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Thread: Newbie with 307 Questions?
          
   
   

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  1. #17
    techinspector1's Avatar
    techinspector1 is offline CHR Member Visit my Photo Gallery
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    May 2003
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    Zephyrhills, Florida, USA
    Car Year, Make, Model: '32 Henway
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    I'm gonna put the whole thing together and run a DynoSim on it, but I'm waiting for a reply from Northern Auto Parts to tell me what the compression height of their Sterling (Federal Mogul???) part #235NP pistons is. Not that you're going to change pistons, but while I'm doing it, I want to start a new thread on a cheapo 307 build using 283 pistons and 400 rods. 307 pistons are hard to find anymore, but there are still 283 pistons available from several sources and they'll work with the 5.565" rods in a 307. I just need to get the compression height nailed down so I know what to say in the thread about block deck height and gasket thickness. If anyone knows this CH info, please post it. I want to use a flat-top piston so I can create a good squish. I hate those fosdick stock Chevy pistons with the hollowed-out crowns.

    For now, I will say that the 305 heads look like a good bet for a budget build. I found some information on the 416 heads while surfing and will pass it on. Chambers are 58cc's, valves are 1.84"/1.50" and stock flow numbers are as follows:
    0.050" 31 15
    0.100 63 37
    0.150 92 61
    0.200 116 78
    0.250 134 92
    0.300 157 101
    0.350 170 105
    0.400 182 107
    0.450 189 109
    0.500 195 110
    The 601 heads may be close to the same. I don't know since I found no flow figures on them.

    Having looked at flow numbers on a multitude of different cylinder heads until I'm blue in the face, I would say that these numbers look very realistic. I'll use them on the DynoSim pull.

    It has been said that these are thin wall castings, so you probably don't want to go nuts hogging them out or cutting for larger valves if you don't have to. Personally, I agree with the idea that the bowl and valve seat area are where the choke points are in any cylinder head, so maybe a little work in there with cartridge rolls to smooth things out a little and call it good would be the order of the day. I wouldn't try to do any port matching at the manifold/head intersection. You'll end up with a cross-section view that looks like an Anaconda swallowed a pig. The increased volume at that point will slow flow down and may result in fuel falling out of suspension. A real good professional 5-angle valve job with a 3-angle back cut on the valves would probably be worth its weight in gold.

    Standard Abrasives has a nice little porting kit that can be used by a home hobbyist to clean up the bowls and chambers. Ideally, an air-powered or electric-powered die grinder would be used with these, but in the old days, I used a 1/4" or 3/8" drill motor to do it. It just takes longer and you have to let the drill motor cool down between grinding sessions. Standard Abrasives also sells individual cartridge rolls and such if you can't spring for the $52 price tag on the kit.
    http://standardabrasives.carshopinc....d/52221/260001

    If you find that you have to replace many valves in the boneyard heads, you might consider buying a complete set of valves with reduced stem diameter in the bowl area. They'll help the flow figures a little.

    And again, if any of you fellow or gals can help me find some readily available pistons for cheap, I'd appreciate you sharing the source. What I need is 283 flat-top pistons, 3.875" diameter with oversizes available up to 0.060" and a compression height in the area of 1.795" to 1.805". Northern Auto Parts has them in the part #235NP for $12.95 each, but I don't know the compression height yet. Thanks, Richard.
    Last edited by techinspector1; 08-25-2009 at 12:06 AM.

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