possible to remove pistons and turn around?
 

i took some eagle hbeams, and ross flat tops to have pressed together. didnt even think to look when i picked up yesteday and i probablly wouldnt noticed anyways but.

i was installing the end pistons to measure how much to have removed off the deck when i realised all of the chamfers are pointing to the left while the valve reliefs are up top. i needed them to all face to the right. otherwise id have to puttem in upside down....im only building a 400 because i had the stuff to do it already...not sure i want to buy new pistons for a 406 cubic inch if my pistons are trashed

Having the piston off set wrong will make for a bit more piston slap / noise when the motor is cold for maybe 5 minutes, but what matters 100% more is that the Rods are facing the right way so the bearing does not ride up onto the radius from the Rod journal to the cheek of the crank.

The Rod bearings are offset in the Rod in other words .

thats the problem, the rods are facing the wrong way, i would have to turn the pistons upside down to get the chamfered side of rod to face the counter weight, otherwise with the chamfered sides will be to the inside while the flat side rides the counter weight.

Would swapping them to the other bank solve this? If the rods
were stamped, the shop might've been following how Chevies
are numbered. :noidea:

i originally thought i obly needed to worry about 4, but then i realised all 8 are turned the wrong direction. only way to make it work is with valve reliefs upside down at the 6 oclock vs 12 in tge cylinder.


i guess i didnt think much of it because he had just finished up a 326, and had another pontiac in the shop. all i can figure is one of his less experienced guys did it. as long as my pistons are salveageable i guess its ok

My Street post on the 421 build shows my Harbor Freight 12-ton Press for drifting them Pressed Pins out. Yea the Piston-rod orientation needs Ds and Ps to have the rod flip.

To keep rod journal chamfer and crank fillet-radius together.
To keep piston pin angle correct for low Thrust surface load ( piston pin is offset)

can they be pressed out without damaging the pistons though?

I was considering getting a set of forged rods to replace the stock ones on my forged pistons. I asked the two shops in town about it. It can be done very carefully. One of the shops said they have done it. No guarantees of success, though.

Yes, usually

fingers crossed.

When they pressed mine the first time at a local shop they fubared one of them. Bent the piston. When I took it back I couldn't believe what he said ... "Yeah, one of them was pretty tight, I was wondering if you'd notice that" .. WTF??

They paid for the new piston, which because it was a single .040 over TRW unit, took about a month to find.

Second pressing went OK.

fingers crossed they can be removed, shoukd here something tomorrow afternoon......guess ill have a 400 crankshaft for sale worse case

Chevy machinists tend to do this. I had it happen once with speed pro 455 pistons. They turned them around with no issues

he put the tangs to being to the bottom of the crank facing up to the cam, that put all the radius to the left. possibly on a stock rod this might be right from whatever specs he was reading from. when i showed him how the rod has to sit, it puts the bearing tangs up, or closest to the cam...top of crank throw. he was a hard time making sense of it but all, i had to show him how the radius was on the wider side of the rod which also i dont think a stock rod has. feelin pretty whipped by the rods he seemed pretty confident he could swap them around. another shop has a fixture that only holds the rod so he was gonna borrow it, otherwise they usually just press them out if there being replaced and damage is no concern.

i told him take his time...get whatever tool neccessary, otherwise this 400 build is done and ill use the rods on something else.

One thing the machinist needs to know is that the rods are in different positions in relation to the chevy which most work with.

The even bank (passenger side) is ahead of the driver side bank. When in block the #2 rod is ahead of #1. Chevy is #1 ahead of #2, so machinists install pistons like that.

So it's 2-1, 4-3, 6-5, 8-7


:)

Breaking a piston, cracking a skirt, crushing the pin box, are all possibilities when trying to remove and re-install pressed-in pins. Even with all the dozens and dozens of adapters with the Sunnen pin press, it can happen. Cast pistons are the most likely to crack and forged the most likely to bend. Once pressed out, I always make sure the pin will pass easily through the piston pin bores. Sometimes it takes a little touch-up in the hone. We probably damage maybe 1 out of 50 or so. Generally they can be repaired. Maybe 1 out of 100 is actually ruined. I make my students verify and mark each piston and rod before we press any new ones on. But mistakes are made every now and then.

that is the mistake he made too, when i explained right bank riding the front counterweight of each journal....he realised right then....with a...ill gettem pressed off...i femt like it bruised his confidence abit but i knew cgevys is what he does mostly with a pontiac here n there.

got lucky.....pistons were saveable

Great news