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Thread: Timing control with GM large cap HEI.

  1. #1

    Default Timing control with GM large cap HEI.

    So I've recently installed the Sniper EFI. Things are working OK so far. I have a few minor issues that I need to address/figure out. Now I want to start using the Sniper to control my timing. Here is where I'm at so far.
    engine specs.
    350 SBC
    10:1 CR using flat top pistons.
    "RV cam" with 1.6 roller rockers = .490" lift
    Air-Gap intake.
    Long tube headers. 1 5/8" primaries. 2.5" collectors. true dual exhaust with DynoMax Super Turbo mufflers.
    Sniper EFI
    GM style coil in cap HEI
    375 HP/425 TQ.
    Used a Tanks Inc in tank fuel system, Walbro pump and sump with Russell lines. Return line goes back to the tank.
    installed in a '73 Chevy K5 Blazer built as a prerunner for the dunes/off-road.

    So I have a large cap, coil in cap HEI distributor. I have a kit to lock out the vacuum advance and mechanical advance. I have a plug adapter and know what need to do electrically to use this distributor. My questions are as follows:

    Will a 8421 adjustable rotor work in this distributor?
    If not, does anyone make an adjustable rotor for this distributor?
    If not, can I still use it without an adjustable rotor and how would I set it up as far as setting timing and delays?

    Thanks for any help. I'd like to keep this distributor as it's brand new. I built the engine and now have about 2300 miles on it. Started it with a carb, 670 Truck Avenger, but got tired of messing with it and so went EFI. Did a 2000 mile break-in run down to Baja and back with no issues.

  2. #2
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    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  3. #3

    Default

    Thanks Danny. Got some reading to do now. I try to search for that info, but guess I wasn't using the correct search words.
    '73 K5 Blazer, built 350 SBC 375 HP/425 TQ, 12" F/18" R suspension travel. Deaver springs with King shocks, D44/12 bolt, 3.73 gears, lunchbox locker F/Auburn Posi R, crossover steering, 35" BFG Mud Terrains, Vintage Air system, PRP suspension seats, lots of custom work, all built by me.

  4. #4
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
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    You're welcome.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  5. #5

    Default

    OK, read through everything in the links, including the extra links in those threads. Wiring & setting up the distributor is not an issue. I got this.
    Only part I'm not sure of, and couldn't tell in what was posted in the various links, was how to setup the timing with no adjustable rotor.
    So do I set it up at 15° advance like with a normal setup? And then make the necessary adjustments with the Sniper EFI computer? Or do I need to set up the reluctor wheel at 15° advanced using the vacuum advance and lock it down, then drop in the distributor with the rotor lined up on the cap at 0°? Basically doing what is stated in the instructions with an adjustable rotor.
    '73 K5 Blazer, built 350 SBC 375 HP/425 TQ, 12" F/18" R suspension travel. Deaver springs with King shocks, D44/12 bolt, 3.73 gears, lunchbox locker F/Auburn Posi R, crossover steering, 35" BFG Mud Terrains, Vintage Air system, PRP suspension seats, lots of custom work, all built by me.

  6. #6
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    If it has a magnetic pickup, set it up as instructed for an MSD magnetic pickup distributor. After locking out the centrifugal & vacuum advance, install the distributor in the Ignition Reference Angle position (usually between 50°-60°), synchronize the ignition timing (at idle & Inductive Delay at higher RPM), and check rotor-phasing. Adjust the Ignition Reference Angle slightly to produce the best rotor-phasing. Although the Ignition Reference Angle must be at least 10° higher than the maximum amount timing programmed in the Base Timing Table.

    The ECU needs an Ignition Reference Angle, so it can control the synchronized Base Timing Table.
    http://www.masterenginetuner.com/top...all-fails.html (Crank Reference Angle Importance)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  7. #7

    Default

    OK, thanks. Yes, it's a magnetic pickup.
    '73 K5 Blazer, built 350 SBC 375 HP/425 TQ, 12" F/18" R suspension travel. Deaver springs with King shocks, D44/12 bolt, 3.73 gears, lunchbox locker F/Auburn Posi R, crossover steering, 35" BFG Mud Terrains, Vintage Air system, PRP suspension seats, lots of custom work, all built by me.

  8. #8
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    Location
    Connecticut
    Posts
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    OK, then install it as an MSD magnetic pickup distributor (without the adjustable rotor).
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  9. #9

    Default

    OK, lets see if I'm understanding everything right.
    My advance is set at 36° at WOT. So I would want my Reference Angle set at 10° more than that, or 46°. When I install the distributor, I want it set at 46° advanced and insure the reluctor points are lined up. Then I need to check & make sure the rotor point is in the vicinity of the contact on the cap, but with enough room so that as the timing decreases to 15° at idle, it will still be in contact. That sound right?
    '73 K5 Blazer, built 350 SBC 375 HP/425 TQ, 12" F/18" R suspension travel. Deaver springs with King shocks, D44/12 bolt, 3.73 gears, lunchbox locker F/Auburn Posi R, crossover steering, 35" BFG Mud Terrains, Vintage Air system, PRP suspension seats, lots of custom work, all built by me.

  10. #10

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    Quote Originally Posted by Crusty Old Shellback View Post
    OK, lets see if I'm understanding everything right.
    My advance is set at 36° at WOT. So I would want my Reference Angle set at 10° more than that, or 46°. When I install the distributor, I want it set at 46° advanced and insure the reluctor points are lined up. Then I need to check & make sure the rotor point is in the vicinity of the contact on the cap, but with enough room so that as the timing decreases to 15° at idle, it will still be in contact. That sound right?
    Phasing & Reference Angle explained in detail by me: http://www.chevelles.com/forums/89-e...nce-angle.html
    Last edited by Dr_Grip; 12-07-2017 at 07:23 AM.

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