OK...I know there are better ignitions that the Pertronix Flamethrower dist and coil that I am using, but for now...that's what I have in my ZZ502.

When I first installed everything a few months back, I dropped the dist in with the out of the box set up which used the mid curve springs. Following other advice, yestderday I finally swapped in the lightest advance springs so that my timing comes all in as early as possible.

With my initial timing set at about 10 degrees, and based on my seat of the pants dyno, I seem to have lost a little of the initial hit when I smash my loud peddle. Then the power comes on more smooth rather than sudden.

The engine seems to run smoother over the power band, especially off idle where I used to have a stumble (I also reset my idle mixture a tad), but it seems like the power is more gradual. Once I get it into it's power band....it pulls like a bull still. This annoying run-on problem I've always had also seems a little worse.

Need advice. Should I take out or add more initial timing and how much?

Tim

You mostly want to play a little, and see what the motor wants.

The more radical the cam is, the more timing it will want at low rpm. (many really radical cams run best locked out, no advance at all, 34 degrees all the time!)

I would start with the initial timing. I like a lot, and run 18 degrees. I'd consider 10 not enough even for a stock engine. I'd consider too much when a hot motor would no longer crank fast enough to start.

Put the stiff springs back in, crank in more initial, and just drive it around and see how it feels (have the vacuum advanced hose connected while testing! but disconnect it when changing the timing). Don't hammer it, and try not to make it ping. If it does ping, it would be very nice to know the rpm and manifold vacuum where it happens (I run a vac gauge in my dash, and have been known to tape one to the windshield while tuning if there wasn't a dash gauge!)

Once you have the initial where the motor is happiest, it's time to limit the mechanical advance to 32 to 36 degrees, depending.

Then start playing with springs.

You are after the best response and highest cruise vacuum levels you can get.

If you get part throttle pinging, you can tune it out, either be delaying the mechanical advance, reducing or delaying the vacuum advance, or both.

For max performance, the last step would be determining the optimum total advance on a dragstrip or chassis dyno. (Do it by changing the initial, and once the number is figured, put initial back to your "best" setting, and change the mechanical advance limit to get your total number.)

Fuel mixture plays a big part too. The fastest motor is "just a touch lean" but that motor may ping under certain conditions, and require timing changes to tune the ping out. A rich motor often won't ping, so it's easy to be cranking in more timing when what you really need to do is pull some fuel. A wideband can be a big help, tho the one I just stuck in my dash is mostly telling me I need efi to properly control fuel flow at part throttle.

Thanks, Jim.

Why can't I just tap it someplace with a hammer, strategically apply a little duct tape and/or JB Weld and have it work right and feel good in the seat of my pants?

Please forgive me...I'm a complete idiot when it comes to ignition systems, and distributors intimidate me. I'm one of those guys who will do everything I can to avoid touching one and if I do touch one, I'll only do it after marking it 10 different ways with 3 different color sharpy pens so I know exactly where all the parts (rotor, housing, vac can) were looking before I started.

How do I go about limiting the mech advance to 32-36deg?

I'll listen for pinging next time I'm out. So far it has not been an issue.

Can I measure cruze vacuum accuratly just by throttling it in my garage, or does the engine need to be under load?

When you talk fuel mixture adjustments, I asume you mean I'd need to micky with the jetting,etc. And not the idle mixture screws. Carbs also intimidate me...I'm one of those guys who would prefer to just buy a new one and see if it works better out of the box before I start clowning with the parts on the perfectly good one I have.
...Or go blow $3K on an out of the box EFI and take a year to install it.
My current carb is and Edlebrock Performer 825cfm. Yes...I know there are better out there, but the long term plan is in fact to go EFI.

My cam is the mild stock cam that comes in the ZZ502.

Tim

JimM gave some really good advice on how to tune your timing

to limit your mechanical advance you need to adjust how far out the weights can move, I don't know what your distributor uses, but my MSD has a few small bushings I can swap out to change the mechanical advance

no, you cannot measure your cruise vacuum readings in the garage, you need to have it on the road, just put the vacuum line out the rear corner of the hood and under a wiper blade to help hold the gauge in place

and yes for the fuel adjustments you need do more than just the idle screws
but luckily your edlebrock is easy to make changes
just take of the air cleaner, there are 2 screws holding small gold colored covers over the rods, just loosen them, pull the rod, holder and spring out, clip a new rod in and put it back together
as jim said you should try leaner first
if you still have the edelbrock manual they have tuning charts in the back
page 30 and 31 i think
i would guess that 19 would be a good start, its just a rod change
if you dont have the manual, heres a link (http://www.edelbrock.com/automotive_new/misc/tech_center/install/1000.shtml)

Thanks, Jim and 400bird.
I appreciate the great advice.
I hope that in my stabs at humor, I'm not coming off as a smart @$$.

I'll try some of these tips out.

Now that I think about it, my Pertronix distributor advance kit did come with these L shaped mech advance limiter tabs that go under one end of the springs...I'll check the chart out and see if I need to use any in order to limit my total mech advance to 32-36 deg.

I'll need to get a longer vacuum line for my vac guage so I can go driving and get some measurements....the wife doesn't like being duct taped to the hood...so the longer hose and routing the gauge to my interior is the right way to go.

At idle (800RPM), the vac bounces around at 10-12. When I throttle it at a stand still (no load), the needle stabilizes and shoots way North, but I did not record the values at any RPM other than 800.

I'll need to buy a carb kit also so I can swap some rods.

I did have all my spark plugs out for the first time since installing the engine. After the first 3000 miles, they all are varying shades of tan and brown and no black spots. One was noticeably darker than the rest, but not to the point of being alarming or fouled.

I reinstalled them and will replace them at 6000 miles. Any recommended plugs for a ZZ502?

Thanks!
Tim

Tim the guys are right on, but let me give you my take: you have no choice but to set your total to 36* and let the initial fall wherever it does. You have no choice unless you want to get a custom curve done on it. Hopefully, setting the total to 36* should give you at least 16*, which should be enough for cripsy low-end. I would agree that 18* initial; would be better, but that may push your total past 36*. Testing has shown that 36* is where these crate motor like to be. Then connect your vac advance to manifold vac so you get some extra idle/cruise timing. I run 16/36 w/an additional 14 vacuum, so my idle timing is 30* - any less it doesnt idle as good. FYI, I tried 18,20,22,24* initial and cant feel a difference from the 16* I'm running now. Make sure the springs are strong enough so that the advance doesnt dither in/out at idle - just watch the timing light at idle and see if the mark is jumping around.

I have ZZ502 heads and I'm running NGK BKR6E-11, this has the small 5/8 hex on it, and it was the X-ref for the ZZ502 plug. So far so good

BTW - you sould have alot more vcuum than that. This leads me to believe you dont have enough timing or your carb is outta whack. I get 11-12" at 700 w/a bigger cam and 50 less cubes.

Thanks, Vince.

I'm sure you're right about the carb. It is a refurb Edelbrock Performer 825 that was on my old 396 for a few years, and never saw more than 100 miles in that time. Then it sat on a shelf in my garage for several months while I swapped the engine, trans and rearend out. I just bolted it onto the ZZ502, sprayed some cleaner on it to dust it off, fiddled a little with the idle mixture and started driving. I've heard carbs don't like sitting around for long periods of time.

I've tried setting the idle mix using both a tach and vacuum gauge but they each move around too much at idle for me to get a good read on when they are truely maxing.

The idle screws are each out a little over 1.5 turns.

The car swallows WRX Sti's and Evo's before ever hitting 3rd gear , pulls away from Cobra's etc like they're stuck in mud, made an 06 GTO show up in the rear view in 3rd after giving him a couple lengths jump off the line, has pulled away from a few Motorcycles at the top of 3rd from 2nd gear starts, makes Vettes feel like they're stuck in a middle age crisis somewhere in mid 3rd, and also has pulled away from a Saleen E Mustang before hitting 4th, so it's been nothing but grins to drive. Now I'm trying to tune it for optimal performance using what I've got.
I have often suspected I might have sucked an intake gasket or something since the engine uses a lot of oil(a quart or more in less than 500 miles) and maybe this is why the vac is a little low and unstable at idle, but the spark plug read does not show any oil fouling and the vac guage stabilizes when I throttle it.

Now I just need to carve out some time to try some of this great advice you guys are giving me.

My carb and distributor and their magical operation are becoming less like a werewolf living under my hood as I learn more from you guys.

Thanks!
Tim

If you have the advance limiters for your dizzy, you do not have to "let the initial timing fall where it may." For street cars, timing and mixture below 2000 rpm are REAL important to driveability, so do it right, initial timing and idle mixture first, then use the limiters to set the total.

Edelbrock carbs are OK. I'd never had one till a 600 came with this car, and I tuned the heck out of that, then replaced it with an 800 carter. They both work nice when tuned right.

1 1/2 turns out on the idle mixture is a lil on the fat side of normal, 1 - 1 1/4" would be more like it. One thing you really need to do is pop the top off the carb and check and set the float level. This being off can really screw up an ede. There are good directions in the manual. While you're in there, you can get to know it a bit, then it won't be so scary.

Work with it and learn it. Anyone who can swap an engine can certainly tune the engine, just a matter of careful adjustments, one at a time, and then checking the results. I use a sharpie marker too.

I built a 383 stroker with msd ignition but it sounds like the same adjustments. all the info everyone gives seems correct. I installed a timing light revved my engine to full advance set to 34 degrees. Then play with springs and advance bushings until satisfied. I always start with about 34 degrees on any engine that is not too radical. After seeing mine and a few dynoed it seemed as if they were all creating the best power curves at 32 to 36, 34 seemed the best. hope this helps

I'll run ya anytime you want with my middle age crisis Vette. I'll bet you'll be in for a big surprise. :p

I'll run ya anytime you want with my middle age crisis Vette. I'll bet you'll be in for a big surprise. :p

I'll take your word for it, Bob. You seam pretty sure of it.

I just want to get this car to the track to see what it really can do. I'm guessing I'm in the mid 11's somewhere by comparison to the way I pulled away on that Saleen "Extreme" Mustang. It was the quickest of all the competition I've seen so far....but I am on the hunt for a ZO6....just for fun.

For now I need to get out from under this "Honey, do..." list so I can try out some of this tuning advice.

Tim