smokinsi

Hey I was wondering if I put my pistons in backwards so the exhaust valve indents were line up with the intake valves, would it start?

I just put in JE pistons and when I start it sounds like the valves are tapping and it idles ruff. The guys I bought the pistons from said forged pistons would be loud until they warmed up. I haven't let it run long enough to warm up yet cuz I'm scared.

When I turn it over by hand it feels fine. Would it hit the valves if the pistons were in wrong?????????????

Please help..

Evs-One

what was your piston to wall clearance?

What dome are the pistons?

smokinsi

The diam is .005 oversized. The directions say .0025 + .001 to .003 for SC apps.

I don't know what dome they are but they are 9.9:1

monicle

it doesnt matter. the vavles are exactly parallel to eachother so the dimples in the piston are the exact same depth. it makes no difference which way they were installed.

delScho

If it's a taper cut piston, you're probably hearing the piston slap. It's common with performance slugs.

skunktuned

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by monicle &raquo;</TD></TR><TR><TD CLASS="quote">it makes no difference which way they were installed. </TD></TR></TABLE>

Wow, that's the first time I've ever heard someone say that. I have never seen a piston with a centered wrist pin. Unless the piston is perfectly symetrical in every dimension, you're main concern should be the wrist pin offset. Basically most, if not all, pistons have the wrist pin slighty offset towards the major thrust side to reduce piston slap on the power stroke. If I were in your shoes I wouldn't run the engine, get in there and turn that slug around.

If you have or have seen pistons with a centered wrist pin please send a pic. It would be really interesting to me as I have been taught that pin offset is a basic characteristic of piston design. As far as I know if a wrist pin were centered, you'd have slap at all times. enlighten me.

monicle

as far as I knew most aftermarket pistons have centered wrist pins. stock pistons thats a different story. I might be wrong though.

monicle

here is a page that compares many of the top name pistons. http://www.importbuilders.com/pistoncomparo.html
as you can see many of them do not have offset pins, including je pistons.

in4ni

In my experience (about 500+ engine assemblys) I have never seen a piston that has the wristpin in the center or a piston that didnt have a notch indicating the front. the pin offset cannot be seen very easily it only about .040 offset.
And yes if your pistons are in backwards you will hear the piston skirts slap.

just my 2 cents

smokinsi

Don't know how I fucked it up but after pulling the head I had 1 piston backwards. I didn't see any marks on the piston or the valves so I assume the noise was the piston slap in4ni mentioned. The pistons didn't have any markings on them just had slightly larger cut outs for the intake valves.

It stops pulling after 6k or so, so I've still got issues somewhere. I'm going to check the compression today.