i have standard size JE 8.6:1 comp. pistons, but i herd you cant just throw them in as if they were OEM pistons, because they would slap or something like that, im just looking for answers from people who have installed std. JE 8.6 pistons in there 420a, i need the number for the machine shop asap...

mike

If you have STD bore pistons then all you'll need to do is hone the cylinders. You also need to take the pistons to the machine shop with the block if you're going to bore out the cylinders.

>You also need to take the pistons to the
>machine shop with the block if you're going to bore out the
>cylinders.


what does he need the pistons for? to match hone them? i know there has to be a certain amount of space between the piston and the piston wall for the rings, i think thats the important number... i dont want them to slap

>what does he need the pistons for? to match hone them?

You need to go back to school. A good machinist will want your pistons to measure them for your application. Sure, he can look at a paper, and see what they're SUPPOSED to be, but he'd rather get his hands on the pistons that will be going into the engine so that he can mic them himself.

You can't just buy a set of forged pistons and slap them in after a quick ball-honing. Dork.

The piston-to-wall clearance on a typical cast piston, like the ones found in the 420a's is like .0025" to .003" on a good day, with a strong tail wind. The tailwind thing is a joke.

Your JE's will need more piston to wall clearance because they expand more than cast pistons will. They're going to require at least .004" if not more to account for expansion.

>i know there has to be a certain amount of space between the piston
>and the piston wall for the rings,

Almost. The clearance for the piston is there so that the piston stays together. If you heat up that forged piston, it'll expand. If the bores are too small, the piston will literally have the top pulled off from it.

>i think thats the important number... i dont want them to slap

They're going to. Any good piston slaps, when the block is properly machined. If it's not properly machined, then I wouldn't stand near the car while it's running.

What's the matter, you don't like the sound of horsepower rattling around under your hood? That's like a pussy begging you to unleash your pork sword. Dip it, you know you want to :thumbsup

as i understand it, those je pistons are going to slap no matter what until the engine warms up and everything expands to fit perfectly. i think that is right....(shrug)

Don't (shrug) when you're right. Forged shit makes noise. That's why it's more expensive (duh). Also not every piston that comes from the mold is the same. Some (believe it or not) or bigger or smaller. On top of that fact the main reason that I would have my block chalked on a boring machine is because A)they don't use a ball hone to break glazes and more importantly (B) I like moly rings. You can't NOT use a silicon impregnated ball hone(which most are) when using moly rings. THEY WILL NOT SEAT! Have fun.

well erik, i didnt know if i was right. thanks for the confirmation. i just didnt want to give bad information and be sure about it.

what it all comes down to is this: he should have read my post and been done with it. :thumbsup

Amen.

Wait, you are doing a rebuild with standard sized forged pistons? I don't think that this is wise. MAke sure that you know what you are doing. Check for bore taper, out of round, etcetera, and make sure that the block will spec out properly with the pistons that you are getting. I think that you are just asking for trouble, though.
-=B-=

the guy as for a simple number dune bugs. It should be about .020 over. Bring your pistons with you to the machine shop. The guy will know how much to bore. But it should be .020 over.

everything said looks good im with the1bill i really dont like to see STD bore pistons unless the person had it checked out before hand the right way...

i always recomend somone to bore it if they have the slightest doubt that they aren't still within std bore specs..

Mototool thanks for the information and ina Mature manner!

:thumbsup

>the guy as for a simple number dune bugs. It should be about
>.020 over. Bring your pistons with you to the machine shop.
>The guy will know how much to bore. But it should be .020
>over.


No V. That would be with .020 OVER pistons, not STANDARD BORE pistons.

I'd check them to make sure they're round, give them a good hone, Mic the piston, mic the bore, check for about midrange clearance per JE's specs, install it, and pray.

Of course, i'd probably send them back and get .020" over pistons before i'd do any of that stuff.

JE took piston-to-wall clearence into consideration when they designed and manufactured the STD bore piston. Make sure the machinist has the pistons and spec sheet when he works the block.

do yourself a favor and dismantle the engine and check the bore out b4 you buy pistons. I didn't I assumed the bore was fine, then when I was done I got higher compression on the outside than there were on the two inside pistons corresponding to how it was when I had the stockers in there. Not to mention a lotta piston slap

i got a good deal on a howell bottom end kit with extream eagle rods, the kid sold me the whole kit for $700, so i am stuck with the STD pistons, i have three blocks, my 96k miles block, a 52k miles neon r/t block, and a 110k mile avenger block.... so he should be able to get a good block out of the three, i didnt get the instal instructions... just the diagram with the pistons and piston info on it, i didnt realize all forged pistons slap... thats cool if its what they are supposed to do... idk what rings the kit has, they are the total seal rings that howell gives with the kit, and i tried to send the std pistons back to get .020 over but they wanted to give it to me in the ass, so im just gonna stick with the std pistons, im not going for rediculously high horse power numbers.... this care makes me wish i would have waitied a year to buy.... missed out on a 97 gsx last week, identical to my RS and the gsx was a lil more money... anyway, stuck with the 420a now.... all the help you can give is needed, i really dislike negative posts tho, im asking for help, not opinion.... so please help me out in any way possable, i have all the supporting mods, its just down to getting the bottom end put together

IMO, I would never put standard bore pistons in, when rebuilding a motor. Even though your cylinders may look "good", you can never tell of any out of round, ect.. I would always have the block bored .020 over, using .020 over pistons. This will assure you that you have perfect cylinders. No need to skimp on building a good, high HP motor like that..

hopefully out of 3 blocks you can get one thats still good in standard bore...

are these parts used or new in box?
if used make sure the rods are hones/bored to the proper size for your bearings... ive had to adjust 2 sets of eagles because of the bearings....

if u didn't get bearings check out some clevite 77's u might need to get 10 under if your crank needs ground,

if it was me id sell or toss aside the total seals and get some speed pro rings for your pistons they have a moly coat on the upper ring and seems to be one of the best quality rings on the market..

Bill

all the parts are brand new in the box, with std 77 rod bearings, everything i got is std other than the 8.6:1 pistons, not to stray off the path but how much should be taken off from the head and the block to get close to 8.8:1 compression, my origional plan was to get 0.02+ weisco 8.8:1 pistons and the x-tream eagle rods, i didnt just deside to do this 420a turbo thing because i got a good deal on the howell kit... this is just what im going to use now, so the motor is getting STD JE pistons and total seal rings... this is just a venture into the 420a side of things, i have always had 4g63T 1g's, also, not that it matters to me, but i am curious what the horsepower numbers are projected to be after this build...