24 replies to this topic

[A9X34]

Holden and Chev V8's are known for wearing out cam lobes from time to time, especially if new cams have not been run in properly (approx. 2000 rpm for 20 min or drive it but never let it idle) I would suggest remove the rocker cover and coil lead and have someone crank it over while you watch to see if all the valves move the same amount.

 A worn lobe won't move the valve as much and depending on how worn one is and if its an inlet or exhaust will give different issues.

 Inlet worn a little may only drop power or miss in the higher rpm, the more wear the lower in the rpm range it will do it.

 Exhaust worn a little you may get a high rpm back fire the more wear the lower in the rpm it will back fire (exhaust gas doesn't have time to get past the valve so it goes up the manifold when the inlet opens)

 I have also seen where the lobe may be half worn away but the base of the lifter is so concaved that the base is so thin or a pin hole that it bleeds oil pressure out the bottom of the lifter. This probably won't affect the oil pressure reading but allows the lifter to compress.

 Hope this Helps

[S pack]

My money is on a faulty hydraulic lifter if hydraulic lifters are fitted.

[UCSLE]

I had a problem once where the starter motor didn't disengage properly making a clanking noise . Check to see in the starter motor gear is returning properly , it might be a bit hard to notice, you have to see it before it makes the clunk and it might not happen all the time.  Also does the idle drop every now and again ? , the ticking noise maybe a sticky valve.

[A9X34]

 Yes a sticky valve could also be another cause. I had that problem when I had some chev heads overhauled years ago and the guide clearance was too tight. When the engine temp came up a valve would occasionally nip up and bent when kissed by the piston. Had to have the guides reamed again for better clearance.

[rexy]

Get a piece of hose, stick one end in your ear and touch the other end around the engine to localise the noise. Plenty of leakage on that gasket pic. How tight did you do it up when you replaced it? Ideally I would get rid of it and use a high temp silicone, it never leaks.
Bet it's still an exhaust leak.

[RallyRed]

had a LX SL/R 5000 back in the day.....had a ticky sound from the passenger side bank.
Had stock rockers etc.....pushrod had poked a hole thru the rocker arm. When stripped down, the cam lobes were also very worn and you could see the 'grain'
of the metal, rather than the nice shiney surface expected.
Maybe yours is just a dodgey rocker?

[lakeside]

It will be the rear lobe of the camshaft. It just a common problem with Holden V8's.

[Rockoz]

How hard did you rev it?

What condition are the replacement springs? Rusty at all?

Being the same spring may be that crappy springs have been used as replacements.

[Lima31]

Nice, I managed to break a (not cheap) hydraulic lifter once, definitely harder to get to ...

 

 DSC_0467.jpg   159.34K   2 downloads

[Bigfella237]

As mentioned earlier, Holden V8s have always worn lobes off the back of the cam, in every engine I've built for years now I've drilled, tapped and plugged the oil return hole in the left side of the lifter valley, this forces the oil returning from the rocker gear to pool and run over the camshaft instead of draining straight back to the sump. I've never seen one of my engines with the same problem since.

 

I must say I've never heard of a worn cam lobe breaking a valve spring though, that would normally be caused by just the opposite (to much valve lift). I see someone has fitted roller rockers, studs and guideplates, I wonder if whoever built the engine did their valve lift multiplied by rocker ratio sums correctly?

 

Have you checked to see if you're getting coil bind at full lift?

 

EDIT: I forgot to mention, an 1/8" gas plug fits almost perfectly but unless you're drilling and tapping with all the other machine work at rebuild time, it'd be almost impossible to do without getting metal shavings fall through onto the crank.

Edited by Bigfella237, 11 November 2014 - 07:18 AM.

[Rockoz]

Read that one of the race teams. probably all of them, back in the early 80s used to grind a flat on the lifters on the bottom section.

Was 10 thou from memory.

Resulted in a slight drop in oil pressure but kept the oil up to the camshaft making them last longer.