Engine Timing

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Let me toss a few thoughts:
Total timing: This is the total of the initial advance and the mechanical advance added together. It does not include vac advance. When someone says "all in at 3000 rpms" or something like, they mean the mechanical advance. 

Vac advance: This can be hooked to either ported or manifold vacuum. Ported is generally off of the carb and is only active when the car is at higher throttle settings. Manifold vacuum is from below the carb and is active at idle and cruise. 

If you want to tame down that engine, my personal suggestion would be to use the vac advance and put it on manifold vacuum. If you set the initial(w/o vac hoses hooked up) at around 10-12 degrees with 24 degrees of mechanical advance you will have around 36 degrees of total for good WOT power. If you have the vac advance functioning, it will give you another 12 degrees or so at idle, for a total of 24-ish at idle. You can set it at 24 initial w/o any vac advance and it will work fine, BUT you may have issues with the starter being overworked and other things. The vac advance will also give you another 12 degrees of timing at cruise, which will improve your highway mileage. Bear in mind that as soon as you put your foot into it, the vacuum goes to zero and you will only have the initial and mechanical, ie 12 inital plus 24 mechanical for a total of 36 or something similar. As soon as you go back to light throttle it kicks in the extra timing for mileage and to clean up the idle with that large cam. 

The vac advance canister can vary, either by having it adjustable or by buying different ones. I am not an MSD user so I don't know your options there. I believe it might use the standard Delco-remy cans, which means you can buy them in various calibrations for various vacuum signals. You want the vac advance to be fully advanced at about 2-3" below your idle vac. This will pin it at idle so you don't have "hunting" timing. 

Set your timing by doing the mechanical and total first. Then get a vacuum canister that is 2-3" below, as above. My guess is a B28 is what you need, but that depends on your vacuum signal. Try it out and you may need to play with the advance springs a bit to get the best feel without pinging. 

I hope that helps!

Chris 

PS: Looking at what you have, it is timed like a race car and has the timing very advanced at idle to keep some idle quality. It also sounds like advance is coming on nearly instantly, judging by the one "modified" spring. It is virtually locked. You can accomplish most of the same things and have a more streetable ride using vacuum advance. 

PPS: My own mild 390 likes 34-36 degrees of timing as well. I don't have vac advance because I am stupid and like old vintage systems that did not have it. I wish it did! If I was building a car for strictly function rather than a "restoration" I would install it. 

PPPS: Bear in mind, stick cars don't need to have the timing come on super fast. Let's face it, you aren't likely to be doing any "spirited" driving at any rpms below 3000 or so anyway and with the stick you can control the gears and rpms any way you like. The advance curve is really about part throttle driveability in a stick car, rather than performance. Make it so that it has enough initial and mechanical advance to feel good coming off idle and part throttle driveability. As far as WOT hp, by the time that becomes a factor you will already be well above the point of having all timing in, rpm wise. Automatics are different, but this is a stick car. There is little value for you to be cramming all the timing into it that it will take, just because the engine will take it. I would have it all in by around 2500-3000 rpms and have the vac advance to temporarily add in some extra timing to improve idle quality and highway mileage when appropriate. 

Edited by ccowx - Sep/11/2016 at 10:13pm

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ccowx Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Nov/03/2010 Location: Yukon Status: Offline Points: 3510	Post Options Post Reply Quote ccowx Report Post Thanks(0) Quote Reply Posted: Sep/11/2016 at 10:03pm
	Let me toss a few thoughts: Total timing: This is the total of the initial advance and the mechanical advance added together. It does not include vac advance. When someone says "all in at 3000 rpms" or something like, they mean the mechanical advance. Vac advance: This can be hooked to either ported or manifold vacuum. Ported is generally off of the carb and is only active when the car is at higher throttle settings. Manifold vacuum is from below the carb and is active at idle and cruise. If you want to tame down that engine, my personal suggestion would be to use the vac advance and put it on manifold vacuum. If you set the initial(w/o vac hoses hooked up) at around 10-12 degrees with 24 degrees of mechanical advance you will have around 36 degrees of total for good WOT power. If you have the vac advance functioning, it will give you another 12 degrees or so at idle, for a total of 24-ish at idle. You can set it at 24 initial w/o any vac advance and it will work fine, BUT you may have issues with the starter being overworked and other things. The vac advance will also give you another 12 degrees of timing at cruise, which will improve your highway mileage. Bear in mind that as soon as you put your foot into it, the vacuum goes to zero and you will only have the initial and mechanical, ie 12 inital plus 24 mechanical for a total of 36 or something similar. As soon as you go back to light throttle it kicks in the extra timing for mileage and to clean up the idle with that large cam. The vac advance canister can vary, either by having it adjustable or by buying different ones. I am not an MSD user so I don't know your options there. I believe it might use the standard Delco-remy cans, which means you can buy them in various calibrations for various vacuum signals. You want the vac advance to be fully advanced at about 2-3" below your idle vac. This will pin it at idle so you don't have "hunting" timing. Set your timing by doing the mechanical and total first. Then get a vacuum canister that is 2-3" below, as above. My guess is a B28 is what you need, but that depends on your vacuum signal. Try it out and you may need to play with the advance springs a bit to get the best feel without pinging. I hope that helps! Chris PS: Looking at what you have, it is timed like a race car and has the timing very advanced at idle to keep some idle quality. It also sounds like advance is coming on nearly instantly, judging by the one "modified" spring. It is virtually locked. You can accomplish most of the same things and have a more streetable ride using vacuum advance. PPS: My own mild 390 likes 34-36 degrees of timing as well. I don't have vac advance because I am stupid and like old vintage systems that did not have it. I wish it did! If I was building a car for strictly function rather than a "restoration" I would install it. PPPS: Bear in mind, stick cars don't need to have the timing come on super fast. Let's face it, you aren't likely to be doing any "spirited" driving at any rpms below 3000 or so anyway and with the stick you can control the gears and rpms any way you like. The advance curve is really about part throttle driveability in a stick car, rather than performance. Make it so that it has enough initial and mechanical advance to feel good coming off idle and part throttle driveability. As far as WOT hp, by the time that becomes a factor you will already be well above the point of having all timing in, rpm wise. Automatics are different, but this is a stick car. There is little value for you to be cramming all the timing into it that it will take, just because the engine will take it. I would have it all in by around 2500-3000 rpms and have the vac advance to temporarily add in some extra timing to improve idle quality and highway mileage when appropriate. Edited by ccowx - Sep/11/2016 at 10:13pm

Bandana Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Jul/26/2016 Location: NC Status: Offline Points: 473	Post Options Post Reply Quote Bandana Report Post Thanks(0) Quote Reply Posted: Sep/12/2016 at 7:52am
	Thanks for taking the time to articulate this thought process so thoroughly. Your comments pretty much parallel what I have been thinking. I have some work to do to get this work underway. First thing is to get a spring/bushing kit ordered and use some paint to get the timing marks on the balancer to show better for these old eyes. When I checked the timing Saturday it "looked" like I had around 12-14 at idle but only around 24-25 at 3000rpm - with the vacuum plugged off. 38-39 at 3000rpn with the vacuum connected. This really threw me as I was expecting the all in mechanical to be in the 34-36 range with no vacuum. I stress that I had a heck of a time reading markings which is why I need to highlight them before I try anything. I can't believe it even runs with only 25 at full mechanical. The car does pull real strong up to around 4000 rpm then hits a flat spot and goes dead so maybe it is actually that low? Let me get some parts ordered and try to get some clear readings. Thanks for everyone's help so far!

Bandana Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Jul/26/2016 Location: NC Status: Offline Points: 473	Post Options Post Reply Quote Bandana Report Post Thanks(0) Quote Reply Posted: Sep/23/2016 at 1:23pm
	Sorry been sidetracked much of the past two weeks and just today got back to fiddling with this thing. Last night I cleaned up the balancer so I could read it better. Just checked the timing and I'm more confused than ever. Initial was around 20 degrees with vacuum unplugged. I could get it down to around 14 or so before it wanted to die . The strange thing - at idle the marks would bounce around a bit. As it went up in rpm the marks settled down nice and steady - BUT never went above 20 degrees at 4000 rpm!!!!! When I reconnected the vacuum it would advance to near 40 but without vacuum does not advance at all!!!! ???. The cams in the dizzy move so they are not locked. Have not checked to see what we have for a bushing yet... Thoughts?

Bandana Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Jul/26/2016 Location: NC Status: Offline Points: 473	Post Options Post Reply Quote Bandana Report Post Thanks(0) Quote Reply Posted: Sep/23/2016 at 6:25pm
	Some more update after messing with it for a few hours today. The bushing in the dizzy measures at 0.340" so about the size of the MSD blue busing which should be good for 21 degree spread. After measuring the bushing I reinstalled it and put the lightest springs in the MSD kit on the cams along with a dab of dielectric grease on the cam pads.. After starting, the motor would not idle. Going back and forth between the idle screw and bumping the timing up I was able to get the initial around 16 degrees - and the mechanical started to come in around 35 degrees - but I had to advance the dizzy quite a bit from where it was to get there. Reinstalled the vacuum line and it brought the total up to around 50! I was feeling better about the set up and then when I shut the engine down it had a bit of dieseling.... Sooo, I retarded it back some and my initial readings got so erratic that I couldn't read it. I removed one of the cam springs and set the dizzy back about where it was and gave up for the day!!! Man is this thing frustrating.

BDCVG Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Dec/19/2007 Location: Endless Mtns. Status: Offline Points: 993	Post Options Post Reply Quote BDCVG Report Post Thanks(0) Quote Reply Posted: Sep/23/2016 at 9:25pm
	There has to be something else in Your way. Dist. off a tooth ? Weights not moving all the way or too far? Edited by BDCVG - Sep/23/2016 at 9:28pm
	1970 AMX 390 5 spd full Control Freaks front and rear suspension 2014 E63 AMG-S wagon 1965 Austin-Healey 3000 MK III

Bandana Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Jul/26/2016 Location: NC Status: Offline Points: 473	Post Options Post Reply Quote Bandana Report Post Thanks(0) Quote Reply Posted: Sep/24/2016 at 6:31am
	They seem to move all the way. If you recall I was able to get to around 35 degrees with upwards of 50 with vacuum. Something does not seem right. Andy Giles did the rebuild on this motor when it was done and he's supposed to be pretty good from what I hear. I'd like to think he didn't mess up setting the dizzy - or degreeingvthe cam....🤔

BDCVG Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Dec/19/2007 Location: Endless Mtns. Status: Offline Points: 993	Post Options Post Reply Quote BDCVG Report Post Thanks(0) Quote Reply Posted: Sep/24/2016 at 9:22am
	Well I have almost the exact same specs. '70 390 10:1 comp. Summit 8601 cam which is very close to the cam You listed. MSD Dist. 14 deg initial Blue bushing 1 lt silver spring and 1 hvy. silver spring. That makes 35 total at 3400 rpm. I do not run a vacuum line because it made the car ping in 5th gear. Maybe these #'s can help.
	1970 AMX 390 5 spd full Control Freaks front and rear suspension 2014 E63 AMG-S wagon 1965 Austin-Healey 3000 MK III

Red20 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jan/29/2013 Location: Oceanside CA Status: Offline Points: 1556	Post Options Post Reply Quote Red20 Report Post Thanks(0) Quote Reply Posted: Sep/24/2016 at 3:33pm
	My timing is set up pretty much identically to BDCVG. Engine is a little different. 9.0 to 1 compression 360 with performer cam. Blue 21* bushing in an MSD distributor. 14* initial and 35* total with no vacuum advance. One light silver spring and one heavy silver spring. I could probably get better cruise and transition drivability with a vacuum canister, I just didn't use it on this build. If I did, I'd pull the initial back to around 10-12* and have the vacuum advance all in a couple of degrees below my idle vacuum (16-17) on manifold vacuum. Still a 35 total advance. The biggest mistake I've made in the past with vacuum advance is having a small intake vacuum leak, so I ended up having to crank my initial up too far to get a smooth idle. That caused detonation under part throttle load conditions. Be sure your vacuum system is rock solid before you begin tuning. That also gave me issues with my MAP signal when I was running an EFI setup.
	1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018 1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER

Bandana Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Jul/26/2016 Location: NC Status: Offline Points: 473	Post Options Post Reply Quote Bandana Report Post Thanks(0) Quote Reply Posted: Sep/25/2016 at 5:14pm
	Thanks for the tips guys. Didn't do anything to it over the weekend except take her out to a small show Saturday. Supposed to be rainy for the next couple of days so maybe I'll tinker on it some more. Will report back. I bought some timing tape so first task is to put it on so maybe I can see the marks more clearly....

Red20 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jan/29/2013 Location: Oceanside CA Status: Offline Points: 1556	Post Options Post Reply Quote Red20 Report Post Thanks(0) Quote Reply Posted: Jan/05/2017 at 11:39pm
	Bandana, I just read over this thread from a few months back as I am gonna be tinkering with timing a bit this weekend and wanted to reread some of the thoughts we all discussed here. So how did it go finishing up getting that 401 running right? I'm curious how you ended up
	1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018 1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER