piston question

idriveacab · #1 10-07-2005, 03:14 PM

ok the pistons i got are je 12.5-1 comp at standard bore, i heard because they are forged they wont go into the block without the block being bored. anyone know if this is fact or fiction

idriveacab · #2 10-08-2005, 03:10 PM

anyone???????????????

sheetmagnet · #3 10-09-2005, 01:03 AM

Quote:

Originally Posted by idriveacab

anyone???????????????

Well if they are standard-bore, they should fit with standard-bore rings... do they have deep fly-cuts?

idriveacab · #4 10-09-2005, 01:38 AM

yeah im looking at wall clearance not valve clearance, im on another forum and i found the info i need. if anyone needs or has more info ank or tell and i will try to help.............................i found i have to pull my block and have it ported even if the je pistons say they are stock bore because they expand when they get hot past normal operating tempetures because they are forged. i will be using nitrous so it will be beyond normal operating temps............................................. .................................................. .........................................i have the head already off is there much work to getting the block out now?

sheetmagnet · #5 10-09-2005, 02:12 AM

No. Unplug everything, unbolt your motor mounts and disconnect your tranny (or unclip your CV shafts and trans mounts and sensor clips and linkage and yank that too)... but anyway you can yank it right out of the top if need be...

How much is the bore recommendation? Do they do a flat-bore or recommend new steel sleeving? I would recommend a sleeve press-out and bore the block, and replace with a sleeve that is already bored over (due to your higher comp. ratio and nitrous) but that's just my preference.

idriveacab · #6 10-09-2005, 02:51 PM

they are saying the bore should be .0025" - .0035" over. they didnt say anything about sleeveing it.

sheetmagnet · #7 10-09-2005, 08:53 PM

Quote:

Originally Posted by idriveacab

yeah im looking at wall clearance not valve clearance

Well your valves still might not touch the pistons and vice-versa, but you are still bringing the piston closer to the valves by going to 12.5-1 compression pistons... that's why I asked about fly-cuts, because I didn't know the answer (yet). I am not very familiar with JE pistons in regards to putting them in a neon... something I haven't done or personally worked with (yet), I just know that depending on the application, they sometimes are a necessity in situations like this. I asked because the compression is higher because the wrist-pin and rod is farther away from the top of the piston (i.e., the piston and rod together are "taller." Stroke length remains the same, but the new pistons will travel approximately 0.0040" closer to your head and valves (about every 0.0015" decrease between the head and the piston will boost the compression about 1 full point).

As far as boring the block... 25-35 sounds ok but did they say what kind of rings they recommend? (I'm guessing that gapless would be out of the question). Of course even if it didn't didn't need a bore, a good honing and dip is always a good idea before throwing the new pistons and rings in there.

idriveacab · #8 10-10-2005, 03:15 PM

yes they have flycuts in them im going to try to get a picture of them on here. they are je pistons also they recomended je rings so i have je rings............................................. ........................im going to be decking the head .10 also so its going to be closer.

neon_rt · #9 10-10-2005, 03:39 PM

Forged pistons need more clearance on the bore because they flex more than cast pistons do under extreme useage.

idriveacab · #10 10-10-2005, 04:17 PM

yeah im getting it bored

idriveacab · #11 10-10-2005, 06:34 PM

got pics

idriveacab · #12 10-10-2005, 06:43 PM

idriveacab · #13 10-10-2005, 06:45 PM

12.5-1 je pistons with eagle rods

sheetmagnet · #14 10-12-2005, 01:42 AM

Good pics... but about the pistons and the deck...

Sounds like a nice setup. But between those two, you'll be looking at a final comp ratio of about 13.2:1... You could probably get away with this (with few or no other internal mods) by running 93-94 octane, which I assume you will anyway (unless you still plan on burning 87 and retarding timing like crazy, which would make you a retart yourself, which I gather you or not)... but anyway are you running the stock cam? Injectors? ECU, etc... just curious because the mods you are doing are really good mods and open the door for other mods that would benefit greatly from this. For example, a header, downpipe, and custom cam would add a tremendous breath to just the pistons and deck alone...

sheetmagnet · #15 10-12-2005, 01:53 AM

And for the record I am jealous... I would consider your mods for my car, but I gotta drive it every day to work and I don't have the funds to purchase a 3rd vehicle to account for that (wife drives car #2)... so I guess I can just smile and dream for now :-) Oh yeah and how does your block look... is it 100% smooth where the old ring travel was? If you can see where the travel was, I would recommend at least a slight surface honing to "blend" the consistancy of the walls together before you throw your new hardware into it. It will add a lot of life to your "new motor."

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