Ok I just got my B18a1 bored .0040 over std. which made the bore 3.110. Wiseco says boost applications should run .0035. They also said I'm to loose and should reconsider my setup. I researched this before I took the block to the machine shop and I read on hear that drag cars run .0045 over and street run .0035. So WTF am I supposed to do.

IS .0040 TO LOOSE???!!!

 

no, just let her warm up alittle

 

I used to run .0045 on all my setups. Made alittle noise cold for maybe 1 minute then it was fine.

 

my h22 is at .0045 you'll be fine

 

how much power are you going for ?

 

425 whp max... Daily 350-375 track tune 115 oct. 425 hp

 

The guy I spoke to at Wiseco said .0045 was great for that power range in an ~87.5mm piston. I guess if you're using a significantly smaller piston, maybe the necessary clearance might be a little less. . . .

 

Did you factor in the coating on the skirts wearing off? IIRC it is .0005" thick, which if that is correct you would be at .0045" after running the car for a while once the coating wears off.

I think that is why they recommend a tight .0025" on the spec sheets to factor in the coating.

 

The guy I spoke with knew I was talking about brand new pistons, and he just said that dimension. We had quite a discussion about this on here a little while ago, and the only guys who reported any issues were the ones who went too tight.

 

Yeah thats what I found when I searched on here. I told my machinest and he acted like I'm a retard and said "where the hell you geting this information from?"

Anyhow I asked the shop if they could bore to the nearest .0001 that I asked and they said yes so I SPECIFICALLY asked for .0037 over std. which would have put the bore at 3.1097 but it measures out 3.110...

 

i honestly wouldnt worry about it. so maybe the motor will only last 60k miles instead of 65k miles. make sure you've got good ring gaps and run some boost through that bad boy.


ive run motors at .0040 and no problems. made 425hp too no less lol

 

built mine for .0035. little loose when cold but once warmed up was just fine. just like what the other guys said

 

Machinist/rebuilder acted if you were a retard? I get that too...sometimes they're ******.

I had mine bored at 0.0040", arias 86mm dia grade 2618 pistons (low silicon) which was recommended. It depends, if you're running grade 4032 (higher silicon content thus lower expansion rate) then hell yeah you're running too loose and may loose compression.

car is coming out this friday, expecting noisy at every start up for the first 1-2mins.

 

that was what brought the .0045 over to my attention was the ring gaps. Wiseco pregaps their rings (which is dumb of them I think) so now the gaps are LARGER than what I want. not by much but my gaps are as follows

Top .0022
Bottom .0028

I wanted to run the gaps .0020 and .0024. But thats what I'm going to have to do...

 

My engine is somewhere in the .0080 range, been running for 2 years without much blowby at all. You'll be ok with .0040.

 

i run .0055 (5.5 thousandths) and its been great, sure it makes a clacking noise until i make a test pass but thats when you know you arent going to scuff a cylinder wall pushing 800+

 

my motor is at around .0055 pushing 950+hp... motor actually isnt loud at all.. and no blow by

 

I am .0045 and daily driven for a little over a year. Still makes good power. It is a little noisy but it goes away.

 

you can get the skirts moly coated from swaintech to eat up some clearance.

 

You are fine just let it warm up when you drive it. I have seen as much as .008 clearance on a piston. I would not worry as much about piston slapping around as i would worry about burning oil causing detonation.But you should not have either

 

Some machinists used to knurl the piston skirts if piston/wall clearance was a little loose. You might ckeck that out to see if it's still considered a reasonable approach.

 

I would not do this. knulring is a temperary type fix
trust all the people that are telling you will be fine
piston clearance is not one of the things in a engine that makes huge power differents unless you have no compression. but that would have to be alot of clearance and bad rings. If you have to much clearance you will have slap but it will take a lot. i ran a engine with .006 and it would sound like a vw deisel till it got warm then go away and sound smooth. i would want what the spec sheet calls for but if you look it calls for different clearances for different applications. you will be fine i would rather be loose than tight

 

.006 here... raped like a hot stepsister... slappy when cold, gets quiet after a few minutes... just make sure to warm her up

12k miles at 660WHP beaten like I stole it....every time i get in it

 

surely you need to consider power/performance goals. factory specs on 26xx pistons are usually around 2.5 thou, but say add 1-2 thou for high power turbo or nitrous applications?

and 4xxx pistons are more like 2 though +1-2 though for high power turbo/nitrous. so your 4 thou on 26xx pistons aiming 400hp+ should be fine?


p.s. anyone know of anyone using factory cast high silicon pistons at 3 thou ???

 

I had run a set of ENDYNES (Manufactured by Wiseco) at there .0032 recomended spec AFTER contadcting them and telling them that I was going for north of 600WHP and that me and my machinist were cincerned about their tight specs..... They INSISTED that .0032 was plenty.

HEres what it got me after a few 600 pulls



I listened to him (he cited their higher silica content blah blah blah).... Sorry I did. I ruined the ****ing motor when the pistons grabbed tghe sleeves. He blamed my tune (which was spot on)... and about everythig other than the fact that they needed to be run looser than his spec *(which i ran at the LOOSE end of his spec). He said it went lean... It didnt, he said it was detonation.. It wasnt... Just to tight....


Bottom line is that I moved to CPs (after Endynes leaving me holding my dick in the air) ran them at .0045 and had 0 issues at 620 WHP for over 10K miles. HARD CONTINUOUSLY BEATEN MILES. BEATEN RELENTLESSLY on the street like I stole it every time I drive it.

I overrevved it and had to take the motor apart to check **** out and everything looked cool but the oil pump gears broken into a bunch of pieces. I straight honed the cylinders to get a nice hatch on the for the new rings (PISTONS LOOKED MINT) and get the bores square. Put new set of OEM bearings in it and piston to wall measured out at .006. Its a tad slappy when cold, but gets quiet after a bout 2-3 minutes of warming up andpulls 22" vacuum at idle when warm, and made 661 WHP a couple months ago


YOULL BE FINE AT .004. ESPECIALLY IF YOURE TRYING TO MAKE POWER


TRUST ME