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Thread: 302 AFR/Timing

  1. #1

    Default 302 AFR/Timing

    I'm about to set the base files in my ECU, so I can fire up the engine shortly, and wanted to bounce some thoughts across before I make the settings. The engine in question is a roller 302 in a '65 Mustang. It's a block out of a Mercury Mountaineer, Trick Flow TW170 heads and a camshaft with these specs: Duration at .050" 221° int./225° exh, Lift .499"/.510", 112° LSA, . The compression is somewhere around stock about 10:1. So here's where I'm having internal debate.

    Timing:
    Currently my timing at idle is set at 12. However, I have a vacuum distributor, so I'm having mental blocks on how to set this with the timing being controlled by the Holley Dual Sync distributor. Do I still set it at 12° as I always have, or should I compensate for the vacuum effect that my old distributor had and use a higher setting?
    My overall timing has always been right around 36° and that gave me the best numbers on the dyno, right around 385 RWHP at that setting. So the system has a WOT and a cruise timing. When I set my timing I have it all in (36°) at 2500 RPM, so should I set both my cruise and my WOT to 36°? I guess I'm a little lost on the cruise setting and what effect it has. I suspect it's more for the way the current setup has a vacuum effect while cruising around and no vacuum at WOT, but I'm not sure the best way forward to account for that in my settings.

    AFR:
    Idle AFR - I was thinking 14.7.
    Cruise AFR - I was thinking 14.5.
    WOT AFR - I was thinking 13.0.

    Thoughts? Thanks in advance, appreciate your time!

  2. #2
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    Quote Originally Posted by sr1032 View Post
    Timing:
    Currently my timing at idle is set at 12. However, I have a vacuum distributor, so I'm having mental blocks on how to set this with the timing being controlled by the Holley Dual Sync distributor. Do I still set it at 12° as I always have, or should I compensate for the vacuum effect that my old distributor had and use a higher setting?
    Yes, the EFI idle timing is vacuum advance included. So your idle timing should be about 20°.

    I suspect it's more for the way the current setup has a vacuum effect while cruising around and no vacuum at WOT,...
    Yes.

    ...but I'm not sure the best way forward to account for that in my settings.
    Download the Holley EFI software (LINK), and look at the Base Timing Tables.

    AFR:
    Idle AFR - I was thinking 14.7.
    Cruise AFR - I was thinking 14.5.
    WOT AFR - I was thinking 13.0.
    http://documents.holley.com/199r10653rev10.pdf (Holley Terminator EFI Manual - "Target AFR", Page 22)
    http://documents.holley.com/199r11031r.pdf (Holley Sniper EFI Instruction Manual - Target AFR @ Idle, Cruise & WOT, Page 25)
    http://documents.holley.com/199r10485rev1.pdf (Holley 534-201 Stand-Alone Wideband O2 Sensor Kit - Suggested Air/Fuel Ratios, Page 6)

    AFR: I idle @ 14.2 AFR, cruise @ 16.0 AFR, WOT @ 12.6/12.8 AFR.
    Timing: I idle @ 22°, cruise @ 40° (2700 RPM), WOT @ 35° BTDC.
    http://forums.holley.com/showthread....0449#post30449 (Air/Fuel Ratio & Ignition Timing Articles)
    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

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    Quote Originally Posted by Danny Cabral View Post
    AFR: I idle @ 14.2 AFR, cruise @ 16.0 AFR, WOT @ 12.6/12.8 AFR.
    Timing: I idle @ 22°, cruise @ 40° (2700 RPM), WOT @ 35° BTDC.
    I found a site that actually has my exact engine build, minus some peripherals, that run the EEC-IV/V as well as other EFI systems. They recommend I go with 35°/36° WOT as my current distributor loves, but they call for 45°-48° cruise. I live in California, so they say take a couple degrees out simply due to the gas here. So I think I'll start with 12° idle until I'm comfortable that going higher won't affect anything. I'll go with 36° WOT & 45° cruise. As for AFR, I think I'll go with your 14.2 idle to be safe, 12.8 WOT, but probably stick with 14.6/14.7 for cruise. I'm curious though, being as lean as 16 AFR, you never notice any power loss, ping, or running hotter?

  4. #4
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    Quote Originally Posted by sr1032 View Post
    So I think I'll start with 12° idle until I'm comfortable that going higher won't affect anything.
    Ignition timing is your responsibility, but your engine will most likely idle better with a little more than 12°. (Initial timing + vacuum advance = idle timing.)

    I'll go with 36° WOT & 45° cruise.
    http://forums.holley.com/showthread....3420#post83420 (Related Forum Thread)

    I'm curious though, being as lean as 16 AFR, you never notice any power loss, ping, or running hotter?
    If I did, I simply wouldn't continue with 16.0:1 cruise AFR. It's been great.
    Read page 6 of this Edelbrock EFI tuning manual:
    http://www.edelbrock.com/automotive/...ers-manual.pdf
    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

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