at 3k all in as a starting point and look out here comes the engineer and friend to attack that as if I was telling the guy that would be all he ever ever would need to do.

This OP is far from a dyno tune , he had it right with a vac gauge and timing light , I would also suggest NOT spending money for dyno time BUT on a A/F gauge and data log off that as you drive as a means to tune,, cheaper , and very effective..

Anyway the OP I think went to the ford forums where he can get simple answers to set him off in the right direction..................... BAHAHAHAHAHAHAHAHAHAHA

 

Wow.
What a thread.

I see my name referenced on a few occasions, with some correct and incorrect technical references.

Timing, and timing curves, is a subject of great technical complexity, and you cannot determine the "correct" and "optimal" curve for any given engine without extensive testing and evaluation, and without having specific goals and objectives in mind, i.e. best power and throttle response versus lowest emissions and best fuel economy. So, for general purposes, we outline some general parameters for a good performance setup for most conditions (disregarding emissions).

Based on actual dyno testing I have done over the years, we find the following to be a good general guideline:

V8 engines, in the 300-400 cubic inch range, will produce best power when total timing (maximum centrifugal advance) is set to about 36 degrees. This total timing should come "all-in" at about 2500 -3000 rpm, depending on detonation limits of the engine. Larger-bore engines with stock heads will produce best power if the total timing is advanced slightly: 454 and 455 engines will produce best power in the 38 - 40 degree range with stock iron heads. If heads with better chambers are used, the total timing can be reduced for best power: we typically see small-block engines with good aftermarket heads produce best power in the 32-34 degree range, and big blocks with good heads produce good power at about 34 -36 degrees. This "perfect" timing can only be determined on a dyno, so the general number recognized by most engine builders and dyno operators as the "optimum" general "best power" number is 36 degrees.

With this "pegged out" number in mind, you need to determine the best "initial" timing number for the engine. The initial timing will determine the idle quality and initial throttle response of the engine. The lower the initial timing, the lower the emissions will be (generally). Mild-cammed engines will generally take a little less initial timing with acceptable results. The bigger the cam, the more initial timing an engine will want, with no change in the total timing spec. Therefore, the length of the centrifugal advance curve has a big effect on the characteristics and the drivability of a performance engine.

Limiting the total timing to 32 to 38 degrees as outlined above, I generally recommend a mild-cammed engine to run initial timing in the 12 - 16 degree range. I run modest performance engines in the 14 - 18 initial range, with hot performance engines in the 18 -24 initial range.

If you can curve the distributor to bring this advance curve in at a linear rate between idle and WOT rpm, you've done about the best you can do without very extensive testing for optimization within the very narrow rpm band between 1000 and 2800 rpm.

These, again, are general guidelines for a good performance curve, but you will find that this will work exceptionally well for any performance engine as defined by the parameters above without going into extensive dyno testing for very little additional gains.

I have 40 years of racing and dyno experience to back this up. If you disagree, that's fine. God bless you. If you'd like a copy of my papers outlining some of this in detail, feel free to e-mail me for a copy.

Lars
V8FastCars@msn.com

Mike :
I CAN'T HEAR SH!^^! I HAVE DAMAGE FROM THE 88MM ARTILLARY ROUNDS IN THE ARMY; THE RACECARS IN THE '70S; AND FROM TURBINE ENGINES IN THE '80S, BUT I CAN STILL ENJOY A GOOD SCOTCH AND A MARTINI. I CAN TUNE A CAR WELL, EVEN THOUGH I CAN'T HEAR IT, AS LONG AS I HAVE GOOD DRINK TO GO WITH IT. DOES THAT MAKE IT OK..?

Lars

 

In answer to your original post:
Your bigger cam is pulling less (numerically less) vacuum than your old engine. Your existing vacuum advance control unit (aka, "vacuum can") is designed for a stock engine, probably requiring at least 16 to 18 inches of vacuum to fully retract. This simply won't work with your new engine. If you are only pulling 10 inches of vacuum, you will need to run the "B28" vacuum can, which will pull in its full range of timing at 8 inches, assuming you have a stock points-type distributor. This can is available under Wells part number DV1810 from “My Parts Garage.com”. This will work perfectly for a performance engine such as yours.

For a complete technical discussion on this subject, feel free to send me an e-mail request for my Timing and Vacuum Advance tech papers.

Lars
V8FastCars@msn.com

 

I installed the dv 1810 canister from autozone today. The can now advances timing at idle. Thanks for all the responses. My next question is that when i set my total timing to 36 degrees it set my initial at 16 with my vacuum advance plugged. When i plugged my canister back in, it changed my total timing to over 40 degrees. Does this mean that now i need to figure our and change my springs. Would that control the total timing with the vacuum canister plugged in. I guess i dont understand how you set the total timming at 36 and that the vacuum canister is not supposed to advance the total further. When checking vacuum on the manifold port on the carb. It build vacuum until your wot then drops off. Thanks for the help

 

With vac can disconnected and vac source plugged , have a friend sit in car , hold throttle at 2800 steady. Your total timing is then set to 36 degrees. I then tighten down dist and re check it. Now connect the vac can. You should be in good shape. Take it for a drive under varying road conditions and make sure you do not here detonation or what is often called "Pinging"

Based on your first post your car should idle way better and the motor should have a bit more power under full load .

 

Whats wrong with you pulled of course!

 

Please just read my paper.
Lars
V8FastCars@msn.com for a copy.