Q&A

Mailbag: Why Did Ford Change the Firing Order on the 5.0L 302 H.O. Engine?

Ford 5.0L HO

(Image/forums.nasioc.com – B6lovin)

Q: I’m building a Ford 302 engine, and I’m looking at camshafts. I’m curious—why did Ford change the firing order on the 5.0L (302) HO engine?

A: This question gets a lot of mileage on internet forums, and there’s no shortage of speculation on the subject.

According to Ford Motor Co. engineers, the 5.0L H.O. adopted the 351W firing order (1-3-7-2-6-5-4-8) to improve the intake manifold sound quality. Ford’s 5.0L H.O. has a distinct sound that benefits greatly from the addition of a cold air intake system and a pair of chambered mufflers.

Check out the V8 firing order chart and see how the 302 and 5.0L H.O. (listed below as the “5.0L EFI”) compare.

Common Engine Firing Orders

This is another in a series of weekly Q&A Mailbag sessions with Summit Racing‘s tech department, in which there are hundreds more. Click here to see them all.

 

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18 Comments

  1. Okay…let’s go back in time a bit and ask “Why did Ford change its long-established V8 firing order with the introduction of the 351W in ’69? It certainly WASN’T for “intake manifold sound quality”. The 385-series, which predates the 351W retains the “old” firing order while the 335-series, the HO and the Modular use the “new” firing order. Seems like there has to be ANOTHER reason….

    • Alan Hardman says:

      I have a theory that the change in firing order is responsible for the great numbers of 5.0l blocks breaking crankshafts at the second main, probably the single greatest cause of catastrophic failure of these engines when pushed past 500hp, including severe splitting of cylinder blocks.

      • Fat Ford Man says:

        And the NON H.O. pattern would spit front main at 300hp levels… And it doesn’t help the 5.0 has puny mains… Yet 351s live at 700hp all day with the H.O. pattern they were develped with in 1968 (for 69 year)

  2. It’s an upgrade, keeping cylinders 7 and 8 from firing consecutively. Also they had a windsor camshaft that had the specs they wanted, so to save money.

  3. Terry Zeissler says:

    The revised firing order was needed to prevent inductive crossfire burning a hole through the center of number four piston. This would happen under load if the spark plug wires were not routed correctly on the right bank. I had to deny warranty on many 302 engines that we remanufactured for this reason. Not a problem with the 351W no matter where you ran the plug wires.

    Terry Zeissler
    Technical Services Manager (Retired)
    Optimax Engine Reman (A NAPA Company)

  4. Pingback: Mailbag: Breathing Life Into a Wheelchair-Friendly 5.0L-Powered Ford E-150 Econoline - OnAllCylinders

  5. I have a 427 cu. inch DART block in my ‘88 Foxbody Mustang. The motor is a clone of the 351W. The firing order that I see around the rotation pattern of distributer is 1-2-6-3-7-5-4-8. Could someone out there let me know if I’m seeing “things”. (I don’t drink or do drugs) lol. My email address is mikekurki@gmail.com

    • Alan Hardman says:

      You’re reading the distributor clockwise – it rotates counter- (or anti-, if you’re from across the pond) clockwise, as do all Ford V8s from the 1954 Y-blocks through the FEs, MELs, Super Duty, 90° series (small block), Cleveland, 335-series, and 385-series to the last distributor-equipped v-8s produced.

  6. Terry Davis says:

    I have a 5.0 efi from an ’86 LTD crown vic. Is this considered an HO engine? which firing order? Can’t find compatable wiring harness for installing in old coupe

  7. What is the original firing order for
    Fox body 302’s?

  8. If you think for a second the crank determines the firing order of a motor. The pistons must be in the rite place or it wouldn’t work. So the only way you can change firing order is changing the crank. All you do for a cam is advance or retard your timing AKA spin the distributor. So when ford changed the firing order they changed the crank

    • Buddy, the intake has to open at a certain point. The crank doesn’t open the valve, the cam does. If you changed the crank you would open the chamber as the piston came up. That’s dumb. Get your retarted ass off of here please.

      • I’ve got nothing to add, I’m just posting so that we have a folk trio in the comments

      • Wouldn’t Both the crank and the camshaft have to be cut for a certain firing order?? So that the piston is in the right place at the right time and the valves are opening and closing at the right time relative to the position of that piston?

  9. I too, have a theory–not a very good one, but here it is regardless–the 1982-1984 302 H.O. camshaft is the same as the 1973 Ford Torino/Elite 351w camshaft, part number D3OE-6250-AA.
    The 1985 Mustang with AOD and CFI also used this cam.

    Can we at least presume that it might have been more economical or logistical for Ford to create castings for revised crank pin indexes to match the 351w’s than it would have been for Ford to create a new camshaft for the “normal” 302 firing order that would be analogous to the D3OE-6250-AA’s timing?

    I’ll get to the bottom of this. A friend of a friend is a retired Ford engineer.

    • “Crank pin location”, “crank pin index”
      NOPE
      Same crank can use either cam. As Paul said above, the cam allows the air movement that the piston movement creates. In short- change the cam-change the firing order. You will notice that the GM firing order (18436572) matches the Ford firing order when you number the cylinders as GM does.
      The LS series GM firing order matches the 351/302HO firing order when cyls are renumbered.
      The clocking of the crank is the same.
      Cam grinders will make the cam firing order for a GM (18436572),(18736542)[called 4/7 swap], or (18726543) [4/7-2/3 swap), all for the same crank.

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