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Thread: Cam Help Please

  1. #1

    Default Cam Help Please

    I'm building a 427 BBC on a Gen 6 platform. I already have the HP injection system. I thought I had a cam, but I'm putting the engine together today and I opened the box, and it wasn't a step nosed Gen 6 like I ordered and have the rest of the parts for. So I need another cam pronto. I had originally ordered the cam for a Edelbrock system and they specified a 110°-112° LSA, but they weren't able to provide the injection system as promised. Does the Holley HP EFI system care what LSA I use? Edelbrock seemed to be pretty particular about it. Building this one at 11:1 with AFR 265 for street work and reasonable gas mileage with a Richmond 5 speed .77 O/D & 4.10s in a 3500 lb car.
    Last edited by MK Ultra; 01-19-2019 at 07:52 PM.

  2. #2
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    Default

    Quote Originally Posted by MK Ultra View Post
    Does the Holley HP EFI system care what LSA I use?
    Not necessarily, but the engine may idle better with a wide LSA (idle vacuum & idle quality is increased).
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & MT 245/45R17 tires.

  3. #3

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    All EFI systems like a wider LSA. 112-114° is a good start. Your idle vacuum goes up, the idle is smoother, the torque curve flattens out, and mileage improves. The only reason to choose a low LSA is if you want a lopey idle. The HP EFI can handle either one.

  4. #4

    Default

    I've found there's a few tricks to getting engines with large cams to idle well. Cylinder-to-cylinder AFR balance is more important than the cam IMO. https://www.youtube.com/watch?v=S0XLbI-Brn4

    Here's a pretty big cam (279°/285° with 108° LSA), but it idles nice because the intake manifold and injectors are all well balanced. Look at how stable AFR is (Closed Loop is ON). Spending a bit more time on it with the proper TB I could get it better.

  5. #5

    Default

    Having the ECU control the ignition timing helps a lot with a big cam. Adding timing at idle will help smooth out a big cam, and it's much easier to change timing curves in a table than it is with a distributor.

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