Silvia Club of NSW

hey guys, jus want to know if its normal for a freshly rebuilt motor (new forged pistons (ROSS) and Eagle rods+ full serviced head) to make tapping/slappin/knockin type sound???? Iv heard from few ppl that forged pistons are noisier?? can any1 confirm?

of course they're noisier. have you looked at the difference in their side clearances,compared to a std type? most forgies run about 6thou. normal clearance is more like 1-2thou. that's a lot of extra space to let things move about.

forgies rattle around a bit in the bores,especially when the engine's dead cold.

the reason for the extra clearance is expansion. forgies expand differently in comparison to normal hyper eutectic or cast pistons,so they need the extra room to prevent seizure.

forged pistons can cope with more stress than normal cast types,which is why people use them. better reliability. they help hide dodgy tunes too...


Justin...

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STI - Made in Texas,not Japan.

Forgies make SRs sound EVEN MORE like diesels than they already do.

I love my tractor

Well my forged engine sounds like a stock one. Not all forged motors are noisy IMO!

I know a 1JZ is a completely different motor, but my Forgies are quiet and you wouldn't tell the different if you sat the engine beside another engine.

B.

check the manufacturers recommended piston to bore clearance and compare it to other pistons on the market. if its relatively high then your piston has a lower silicon content which means more expansion room is required and you will get alot of noise with a cold engine. you will have to live with it..

if its just noisey ALL the time its probably a crappy rebuild

True not all forgies are created equal when it comes to noise but there is nothing to be alarmed at if they do as it is perfectly normal. You need to be concerned if the noise is excessive or if they don't quiten down a bit after it has warmed up (basically you still have too much slop)

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I didn’t break it, I just modified the operational status...
There are 10 types of people in this world, those that understand binary, and those that don't.

meaning it shouldnt sound like the 10,000 LS1s that had this problem from factory

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M35 Stagea.info @ http://www.m35stagea.info/

Really depends on the brand I have found some forgies may need a couple of extra thou additional clearence. This is probably why some are more noticably louder than others when cold.

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I didn’t break it, I just modified the operational status...
There are 10 types of people in this world, those that understand binary, and those that don't.

yea its not really noticable after it warms up, u really hafter put ur head in the bay n listen for it.. it jus sounds like a diesel engine.. lol. it drives smooth, im guessin it should quiet down a little once i dump the runnin oil n throw the gud stuff in.. plus i haven't really driven it much, jus went up n down the street a few tyms, it may quiten down a bit once it all beds in..


Cheers for all the input guys!! heaps appreciated

running in will make no difference since the clearance remains the same (gets worse as the bore gets bigger and piston skirts are knocked in with age) but thicker oil should make it slightly less audible.

If you have to poke your head under the bonnet to hear it I think you should be fine.

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I didn’t break it, I just modified the operational status...
There are 10 types of people in this world, those that understand binary, and those that don't.