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Thread: Amc 360 timing curve

  1. #1
    primosauce Guest

    Default Amc 360 timing curve

    Installed an tomic efi system on my new 360 swap into a cj7. When we initially fire up the motor just of mechanical and vacuum advance it actually ran pretty well just off of the stock iac set to a mild cam. I drove it like that for a few hundred miles for engine break in and decided to switch over the timing to the atomic. That was two weeks ago, I've had just a heck of a timing trying to get it right. I had it running decent at one point but I just couldn't get the idle to come down. Not sure if it's out of timing or if it's the IAC settings because I've twisted the screws away from where they were orginally.So today I started completely over, here was my process and some motor specs:

    AMC 360

    Bored .40 over which makes it a 367

    Performance Camshafts MC1786

    Duration at .50 Lobe Separation

    int 204, exh 214 int 105, exh 115

    Headers

    Manual Tranny

    MSD distributor is locked out with the MSD adjustable rotor installed. AMC rotates CW (clockwise) so according to the instructions, the rotor should be turned CCW (counter clockwise) and locked at 15* which is what I did. So the Rotor essentially is 15* BTDC compared to the original rotor that I replaced.

    Pull the plug on cylinder one and find TDC on the compression stroke. Used a compression tester with a zip lock back taped to the end of it. Once it started inflating I assumed I had the compression stroke and rolled it up until TDC on the timing cover and just backed up counter clock wise to 15 BTDC on the timing cover.

    Installed the MSD distributor so that it's pretty much in the same orientation as a stock amc motor for consistency and made sure that the rotor is pointing directly centered on the number one wire on the cap. I did that using a sharpy to mark the center of cylinder one on the distributor housing when the cap was on.

    Pulled my air cleaner. Adjusted the front screw on the TB out until the blade in the TB was closed, did the same thing on the other screw in the rear for the rear blade. Screwed both screws CW until it looked like the blades barely moved then turned one full revolution on both screws CW for the mild cam.

    I noticed there is a lot of play on the front throttle linkage and the rear. It says in my instructions for the EFI that the "sync" between the front throttle linkage and the rear is set at the factory but it appears as I'm moving these around that you can move the front around 1/8 to 1/4 inch before it even moves the rear. I'm assuming the account for this somehow internally in the TB but I thought I would mention it. It just appears that it opens the front throttle blade before it does the rear, meaning the front is always going to open farther than the rear because linkage between the two screws if that makes any sense. I can see the front blade open bout an 1/8th of an inch before the rear moves at all.



    Set my initial settings which are as follows

    Engine Displacement: 367

    Number of Cylinders: 8

    Camshaft: Mild

    Fuel Pump Type: Non PMW regulated (I have nothing but MSD, their fuel pump, their return kit)

    Idle RPM target: 750

    Rev limit: 7000

    Timing: Enabled

    Locked the timing out, fire up the motor. It runs but not the greatest. Check with two timing lights, 15* BTDC exactly. Idles really high, like 1700. Let it warm up to 160 degrees ECT. What do I do from here to adjust this IAC? Do I unlock the timing first?

    What should I set my values at for the timing to be fairly close? It ran fairly well just off the standard vacuum timing before I switched to this mess. I'm assuming the a/f targets and all that stuff is the same profile based on the cam when you have the timing control off or on. And it ran fairly well with stock settings, I didn't mess with any of that until the tech support guy told me to adjust the screws out on the throttle body to lower the idle. Not it's all messed up.

    Can anyone give me a base idea of where to start here? I've tried to adjust the IAC but it's always zero, no matter where it's at unless you rev the motor.



    I found some timing curves for 360's, in general they are all pretty similar for the most part. I've tried multiple adjustments with timing, vacuum advance, type of vacuum but in general, it just makes things worse for the most part. At this point, when I start it black carbon liquid blows all over my hands at the exhaust if I put my hand near it. I reset the settings and plan on starting over fresh in the morning. I'll give it one more shot, then it's going back to vacuum advance or to a shop.

    Sorry for the novel of information here but I thought I would toss as much information out as I could to see if something I'm doing is obviously wrong. I put the stock settings below so maybe I could get someone to just replace some of those values with something that gets me closer to where I need to be. I attached the amc timing curve if that helps.





    A/F Targets

    Idle: 14

    Cruise: 14

    WOT: 12.8

    Nitrous: off

    Boost: 11.9

    Pump Squirt 25%

    Power Valve 19%

    Ignition Timing:

    Idle: 850

    Total RPM: ?

    Idle Advance:?

    Total: ?

    Vacuum Advance: ?

    Vac Type: Ported

    Nitrous: Off

    Boost Retard: 1.0















    Attached files


  2. #2

    Default Amc 360 timing curve

    The IAC adjustment is the most important configuration of the system. Spend the time here.

    The front blade should be moving before the back but just slightly. 1/8 to 1/4" is a lot in my opinion. Perhaps MSD will chime in on that part.

    You said you turned the blades to one full turn open once the blades started to move. In my experience that is too much for most setups.

    I would start by closing the blades again, open 1/2 turn from there on both adjustments and then try to get the engine started and warmed up. It may take some throttle play to get there and chances are you will hear a bit of seeking and a loud sucking sound at times.

    Once the engine is warm, assuming it is a manual trans, start adjusting the blades equally front and rear in very small increments. Like 1/8 to 1/4 turn increments. It might feel like you are doing it too slow but methodical adjustment will get you where you need to be.

    Once you get the IAC to be steady between 10-15 things should start getting easier with the rest. As for the settings I would start here:

    A/F Targets

    Idle: 14

    Cruise: 14

    WOT: 12.8

    Nitrous: off

    Boost: 10



    Pump Squirt 20%

    Power Valve 15%



    Ignition Timing:

    Idle: 850

    Total RPM: 2500

    Idle Advance:12

    Total: 27

    Vacuum Advance: 10

    Vac Type: Ported

    Depending on how this goes, you might even try the Street cam profile. From what I see your cam could be either mild or street. pending on the other settings.

  3. #3
    primosauce Guest

    Default Amc 360 timing curve

    I tried those settings, it started up ran a little ruff. IAC was really high but I let it idle. It came down to zero. But the idle was still 1400, adjusted the blades back a bit to get the idle down 950ish. Drove it and it ran but it's really poor on the power. Feels like it lurches when you open it up and it's really holding back. What should I change at this point?

    I see some people just adjust the vacuum advance. Other people adjust Initial timing instead.

    When I look at the atomic screen that shows everything including current timing. The timing bounces all over the place sometimes. I didn't drive it more than a few miles, I don't want to run a fresh motor all out of wack. It definitely ran considerably better on regular mechanical timing with the stock springs that a pro billet comes with. And stock IAC from the factory. We didn't change any of that and it fired up and ran pretty damn good.

  4. #4
    primosauce Guest

    Default Amc 360 timing curve

    I almost feel like I should of left it alone. Adjusting the timing on the handheld doesn't respond like it does when you spin the distributor, should it respond the same?

  5. #5

    Default Amc 360 timing curve

    The first thing that I would do is to master reset the settings and get them back to default.



    I think that you should also be using the stock cam setting.



    Here are the settings that I would try:



    Engine Displacement: 367

    Number of Cylinders: 8

    Camshaft: Street

    Fuel Pump Type: PMW with regulator

    Idle RPM target: 750

    Rev limit: 5500 (not sure why you had 7000, the cam tops out at 4000 rpm)

    Timing: Enabled

    A/F Targets

    Idle 14.0

    Cruise 14.0

    WOT 12.8

    Idle RPM 850

    Total RPM 2500

    Idle Advance 8 degrees

    Total advance 30 degrees

    Vacuum advance 0

    Pump squirt 25%

    Power valve enrich 19%



    Leave the other values at default



    Start car and let it warm up to operating temp. Look at IAC cnt and try to get 15 - 20. If the IAC is low close the throttle blades, the front and rear screw 1/8 turn each. Keep repeating until you get to the desired cnt. If the cnt is high open the blades 1/8 turn each until the cnt is reached.



    Drive the car and see how it runs and let us know,






  6. #6
    primosauce Guest

    Default Amc 360 timing curve

    Ill try that tomorrow morning, should the blades be totally closed? In general I can get the IAC to zero way before I get close to my target Idle. It seems like when the IAC shows any type of number during idle, it's 500 rpm away from target idle. At that point I back the screws out until the idle gets close to my idle but it's pretty much backed all the way out at that point.





    When the atomic ships from the factory, where is the IAC adjusted too?



    I had the rev limit set to 7000 because that was default, never changed it.

  7. #7

    Default Amc 360 timing curve

    I would close both blades and then start to open each to the point that you see them to just start to open. At that point turn earn screw another 3/8 turn open and then start the car with the settings in. Let it completely warm up and then see what the IAC cnt is. Do not keep adjusting the IAC to try to get to your desired RPM. Let me know what the IAC cnt and the rpm is and we will go from there.

  8. #8

    Default Amc 360 timing curve

    Have you checked carefully for vacuum leaks? If you can back the throttle blades off, with an IAC count of zero, and the idle is still well above the target - then I would suspect a vacuum leak. Be sure to check the PCV valve too - some of the aftermarket valves are not orificed properly and they flow enough to act just like a vacuum leak at idle.



    When the units leave the factory, the blades are adjusted such that the IAC count is in the 15-20 range on a bone-stock, 1997-vintage LS1 (346 CID, 15-17 in-Hg at 700 RPM commanded idle).



    In order to set the blades properly, you must start with them too far open, and then start closing them equally - usually 1/8-turn at a time. If you start with the blades too far closed, and try to open them incrementally, the throttle follower algorithm will cause the IAC count to continually increase as it sees the TPS percentage increasing.



    I agree with others that have offered suggestions - starting one full turn open on both screws is probably too much for your application. Instead, try starting 3/4 turn open on both. Yes - the engine speed will be much higher than the commanded idle at first, but as you start to close the blades, the RPM should come down as well.



    Again - this assuming there are no vacuum leaks.

  9. #9
    primosauce Guest

    Default Amc 360 timing curve

    Ok, so I started completely over and wanted to make sure there wasn't any vacuum leaks and check that PCV valve as you fellas had suggested. Yes there was a vacuum leak. The Mainfold Vacuum to the large port on the front of the throttle body comes from the PCV valve behind the throttle body. It was very lose, almost completely disconnected. I fixed that, made sure it was tight.

    Made sure my distributor was still locked at 15* btdc with my timing light when the timing was locked, it was dead on.

    Reset everything to defaults.

    Loaded the following

    displacement 367

    stock cam

    non pmw with return

    idle rpm target 650

    A/F Targets

    Idle: 14

    Cruise: 14

    WOT: 12.8

    Nitrous: off

    Boost: 11.9



    Pump Squirt 25%

    Power Valve 19%



    Ignition Timing:

    Idle:775

    Total RPM:2500

    Idle Advance:8

    Total: 34

    Vacuum Advance:0.0

    Vac Type: Ported

    Nitrous: Off

    Boost Retard: 1.0

    IAC count shows zero unless you rev it

    Idle was still high, backed it down little bits at a time, bout an 1/8th turn until the ilde got to around 850

    What I noticed is the msd wants to retard the timing back to 2 degrees to lower the idle, once you give it any gas it jumps up to 13 or 14, left off right back down to 2

    It will idle there but it's not supper happy, seems like it's pretty lumpy and shacky. It really runs super smooth at about 1500, better than since I started this process. It takes off pretty good, drives fairly well but it dosen't have the power it used to. At 3500 it would really pull hard, now its kinda meh.

    Where should I go from here? Should the timing be so retarded at idle? When you left off the gas it tries to idle for a sec at 8 then dumps it to 2. It also back fires a bit sometimes.

    When I turn the key, is see a couple things that stick out to me.

    IAC position 65

    Ign timing 2deg

    Map 29.7

    any suggestions?


  10. #10
    primosauce Guest

    Default Amc 360 timing curve

    I also checked all around the Tb and manifold for any air leak with some starting fluid, nothing found besides the initial one at the pcv.

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