It keeps on knockin'

Momo · backyard mechanic Joined: 08 Feb 2002 Posts: 561

I've just done the head gasket on my G161. Didn't have it shaved but took a bit off the head on a emmory block to take care of a minor warp. Didn't measure the valve clearances when putting it back together but I'm pretty sure it's not that. What can I check to eliminate other possible causes before pulling the head off again? Can the tappets/rockers/lifter doo dads be adjusted anywhere other than adjusting the valve clearances?? Does incorrect valve clearances result in a knocking sound??? I've set them at both 10thou and now at 8thou and the noise is still there. The noise isn't consistent either, sometimes it's there other times it's not...which leads me to ask my next Q...

Should the rocker cover build up pressure to help with oil spread on/around the cam and lifters - reason I ask is because I have a length of heater hose connected to the hole at the back of the rocker cover that used to drain oil into a coke bottle (old motor) and I'm wondering if I block that off will it possibly help things/oil coverage??

GasGem · backyard mechanic Joined: 05 Nov 2001 Posts: 755

Yeah the pipe from the rocker cover need to breath,

knocking, is the sound deep,
is it when cold,
is it at idle,
is it under load,

more details please,

cheers

Momo · backyard mechanic Joined: 08 Feb 2002 Posts: 561

It's inconsistent that's why I haven't detailed when it's doing it. Thinking bout it tho - I know it's definately NOT when it's cold. Mostly under medium load/acceleration, yet sometimes at idle - can't hear it under full throttle but that maybe cause I can't hear anything under full stick! Doesn't do it when cruzin @ 100+????????????

GasGem · backyard mechanic Joined: 05 Nov 2001 Posts: 755

ok,
you've got me,
cold would be piston slop, old motor,
full load would probably be pinging,

get it on a dyno and have a proper listen, may be even with a screw driver against the cylinder walls, but first try and find the most comon time it occurs, with out floging the shit out fo it,

also maybe give it a comp check, and have a look at your plugs,

cheers and good luck,
Eggy

Momo · backyard mechanic Joined: 08 Feb 2002 Posts: 561

Yeah ta - just got it back from the dyno and he wasn't sure what it was either- BTW is 79 rwkw from a G161 with 32/36 dgv poor/average/good?

Mooch · backyard mechanic Joined: 17 Oct 2001 Posts: 573

u sure it was 79rwkw? if so then that G161 is quite extensively built. that would be a 15sec car mate......

GasGem · backyard mechanic Joined: 05 Nov 2001 Posts: 755

Yeah that 79KW fly wheel maybe, what gear? but last resort is keep driving it till it gets worse and just expect that you may have to replace the engine, if you are in Vic I have a couple,

cheers,

Mooch · backyard mechanic Joined: 17 Oct 2001 Posts: 573

i'd put my money on ur bearings mate. does it do it @ about 70 kays in 4th. when u play the throttle gently?

panelvanman · rice boy Joined: 16 Feb 2002 Posts: 16

just a suggestion old motor had a bit of a hard time. worn bearings by the sounds of it. my mate had a knocking noise in his 83 gem tried to drive it so i could have a look and the piston flew through the block.

Momo · backyard mechanic Joined: 08 Feb 2002 Posts: 561

My bad - I have two dyno reports in front of me. The first was from when I had twin delortos on it and the report reads 'max power 47.1 kW @ 137 kph' and on the top of the page it says 'Power at Wheels'.

The second report was done on Friday and it does read 'max power 79.0 kW @ 146 kph' but at the top of the page it says 'power at engine' - so whoops, your right!!. How does that fair for a G161 - I know it's definately NOT a 15 sec car!! Maybe 15 min?!! AND you can hear it comin' tick tick tick tick - didn't explode today though so it's back to work flat stick 2morow!!

Racegem · backyard mechanic Joined: 30 Jan 2002 Posts: 987

You just beat me to it Mooch,
Top end noise it usually a "tappity, ticking" sound, If it's a deeper "knocking" thud, then it'll be your bottom end. Try pulling off a plug lead while it's idling and slowly rev it. If the knocking quietens or disappears, it's the big end on that cylinder. Big ends are noisy under load, Mains are noisy all the time.
Either way it's motor out.

Yonnee.

Ben Wight · backyard mechanic Joined: 04 Oct 2001 Posts: 946

It could have been that you didn't set your camshaft timing correctly and now your valves are hitting the tops of your pistons as certain engine load/speed.

Ben Wight

Racegem · backyard mechanic Joined: 30 Jan 2002 Posts: 987

Not dissin' you Ben, but If your valves were hitting the pistons hard enough for you to hear it, it would only do it once!
Once you bent all the valves, she'd have no compression, and probably wouldn't idle.... if she started.
My money's with Mooch's, sorry Momofan.....motor out!

Yonnee

Ben Wight · backyard mechanic Joined: 04 Oct 2001 Posts: 946

Actually Yonnee, I have done this before and it made a mediumly pitched knocking noise at only certain engine loads and certain rpm.

It doesn't take much of a hit to make some noise at engine speed, and this hit is not enough to bend the valve to a point where it wont seal effectively enough for proper idling and smooth running. Remember a valve is a lot harder than a piston, steel versus aluminium.

I had a pretty wild cam in at the time, so a slight idle difference would not have been noticable anyway, but definitely not to the point of noticably not sealing against the valve seats.

Ben Wight

Momo · backyard mechanic Joined: 08 Feb 2002 Posts: 561

Yeah Ben my moneys with you because it's exactly as you describe it, sometimes under load, sometimes at a particular rpm but yet it's inconsistent. The cam gear only had one possible selection so I figured maybe it was a particular gear for that cam (ie: that it had already been degreed in - where were you when I was asking about degreeing in a 30/70 cam? I was told to ask if anyone had a cam card for a 30/70 cam by a mate and someone here told me that just because we both had a 30/70 cam mine would be degreed the same as yours! Anyway - I just want it fixed but I can't keep paying this guy at the dyno shop. Want to eliminate as many possible causes before I go and pull the top off again but I don't think I've got any choice.