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Thread: 305 AFR too small for 509cid?

  1. #1

    305 AFR too small for 509cid?

    I could get a quite good deal out of 305 AFR heads. They are with CNC bowl blend and chambers option and with 2.25/1.88 valves. My bracket race only engine is 509cid Gen V BBC (4.5x4.0), 272/278 @ 0.050 cam with .700lift. I will keep the engine below 7200rpm. Compression is about 12.4:1.

    Question: How much horsepower am I leaving to the table comparing to 325 or 345 AFR:s with CNC bowl blend and chamers option? The 325/345 are the same, only intake runner is bigger and with 2.300 valves and I read that the exhaust valve is better flowing too on the 325/345 heads.

    I will not pay about 700$ more for the full CNC 315/335/357 heads. I think best bang for the buck is the CNC bowl blend and chambers options.

  2. #2
    Senior Member EXPERT BUILDER
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    GUESSING YOUR OPERATING RANGE IS 4500-7200 ID THINK THAT HEAD IS A TAD SMALL BUT NOT HORRIBLE.

    IF YOUR CAR IS OVER 3000 LBS ID LEAN TWARDS THESE HEADS IF LESS LIKE ALTERED OR RED ID CONSIDER A LITTLE BIGGER

  3. #3
    Administrator RACING JUNKIE bjuice's Avatar
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    i would not be so concerned with the 2.25 vs 2.30 intake valve as i would the runners being so much smaller.

    you can get that 2.25 head flowing much better with some runner work.

    Plus the 2.25 head will more then likely give you more bottom end than the 2.30 valve........in a heavier car you need this extra TQ if your running 1/8 mile.

    i have said this more than once."i had rather have a Quick car then a fast car". but again all i run is the 1/8 mile. and its all in the 60ft.....1/4 mile is a different animal

    so bascially i personally would much rather have a car making 50 more ft lbs of Torque then 50 more hp.
    Bjuice..

    "I'M YOUR HUCKLEBERRY ! "

  4. #4
    Senior Member RACING JUNKIE
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    I agree with bjuice..but I went from a stock factory square port head with 2.19 valves to a -2x brodix(340 cc runers and 2.30 valve) and actually improved in the 60'. went from 1.35-1.36 down to a 1.31-1.32 and picked up 2-3 tenths in the eighth. That was with a 540 inch motor so it was under-headed with the 2.19 factory head...not sure what the runner volume is on those I have been told around 290-300

  5. #5
    Senior Member SENIOR BUILDER
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    I ran the 305s on a 588 ci, and went to a 357 cnc, the engine had more comp with the 357 head and the new combo only made about 50 hp more. If I had to do it again,,I think I would go with the 315 head,,,or I guess what you have. the 305 cnc,,which is I think the 315 !

  6. #6
    No,

    305 with cnc chambers and bowl blend is different from 315 full-cnc ported head.

    The car weights about 2400lbs, glide and 4.33.1 gears, full 1/4 mile bracket racing so a lot of mph is a big plus.

    The 325 with CNC chambers & bowl blend is only 318cc actually when measured: http://www.airflowresearch.com/artic...le131/A-P2.htm

  7. #7
    Senior Member SENIOR BUILDER
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    yes, I see you are right, never the less. I did only gain about 50 hp going from the stock 305s to the much larger 357s, and I was running about the same dynamic compression on both combos, my engine has more cubes, but you ( I think may have more dynamic ) compression, my opinion would still be the 315 full cnc. I think you would get more velousity.

  8. #8
    Administrator RACING JUNKIE bjuice's Avatar
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    one thing you have to keep in mind that someone brought up on another thread....Hp on paper is just that...you never know how your combo will react to certain heads...it could run like a bat out of hell with those 305's..could go to the 350+ and slow down...combo's are funny..many variables determine this outside of head size.

    i am with superstreeter..my motor builder PAR said by going with the bb4x oval port head with the 2.357 valves with well over a 400 flow would pick me up approx 50 hp over my bb2x heads..... all for the low price of $4,000.......hmmmmm lets see 50hp vs 4,000 hard earned bucks (nowdays)

    i stayed with my set up !..you couldn't feel 50hp in your pedal or your a$$. and probably couldn't see much difference on the board either.

    i gues what i am trying to say is do not get caught up in the hype of what this stuff says on paper...ITS NOT REALITY.


    Brian
    Bjuice..

    "I'M YOUR HUCKLEBERRY ! "

  9. #9
    Senior Member EXPERT BUILDER
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    bottom line i believe is your vehicle is light your application is full on drag.this is all pointing to let those heads breathe (i say go a lil big)and rev her up and let er go!!! my vote goes twards the 325 or even consider the 335 if you wound it up more than 7000 rpms eh...just my opinion

  10. #10
    Junior Member APPRENTICE
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    afr 335 cnc heads

    I HAVE A PAIR OF AFR 335 CNC HEADS FOR SALE, COMES WITH ROLLER ROCKERS AND STUD GIRDLES $2000

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