valve clearances

[suprra_girl]

well.. i've just been working on a 1jz and the top end is quite rattly

well actually it's a 1.5

heres the specs

1.5j
.050" je forged pistons
custom rings.. i would assume je
shotpeened rods
nascar bearings
rebuilt head, valves reseated, new seals etc

soooooooo... can forged pistons make the engine rattly? i've heard they can, but most of this sound is top end tappy rattly

so my first thought... check the clearances and omg :nono:

theres only two valves on the intake side i can fit .015mm feeler gauge in

measurements range from .005 to .015
only 3 on the exhaust side are below minimum spec of .025mm

so a few things

1. confirm that measurements should be...
intake = .015-.025
exhaust = .025-.035

2. will this cause the rattling? none were above max spec

3. with the clearances too tight, what will this do?
i suspect that the valves will stay open all the time? the ones below spec? power loss.. what else does this do?

Thanks

 

[drunk_medic]

I've heard of JE pistons doing that, but just because I've heard that doesn't mean that is the case with your engine noises.

Valve clearance can cause a rattling, or "tapping" noise, and this very well may be the case if you are hearing it mostly in the head.

 

[7MGTEJoe]

Forged pistons can rattle a bit while they're warming up. They have a higher thermal expantion rate so they need more piston-wall clearance when cold. They should quiet down once warm though.

Have you tried playing with a mechanic's stethoscope (or a long screwdriver with the handle to your ear and the tip touching the valve cover) to isolate the noise?

 

[GrimJack]

I've heard of JE pistons doing that, but just because I've heard that doesn't mean that is the case with your engine noises.

Valve clearance can cause a rattling, or "tapping" noise, and this very well may be the case if you are hearing it mostly in the head.

I've heard of Ross pistons doing this. And I've heard of loose valve clearances causing rattle, but not tight clearances.

Sorry, my knowledge of the correct clearances for the JZ series heads is sorely lacking. Perhaps if you post in the JZ tech section for that?

 

[Allan_MA70]

do the shims if they are out and take it from there

 

[bluemax]

My forged pistons rattle a little when cold as 7MGETJOE says.
The shop I got them for told me they would rattle until warm. It sounds a little like a diesel motor for a about a minute or less. But when its warms up it still has a little rattle ring to it. I believe the clearances are looser. I was told by a boat motor nut that high performance engines have looser pistons and will burn a little oil. And mine does.

 

[IJ.]

If the bore size is correct Forged shouldn't rattle when warm...

They need more clearance as they expand more than cast pistons but if everthings correct they're at the same piston to bore clearance once the motor is at operating temp!

This is why it's bad to rev a cold motor with forged pistons as they crack from piston slap through the oil ring groove return holes and eventually the skirt comes off !

 

[Allan_MA70]

This is why it's bad to rev a cold motor with forged pistons as they crack from piston slap through the oil ring groove return holes and eventually the skirt comes off !

yes you must remeber some things can be warmed up to get the skirt off other things need to be warmed up to keep the skirt on :naughty:

other things that can cause valve train noise include crap oil and crap oil caused by blow by / excessive fuel thining the oil but play shuffle the shims and so forth first see if you can get the clearences nice

 

[suprra_girl]

well we played shuffle the shims and set them to .015 & .020... warmed the car up today took it for a drive etc
bought it back... yes i know you should check clearances cold... but we checked them anyway out of curiosity... one shim that was .015 was .027 warm

should the clearances tighten or loosen when warm?

also when looking at the engine running with the cam timing cover off the intake cam it looks like the cam is out of balance :dunno:
like when you put a tyre on a balancing machine you can see it wobbling up and down?

well anyway... one cam is doing that.. the exhaust cam seems fine.. just intake cam is doing the wierd out of balance thing
do you think it's possible the cam is warped?

thanks

 

[Allan_MA70]

defintly a chance if the cam tower was undone out of sequence

 

[suprra_girl]

i suddenly remembered what happened.....

i remember when undoing the cams a while back the torque values for the caps were all over the place, tight, tight as a muther, medium, looser etc

now have that in the car, heat up that cam.. it's gonna mould to that shape after a while ain't it
so yea my original guess... cam must be warped.. therefore causing wierd ass clearances and the changing of clearances

so we're gonna swap in another cam tomorrow and get the original one checked to see if it is warped to hell