big end

[Guest]

 WRXONP said:

It means the tolerance between the piston and bore is too great and the piston is rocking in the bore . . . . It normally happens when cold with forged pistons as forged pistons need quite a large tolerance (compared to a cast piston) to allow for expansion of the piston. In my opinion . Piston slap when cold is not really an issue. Piston slap when hot means she must be pretty worn in the bores .

ohyeah isee.use my car for example.its been rebuilt 10 00ks ago but istill get piston slap on cold start up's.when she warms up the noise goes away like yu said.does that mean that the bores on my car wernt done correctly or is it cause im just running semi forgd pistons.any one know the MAX psi a semi forged piston can take?im sure back in the 90's subaru must have tested to see how mch the semi forgd piston culd take?

[wrxboy]

ok well it has atleast done it for 3-4months?? i dont give it to much shit tho would that make a difference??

[Guest]

take some vids dude!then well be able to hear what your hearing.hw many k's on ur motor bro?

[wrxboy]

i will try that this afternoon hopefully?? and its on 183k. im just hoping it not what ive been told!!!

[WRXONP]

Like I said though . A big end cant be "on its way out" for a few months . . . . More like a few minutes

[wrxboy]

Well that cheers me up alot mate! I still gotta find out what it is tho

[wrxboy]

its knocking when warm from the drivers side (its not a big end) maybe piston says the second place??

[WRXONP]

In the head or the block ? What ver is your car / motor ?

[wrxboy]

i dont know ae?? its a v3 or 4 i think its v3 a 1997?? if it is the piston do you know how much it will cost?

[WRXONP]

Ha ha might need the block bored out and larger pistons fitted . . Are you from auckland bro ?

[wrxboy]

if i do il just buy a rebuilt motor, and no south island ae why that?

[WRXONP]

Aw ok bro . That sux . Was going to say I could have a look and let you know what I think and discuss ha ha -but its all good . Worst thing it could be is a broken ring land im guessing but could be just worn bore . . Does it smoke ? Use oil ? Its hard to diagnose over the internet

[wrxboy]

Yea I'm sorry ae I'm really appreciate you trying mate. If I'm correct it doesn't smoke or use oil and it runs fine.the compression is also good that I'm aware of.

[WRXONP]

Aw yeah . . . Sounds like to me its just a bit of piston slap bro . Ever used a screw driver as a stethoscope ?

[wrxboy]

No I've heard of it but haven't tried it? Does it work? Doesn't piston slap stop when it's warm? Because this doesn't. Would it be the drivers side back piston don't they sometimes get starved of fuel because the fuel pumps are to small?

[WRXONP]

Yeah thats the cylinder that will get lean 1st if it ever goes that way . And yes it works just like a stethoscope . . Use the biggest screw driver you got and you put the end where ever you want to hear it (metal on metal) and put the handle right on your ear . You will be able to put it on various spots on the head and block and you will tell where the noise is coming from when its louder through the handle works a treat I bet you will be suprised.. Is the noise louder when cold and quieter when hot ?

[wrxboy]

Yup it's louder when cold why? Il have to try that lol

[wrxboy]

When it's cold you can hear it inside the car clearly when warm you can only hear it under the bonnet. But it's getting worse

[WRXONP]

Thats normally piston slap if its louder when cold . Its when the pistons not swollen up to full size yet . . . And quieter when got cos its swollen up bore might be out of round

[wrxboy]

The second garage looked and they don't know what it is!

[WRXONP]

Could be cracked ring land ? Id suggest getting a cylinder leakage test before you do any thing

[DRFVDR]

I would take it to a subaru specific garage,ask some of the southland guys who are the best,