302 and 351 Heads

Discussion in 'Technical' started by Elephant, Apr 27, 2020.

  1. Elephant

    Elephant Member

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    If I were going to buy some aftermarket heads (partial to AFR) for my 306, are there any that would satisfy both my mild 306 (268h cam, Holley 600 vac secondary, Weiand Stealth) and be decent when swapped over to a 351w? My goal is to put in a 351w but that will take a while. I'm about to pull my 306 to do the RC front end and fix oil, leaks, etc. Thinking about trying to get a bit more power from the heads while I can.
     
  2. Krazy Comet

    Krazy Comet Tom Supporting Member

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    You may want to watch this.

    Engine masters produced only 14 HP less using the small 165 AFR head vs the 195 head on a 410 cu in Windsor.

     
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  3. Hotrock

    Hotrock Rick, an MCCI Member Supporting Member

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    Krazy Comet's video really reflects the capabilities of small AFR 165 heads.

    If you are absolutely sure you will be switching to a 351W I would go with the AFR 185s. The 185s have the same exhaust side runners as the AFR 165s with larger intake runners. Therefore, the same headers fit both heads.

    Just a special note, the AFR 185s have larger intake valves than the AFR 165s and therefore would requires special pistons for both the 302 or 351.

    As for me, I went from a 351W with no shock tower modifications to a 302 roller with AFR 165 heads for my street/strip Comet. It all depends on the planned use of your car. If I were to make a step up it would be a 331 or 347 stroker with my set of AFR 165 heads. For now I like my hot little 302 street car!
     
    Last edited: Apr 28, 2020
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  4. bmcdaniel

    bmcdaniel Senile Member

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    Yep, the AFR 185 Renegades work great in both applications. Run a cam with valve events tailored to a 302 for now and when you go 347 or 351 adjust the cam accordingly and slap on the the 185's. I would also step up the carb at that time, but that's just me. Don't want to start the pi$$ing contest about carbs at this point.
     
  5. Elephant

    Elephant Member

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    Great information, y'all. I watched that video and it was indeed useful. I agree that 185s seem the way to go with my end goal being a decent 351w build. I don't intend to go to any tracks I just want a fun street weekend cruiser, one with more power than my current setup. I'm wondering if my Comp 268h is going to be a bad match for those 285s?

    And yes, carb will be upgraded with the 351w. I won't be bringing that over. I don't have much motivation to change it out now, however, unless I can get one that again works in both situations.
     
  6. bmcdaniel

    bmcdaniel Senile Member

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    If you use a roller cam block the go to off-the-shelf cam for a 347/351 is the Comp XE274HR.
     
  7. Elephant

    Elephant Member

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    I will for the 351. My 302 is a non roller.
     
  8. baddad457

    baddad457 Member

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    Another thing to pay attention to is chamber volume. On a 302, you'd want 58 cc chambers, on a 351, 64 cc chambers are acceptable.
     
  9. Krazy Comet

    Krazy Comet Tom Supporting Member

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    Here's a intake shootout using the 165 cc heads(same set in prev vid link) on stock bore/stroke 351. Cam XR282.

    351intakeshootout.JPG
     
  10. bmcdaniel

    bmcdaniel Senile Member

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    I remember Joe Sherman saying that when he was at Edelbrock they developed the Performer RPM to replace the old F4B. Said the RPM was worth about 20 hp more and almost as much torque over the F4B.
     
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  11. RMiller

    RMiller My name is Rick

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    Those numbers don't tell the whole story, the RPM was stronger by a good bit in the mid range compared to all the others. That info is from Engine Masters on Motortrend, probably one of my favorite shows to watch!
     

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