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stock 345 head flow figures

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  • stock 345 head flow figures

    Hey guys, here's some information that will hopefully please some of the curiousity out there. I just got the flow figures for a stock 345 emissions head. The head was set up for a 4.155" bore (+.030 over 392), so the results will vary slightly for you 345 guys. But I did talk to the guy running the flowbench and he said that the smaller bore would only marginally sway the numbers, and that most of the differences would be on lifts over .300". There was no porting or fancy valve grinding done to this head what so ever. It had factory valves, with stock spec 45 degree seats. All the figures list are at 28" of H2O.


    lift CFM
    .100 68.8
    .200 114.1
    .300 157.4
    .400 178.2
    .500 185.3
    .550 187.5
    .600 191.9
    .650 193.3


    lift CFM
    .100 48.8
    .200 82.3
    .300 104.1
    .400 120.3
    .500 129.8
    .550 133.6
    .600 136.8
    .650 139.0

    Also if you're curious as to how these measure up to some of the stock high performance Chevy heads, I compared the numbers with a stock 292 (doublehump) Chevy head that the same guy had flowed. The intake on the IH head was roughly 10-15% less across the board, while the exhaust had an interesting mix. On lower lifts less than .200" the Chevy head flow noticeably more, at .300" they were about equal, and above that the IH head flowed increasingly more than the 292 as the lifts increased.
    I am also in the works of either finding someone to port these 345 heads, or possibly maybe doing it myself later this winter, or early spring. And I'll be back here to post the results (hopefully good ones). I'll be looking into increasing valve sizes, port volumes, and reshaping combustion chambers. And if the place with the flowbench lets me, I'll get new flow numbers with each major mod done to the heads to see what the best route to go is.