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Thread: How to cut out a hole in the bonnet?

  1. #1
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    Question How to cut out a hole in the bonnet?

    Hi guys. Finally got my ITB's in and with the sausage filter on I need to make a hole in the bonnet. Being an SV it doesn't have to be accurate and surround the filter, its more to put a mesh grill in for clearer air flow. The filter does protrude a few mm's at the front but it will compress in a little with the hood on.

    What is the correct tool/method to cut a painted bonnet? Any tips appreciated.

    Adam
    Attached Images Attached Images

    2010 Roadsport SV 170

  2. #2
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    I don't have much advice for the cutting other than "take the air nibbler and go for it". But I would recommend finding a way of allowing outside cool air to the intake (and shutting off from the engine compartment). That is probably the cheapest way of gaining a few horsies. If the common rule of thumb is right, a 50 degree lower temperature taken from outside is worth about 10% gain of power. It could make your car an SV187 ;-) Well, assuming the ECU knows about it.

  3. #3
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    Power wise already a little past that, I had to get an unlocked ECU to tune with the mods I made. It was closer to the R400 spec than R300. Now hopefully somewhere between a R400 and R500..

    I want to start with the simple approach rather than fabricate an airbox etc. Getting the hole cut cleanly is the next big task!

    2010 Roadsport SV 170

  4. #4
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    Where do you live?

    Send me a PM and I will tell you how I enlarged mine and folded over a bead around the cutout, the bead makes it more rigid around the cutout but I don't think the paint will do well. Mine is unpainted. If you don't want the bead some use a strip of rubber edging around the hole. I don't know where to get the edging material. Maybe Caterham?

    If you are going to use the bead, just get a nibbler as Gert says, make a layout and start cutting. Practice first on some of the area that is being removed to see how it cuts.

  5. #5
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    Quote Originally Posted by Doug Liedblad View Post
    ........I don't know where to get the edging material. Maybe Caterham?.......
    Autozone/PepBoys/Napa have self-adhesive door edging. You heat it with a hot air gun which makes it pliable and melts the hot glue inside the groove. I used it around the edges of my aluminum dashboard.
    McMaster has a dazzling veriety of rubber and plastic edging but you need to glue that down.

  6. #6
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    I have a nibbler that I bought to do this job and I can loan it to any 7 builder
    Rod Swanson

  7. #7
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    Harbor Freight sells air nibblers for under $30 they work just fine on thin gauge aluminum

    I highly recommend the air nibbler and if you practice cutting to your layout lines it should come out OK.

    Layout a hole or two smaller than you need and practice a time or three and it will come out OK.

  8. #8
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    Thanks, thats the plan.

    2010 Roadsport SV 170

  9. #9
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    Quote Originally Posted by Doug Liedblad View Post
    Harbor Freight sells air nibblers for under $30 .....
    Put a drop of oil on the nibbler cutter every couple of minutes. The aluminum tends to gum it up to the point it may get stuck.

  10. #10
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    Mine's covered w/ something similar to this. Disguises any little, um, variances in the edge.
    Chris
    ------------
    A day you don't go a hundred is a day wasted

  11. #11
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    Gert is correct, the oil will help.

  12. #12
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    The hole came out great, we used a air saw. cut was clean but the trim made it look better still:

    8413_3.jpgintake grill1.jpg

    2010 Roadsport SV 170

  13. #13
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    Nicely done! Looks great.

  14. #14
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    Quote Originally Posted by centerfireman View Post
    Nicely done! Looks great.
    Thanks. Now the decision on making a matching hole on the exhaust side....

    2010 Roadsport SV 170

  15. #15
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    nice job!!

    two questions:

    first, how did you mount the mesh to the inside of the bonnet?

    second, did you consider adding an aluminum scoop to the hole? that's what i'm thinking . . . has anyone done this? if so, any advice on making the scoop and attaching it? rivets? do any of the after-market sources make a scoop?

    thanks!

    alan

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    Quote Originally Posted by werthie View Post
    nice job!!

    two questions:

    first, how did you mount the mesh to the inside of the bonnet?

    second, did you consider adding an aluminum scoop to the hole? that's what i'm thinking . . . has anyone done this? if so, any advice on making the scoop and attaching it? rivets? do any of the after-market sources make a scoop?

    thanks!

    alan
    I would do a scoop if I was also going to repaint, at this time I didn't want to do that so sticking with the exposed grill for now.

    The grille mesh was found on ebay - look for seller metrorestyling, search for bonnet grille. Since I didn't trust myself on cutting the hole I left it with a friend at his shop, they sourced the trim material and I will also ask what they used to stick it up there (looks like the mastic stuff builders use to stick mirrors to interior walls).
    grill1.JPGgrill2.JPG

    2010 Roadsport SV 170

  17. #17
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    Quote Originally Posted by werthie View Post

    second, did you consider adding an aluminum scoop to the hole? that's what i'm thinking . . . has anyone done this? if so, any advice on making the scoop and attaching it? rivets?

    alan
    Like the scoop Lotus fitted to the original Seven S2 when fitted with the dual Weber Cosworth 1340 engine back in 1962?

    EscondidoRon

    '62 Lotus Seven
    '84 Turbo Esprit (x2)
    '14 Evora
    '77 Esprit S1 (RIP) :(

    "A man must keep a little back shop where he can be himself without reserve. In solitude alone can he know true freedom." -Michel De Montaigne 1588

  18. #18
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    The trim was vacuum tubing cut to make it grip on, the goop is 2 part steel putty. Like the scoop above!

    2010 Roadsport SV 170

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