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Thread: B20a Cams

  1. #76
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    Re: B20a Cams

    Bringing this back up I've been looking at more parts for my B20A build, really want the head to flow more and get much higher compression.

    Stock B16/18 pistons should work for me as the wrist pins if I remember rightly on EDM B20A are 21mm so direct fit, you can get those in a 82mm bore size which is extra CC's so that's good and extra CR ratio, bad news is the stock pistons are Compression height of 30.75mm the B16/18 pistons are 30mm so you will loose bit of compression by putting these in, only other option is spend loads on aftermarket rods and Wiseco pistons which only do 81.5mm bore and 10.5:1CR ratio. Other option is take .25mm off the deck and .5mm off the head, as a matter of course I've taken .5mm off the deck with no issues and you can quite easily get 1mm off the head more if you don't mind scrapping the head if you blow a few head gaskets. Which if your using slightly raised flat top B16/18 pistons combined with .75mm less metal in the way on head and block you should get a nice healthy CR ratio at around 11:1 if you don't take too much out the chamber when cleaning it up.

    Now for the trick part and answers the above question on the valve locks, you can either get new ones that fit or better option use B16/18 valve guides which are the same external diameter which will then enable you to use B16/18 vavles which have benefit of two things, more choice in parts for me supertech seem to offer the best value/performance/quality valves they do them in stock sizes or 1mm over size which would mean we could have a B20A with 34mm inlet valves and 29mm exhaust valves, you would also have the benefit of the stems dropping from 6.5mm to 5.5 mm the supertech ones are also waisted down to 5mm so this really helps get extra air/fuel in and exhaust gas out.

    Combine that with Brian Crower cams and either ITB's or Webers you could be looking at quite an evil engine and you'd have not spent that much on parts as they're all off the shelf common parts from other engines. Personally I'd use uprated rods which if you fit new bronze bushes in to fit 21mm is fine but you need to have oil squirters drilled into them as all aftermarket rods see to have these missing with their excuse is it's not a road car so will be spinning at high enough rpm to splash enough oil around, you could have these machined in but factor that extra cost in.



  2. #77
    SEi User Hauntd ca3's Avatar
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    Sep 2007
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    1988 ca3 si exclusive
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    new zealand
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    Re: B20a Cams

    Hey Rjudgey
    Here are some ferrea part numbers for valves .
    F1854p and F1852p
    Mitsi 6g72tt 1mm o/s in and ex , slide straight into the Honda with recut seats and lash caps on the exhaust valves.
    That's what is residing in my b20a
    Ports don't need bugger all, well according to the guy that looked at mine.
    He builds BDA escort motors, formula ford etc etc.
    10.5:1 cr 290 degree cams 11mm lift with 45dcoes , these are good for 280 at the flywheel @ 8500rpm.
    I'm going itbs and stand alone engine management so should see close to 250 at 7500rpm

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