flat ernie, wouldn't that SBC mallory still have the wrong advance curve..... might as well fix the new mallory so you don't have to do the machine work.....
But the SBC has a tach drive.... I don't think the curves are that far off & it's relatively straight-forward to modify anyway...
Old Mallorys have a very simple bit of tin limiting the curve, easily replaced with another to limit curve. I think spring kits are still available, but oldies with the HP curve are usually pretty good as is. Recurving a classic high quality piece of speed equipment is a LOT more fun than debugging a brand-new Chinese made piece of crap, IMHO.
I recently had Jere Jobe reset the advance of a modified SBC-into-flatty distributor. I used an old two-piece cap Mallory with a tach drive. Dual points, big brass condensor, traditional looks.....what more could a guy ask for? I had it cut down locally to fit an aluminum 8BA front cover. Jobe didn't say it was hard to reset at all.
Had the same problems 5 or 6 years ago. What kills these cheap modern condensers is heat, the chineese laquer in the capacitor dries out, on a flattie they are especially vulnerable. Relocated my condenser to under the dash nice cool place,the longer lead makes little difference. In 4 years no blown condensers. Check modern capacitors in any electronic equipment and they have a max temp rating of 85 degrees I suspect they use the same stuff in these condensers hence the mega short life, stick it away from the motor where it will only see 20 - 30 degrees and the life is many times higher. The misfiring at higher revs I suspect is due to Mallory setting the advance at the factory to stock SBC spec. If you take all the innards out of the dissy there is an adjustable plate underneath, loosen the allen bolts and turn this the opposit way to how it is set almost to the stops, you may need to play around with this to suit your motor, but should allow it to rev up. Rich
i'd still rather start with the right part I think. I've got an nos flat top mallory (yc 365hp) to go in the 283 in my 32. I kinda hate the idea of cutting up an old piece of speed equipment like that even if it's for the more common chevy. I have a feeling you'd look back and regret cutting it up.
Had a brand new Mallory Dualpoint on the 235 inline6 - pain in the a... It eats condensors and even with a lot of tweaking on a dizzy machine we never got the curve right. I was thinking about Tom Langdons Mini-HEI, but I want to keep my 6 Volt. So I went back to stock dizzy (uhmm..well of a inline 6 Corvette) and got a great curve, better mileage power and response with the vaccum can. Next stunt is a modified choke cable and dizzy bracket to tweak the spark from the dashboard. Frank
I'm waitng to hear what GMC Bubba has to say about Chuckspeed's dist after it's been in the machine. PanheadGuy
Well...I'll speak for him. turns out the dizzy ran perfectly... Backwards. The centrifugal advance weights were in backwards and the ignition was all over the place.
As Chuck stated the distributor ran perfect when ran backwards , after a complete teardown it appeared the weights them selfs were ok BUT the advance stops were way out there 30-36 degrees total and the springs were very loose with little or no actual control of the weights etc. ( with some intial advance this unit could have very well seen 40 plus degrees of advance and i feel thats way too much for a flathead etc ??) Bruce you got some orginal litature regarding this spec, i do but was unable to find it this evening? I tightened up the stops using the allen adjustments and cut the total down to 10 degrees distributor ( 20 degrees engine), then readjusted the springs to make a nice curve with all in at 3000 rpm. This way if we add 10 degrees static at the balancer the total spark advance will be 30 degrees at 3000 rpm. If more is needed then you add static or take away if thats too much. As tested the unit would actually advance approx 35 degrees or so and then retard 10-12 degrees. Not good at any rate. I did three units today and all of them were all over the place. Just looks like our quality control guys have been drinking again.
A couple pics , note the adjustment stops for the advance. Before and after the adjustments. Also the springs are very adjustable on these units.
Flathead timing is about 24* total - all in by 2500 or so - at sea level. Knock of a degree of timing for every 2500' above sea level or so... Still think you're going to be a bit too advanced with 30 total...but try it and see. Every engine is slightly different....
Maybe someone should send this link to the boys at Mallory. Kind of a shame that a good family name is going to the dogs because they are letting crap out of their factory. It was good to read the whole post, looks like I can (and should!) learn a thing or two about this stuff!
I agree , the distributor is set at 20 degrees max and then he can start with 2-4 getting the 24 degrees. I only used the intial of 10 as a example. Most factory flatheads only had 2-4 on the balancer.
Wouldn't a Vernier throttle cable work better (more precise adjustment)? I actually had thought of that and that seemed the best to me. I however, have not tried it yet, as any project I wanted to do that with always went another direction (or I had to sell it) before I got that far. So I am asking, because I figure someone else has already tried it.
I can post curve for 21A crab types, a good gneral curve from Ford... Ol Ron (Holleran) has been flogging timing on the dyno lately. His generic recommendations are currently 4 initial, 16 centrifugal, fast curve finished before 2,000 as a starting point. Ford calls for curve to start moving IMMEDIATELY off idle. Ron likes 6 or 7 added by vac--on a flathead, this means use Chevy or MSD, I think, as older distribs lack modern vac system. On Mallory's, most have basic limit set by a post in a slot, said slot partially blocked with a numbered plate to limit it. All you need is to add to this limiter plate and MEASURE result--Mallory makes a gauge, but it is apparently not accurate at all. Remember you can pretty closely measure your mechanical advance right on distrib while working on it: Make a protractor that fits in place where cap would sit. Hold distrib drive still, twist rotor/cam in direction of normal rotation. Resulting measured movement is your advance in DISTRIBUTOR degrees, multiply by TWO to get crankshaft degrees.
Test RATE by measuring off 30 degrees in blocks of 5 or so on your pulley, run with timing light. You want to see advance as soon as engine speed starts to rise, reach number measured above by 1800-200 or so.
You are right. Actualy I have a complete throttle asembly of a lawnmower that can be modified for that propose. I got that idea (not the lawnmower thing) of an 50s J.C. Whitney Catalog where they sold such a gizmo from Almquist called Spark-O-Matic. I probably make a little aluminum plate with a Spark-O-Matic Script an a nicer "ivory" knob for that. Frank
All flatheads used one - Harley Flatheads that is. The left grip twisted to advance or retard the timing using a cable that went directly to the distributor. The "automatic advance" distributor didn't come out until well into the Panhead era... I don't know what you would gain with a normal distributor by doing this. I could maybe see a setup like this if you were using a distributor that had a fixed advance for some reason...
Model A's have the same thing - right on the steering column. the idea has merit if you were to eliminate the centrifugal advance - but that would be silly. FWIW, I'm partial to a wee bit more initial advance with some subtracted out on the topside - with a slightly stiffer set of springs to flatten out the advance curve. this, of course, is on OHV motors - seems like a flattie would respond to a different curve. I really need to find the factory literature; they 'claimed' factory calibration.
Factory specs for '49-53 are useless...21A specs are in service bulletins at home, but a book here says 11 degrees in distributor starting at 600, finished at 1200...Ford specs are more detailed. Will lookup Ford specs.
Hmmm...found one Ford screed on this, crab specs: Starts 400 rpm, ends 3,000...seems way slow. Will see what bulletins say. 22 degrees (crank) in distrib, same as above...26 total with the 4 static. Canadian specs...I guess their advances move slower because all the molecules are frozen.
Tuning as you drive for initial setup (and with no laptop, how about that ), and the ability to yank out the extra lead if you get a bad load of fuel (cause the freeway off ramps almost never show up when you REALLY need them).
I´m experimenting a lot with vintage water injections and other gizmos that makes it usefull to tweak the spark while driving. It is also a nice way to find out what your curve is all about at "real world" conditions. Going up a steep hill I learned that the engine can take more advance than the vaccum can thinks, before it starts pinging. Have you ever seen a 3D Plot of a computerized ignition vs. a centrifugal/vacuum ? You will see that under differnt conditions the electronic curve is way more complex. Not that I belive it would make THAT big difference, I just love to fiddle arround with this kind of stuff. Frank
This would be most useful on engines requiring lots of advance like Model A and B, and also engines with lots of sensitivity to octane and generally prone to spark knock...don't know where Chevy early sixes are on those scales. Engines like Flathead and SBC with fast burning chambers need curves that are easy to get into a simple advance mech and aren'r usually very sensitive to minor changes in diet. Interestingly, the first Mallorys made for Model A, in roughly 1929, had centrifugal advance and a hookup to the stock advance mechanism (the driver), possibly because total advance was hard to build into a centrifugal system. Ford coped with this (Model B) by using a startling amount of static advance...19 degrees crank!
dude - I'm talkin' about the Mallory spec sheet. I'm thinkin' about sending them an invoice for Bubba's time, along with a photocopy of the statement about the damned thing being factory calibrated. If Jim hadn't checked the unit out - I doubt I'd been able to ID the issue on my own - although it prolly would have jumped out at me when I thew a timing lite on it. C'mon guys...think about it...who'da thunk a brand-spanking new $300 dual-point dizzy would have a centrifugal advance so bunged up outta the box that the engine barely ran? Betcha a good portion of the overheating issue is tied to that, too. Someone at Mallory's gettin' a letter...
$300.00??!!!!! Gag, hack (think cat with hairball), puke, ralf, retch (etc.... chunder?). All that for a "factory calibrated" POS. Damn, it sure is a shame you can't seem to count on corporate anything these days. It's one of the reasons I like Edelbrock. At least the family still owns it. Of course having said that I expect to get flamed instantly about how they sold out to _______ group Last week that will now produce em in Uzbekistan because the Chinese charge too much. I certainly hope not.
Why not just go electronic (or change the guts to electronic) & program it yourself? Maybe monkeybiker will chime in with his home-made electronic ignition! Pretty neat & he can modify it with a laptop... I'm all for tinkering...
I've got one of these (no-functional) on my sport coupe. It requires replacing the hold down bolt with a stud and double nut so that the distributor can be rotated while not being loose. As shown it connects to the vacuum advance can to get enough leverage to move it. I think it's cool looking. I never bothered to hook it up. It's just for decoration.
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