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Changing Intake ports to a D shape for better flow.

Discussion in 'The Garage' started by Jack, Sep 13, 2019.

  1. Jack

    Jack XS650 Junkie

    I'm retired this year and now that I'm have some spare time I need to start working on my D port intakes.
    I have two options here,one is to use JB weld to build up the floor which will be anchored with a T-bolt system along with either aluminum mesh or fiber and I've used this in the past but my only concern would be near the short turn where anchoring isn't visible and lifting of the JB weld might be an issue.

    Second option using a flat plate of aluminum .125 that'll be anchored by three radius head bolts threaded from port to bottom of head and locked in place with green sleeve retainer. My question is what grade of
    aluminum should I use for the floor and can I use 5356 mig wire to seal the edges of the plate. Using a tig is out of the question there just no room and I can't use 4032 cuz my mig as no teflon liner, those birds nest can be a pain to unravel. Any input would be highly appreciated.
  2. Signal

    Signal XS650 Junkie Top Contributor

    Not a guru.
    I did some research on welding aluminium castings though. The upshot was you want a filler with a similar silicon content to the casting.
    The rods that we used were 4047 (ALSI12) 5 to 10% silicon.
    an alternative rod is 5356 (ALMg5).
    So answer to question 2 my opinion is yes the 5356 is an acceptable filler.

    With regard to the to the floor material I would suggest using a grade of AL with 5 to 10% silicon.

    Here is a link to a website that has PDF downloads of the contents and properties of various AL alloys.

    I recently used some Lumiweld low temperature aluminium welding rod.
    It is more like solder and a flame is used to supply the heat (although a inlet port is a big ask). A large propane torch may do the job.
    Once up to temperature you can move the puddle of filler rod around with a stainless steel rod.
  3. Jack

    Jack XS650 Junkie

    Signal thanks for the input. Using aluminum brazing rods would most likely cause warping issue and a risk I don't want cuz this head I purchased
    has excellent casting with no chore shifting, just to hard to find a real good head. Silicon % of 5 to10 in flat plate aluminum isn't available from my researching
    more half or less of 1% resulting in a higher coefficient thermal expansion lift at the short turn, might be a problem effecting flow to the valve seat but I'm going
    to purchase some plates and do some testing to see how much expansion occurs.

    I've purchased two types of port reconstructive epoxys that alot of porting pros use and will put the epoxies through sonical vibration testing using two types
    air hammers:wtf: on a test head in an effort to break loose the expoy from its adhesion,so we'll see what works and what doesn't . Keep you posted and thanks again for your input. Jack
    Last edited: Sep 14, 2019
  4. Jack

    Jack XS650 Junkie

    Got some aluminum flat plate today .132 about .007 thicker but I can work that out with 36 grit rolls. New head stand built and the fun begins.

    Been out of the mainstream of posting pictures for some time now,so what are steps in posting pictures?
    Bewarethemoon and gggGary like this.
  5. Dave From Maine

    Dave From Maine XS650 Member

    Jack, not an aluminum expert but I have had the opportunity to talk with one. He said to use pure aluminum to weld any aluminum alloy so that’s what we did on cast aluminum. Stick welding with flux coated rods to reach in narrow spaces.
    That was 20+ years ago things may be different today...
    YamadudeXS650C and Bewarethemoon like this.
  6. Jack

    Jack XS650 Junkie

    xs650 d port.jpg

    Here are the D ports in the rough stage and when intake port is completely restructured ,the cross sectional area of inlet width wise can range from 34 to 36mm with a height of 31mm. These small ports pack a big punch with no ill effects in diminishing flow or velocity.

    Some might question as to why I'd go to such trouble reconstructing a perfectly good intake port that as more than proven its self in supply sufficient flow for decades with the likes of shell, lilley,etc. I simply got bored porting the stock head and wanted to venture outside the box in attempt to reduce the xs intake port volume and increase floor width at the same time opening up the corners of the short turn.

    There are two benefits in widening to flatten the floor and raising it. There are two pressure differentials in the port floor and roof, with floor being the highest and the shortest for flow to travel and roof being a low point and furthest to travel . By flattening the floor, raised and widening,flow speed is reduced in preventing flow over shooting the short turn and preventing unwanted turbulence at the valve and pocket bowel. Second,by raising the floor at the short turn gives a less erupt turn allowing the flow to take a longer path increasing it's momentum
    and giving an option of short turn radiuses biasing flow either down or up the flow curve with cam lift.

    I got the idea of D porting from rebuilding a Kohler Command engine and these engines when hot rodded can deliver upwards to a 100 plus HP at 6 plus thousand RPMs with very,very tiny D ports. It was enough to convince me to go for it and the results where an eye opener that smaller ports can deliver without compromises.

    The flat aluminum plate was a no go ,expansion and difficulties securing it put the icing on the cake. JB weld is the only alternative, it will be built up in thickness still wet with several layers of sheet rock HD tape, you can't tear this stuff it's that tuff. Put a sample in the oven
    at 375 degrees for three hours, then proceeded with air hammer sonic vibration testing for an hour and the JB weld held its adhesion with cracking.

    Keep you posted when time is available ,a lot going on with house duties and if you want port dimensions I'll record them.
    Last edited: Sep 22, 2019
  7. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    Following, How will you go about adapting that shape to the carbs?
    Mailman and Bewarethemoon like this.
  8. Bewarethemoon

    Bewarethemoon XS650 Addict XS650.com Supporter

    Also watching this thread with interest, fascinated by the processes people undergo in porting, I plan to message you soon for advice on ‘cleaning-up’ my head.

    YamadudeXS650C and gggGary like this.
  9. halfmile

    halfmile XS Builder Top Contributor XS650.com Supporter

    Those "D" ports look like the exh ports on my reworked Brodix #12`s.:thumbsup:
  10. Signal

    Signal XS650 Junkie Top Contributor

    When Jack has finished this thread can it be put in the technical section.
  11. Jack

    Jack XS650 Junkie

    the manifold will be gradually build up like a ramp to form the D with JB
    gggGary and Bewarethemoon like this.
  12. Jack

    Jack XS650 Junkie

    Without visually seeing the ports I'll help you the best I can and as you know the ports in most cases have severe casting deficiencies port to port and the valve seat machining into the bowel in some cases makes it difficult for a valve seat 3 angle cut with a stock valve, you have to accept it or install a larger valve to get the cut for flow increase. The porting pictures are floating around on this site,i'll have to find them and a few others that I have to better explain what areas should be addressed in touching up the port for better performance based on my experience. I have an inside divider tool marked in increments that I use for
    port measurements and will list the dimensions the best I can .
    gggGary likes this.
  13. Jack

    Jack XS650 Junkie

    I was experimenting with a welded up bath tub combustion chamber for my long rod and was struggling getting the flow numbers up due
    valve shrouding. So I decided to try the D port,sent the head off to be flowed and the #s picked up everywhere up to 440 lift. It'll be
    interesting to see how it flows with an open chamber.
  14. 650trader

    650trader XS650 Enthusiast

    Have you ever proven this theory on a dyno ? Seems a bit out there.
  15. Jack

    Jack XS650 Junkie

    What theory would that be? Ford pinto either came with oval or D shaped intake ports for the turbo version and Kohler engines came with D ports
    so it's not a bit far fetched out there. It's a known fact the XS ports volumes can be excessive and when you factor in the crank short stroke reducing
    intake port volume enhances performance which as been proven by some of the best Xs racing tuners. To this date I know of nothing written is stone
    which would indicate the best method in accomplishing this in reshaping the intake port. It's about reducing port volume without hindering flow and velocity
    whether by filling the round port, oval port, rectangular port and D port. What you're looking for is a gain or lose in flow and there where no loses in D shaping the port. You might wanna educate yourself on Chevy BB oval ports vs rectangular ports and you'll have better understanding why I went this route.
    The D ports were tested by Hughs Hand Built with good results and would of been better if I had shaped the floor myself but it ran and had excellent throttle response.

    Attached Files:

    Okie, TwoManyXS1Bs and gggGary like this.
  16. Jack

    Jack XS650 Junkie

    Heres a kohler command with D ports, big valves , stroker crank, roller camshaft, chevy roller rockers ,roller lifters,etc pushing some series HP.
    Scripto VU, TwoManyXS1Bs and grizld1 like this.
  17. Jack

    Jack XS650 Junkie

    Here are some flow # for stock head Vs D ported head in two stages. Just look at the gains not #s
    stock 100 lift 76 ,200 lift 118, 300 lift 162,400 lift 181, 440 lift 190
    round port with bath tub combustion chamber
    100 lift 83,200 lift 114,300 lift 137,400 lift 184,440 lift 187
    D-port floor raised 3mm with wing built in front of guide boss
    100 lift 91,200 lift 132, 300 lift 170,400 lift 185,440 lift 198
    D port with wing removed in front of guide boss
    100 lift 80,200 lift 119,300 lift 181,400 lift 201,440 lift 205
    All these D port # gains were accomplished with port volume reduction and increased port velocity.
  18. Jack

    Jack XS650 Junkie

    Here are the various ford ranger 2.3 heads,D ports are on the bottom and Ford went to this shape cuz the round ports volumes where to big effecting bottom end performance . The fix was D porting intake reducing port volume boosting port velocity without dimensioning CFM flow.

    Attached Files:

  19. grizld1

    grizld1 Grumpy old man Top Contributor

    Great stuff, Jack! BTW, no theory can be proven, only tested. It's a basic principle of formal logic: Thou shalt not affirm the antecedent.
    TwoManyXS1Bs and gggGary like this.
  20. Jack

    Jack XS650 Junkie

    Hey Griz, life is to short and I'm not getting younger to worry about paper scribbling and theories but I will always listen with open mind.
    You would'nt believe want some people in the US,Aussie and UK are do in modifying norton,bsa and triumph heads,just wish the XS had more meat
    in the head to adapt the XR750 oval port. I might attempt a junior version of that port sometime down the road, it swirls, it flows big time in race version,
    truly remarkable port with multi functions wrapped in one.
    TwoManyXS1Bs, Mailman and grizld1 like this.

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