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  1. #1
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    Default 202/3.3 black motor head

    Just finished this head for (believe it or not) a rally car, came up pretty good & I thought some of you 6 banger guys may like a looksee:

    Flow figures:

    Intake:

    lift - flow
    .1 - 56.9
    .2 - 106.8
    .3 - 145.4 - 224hp
    .4 - 178.1 - 275hp
    .5 - 189.4 - 292hp
    .55 - 193.2 - 298hp
    .6 - 197 - 304hp
    .65 - 198.5 - 306hp

    intake with manifold

    .1 - 56.5
    .2 - 104.4
    .3 - 140.8 - 217hp
    .4 - 165.5 - 255hp
    .5 - 174.7 - 269hp
    .55 - 178.1 - 275hp
    .6 - 180.6 - 278hp
    .65 - 183 - 282hp

    Exhaust
    .1 - 47.8
    .2 - 95.4
    .3 - 130
    .4 - 145.2
    .5 - 154.4
    .55 - 158.4
    .6 - 161.2
    .65 - 163

    in/ex ratio

    .1 - 84%
    .2 - 89.3
    .3 - 89.4
    .4 - 81.5
    .5 - 81.5
    .55 - 82
    .6 - 81.8
    .65 - 82.1





















  2. #2
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    Default


  3. #3
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    Cool !

    TK , have u thought about milling the throttle shaft and reducing the butterfly thickness to regain some of the lost cfm its worked on carbs maybe a consideration .

  4. #4
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    Throttle shafts are on the agenda - ran out of time before I had to go do other sh|t.

    Probably 4-5cfm with shafts thinned & screws trimmed, throttle blades will stay as is.

    Ideally I'd go for 46mm throttle blades rather than the 44mm it has now - but there is a budget on this thing & it'll make enough steam for now, customer is only chasing 'anything over 200hp, gotta be flexible coz I'm gonna end up in the wrong gear on a corner pretty regular'.

    I reckon it'll do that standing on it's head, down the track if he decides to chase some more power 46mm throttle blades will see a good gain.

  5. #5
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    TK - It's been a while seen I have had a good look at a black 6 head - but my first thought was that those ports look pretty bloody big - look like they have had a decent bit of work.

    As per usual - nice work on the porting.

    Nice manifold too!

    Love to hear this gal on song! Reckon she might come alive in the upper rpm.

  6. #6
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    What comp and cam is he using?

  7. #7
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    The ports are pretty big for a black head - she's close on maxxed out.
    You have to push them, even at the size I have the ports now it'll go into choke at around 7000rpm or a bit over!
    The head is the biggest limiting factor for these things, fortunately in this instance power above 6500rpm is not required, a strong torque curve with peak power around 6000rpm was the ask & the head is capable of doing that without getting funky.

    Something interesting that showed up on the flow bench that I sort of planned:

    At .650" lift with no intake the port started to go turbulent - due to the way I set up the short turns, I did not lay them back as much as I would for a high lift head, they are set up to flow as much in the .300"-.500" range as possible, sacrificing high lift flow for average flow where it is needed most. As a result at lift about .100" above what the engine will see the airflow over the turns started to seperate.

    Kinda expected, but the cool bit is what happened with the intake bolted on - I left a step on the floor of the intake, the port has a dead spot on the floor at the head face so I left the step to keep CSA through the intake runner in tune with the MCSA at the pinch of the port & just let the airflow skip over the dead area.

    As a result of the airflow not using the floor of the port as heavily & having a better approach to the short turn with the intake on the airflow remained stable past .700" lift.

    All in all I'm pretty dang pleased with this head.

    Motor will run 10.5:1 comp - in rally use fuel supply can be an issues & sometimes it'll need to use pump 95 rather than 98. Combine that with heat soak from 30+ minute sections under race conditions & the very real possibility of having to lug from low rpm in the wrong gear I figured it was better to give a bigger than normal safety margin.

    Cam will be in the mid/high 240's, probably on 106 lobe centres, still nutting out exactly what will work best.

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