cam

Discussion in 'Ranchero Tech Help' started by blackcat6655, Nov 20, 2013.

  1. blackcat6655

    blackcat6655 In Second Gear

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    will a cam for a 302 work in a 351w? not a roller just a regular hyd cam.
     
  2. ribald1

    ribald1 Banned PLATINUM MEMBER

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    Yes, no, maybe.
    It will fit, firing order and balance weight would have to be changed in almost all cases.
     
  3. aquartlow

    aquartlow In Maximum Overdrive

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    I know it's been a while since dealing with a small block, but I always remember/heard you just had to change the firing order to use a 351w cam in a 302(or vice versa). I have never heard of having to change the balancer as well. Most aftermarket small block cams are based on the 302's 15426378 firing order as apposed to the 351's 13726548.
     
  4. DonC

    DonC In Maximum Overdrive SILVER MEMBER

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    I'm with you on the balancer, it would need to change if the rotating crank mass changed which it sounds like the bottom end is still a 351.
    If I remember right the HO 302's with roller have the 351 firing order. Main thing is to just wire up the firing order for the whatever the cam is.
     
  5. ribald1

    ribald1 Banned PLATINUM MEMBER

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    It is my understanding that the harmonics are different with the different firing order.
     
  6. burninbush

    burninbush In Maximum Overdrive

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  7. Rockdodger

    Rockdodger In Third Gear

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    351W cam

    I ran a '69 351W with a 302 cam/firing order for years with no problems. I think Ford changed the firing order on the 351's and later 302's to put a little less stress on the crankshaft. (e.g. cylinders 1 and 5 (which use the same crank journal) firing consecutively on the older 302/289/260/221 Windsors.) I'm pretty sure there's no difference in the harmonic balancers on Windsor engines until the balance factor was changed some time in the eighties, probably coinciding with the change in firing order for the 5.0.
     
    Last edited by a moderator: Nov 30, 2013
  8. 71ranchero72mach1

    71ranchero72mach1 In Second Gear

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    That is 100% correct.
     
  9. ribald1

    ribald1 Banned PLATINUM MEMBER

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    It does change the harmonics, but as the change in balancer used happened before the firing order change either it is not an issue or FORD was planning ahead.
     
  10. 71ranchero72mach1

    71ranchero72mach1 In Second Gear

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    They're all 28 oz balancers. The only difference between the balancers was when they changed the pulley from a 3 bolt to a 4 bolt. You can interchange back and forth both ways, so you can put a late model engine in your older (pre-70) car, and put your old 3 bolt balancer on and still have all your original accessories and pulleys line up.

    Lucas
     
  11. burninbush

    burninbush In Maximum Overdrive

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    Yes ... as nearly as I can tell, all 351w motors of any age need 28oz balance, and the dampers will interchange with 289/302 as noted above. Flexplate [or flywheel] must match 28oz.

    Ford did change to 50oz balance in the mid 1980's 302. Those obviously need a different damper and flexplate. I think you'd have to look at the crank number to tell which you have.

    Firing order has nothing to do with crank balance or damper.
     
  12. ribald1

    ribald1 Banned PLATINUM MEMBER

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    The damper changed, then the firing order changed, then the balance changed.
    Perhaps you know the reason for that?
    I don't, I can only speculate. They deal with millions of engines every year, I rarely deal with a dozen. I do know that the retooling was not cheaper than keeping things as they were and just changing the firing order.
     
  13. burninbush

    burninbush In Maximum Overdrive

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    Uhmmm .. you have the order of the changes wrong. To be clear, neither the firing order nor the damper ever changed on the 351w motor, from the day they were first built [1969?]. They were all 28oz external balance.

    No clue why Ford used a different firing order on two very similar motors.

    It was only the 302 that changed firing order and balance late in its life, why I dunno, after building them for 20 years at 28oz. Maybe Ford was just simplifying their camshaft inventory.

    The 302 damper changed to 50oz to match a new 302 crankshaft. They are interchangeable with the older cranks providing you use the matching damper and flexplate.

    I =think= it is safe to say that 50oz balance, roller cams, and EFI go together, but I know of exceptions to all of that, e.g., mid '80s 302 pickups and Broncos with batch EFI but flat cams with the old firing order.

    Look at any advert selling dampers for a 351w and you'll see it also is the correct part for a 28oz 289/302. Which is to say, motors with different firing orders using the same damper. External balance weight is based on the balance inherent in the crankshaft, has zip to do with firing order.
     
  14. DonC

    DonC In Maximum Overdrive SILVER MEMBER

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    Decent read below on why the change in balance. This makes sense of the counterweight changes in the 302, to save money is the main reason. I have heard that changing the firing order helped with exhaust scavenging and intake pulses to improve power a small amount. I know you can get a changed friing order cam for the old small block chevies, supposed to help with power and smooth out the motor too.


    Why Coast High Performance Recommends Balancing your Small Block Ford at 28oz. over 50oz.

    Although Coast High Performance has plenty of experience in balancing your rotating assemblies and builds to whatever requirements you prefer, we highly recommend choosing an external 28 ounce balance over a 50 ounce balance in Small Block Ford applications (unless you have purchased an Internal balance crankshaft).

    In the late model 5.0 builds, Ford's factories primarily utilized 50 ounce balancing. The 50oz. cranks used in these builds were designed entirely different from today's aftermarket performance crankshafts; the primary difference is in the size and material content of the counterweights. These cranks were designed to be economical, utilizing less material in the crank (notably, smaller counterweights) in order to lower manufacturing costs, as a result allowing only a 50 ounce balance.

    Today's aftermarket crankshafts were designed primarily with 28oz. balancing in mind. There is much more material in a 28oz. crank than a comparable factory 50oz. one (see photos below)--the difference being that crankshafts designed for 28oz. balancing utilize full counterweights and less end-weight for better stability, thereby improving the structural integrity, strength and performance capability of the crankshaft.

    While it is possible to balance an aftermarket crankshaft to 50oz, the amount of material that must be taken out will leave the crankshaft heavy at its ends. At high RPM use, this leaves the crank prone to flexing and stress at its center. This problem is greatly minimized using a 28oz. balance, as it keeps the integrity of the crankshaft intact since less material will have to be removed from the counterweights. Another reason why we prefer to use 28oz. balancing is because the extra holes drilled into the counterweights of a 50oz-balanced crank will cause aeration of the oil, minimizing its life and increasing engine wear over time.
     

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