recently I lost my built motor to inadequate piston to cylinder wall clearance and i was looking for some input for what the best clearance would be for a boosted setup. I use this as a race car..

TURBO (15+ psi)
Garrett T3/TO4E 57 trim w/ .48 a/r

Sleeved B18A LS Vtec
CP 84mm 9:1cr pistons

I was reading on http://www.theoldone.com/artic...s.htm
and he suggests a .0028-.0029" Clearance for Forced induction apps. Anyone have any suggestions with their own experience?

 

What hp and what pistons

 

i went with .0035 for my 84mm CP build and its still running strong with minor piston slap

 

.0025 - .004 is what we aim for .0035 on race motors

 

Pistons are listed in original post. I made 317whp and 290tq on a "Dyno Dynamics" last year, so I would be expecting around there or a little better this year. Only planing on revving to 7500rpm max.

 

i build turbo motors at 0.004 to 0.005 depending on power goals

 

Since you said you use this is a race car and not a street car I would aim for .0035 or maybe even a thousands looser to let the pistons expand under high heat conditions.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JDogg &raquo;</TD></TR><TR><TD CLASS="quote">i build turbo motors at 0.004 to 0.005 depending on power goals</TD></TR></TABLE>



It's better to build a little bit on the loose side. Let's face it, these built motors are not going to need to last 100K+ miles.

 

Did .0035 on mine, that was d16 with Wiseco's. Runs perfect so far, no boost yet tho

Justin

 

we're running .0025 on our 750HP race LS/VTEC and its made about 30 passes so far with no issues.

http://www.youtube.com/watch?v=qFuv-DyWjRk

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SovXietday &raquo;</TD></TR><TR><TD CLASS="quote">



It's better to build a little bit on the loose side. Let's face it, these built motors are not going to need to last 100K+ miles.</TD></TR></TABLE>

Some people do want built motors to last this long. CP has the piston to wall clearance built into the piston. On turbo pistons they get .0035. So because you have 84mm pistons, you would have wanted to hone the block to exactly 84mm on the spot. Pistons come under size. If this was done, there would have been no clearance issues as it works great for street engines on up to large hp cars.

 

we have run motors with 0.0045 clearance for over 40k miles with out isses..

there are NO downsides to running 0.0045 compared to 0.0035.

both cp and wiseco say the clearance is built into the pistons, but i have seen cases using both mfrs where the clearance did not come out right doing this. ALWAYS go back and double/triple check.

also keep in mind that smaller bores need less clearance, the bigger the piston the more it will expand.

most of hte motors i build are 84-85mm bores.

its like i always say/learned.... if you build it loose only you know about it, build it tight and everone will find out

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ninesecrx &raquo;</TD></TR><TR><TD CLASS="quote">So because you have 84mm pistons, you would have wanted to hone the block to exactly 84mm on the spot.</TD></TR></TABLE>

You guys sleeved a block that I'm building (84mm) and I sent you the pistons (Arias) with the block, can I assume you tailored the sleeves to a specific piston to wall clearance?

 

Anyone have an opinion to what is too loose?

 

golden eagle put my cp's at .004

i'm much happier with some piston slap than a broken motor

also always make sure to gap your rings to spec and ur application

 

.0045

 

.0030" on my Endyn's (Wiseco), but if your gonna run it hard, I'd suggest .0040". I've seen a lot of pistons ruined due to improper clearancing, imo.

 

On my last motor with Wiseco pistons I went with .0025 as suggested from them. My motor overheated and the pistons expanded so much that I cracked a piston. On this new motor I went with 83mm CP and .004. I have some noticeable piston slap when the motor is cold but sounds like stock when warm. More room for error.

 

Your right right in that .0035 to 0.004 thats what I do and would do. I agree Tight aint always right and lose might not make it to 100k miles but it will stop you from blowing your motor. Unless i'm wrong I believe CP recomends 0.0035 for boosted application on your bore size. the extra thousand is just a sefty net.

 

I sorry I ment thats what cp recomends for 81mm.