F20 build, knocking/crack noise
10-19-2008, 08:58 AM
#1
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F20 build, knocking/crack noise
hi
i'm looking for a bit on knowledge and help on a cracking noise i'm getting from the engine i've been building.
the noise sounds like a valve touching! and horrile crack, it happens randomly when reved just above idle about 1500 -200rpms.
it sounds like it is from the top of the engine and the noise will jump from what sounds like cyclinder to cyclinder in no particular order. its not constant and will only happen a few times at once
a friend with alot of engineering back ground said it sounded like valve slap, again i could not see any signs of this.
i have had the head off for the second time today there is no evedence of valve touching, the cam timing in 100% spot on. i stripped the rockers and could not see any damage or signs of bad wear. the vavle springs were removed and re seated.
i've stripped and build a f20c2 for my caterham project.
the engine has been buleprinted built to the best of my ability.
the set up is as follows
baffeled sump
ported and polished head
ported and polished inlet manifold
spoon throttle body
spoon valve springs
will spoon valve spring work with a standard cam set up?
thanks for any help in advance
cheers phil
i'm looking for a bit on knowledge and help on a cracking noise i'm getting from the engine i've been building.
the noise sounds like a valve touching! and horrile crack, it happens randomly when reved just above idle about 1500 -200rpms.
it sounds like it is from the top of the engine and the noise will jump from what sounds like cyclinder to cyclinder in no particular order. its not constant and will only happen a few times at once
a friend with alot of engineering back ground said it sounded like valve slap, again i could not see any signs of this.
i have had the head off for the second time today there is no evedence of valve touching, the cam timing in 100% spot on. i stripped the rockers and could not see any damage or signs of bad wear. the vavle springs were removed and re seated.
i've stripped and build a f20c2 for my caterham project.
the engine has been buleprinted built to the best of my ability.
the set up is as follows
baffeled sump
ported and polished head
ported and polished inlet manifold
spoon throttle body
spoon valve springs
will spoon valve spring work with a standard cam set up?
thanks for any help in advance
cheers phil
10-21-2008, 03:58 AM
#2
Try disconnecting the VTEC solenoid elec plug.
I'm guessing you may be using an aftermarket ECU. If your VTEC control output isnt working correctly, switching prematurely, or has the logic backwards, you may be hearing the VTEC actuators starting to click in as the oil pressure builds with revs.
Just a guess, but the sliding pins that engage vtec to engage with a sharp click or crack noise if the pressure is marginal.
If the engine is cold you may be hearing some piston slap. I find you can get more piston slap on a recently rebuilt engine if the wrist pin is stiff with assembly lube, or the rings have not burnished any cross hatching hone texture smooth. If it is piston slap it will clear as the oil washes the assembly lube and the wrist pin/piston heat up.
Chris
I'm guessing you may be using an aftermarket ECU. If your VTEC control output isnt working correctly, switching prematurely, or has the logic backwards, you may be hearing the VTEC actuators starting to click in as the oil pressure builds with revs.
Just a guess, but the sliding pins that engage vtec to engage with a sharp click or crack noise if the pressure is marginal.
If the engine is cold you may be hearing some piston slap. I find you can get more piston slap on a recently rebuilt engine if the wrist pin is stiff with assembly lube, or the rings have not burnished any cross hatching hone texture smooth. If it is piston slap it will clear as the oil washes the assembly lube and the wrist pin/piston heat up.
Chris
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