ALFAGTV6.COM

[brian164]

i got a new alfa
just collected it and drove it about 200 miles home
its my first v6 alfa
having played with juniors, alfetta gt, gtv

but it has a knock
sounds like its coming from the heads
loud at start up and softer once the engine has warmed up
engine has 171000 miles, but there is no smoke and plenty of power
so i am presuming there has been a recient rebuild

i removed the front (left) tappet / valve cover
gasket looks to be only a few months old

valves have been set on the tight side
sticker on radiator says .5 for intake and .25 for exhaust
and both are less than that

please advise what you think it could be

and how i can go about eliminating possible causes

thanks

[Barry]

Hello Brian,I would say if you drove her for 200 miles and she `s still running ,you can eliminate a bearing fialure..
Check cam timing..check valve clearences all round and loosen those exhausts..you`l probably find a bit more power there..A big intake clearence can indicate a broken shim as well..

While idling,remove a coil plug connector in sequence and see if the knock goes away..you are now :unloading the cylinder in question..This will indicate a small end bush or even slightly knocking big end..Does it knock under acceleration or on over run?

Is it a :kack kack: knocking noise or a deeper :klock klock : noise? Why I ask is I have had a rocker that had bent and touched the cam cover before..this gave a loud but "thin" sounding knock.

The next one up is a loose valve seat..dont laugh,ive had a loose valve seat that lasted my whole holiday away from home..about 1000km,s..

Stupid question,you sure its coming from the engine and not from an external source like the box?
Check for loose pulleys and tensioners...end float on the crank..hech,where do I stop?

good luck,let us know what you find..

[x-rad]

Piston slap? Rod knock?

when exactly does it occur...throttle up...throttle down...all the time?

always good to start with a compression check. there are some good posts on knocks throughout the engine section

I think it's definately a moving internal component which expands as it heats, decreasing the sound...

[Michael]

Hi:
Interesting post - my 12v 3 Liter has exactly the same issue. I'll not call it a problem since it does not seem to affect the performance or reliability at all. When I start the car (cold engine), there is a pronounced knocking noise which pretty much goes away when the engine is hot - also sounds like its from the left cylinder head region. Its been that way ever since I installed the 3 liter ... which was in 1999 or something. I had had the heads completely rebuilt (Sperry stage II) and installed new S cams. Since then, I've done +40k miles, countless track events (lots of runs right up to redline ) and the Alfa still pulls as hard as it ever did … no oil consumption, no smoking etc. My theory is that the oil drains away from the front of the cam over time and takes a few minutes to get replenished when the engine starts. When removing the valve covers, I've noticed a lack of oil in the well beneath the cam. If this is indeed the source of the issue, I've not noticed any increase in wear for that cam lobe and I tend to check the valve clearances pretty frequently.
YMMV
Cheers,