My 1985 HO motor has a non HO firing order?

Discussion in 'Technical' started by garrettmuir1227, May 6, 2014.

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  1. garrettmuir1227

    garrettmuir1227 (Almost) Certified to Work on Your Porsche

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    So i just spent the day trying to fire up my 74 comet, which has a 1985 HO 302 in it. It kept backfiring so i figured timing was off. I kept moving the distributor around and got nowhere. So my auto teacher suggested i try the other non HO firing order, just to hit all the bases. So i figured okay i guess, an i swapped the wires around. And boom it fired up almost immediatly. What the h**l happened?? Lol i was astonished because it is definitly an HO block, not one that was made into a roller. So what coulda caused this weird firing order to happen?
     
    garrettmuir1227, May 6, 2014
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  2. Krazy Comet

    Krazy Comet Tom

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    Cam determines the firing order, not block...

    Either it's had the cam swapped or isn't a HO... The exception would be '85 automatic HO, those are non-roller and use the std 15426378 firing order...
     
    Krazy Comet, May 6, 2014
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  3. garrettmuir1227

    garrettmuir1227 (Almost) Certified to Work on Your Porsche

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    Seems like you hit the nail on the head. It is both an 85 motor and a preformer rpm cam. Maybe i have the weirdo HO haha
     
    garrettmuir1227, May 6, 2014
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  4. garrettmuir1227

    garrettmuir1227 (Almost) Certified to Work on Your Porsche

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    But it is factory roller. I know that for a fact
     
    garrettmuir1227, May 6, 2014
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  5. 71gold

    71gold Frank Cooper Supporting Member

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    what brings you to that conclusion...:huh:
     
    71gold, May 7, 2014
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  6. baddad457

    baddad457 Member

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    The RPM cam determined the firing order, not the block. There's no such thing as an HO roller block. All the 5.0's made after 1885 were roller blocks, this includes ALL 5.0's made, not just the Mustang motors. The 86-91 pickups and vans had roller blocks equipped with flat tappet cams as did the 85 Stang's with the HO motor backed by an automatic transmission. In 85, only the manual transmission Stangs had the roller cam. The 86-91 Crown Vic/Towncar/Marquis 5.0's all had roller cams, but with the older firing order. This cam was also used in the pickups and vans in 92-93. The 94-97 pickups and vans got a different roller cam which used the 351W firing order, this cam was later used in the Explorer/Mountaineer 5.0
     
    baddad457, May 7, 2014
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  7. Krazy Comet

    Krazy Comet Tom

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    Weirdo?? No such thing, cam & cam alone determines firing order... If it's been swapped then the replacement has the std firing order, no big deal... Isn't anything magical about which firing order is used, though the HO produces a different sounding exhaust note...

    Contrary to what seems to be the popular belief, there is so special HO roller block, a roller block is a roller block... Whether it's orig from Stang, LSC Lincoln, F-150 or grandma's Grand Marquis makes ZERO difference... Pistons will be different in some of the engines I mentioned but blocks are all the same...
     
    Krazy Comet, May 7, 2014
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  8. garrettmuir1227

    garrettmuir1227 (Almost) Certified to Work on Your Porsche

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    okay so basically since its an 85 its possible that the car came with the std. firing order? or its possible that the cam i installed has the std. firing order? or maybe both? interesting, i always thought if it was an HO it would have HO firing order.. i guess thats not always the case. oh well lol whatever the case is its a roller now :thumbs2::huh:
     
    garrettmuir1227, May 7, 2014
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  9. 14yearold

    14yearold Banned

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    I believe that's the 351 w firing order we were gonna swap our 91 thunderbird 5.0 ho to a 351w because it wouldn't effect the computer
     
    14yearold, May 7, 2014
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  10. Krazy Comet

    Krazy Comet Tom

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    Yup, all 351 whether Windsor or Cleveland have always used the 13726548 firing order, no exceptions (unless someone swapped cams)... For whatever reason Ford went with the 351 order on roller 5.0 HO engines, I believe all the '82-'84 HO and '85 automatic mentioned used the std 15426378 firing order...

    Only 5.0 Birds to use the 351 firing order were the '91-93 with HO 5.0, the '86-'88 used the Lo Po 5.0 same as in Crown Vic & Grand Marquis... The '89-'90 T-Birds didn't have a V-8 option...
     
    Krazy Comet, May 7, 2014
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  11. 14yearold

    14yearold Banned

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    that's what I thought we would have one bad tbird right now
     
    14yearold, May 7, 2014
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  12. baddad457

    baddad457 Member

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    Just because it's a roller block does NOT mean it was an HO 5.0. Apparently you're not comprehending what we've been telling you here. There were many more non HO roller blocked 302/5.0's than there were HO motors. EVERY 302/5.0 (whatever you want to call it, same difference) made from 1986-on used a roller block, no matter what vehicle it was installed in at the factory.
     
    baddad457, May 7, 2014
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  13. RMiller

    RMiller My name is Rick

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    I didn't think the Performer RPM cam was available in anything other than a flat tappet configuration. The fact that you had to use the non-HO firing order supports that too.
     
    RMiller, May 7, 2014
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  14. Blue Brick

    Blue Brick Member

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    Nope. All 82 and later 5.0 HO use 351 FO including the 84-85 CFI HO. SO 5.0's use the 302 FO.
     
    Last edited: May 7, 2014
    Blue Brick, May 7, 2014
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  15. jasonwthompson

    jasonwthompson Member

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    Ford changed the firing order on the 351 to supposedly reduce stress on the crank.
     
    jasonwthompson, May 8, 2014
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