Establishing Initial Timing

JoeSBP

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Gentleman, I have humbly come here to ask for a bit of experienced advice. I know my way around a garage, but I have just realized that I have never truly had to "tune" the timing on an engine. This is the first engine that I can't just set the initial listed from the manual, run a vacuum advance and walk away. So my question is what are the tried and true methods for the at home mechanic to dial in initial timing and curve for a given motor? I have seen other guys post up every tiny detail of their build, and the senior guys here suggest settings. What I'd like to know is how y'all are establishing that. This is my first legitimate performance engine, and I want to learn. Feel free to post any links to the world wide webs to videos, articles, sites etc that dig into it. Thanks in advance! Joe
 

318willrun

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Well, lets get a starting point. Let's say you have a very mildly built small block and you have the initial timing set at 5* BTC and it's idling at 700 rpm's. With the vacuum advance disconnected, bump the timing up to 7* BTC. DID THE MOTOR REV UP A LITTLE? If it gained rpm's, then back the idle rpm's back down to the desired 700 rpms. Advance the timing again to 9*. Same procedure. If it gets to the point where it starts hard (hard to turn over full warmed up), back it off to where it did not start hard. With a very mild small block, you will end up somewhere between 14*-22* initial timing. Some times the grade of gas will be a factor. Example: You may have to run 5* less if you have 9 to 1 compression versus 8 to 1 compression because of the gas to keep it from "pinging". No Pinging!!! lol.... at low rpm in high gear, slightly give it gas going up an incline, it should not ping. Neither should it "ping" under WOT. Pinging can be controlled by full advancement, vacuum advance, and how fast your full advancement comes in....

However, when you move up initial, your full advance timing will move up as well, so that is why you'd use a limiter plate or something that keeps the timing at full advance right where you want it. So if you want 36* full advanced, but your engine likes 17* initial, then you want your dizzy to allow only 19* of advancement. NOW, you have to decide what rpm you want it to reach full advancement....3500 rpm's???? 3000 rpm's???? Size of springs and weights in the dizzy will determine what rpm you get to fully advance timing.

This will ballpark you, but let the engine be the deciding factor as to what IT likes best. For me, if I'm running a vacuum advance, I don't push my initial up to the "start hard" point. In fact, even when I'm not using a vacuum advance I'll stay a little more away from that than most folks, but that's just me......
I'm sure others will chime in.... Hope this helps
 
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Rapid Robert

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Well, lets get a starting point. Let's say you have a very mildly built small block and you have the initial timing set at 5* BTC and it's idling at 700 rpm's. With the vacuum advance disconnected, bump the timing up to 7* BTC. DID THE MOTOR REV UP A LITTLE? If it gained rpm's, then back the idle rpm's back down to the desired 700 rpms. Advance the timing again to 9*. Same procedure. If it gets to the point where it starts hard (hard to turn over full warmed up), back it off to where it did not start hard. With a very mild small block, you will end up somewhere between 14*-22* initial timing. Some times the grade of gas will be a factor. Example: You may have to run 5* less if you have 9 to 1 compression versus 8 to 1 compression because of the gas to keep it from "pinging". No Pinging!!! lol.... at low rpm in high gear, slightly give it gas going up an incline, it should not ping. Neither should it "ping" under WOT. Pinging can be controlled by full advancement, vacuum advance, and how fast your full advancement comes in....

However, when you move up initial, your full advance timing will move up as well, so that is why you'd use a limiter plate or something that keeps the timing at full advance right where you want it. So if you want 36* full advanced, but your engine likes 17* initial, then you want your dizzy to allow only 19* of advancement. NOW, you have to decide what rpm you want it to reach full advancement....3500 rpm's???? 3000 rpm's???? Size of springs and weights in the dizzy will determine what rpm you get to fully advance timing.

This will ballpark you, but let the engine be the deciding factor as to what IT likes best. For me, if I'm running a vacuum advance, I don't push my initial up to the "start hard" point. In fact, even when I'm not using a vacuum advance I'll stay a little more away from that than most folks, but that's just me......
I'm sure others will chime in.... Hope this helps
hook vac gauge to manifold port. advance dist till you reach maximum vacuum all the while reducing your idle speed back to your lowest in gear warmed up RPM which is what it will be at at the stoplight (E brake on). then reduce the INITIAL until the VACUUM drops 1 in hg. this is your ideal INITIAL. if it will crank over when hot you are set, if it is cranky then reduce the INITIAL 1 degree & repeat & go 2 deg if needed OR wire in a momentary normally closed contact switch to the ign & press it to disable the ign then crank it with the switch & release the button while it is still cranking. then shorten the slots for your eng & 35 is a tried and true total for a SB (31 if mag heads) & this is with the can capped (initial+slots) & the FBO $22 plate is by far the easiest.cheapest way to rework the slots. then toss the one heavy spring with the elongated loop on one end & sub in a mr gasket or MP light spring in its place (keep the OE light spring) & from this starting point you want to mix and match springs so that you are aways under the pinging point at WOT up thru the gears on your hottest/driest day (most likely to ping). there are chebby springs & hardware stores have some & no matter what combo of light/heavy the curve will advance in a linear rate. then plug in the can to ported & adj it with a 3/32 allen wrench so that you are aways under the pinging point in everyday driving under varying RPM and load (in hg) conditions alsoon your hottest/driest day. CCW slows the curve (not the total but the amt ofr a given in hg). you want to push the pinging point fairly close so nothing is left on the table but there is silent ping so give yourself a cushion as pinging is EXTREMELY damaging & any pinging you can HEAR is WAY WAY too much timing at that point. aof of work but alof of gain to be had. also reduce lower shaft axial play to .005". (speedway mtrs has a nice/cheap kit of 1/2"ID FLAT washers). reduce lower tang to intergear notch rotational play to near zero. check rotor phasing. reduce rotor blade clearance to cap terminals to .015 (drill out the rotor rivet & replace the metal tang) & NAPA has a rotor with a .060" longer blade MO3000 for $8.xx but you may need more length than that. add a side oiler like the 60's point dist had (they are available). tan cap with brass terminals and ribs underneath. several 1/2" vent holes in top/sides to release ionized air molecules that can promote crossfire just like sitting under a wide tree in a thunderstorm, the lightning does not all go down thru the tree trunk, alot goes from the outer perimeter branches straight down vertical to the ground (in the ionized air) & zapps anything in its path! most electronic dist have tight bushing clearance but do check & lowes has bronze bushings and an adjustable Grainger 15/32-17/32 reamer is cheap
 
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318willrun

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^^ some good stuff in that post ^^^ however, I'll just say 35* total timing is just ball park. I let the engine decide where it likes to be timed by using the E.T./mph from a drag strip, along with my ears (NO PINGING!!). My low dollar 318 is at 42* total timing and that is where it performs the best. No pinging on any gas.
 

BillGrissom

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My ultimate plan is to install a Holley Commander 950 engine controller I have in a box and let it adjust timing based on a knock sensor. I have parts from a Chevy (1985-95, 8-pin HEI, knock sensor & module) which make that fairly easy. The controller keeps creeping up the timing until it senses knock, then backs off a few degrees, then creeps again. I think most modern cars work that way. A Mopar e-distributor w/ centrifugal & vac advance will handle the gross changes.
 

RustyRatRod

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All that is "good stuff" bot really totally worthless without all of your engine specs. Once you give "that" then we can get on with it.
 

Slantsix64

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Just give it all she can take before light ping, get an Fbo limiter plate take some timing out swap out the heavy spring for a light one and repeat if it pings or hard starts run timing back a bit 34 total is the base line depending of camshaft and compression well determine what she likes, i have 9:5:1 260/264 .453/.470 at 106 intake center line she likes 30 total timing anything after that she bitches. you can feel when your giving it to much initial timing the cars idle speed does not raise an idle turns shitty.
 
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