i just looked at the msd spring and bushing chart to guestimate what my timing is..

I know initial is 15.. (measured with calibrated snap-on light)

im not using a vacuum advance...

im using the silver limit bushing..  which gives me upto 25 degrees on centrifugal timing.. for a TOTAL timing of 40

and im using the two light blue springs in the MSD kit..

i reach 36 degrees around 2700 and i reach my peak of 40 at around 3600

here are the instruction for selecting an advance curve from MSD..

they suggest setting initial as high as you can go.. then using springs to adjust as well..

http://www.msdignition.com/pdf/8350_8352_8354_frm23728.pdf

Good description Ben.  I'm backing you up on this one.

Ben and Ken, I believe we are talking apple's and orange's here from reading your latest posts, tell me if I'am wrong, I thought we were talking about a 78 with a cam change and a question about initial timing and I'am assuming he has a stock distrubitor with a vac. advance, not a MSD with no vac. advance and full mech. advance, but for the sake of the debate I will assume that all you have told me is correct, although I pertty much know how they opperate I don't fool around with weights and springs, why, because I don't have a distributor machine and if I did I wouldn't know how to opperate it, swapping springs and weights from a instruction sheet, the time it takes and not to mention what I would do if I dropped one of springs into never never land would really piss me off, so here's what I'd do, I would set my total timing at 36 degs., turn the dial back to 0 on the light, then check my initial, if I had lets say 3.5 initial, I would kill the motor, pull the distributor and take a ride to my engine builder and tell him I want 36 degs.total @ 3000 RPM with a Initial of 10-12 degs. and spin it on his machine, a couple hours later I'd go and pick it up, come home and reinstall, time my initial 10-12, DONE, and sleep good knowing it was right.

Hi All,

my 78 has the stock dist.

and I know the adv spring are shot .

I wanted to know what to set it as a starting point and then I can play around with it.

thanks for all the extra info its stuff i never knew!!!!!

pete k

Ben, may be we are both missing the point, I'am running a tack drive HEI with vac adv. built by Performance Distributors out of Memphis Tenn, they requested my cu in, weight of the car, comp ratio,cam spec, trans, gear ratio, carb, what type of driving, and sent me a hand built to my spec's distributor with 24 mech.degs total BUILT into it, that means when the weights were fully extended could not go any further I had 24 degrees, no more advance out of the distributor,thats it,the spring- weight combination was as such as to allow a middle of the road advance curve with 24 degs.total all in at 3000 RPM, so the only way I'am going to get a total of 36 is to crank 12 degs into my static initial timing, so I drop in the dist. hook up the "dial back" timing light, turn the dial on the timing light to 36, bring the engine to 3000, lock it down when the mark on the dampner reads O on the timing tab, let it return to idle, turn the dial on the light to 0 and I now have a 12 degs static initial timing, (12+24=36) after a ride and If I felt 36 was to much I crank in 10 initial gives me 34 total at 3000, if I want more I crank in 14 and that gives me 38 mech degs. at 3000 and so on, after the initial 3000 RPM run up to get my starting point of 36 all I have to do is time it in the normal way at idle with the light set on O, like I said chevy's make the most power + or - 36 total on a mild to med. street machine, that doesn't include what the vac adv. brings to the party, anips38484.8890162037

 bravo guys---have you ever looked in the factory service manuals at the spec sheets for distributers and at timing specs---so many different distributers,weights,vacuum advance and timing settings---different curves for both mechanical and vacuum advances---different initial and total timing settings depending on engine hp rating---wow---let's line them up on the 1320 and see who comes out on top----then we'll check mpg figures--marty     (totally stock LS5--including dist timing)

Well not to add to the debate, but Cam design, cam timing, engine stroke, plug type, plug gap, dwell time and coil type can be added into the mix to what an engine likes for timing.  I'm not one for picking one way to time over another.  I prefer to stick to initial, plus what ever is designed or set into my distributor and stick to a total advance.

I have never set timing the way Ben has described it, but it makes 100% sense to me.  IF you think about it using manifold vacuum is the best way to set fuel air mixture on a carb at idle.  However since I have never set dist advance as Ben has described I'm not sure how that would affect carb tuning.  I guess what I am saying is I'm not sure how I would go about tackling which task first.

I have always set timing first and then went about tuing the carb.  If you adjust the distributor first and tune it for max vacuum you would have to do some adjustment on carburetor, because rpm will rise as vacuum rises.  so if you lower the idle rpm then I would suspect you would need to come back and adjust distributor again.  I guess you could keep going back and forth like you do with a carb until the idle speed and distributor adjustment balance out and no changes occur to engine vacuum.  Then from that point you could work on idle air fuel ratio for engine vacuum.

Ben, can you give me some insight because the ideal of tuning distributor advance is new to me and i'm not sure how carb tuning would play into that mix.  You would think after working at Holley all these years I would have hear this method, but I have not and I would like to be educated and possibly learn something new.

Thanks.

    sometimes ignorance truly is bliss. 

Yes, if you set the carb, then the timing, you will have to reset the carb again.  And then that does mean you may need to recheck the timing.  When you get them close to each other, you won't see one changing the other any more.  But if they are way off, the differences can be huge. It is a balancing act.  Everything is.  Does this mean more work to get it just right?  Yes.  No way around it.

Part of the hang up between Ben and Joe comes with procedure.  Joe is looking at 3000 RPM as a set point.  Ben is not.  Ben is using a entirely different method.  Ben is looking for peaks.  Joe may not find peaks at 3000 rpm, depending on the distributor settings.  It MIGHT peak at 3000, it may be way past, and it may not have gotten to peak yet.

Joe is setting max mechanical advance up from inital.  Ben is setting max timing, then adjusting mechanical advance  back down to inital.

Both are say similar things, and getting similar results.  Both methods work.  But Joe is assuming the 36 is ideal at 3000 rpm.  It may be, but may not depending on compression, ignition system, cam, etc.  Ben's method take into account for all of these.  Joe's is long run easier.  Ben's takes more fiddling to get the weights and advance limits correct.  You can't forget the vacuum advance.  Without creating a specfic number, Ben takes that into account as well.

Bottom line, Joe's is easier to follow, and will create good results that will improve the way the engine runs, but leaves a few thing to assumptions.  It deals with hard numbers.  Ben's is more of a pain to make multiple test, but as a result does not make the assumptions that hard numbers can lead you into. But it does take the particular engine, car, drivetrain, weight, etc,  and therfore may or may not make even more power.

One way helps a lot.  The other way could buy not might help more. Are you after Big improvements, or absolute maximum improvements.  Does this mean you might set the peak with vacuum and find the inital is too far off to get the car started when warm? Sure.  Then you change initial weight stops and springs, and try again.  Yes, more fiddling.  And when you get all done, you may need a different carb set up.  Possibly a jetting change.  Of course that could screw up timing response.  Again, it's a balancing act.

You could set up one engine perfect, and change the final drive or tire size and it would change.  Lighter or heavier cars need different settings in identical built engines.  And when we build engines there are hundrends of variations within the engine itself.  There are no hard and fast rules. Just good guildlines.  Most of us will never go that far.  Serious racers do, and usually on a dyno.  I'm still backing up Ben.

kstyer38486.3563657407

Ken, the numbers I used are hard numbers used by GM and just about every one else in Chevy land, never the less, the question I have is with Ben's method what if maybe you have a bad hole or two, maybe some leaky or burnt valves, weak valve springs,some worn guides,or a hidden vac. leak somewhere, marginal carb,can't forget a leaky head gasket, then what do you do?   anips38486.6412037037