forged pistons

[hungryjoseph]

everytime i ask questions about this I never get answers, and I find nothing in searches lol, i'll try again

that's why my car isn't moving lol.

I didn't realize that there were different piston grades. I have the grade 2 54c stamped pistons and I ended up ordering a grade 1 piston. which apparently weighs different and the clearance to the cylinder is also different according to the FSM. i've called a few places and basically I will have to wake 3 to 4 weeks for the right piston to come in from japan. the next option i'm looking into is getting forged pistons because I know i can get them in a week, but there are alot of things I don't know. This is my first time rebuilding a motor. I hear a lot about how forged pistons expand more than the oem ones. I saw in the FSM that even though the piston bores were all 86mm, there were different grades made in tolerance of .01mm. with aftermarket pistons, there are no different grades, they're all the same grade (from what i've seen). so does this mean i would have to measure the piston and get the block machined for the correct clearance? aka not a drop in solution? how exactly do i account for the piston expansion? I don't have a micrometer or dial bore gauge but I could probably get my hands on them if i really needed them. I see alot of people online just get pistons, hone their block, drop them in and go. so the FSM is confusing me

[Hijacker]

I've never heard of anyone claiming forged pistons to expand more than OEM pistons. In fact, some companies use particular metal alloys to limit expansion. But given that you melted the ringland of the piston, I would inspect the bore to make sure it's not scored. If it is, have it bored out .5mm and throw some 86.5mm pistons in. If not, either drop OE back in or find a set of forged that are 86mm in diameter.

[V8slayr]

The same thing happened to my piston when my motor let go. Destroyed ringland and scored cylinder. Trust me, if you are already in the motor you definitely need to go ahead and bore(if needed) and hone the cylinders and go w/ forged pistons. Everybody knows our pistons are the weak link and it is alot of work to tear the motor all the way down. Just take the extra time/ save a little more money and go forged while you can. Search for some deals on pistons too. I found my brand new in the box CP 87mm 9.0 pistons for 420 shipped on craigslist. I would have spent almost exactly the same for OE pistons.

[hungryjoseph]

thanks for the replies. there is no visible scoring on the cylinder walls. it's been honed already, hot tanked, and resurfaced for my metal headgasket. so what you guys are telling me is that the 86mm cp/weisco/whatever will work fine with my bore and I shouldn't need additional machining (assuming it is not scored, which it doesn't look to be). I really don't like this engine but I'm working with it because it's what I have right now. but I will install forged pistons if there is no additional machining required for it. i've heard that they expand more than oem pistons from suburu owners who have rebuilt their engines, thats where my question really stems from, and also a few other people around me who talked to me about measuring for their expansion

[V8slayr]

I'm with Hijacker on the expansion thing, never heard that. Do what makes you feel comfortable. I don't know if you are assembling your own block but I just trusted my local engine builder w/ mine, and they are fantastic.

[boro drift]

thanks for the replies. there is no visible scoring on the cylinder walls. it's been honed already, hot tanked, and resurfaced for my metal headgasket. so what you guys are telling me is that the 86mm cp/weisco/whatever will work fine with my bore and I shouldn't need additional machining (assuming it is not scored, which it doesn't look to be). I really don't like this engine but I'm working with it because it's what I have right now. but I will install forged pistons if there is no additional machining required for it. i've heard that they expand more than oem pistons from suburu owners who have rebuilt their engines, thats where my question really stems from, and also a few other people around me who talked to me about measuring for their expansion

Forged pistons do expand more than cast pistons. Back in the day, it used to be as much as .008". But, technology has come a long way, my JE's have a .004" tolerance. What ever piston you buy, you need to have the piston to bore clearance checked, there should be a spec sheet that comes with your new slugs.

[sr_240sx]

Did you have put sleeves???? for that bore 87mm

[DuckyD]

Did you have put sleeves???? for that bore 87mm

Not to sound like a d*ck but you can see from his picture that he didn't sleeve the block. A sleeved block would look like this--> http://www.cdpautomachine.com/...0.jpg

[Wretched]

Anytime I do aftermarket pistons, I take the block, pistons, and the specs to a trusted machine shop.

[hungryjoseph]

i guess i will put some useful information on this thread with everything i found out.

piston to bore clearance is very important and is ussualy around a .0035 to .004 inch clearance for the cp pistons. Forged pistons expand more than cast pistons and that larger clearance is there for that expansion.

Did you have put sleeves???? for that bore 87mm

it's not sleeved. and it's not 87mm.

Anytime I do aftermarket pistons, I take the block, pistons, and the specs to a trusted machine shop.

the one thing i realized is that with the money i spend paying them, i could buy my own tools to do it myself. the only thing i want to pay them for is the actual machining, which i could never buy the tools for lol.

[47ronin]

ok so this is a very newbie question, Is there an added benefit for sleeving the block, other than its just what you do when you bore to much over time?