hello, i have a vortec 355 with a voodoo 60103 cam. Im tryin to get my advance set up, the optimal timing for votec heads is generally 32 degrees and thats what my engine likes the best it seams. Here is my problem, i cant get more then 12 degrees mechanical advance from my stock HEI, i have a mr gasket recurve kit, and no spring lets me get more the 12 degrees, they just change where it comes in at. right now im getting 12 degrees in by about 2800 rpm using medium springs, and i have to keep my initial timing at 20 degrees to get the 32 i want at wide open, this however causes pinging under cruise load. If i lower initial to about 14, it runs great cruzing, but not as good WOT. So basically i want to get 18-20 for degrees from my HEI, and dont know how to modifiy it to do so, i rememeber seeing something about grinding on the midplate to allow it to rotate more or something. Just looking for suggestions, and also note im in college and basically have no money, so im really just looking to work with what i have and mabye a few cheap odds and ends parts i might need. Thanks

try flipping over the center plate.

How much timing are you getting from your vacuum advance?
Maybe you could try limiting that instead.

Like stated above try some vac adv tuning,it may fix the problem since it only ping which at low load part throttle cruise.

Are you using 93 fuel,if not try some?

If you want to retain the 20 deg base with 12 mech for 32 total try unhooking the vac adv and go for a ride to see if it wont ping with with it unhooked.

If the ping stops buy crane's adjustable vac adv which i believe also includes a vac adv limiting plate and between these 2 items you should be able to tune/dial in some vac adv needed for crsiper throttle resp etc but cut it back enough to to not ping on 93.

Perf cams like more base/inital timing and thats why it runs better at 18-20 base timing then with 12-14 base like you found out,it looses power/perf when base timing is retarded by 6-8 deg .

I would leave the 12 deg in dist and 18-20 deg base to reatain perf in lower rpm and to get the 32 deg total required for vortec heads. Also make sure to run 93 fuel when trying to dial in the vac adv tuning setup to get rid of ping.

If your successfull in getting rid of ping with vac adv tuning on 93 fuel then you can later try some 91 fuel and do small tweakes from there to see if you can dial in the lower grade fuel to not ping during cruise or WOT too. But make sure to document the adj you make to try 91 fuel so you cant get back to where you had the 93 fuel dialed in to not ping so you dont have to go through the tuning process again to get the 93 fuel back to where it wont detonate/ping.

But i would not just retard the base & recurve the dist for more mechanical to get the total up to 32 with less base timing to stop the ping. When in lower rpms just under 3k rpm & below when the mech adv isnt at full 32 deg yet it will cause the motor to use more fuel due to retarded base timing,loose power,run hotter,etc esp at slow speeds or when in stop/go traffic not up to cruise rpm.Take the time to tune/dial in the vac adv with 93 fuel along with 20 deg base & 12 deg mech for the 32 deg total the vortec heads like,thats your best bet for best possible perf and the right thing to doin this case.

Scott

Vacume advance does not affect the pinging, ive tried with and without, i think it is pinging in the area where the mechanical advance starts to come in and the vacume advance is just about gone, it runs better with vacume advance hooked up off idle, but at 2000-2500 where it pings i dont think the advance has an affect, the reason that it is pinging is that there is still too much initial timing when the advance is coming in. Thus the reason i need to get more advance mechanically. The distributer should be able to give me atleast 20 degrees, not 12 like im getting. Im really just looking for a way to alter the mechanical advance.

This statement "but at 2000-2500 where it pings i dont think the advance has an affect" is Incorrect.

The vacuum advance is still activated at 2k,3k, rpm and even above that if your cruising with steady throttle. Its only when you hit the gas hard like over 3/4 throttle to WOT when the intake vacuum drops off to a low enough level where the vacuum advance drops off/is inactive and then the total (base timing + mech in dist) is whats left for the motor to run on.

Then when you back off the gas and the intake vacuum came back up the vac adv becomes active agan.

Install a timing tape on the harm balencer and get a timing light and rev the motor holding it steady at 3k rpm with vac adv hooked up to see what the timing is.

Then simply un hook the vac hose for the vac adv wit motor still at 3k rpm and the timing should retartd approx 10-15 deg depending on the vac adv unit.

If the timing doesnt retard when vac line is unhooked with the motor at a steady 3k rpm the vac adv doesnt work or your vacuum source is dead/not active.

Check and do what's been suggested and you will likely get it squared away.

Good luck...Scott

when i measured timing with advance hooked up i did not see any aditional advance change compared to when it was not hooked up just free reving it in netrual. I thought that mabye the engine needed a load on it to create vacume for the vacume advance, but if what your sayin is true then mabye my vacume advance is just not workin at all (its an old junk yard HEI, very likely) Even though that is something i should take care of, it still leaves me with the problem of needing to much intial timing to make up for the lack of mechanical advance. an average sbc seams to want 16-18 initial? and 36 total, and a vortec wants so 32 total so that would mean bout 12-14 initial should be best, so at 20 degrees it is pretty advanced.

CHRIS,re-read the 1st & 2nd posts i wrote to you on this and follow what i suggested,i addressed your concern of the inital/base timing and why & what to set it too.

If you follow that along with installing a new napa VC1843 vac adv to replace the non working one that will get things back in working order.

Now you will need to work on dialing in the vac adv to limit/reduce the amount of advance.

You may in fact have to back the base timing a tad /1 or maybe 2 deg max but no more. That's becasue it will really affect perf esp since vortecs only like 32 deg total to begin with but if you go much lower then 20 base & 32 on total the perf suffers on both low and high end .

You have to find the good ballanvce of base,mechanical adv,and vac adv with 93 fuel for your motor and go with it.

BTW,other things like a motor running hot,too hot of heat range plugs,lean fuel calibration ,lean cond due to vacuum leaks,motor using oil,carboned up motor increasing compression or carbon heating up in comb chamber pre-igniting fuel can also lead/add to a detonation problems too so keep that in mind.

If it were my motor i would back off the base to 16 deg ,then i would send out the dist to get the vac adv replaced with a napa vc1843 and have the mech adv recurved for 16 deg max in by 2800 rpm.

Then you will have 16 base + 16 deg mach in dist = 32 total vortecs like along with the vac adv that will get you to approx 47 deg cruise /light load part thrttle timing.

The 47 deg is well below the std 50-52 deg cruise timing for the street but i am suggesting to install the vac adv that only gets you up to 47 deg because your having detonation issues with your setup so i am being very conservative to help stop the ping again assuming your already running 93 fuel and ot 87 or 89.

If your running low oct 87 or 89 and refuse to run higher oct fuel then that changes things and you either have to detune it some lmore oosing more power & fuel economy or step up to higher oct fuel like 93 to keep a better ign timing curve for more power.

Make sure your vac adv vacuum source it truely working too .

BTW,unless i missed it are you running 93 fuel or not???

** last resort is which on 2nd thought is exactly what i would do in this case is to stay with 20 deg base with 12 deg mech in dist for the 32 total for vortecs' & install the new vac adv.

Then simply run the kemco octane booster with every tank full and i bet your ping will be long gone. It costs approx 55-60 cent per gal (if you buy 2 cases/24 qts at dicount/free shipping)to treat 18 gals of 93 to get approx 97.5 oct fuel.

Thats the way to beat this thing and keep your full perf ign curve for better perf without having to pull the dist to get it recurved so you can keep the proper 18-20 deg base timing that perf cam needs for better idle and low end perf & 12 deg mech for the 32 total you need without pulling the dist for a recurve. Thats the ticket here unless you want to try the other route with pulling the dist and retuning as stated above in this last post with no gaurentee it will do the trick esp if your already running 93 fuel.

See the KEMCO SUPREME 130 booster site for details.

Send me your email address so i can send some info on tuning & timing along with info on the kemco too.

Hope all this helps.

Scott