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Knucklehead Saloon

How hard does your EA81 rev and why.

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I just got mine to hit 6100rpm.


Stock motor internals, stock intake manifold, stock exhaust, weber 32/36 with 140 / 155 mains, msd 4500v coil, race leads, iridium plugs, 2wd leone distributor. Advanced ignition timing till it pinged and then backed it off a bees wongleflute.


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I don't bother to wind mine out past the stock 5.5k redline.  The turbo kicks in at 1,500 rpm and all the power is in the middle of the rev range anyway.


If you're shifting at 6,100 rpm, you're not shifting at the right rpm for acceleration.

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I revved my first build to valve bounce and after 180,000km the crank flexed a bit too much and mushroomed the centre main bearing seat. Still went still revvedjust hhad a RUmble at revs but essentially the three mains ain't really made for revs

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I'll add, I am referring only to stock un modified engines, operating within their specifications, that is not above red line.

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Not very high in standard form (EA81)


Other reasons  -  2 valves / cylinder single port intake and exhaust port heads / small shared manifolds (limitations to air flow increases for limited performance gains)

                          -  similar for EA82s


                       - OHV  limits high RPMs also


                       - Agree, 3 main bearing crank  - bottom end  not as  strong for high rpms  (EA82 similar)


IF serious about performance gains , EJ engines with 4 valves / per cylinder  bigger manifolds,   better  for air flow increases / performance gains - especially ones with 4 port heads DOHCs,      with freer revving OHCs,     better for higher rpms.

Also 5 main  bearings on crankshaft  - bottom end  stronger for higher rpms.


Wouldn't and didn't bother to try and modify my EA81 / 82s for those reasons.


The only one I would consider modifying is , if  had an RX2 AWD 5MT D/R  with EA82T  would replace heads with  4 port heads / manifolds etc  upgraded internals etc  ,do it properly.

Power gains from 115hp (stock)  up to 200hp


Also EA82 OHCs are more free revving so a better platform to start off with    than  clatterly  old school  OHV EA81s best left stock.


PS  EA81s are mid rangers  ie work best keeping motor spinning between 2500rpm  and 3500rpm  (ie max torque at 2400rpm  max hp at 4800rpm   

Nothing to be gained in exceeding 5000rpm just to prove a point apart from trying to destroy an engine .that isn't designed for high rpms.

Ea81s are bomb proof simplicity (gear driven cam) but over revving them is a sure way to try and kill them.

Edited by subnz
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