the.hamburglar

iv got some friends with built motors and they tend to knocking when they are cold and once its warm they run fine. im just wondering how to aviod this? the motors were built professionally and all the proper toleranes were measured...so says the machine shop.

if they are knocking when its cold and the machine shop did in fact assemble everyhying right, is this normal? id hate to have this happen to me as that would drive me crazy.

im thining about keeping my stock 81mm bore, is this a good idea or should i get the bore checked and if its out bore it to 81.5mm?

b18sihatch

are you referingto piston slap?

jonvo

forged pistons need more clearance when they're cold so they have room to expand when they warm up. they expand a lot more than regular pistons.

rmcdaniels

None of my three motors with forged pistons have ever had any piston slap. Two had Wiseco pistons, one had JE pistons.

purpleh22

Piston slap with forged pistons is common with racing clearances. Some people run them on the tighter end of recommended clearances and hear very little slap.

b18sihatch

i too am going to run JE and i heard that JE's have been known to piston slap but i guess it depends on the building and what clearences they use. i know in my motor i have a good ammount of clearence, however the motor was built for 500whp daily. however it is more than likly just enough clearence to run so piston slap doesnt occure

the.hamburglar

hmmm, are there any pistons that are not as dense and wont expand as much? i think the reason whey the stock pistons dont expand as much is because they are cast right? so without losing strength are there any companies known to have low thermal expansion? id like to make about 300whp with mine as a daily driver. i might be able to get away with the stock bore or do a light hone

HiProfile

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rmcdaniels &raquo;</TD></TR><TR><TD CLASS="quote">None of my three motors with forged pistons have ever had any piston slap. Two had Wiseco pistons, one had JE pistons.</TD></TR></TABLE>

I'm in this same boat too. Dispite running .Wisecos w/.0028" clearances (and the pistons tapper a good amount), adding ~.00035" when the coating is gone, I've had NO piston slap. ANd this is starting it in a 10 degree WIsconsin winter.

SRP's are supposed to use an alloy that doesn't expand so much, but is supposedly not as strong. Have your bores checked - it they are w/in spec, you could get by with a light hone. This may be an issue though, as you may end up with a bit too much clearance. I paid a local shop that does Hondas around $50 for a bore/hone .5mm over, so its not a big deal.

Regardless, you don't want to just jump into a car w/forged pistons and just start beating on it. I let mine warm up 5 mins at least, and not just to get heat in the cabin. I got an alarm with remote start, and killed 2 birds with 1 stone that way.

the.hamburglar

its way more than $50 here for a bore and hone. its like $50 a hole. ya, i dont now what im going to do. i could get away with srp's. dont want to make crazy power.

KeyserSoze

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by the.hamburglar &raquo;</TD></TR><TR><TD CLASS="quote">its way more than $50 here for a bore and hone. its like $50 a hole. ya, i dont now what im going to do. i could get away with srp's. dont want to make crazy power.</TD></TR></TABLE>

If your only looking for ~300 you could definately get away with srp's. I got srp's in my gsr and I think the builder gave me a bit to much clearance thinking that I would get a lot of expansion so it smokes a bit until it warms up then the smoking goes away. Never had any slap though.

purpleh22

Check with current Honda turbo engine builders on the proper clearances to use. I believe standard practice for engine builders used to be 5 thou. and more for racing engines piston to wall clearance. When you tear down after every meet you may not have to compromise on it being set up for longevity/street use.

NJIN BUILDR

I'm running SRP's in my dd and they are quieter than my injectors.But really "who cares how loud the pistons are".

TurbodTegSfaria

got my .5mm hone for 100 bucks, got some wisecos with eagles new acl bearings and when i start my car theres more of a pinging sound than a piston slap..i thought it was just because of the hondata and it will start up and drop right down to idle when cold

Boostedvti

I'm running SRP's in my turbo B16A2.The engine is noisy when cold,but I certainly wouldn't say its bad,not like an old 2 stroke engine noisy.about as loud as my injectors.As soon as the engine is up to temperature it's very smooth.As said above.I like to drive the car steady for the first few mins,at least until the temp gauge is up to at least a quarter before putting the motor under any load.It's better for any motor not to be thrashed when it's cold