I'm building a 399W stroker. It will have in the neighborhood of 10:1 static compression with polished combustion chamber cast iron heads and a XE268H Comp Cams bumpstick. I'll be running Rhodes variable duration lifters. I'll be trying to get the stock heads to max flow as well as the stock exhaust manifolds. Intake will be a Eddy Performer RPM and most likely a 750 Edelbrock carb.

I have a few 351W stock dizzies. But 2 of them are 13/18L and the other is like a 21/16L. I lucked out and one of them has the adjustable vacuum advance.

So my gut feeling is to run with the 13L and add a spacer. One of them has some colored springs which I take it are aftermarket. I'm thinking one light aftermarket and either the aftermarket medium or the factory light. I'm not sure about this, though, I'm thinking with this set-up I may want just a bit more delay on the advance, like 2 mediums. That's not a big deal and I can certainly change that easily enough later, but I would like to get the springs close if possible.

So I think I should be running about 10-12* initial with 24-26* mechanical give or take. The rpm of total advance is a little harder to predict, but I'm thinking with the light set-up maybe 2100 and the heaviest (2 mediums- 2800?) IDK.

So- not to limit this to just re-curve figures, if you can list your initial timing and total degrees of advance and your set-up, this will also be of a benefit to me.

 

Duraspark_distributor_recurve_instructions_page-2
http://69.20.53.62/pdf/271e.pdf
Sounds like you already know about what these links explain, but It might help explain what you're doing to someone else. I recurved mine with the crane recurve kit, not 100% satisfied with the results yet..

 

Per Crane Instructions:
Yellow/stock light spring 3800rpm
Silver/stock light 3500rpm
Yellow/Yellow 3100rpm
All start advance at 800rpm. This does vary somewhat depending on slots used. I've replaced the stock heavy with a yellow and wind up with all in at 2800rpm using a 10l slot. Two yellow's brought it down to all in at 2500rpm. You already know to adjust full advance to your hp/torque band for the rpm you want depending on how you built the engine.

 

I can't find a Crane kit. All I can find is Mr. Gasket which consists of 2 medium springs for $4.95.

What was in the Crane kit when they were still making it?

 

I just got to looking and it looks like I lucked out again as between the 3 dizzy's I've got a pair of light, a pair of medium, and a pair of heavy springs, so I can do any combonation I want.


The bigger problem is I'm not sure what I want. I think I'm just going to put it back together with the 13L slot as is and 2 medium springs and recurve it after I get it running. I didn't take it apart, (and it is totally apart) to recurve it, but to clean and lube it and make sure it was in good working order. Good thing I did because one of the weight bushings had disintegrated and the shaft was starting to get scored from some trash at the very top. Not to mention any lube in it was pretty gummy.

 

CRANE 99607-1 ADJUSTABLE VACUUM ADVANCE KIT FORD/MERC:eBay Motors (item 280425386813 end time Nov-30-09 07:21:38 PST)
Not sure if that link will work, but thats the one I found on ebay. It looked like it had been hanging on the wall in some speed shop for 20 yrs. I couldnt find it in jegs or summit and I dont think they make them anymore but it came with the set of springs an adj vac advance and an allen wrench, as well as the instructions I linked to above.

 

Mine had the 15L in it, with the stock springs I was only getting 15 deg mech. I'm getting the full 30 now, but I can set my base timing up to 15+ and cant get it to ping. I think I need to widen the slot so I can more total advance, but I've never messed with recurving before and I'm not sure what to do. I read somewhere yo shoot for about 40deg total (no vacc). Any input or links to further explain would be appreciated

 

The link is right above you. Wait a minute.... You provided the link. All the info is there.

 

I'm just not sure if I should widen my slot so I can set my base timing to 10 and still end up with the 45 deg I have now, or maybe try to get more than that. Right now I can set my base timing up to the point where it wont crank (20 deg IIRC) and still get no detonation under a load. I think I may have another problem and dont wanta get the curve all screwerd up trying to fix it.

 

Is 15L the wide slot on your dizzy? If you need more I have a 13/18L I could sent you and if you like it I'll trade you for your 10/15L in case I want less when I get mine running. I don't need both of my 13/18L's.
You wouldn't probably want anymore total timing but you might want less initial.

 

I can't find my chart right know , but with 10.5:1 comp you don't want 40-45 degrees advance. More compression, less total advance. Going from memory, which isn't too good, I'm thinking 32-36 degrees total would be about right. 10L slot x2 plus 12 initial will give 32 total. Low compression and high advance numbers are one reason the late 70's engines were so low powered. The key is getting the advance full in where you want it in your power band.

 

Bashby- Are measuring total advance with the vacuum advance unplugged? I can't imagine 45* total advance without it, it should be more like the 32-36 just mentioned.

 

Yes vac adv unplugged, 15L gives 30 deg plus 15 base= 45 deg. Iwas under the impression that you want to advance it until it pings then back it off a couple deg for the best performance.

 

Here is another Duraspark link that goes into more detail about compression/timing advance. Depending on what compression you are running, over 40 degrees is not out of the question. Good reading: The Ultimate Duraspark Distributor Timing Guide. - Four Eyed Forums

 

Nowhere in that article did it mention a total mechanical advance of over 42 degrees. The only time a figure over that was mentioned was with mechanical advance being too much and the figure of 46 degrees was stated as being way too much.

The 38-42 figure was for basically a stock engine with the numbers going down as compression increased.

If Basby is running 10:1 (which one poster said) 45 degrees total seems highly unlikely. The higher duration cams used a higher static timing, which is why welding up the slots or using smaller plates is the usual modification. So while 15* initial isn't out of the question adding 30 more seems unlikely to me, but I've been wrong before.