How do you guys set your timimg?

[747mopar]

Alrighty, now that my motor (456) is all sorted out, broke in and running healthy it's time to get it dialed in. I'm using a mechanical advance distributor, 6AL box, (never messed with mechanical advance) and an 870 Holley Vac Sec. It idles great (a little lumpy), stays at 160 degree's and has excellent throttle response and seems pretty happy until you get around 3,000 rpm where it starts to get a little rough. Since I just got it broke in I haven't done much tuning except leaning it out a bit at idle, next trip to the garage will be tuning it in. I suspect that the advance needs some tweaking so I thought I'd ask for any pointers your willing to share or in timing in general, it seems to have a pretty narrow window where it's happy but runs and idles very well. Please, feel free to share any tips on carb and timing tuning as I'm pretty well self taught and would like to hear what everyone else does (might save me some time).

 

[snakeoil24]

I would use vacuum advance for sure. It saves fuel and keep cylinders from loading up as much at Moderate speeds.

 

[benno440]

http://www.diamondbackengines.com/

read the whitepages down the left column, most helpful info i have read.

 

[747mopar]

I would use vacuum advance for sure. It saves fuel and keep cylinders from loading up as much at Moderate speeds.

I had it so I thought I'd give it a try (I'm at least going to get it dialed in to see if I like it).

 

[Budnicks]

a good old trick that has worked very well for me on the 1st few times out... you have it running well & just need to find it's sweet spot... loosen the distributor so it can be moved when it's started, but not too loose, turn up the idle to about 2500rpm, then turn the distributor to where it seems to have the highest RPM & vacuum to if you can do both & back off a degree or 2, note where it is at both times... lock it down & test it & then if necessary back it off a degree at a time, if it's having detonation issues from poor/crappy fuel... IMHFO you could be really lean & getting a lean surge at the part throttle 3000rpm you were talking about, happens allot with mixing parts, like aftermarket cams, rockers, intakes & heads etc... It also could still need some carb jetting or mach. advance tuning also... good luck, you've earned it

 

[747mopar]

http://www.diamondbackengines.com/

read the whitepages down the left column, most helpful info i have read.

That was pretty funny, I clicked on the link and there was a little globe spinning around showing everyone on the site "me and you", hah pretty cool. That is a good sight, I'll come back later when I have more time and read it all. Thanks

 

[Budnicks]

That Diamondback Engine, "Ignition 101" is a pretty good read...

 

[747mopar]

a good old trick that has worked very well for me on the 1st few times out... you have it running well & just need to find it's sweet spot... loosen the distributor so it can be moved when it's started, but not too loose, turn up the idle to about 2500rpm, then turn the distributor to where it seems to have the highest RPM & vacuum to if you can do both & back off a degree or 2, note where it is at both times... lock it down & test it & then if necessary back it off a degree at a time, if it's having detonation issues from poor/crappy fuel... IMHFO you could be really lean & getting a lean surge at the part throttle 3000rpm you were talking about, happens allot with mixing parts, like aftermarket cams, rockers, intakes & heads etc... It also could still need some carb jetting or mach. advance tuning also... good luck, you've earned it

Thanks Bud, that's basically where I'm at right now with the initial (I do just as you mentioned but haven't put a vacuum gauge on it yet). I hope I'm not lean anywhere (it smells pretty rich) at all times. The link Benno provided already cleared up allot of my questions on how to set the advance, advance curve, etc. That's why I love this sight, post a question and before you no it allot of knowledgeable guys are chiming in. I'll be way ahead before I even begin haha "yeah right".

 

[Budnicks]

I hope it helps !!

it could be a fat stumble too... if it really "way too rich"

I kind of doubt it thou !!

 

[383man]

First I set my dist mech advance to what I like which is all in by 1800 to 2000 rpm. I set my mallory dist up with about 18 degrees of advance and then I bring the rpm's up to about 3500 and set my total at 37 on my 440/493 eng as it seems to like it there. Basically I let the initial fall where it does because you cant change it without changing the total timing or going back in the dist. But at 37 total and 18 in the dist the initial would be about 19 degrees depending on where I set the idle speed. Ron

 

[MarPar]

i usually use a timing light...lol

sorry i couldn't resist! :toothy2:

im dialing in my car as well and i have yet to read the diamondback papers; but it looks like a ****-ton of good info.

good to see you finally buttoning her up, 747. long time comin!! and hard-earned might i add!!!

 

[Moparsmitty]

That Diamondback Engine, "Ignition 101" is a pretty good read...

X2 Lots of good info about other stuff too.

 

[fatecaptured]

If vacuum advance is so great , why do I see so many disconnected?

 

[Gpuller]

Really depends on how much vacuum your pulling. If your not pulling enough vac to make the advance work then just plug it. My 440 pulls crap for vac, it likes 20 deg initial and 35 deg total at 3,000. Not running vac advance.

 

[Budnicks]

If vacuum advance is so great , why do I see so many disconnected?

IMHFO because it's just much easier/simpler to just unplug it... instead of fixing/tuning the vacuum advance &/or limiting or speeding up or slowing down the mechanical adv. weights or springs etc., or fixing what's actually wrong, would be my best guess... MP CEI Distributor, has an adjustment screw in the vacuum adv. pod on their dist.'s, I have mine turned all the way in so it gets the least amount of vacuum assisted advance & I set my total @ 35* BTDC & the mechanical adv. is re-curved/limited w/heavy springs, to slow the rate of advance down a little & my timing is set @ 19* BTDC initial.... But that's what my specific engine combo likes, yours could be completely different... it's not ever one setting, fits all combos, every engine is different, even if the parts are the same... And depending on your specific camshaft, how it's installed/degreed in & if it's retarded or advance, what specific amount of Duration {more duration the more initial timing it will want/need usually}, or what Lobe centers or Overlap or even lift, or the pre-load or valve-lash you have, the specific style/size/design of the cam, rocker ratios, compression ratios, quench area, ring seal, head mods, porting/valve size, fuel type &/or octane, exhaust style/size, ignition system mods or how much spark & what type of plugs & heat ranges, etc.... If you don't want to run vacuum advance, just get/use a properly tuned mech. adv. type distributor, plenty of them out there or just simply unplug it block it off, if that's what you choose/want to do...

 

[67Satty]

...has excellent throttle response and seems pretty happy until you get around 3,000 rpm where it starts to get a little rough. ...

I had the same thing happen after I got my new engine running. Did some searching on the forums and found that the distributor reluctor gap being set wrong can cause this, pulled my distributor cap, checked the reluctor gap and sure enough it was way, way wider than the .008 is should be. BTW, the distributor was brand new and purchased from a well-known guy who set up a custom distributor curve for my combo but I guess he didn't set up the reluctor gap on it while he was at it.

Another method you could try that worked for me is to hook up a vacuum gauge, move the distributor back and forth until you get the highest vacuum reading, then back it down by one, then recheck with your timing light to see where you ended up. I tried this on mine and my initial ended up being right where the guy who set up my distributor said it should be for my combo, so he really knew what he was doing (other than not setting the reluctor gap but maybe I should have known to check that myself first).

 

[383man]

As you can see the reason my vacum advance is not hooked up is because my dist does not have one ! Its a race type dist but I like it for the way I have it set up. Great throttle responce and good power. If I had a dist with a vacum advance I would try and dail it in to see if it would help it run cooler and help the milage since mine is mostly a street car. Ron

 

[747mopar]

As you can see the reason my vacum advance is not hooked up is because my dist does not have one ! Its a race type dist but I like it for the way I have it set up. Great throttle responce and good power. If I had a dist with a vacum advance I would try and dail it in to see if it would help it run cooler and help the milage since mine is mostly a street car. Ron

Nice car, mine is a mechanical as well.

- - - Updated - - -

I had the same thing happen after I got my new engine running. Did some searching on the forums and found that the distributor reluctor gap being set wrong can cause this, pulled my distributor cap, checked the reluctor gap and sure enough it was way, way wider than the .008 is should be. BTW, the distributor was brand new and purchased from a well-known guy who set up a custom distributor curve for my combo but I guess he didn't set up the reluctor gap on it while he was at it.

Another method you could try that worked for me is to hook up a vacuum gauge, move the distributor back and forth until you get the highest vacuum reading, then back it down by one, then recheck with your timing light to see where you ended up. I tried this on mine and my initial ended up being right where the guy who set up my distributor said it should be for my combo, so he really knew what he was doing (other than not setting the reluctor gap but maybe I should have known to check that myself first).

I'll check it, thanks

 

[badmopar67]

I set mine at 2500 rpm's and 38 degrees total timing when at idle it's 10 degrees btc and I run 93 octane. that's with mechanical advance and lightened springs.

 

[747mopar]

Checked the reluctor gap tonight (papers say .010-.020) it was .038. "Seriously" brand new and they couldn't even check that, Thanks Satty. Didn't get to try it out because I didn't feel like huffing fumes and it's hard to work in the dark (outside). Would that cause it to be stubborn to start? A problem I'm having right now is starting, I think it's ignition but maybe not. I've tried different ways of staring it to narrow it down, just tapping the gas enough to close the choke, giving it a couple snorts from the accelerater pump to see if it wasn't getting gas, nothing changes. It usually tries to fires as you let off the starter but eventually starts and runs perfect. Tested the bat feed and ign source to the ignition box and both show 12V until you start cranking and then drop to 9.9V which I don't think is uncommon. Next step is to test the spark while cranking it at the cyl.