I have decided valves are stupid - Help/Ideas required

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Entaran

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Joined
Mar 29, 2005
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5,194
Location
Ballarat, Victoria
Scenario:

Head is on engine, timing belt on, valves, cams etc all in. Everything is torqued/tensioned to spec.

The car is at TDC on Cyl 1. All timing marks line up perfectly, dowel pin on the crankshaft pulley is in the right spot and so forth.

Issue:

After 90 degrees or so of rotation in either forward or backward direction, a distinct metal clink can be heard as the valve in cyl 4 taps the piston (hand rotation)

Resolution:

???????? - Has myself and two mechanics stumped.
 
firstly why are u turning the motor backwards? lol... r u sure its hitting?.... did u clean up cylinder 4?
how do u know its at TDC? (did u do the screwdriver trick to see where it rests?)

Jon
 
No, Acutally we used a snapon camera and stuffed it down the spark plug hole to check if it's at TDC. Which is the same way we know the valve is tapping the piston.

Turning an engine both ways is common diagnostic technique.
 
Lol.
Might sound stupuid, but are the valves the right length? You sure you set the belt up properly?
 
The lifter is locked at an over extended position (fully pumped) and allowing the valve to travel further than it should be travelling..

Just a guess!!
Apart from that, no idea...
 
Also, what cams / cam gears and valves are you using?
What pistons?

And is it definiately cylinder 4 ONLY?

Could they be poorly ground/made camshafts?
Is it possible to see if the valve is sealing at all? (pull off manifolds to inspect)

Has the head come off yet ?
 
Cyl 4 only SO FAR. We can't turn it by hand any further due to it physically hitting the piston.

It was idling before, it's being weird now, so yes the valves are correct (they are the same ones I thought I bent but I was wrong, they are fine)

272/272 fidanza's set to +0 (exactly the same position as the stock ones, we checked)

Will yank all the lifters and drain them.

I have a feeling the belt jumped way too many teeth when we pulled it off and the crank is physically out. But will inspect in the morning. Everyone I know is totally freaking stumped.
 
Fidanza cam gears have 2 dowel holes in them.

1 to suit the evo 4+ and one to suit our motors.

Make sure you are using the correct dowel hole.

There is a hole marked evo on it which is for the late model motor.
The one that is not marked is for ours.

This will make the cam off by a tooth EACH. (I'd say about 5 degrees).

A quick test would be to adjust the gears so they stop hitting and see how many degrees it takes to not hit.

While your at it, you should get the mechanics OR yourself since you did the valve springs to make some weak valve springs out of wire or something and play with your cams and measure your max adjustment on the cam gears..
 
Another way of checking accurately is, are the cams dialled in correctly... Get the cam card or confirm with the cam manufacturer what the lift at TDC for the inlet and exhaust. Then pull the dial indicator out and exactly confirm TDC ( and that it does line up with the crank sprocket mark or TDC mark on the belt cover.) Then measure the actual lift as specified in the cam spec chart for inlet and exhaust.

If these are all exactly right you have eliminated valve timing errors and can proceed to the next step of scratching your head !

I do this as a matter of course for any competition style motor I build, as assumptions are at the root of all mechanical evils !

Cheers Mike
 
Thanks mike, yeah gonna whip out the dial gauge and reinstall the cams from scratch. "By eye" they look like they're spot on, but it's worth checking twice.

And yeah baz, they're in the right hole mate :)

I just don't get it because the car was idling previously quite happily, then we fixed the timing belt (which had skipped two teeth forward exhaust side) and now everythings all up **** creek.

Will get it sorted today. If we can't get it to work, the heads coming off and going in the bin.
 
Long ago fixed. Thanks guys.

Turned out the intake cam had rotated a tooth and the crankshaft had rotated a tooth for a total of two teeth out in direction of engine rotation.
 

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