Pistons in backwards

[David Stillie]

I took the heads off an 440 engine I got with a project car. The pistons are installed backwards! This engine was built by a professional machine shop and was broken in on their dyno. The pistons are KB Hypereutectic quench dome. The was no contact with the valves, probably due to the generous valve reliefs and mild cam. My question is, is it possible that this was done on purpose? They only advantage I can guess is the ability to use a closed chamber head. I have open chamber iron heads so I will be pulling them out and installing them properly, although my quench distance will be over .060"

 

[mtbase]

I can't imagine that it was done on purpose.
I'd go back and voice a complaint. A less observant "home mechanic" might have swapped heads and ruined everything.

 

[91r/t]

Probably a Friday afternoon" hey lets hurry up and slam this together so we can get outta here" type of deal.

 

[PurpleBeeper]

Holy crap! That's the second time in 6 months I've seen that on this site. I am VERY surprised the pistons didn't contact the heads, let alone the valves. Maybe it's just me, but if this was PROFESSIONALLY done, I'd be wanting a re-hone & a new set of rings...wow.

 

[peabodyracin]

I'm not sure looking at the photo how you determined they were in backwards. Is it from the position of the dome or something else? I believe the dome should be at the base of the piston as installed. At least in my experience they are. Here's a photo of mine for example. Sorry but I must be missing something or the photo has me fooled.

Years ago guys used to reverse pistons with the theory that the wrist pin hole was slightly off center on the piston to reduce piston slap. Reversing them supposedly reduced drag on the cylinder walls. I even did it myself once building a SBC for a drag car. Certainly not advised for a domed piston though.

 

[dryheat]

Eyebrows up ~~~ check the bottom end as they may have just mistaken their odd / even side.

 

[David Stillie]

The "dome" is supposed to go into the quench area of the head. The pistons have a centered pin, so there is no advantage to swapping then bank to bank.
The engine was built four years ago, so there is little chance of recourse. I guess someone just screwed up.

 

[Kern Dog]

I was thinking that they are not backwards as much as they are upside down. If those same pistons were merely moved over to the other bank without rotating them, they would be right. The trouble is, are the rods pressed onto the wrist pins and pistons so the big end taper is to the fillet radius/outside ?
As mentioned, the old racers trick of installing stock flat top, non valve relief pistons opposite of the notch was done to reduce piston drag at the expense of a slightly noisier piston.Maybe you'd get 8-10 HP with that?
I have built a few engines and only once did I mess up the orientation of the pistons like this and it was two, cylinder 1 and 2. Oil pressure was fine but the cam went bad within 200 miles and when I stripped the engine to clean all the lifter debris, I caught my mistake. The rod bearings looked fine even though the big end taper was to the inside. #1 and 2 share a journal/pin so maybe that is why the wear was not bad? Maybe that and the low miles of run time.

 

[Mike67]

 

[69Bee]

Driver side (odd) leads the pass side (even). The even rods are to the front of each crankpin, and the odd rods are second. Because of this, you can not just swap the pistons/rods side to side, you have to reverse the pistons (rotate) on the rods. If you just switch rods side to side, the bearing will hit the crank radius and lock up.

 

[lewtot184]

they're upside down/backwards. used several sets of those type and thy are left and rights plus the dome should be towards the inside of the engine. how dumb can people get. they give instructions with those pistons. end gaps may be screwed up to.

 

[snakeoil24]

Somebody was smokin a joint while installing the pistons.

 

[lewtot184]

or the piston rod assemblies are in backwards?

 

[33 IMP]

The engine was put together by a chevy guy who assumed that the " dome" had to be in the chamber. Didnt have a clue that it was there to provide quench. Miracle Engine Builders, if it runs it's a Miracle.

 

[dvw]

This engine was built by a professional machine shop and was broken in on their dyno.
Why did you remove the heads? What does the shop say?
Doug

View attachment 609442

 

[David Stillie]

I pulled the heads to port them. The engine is now completely torn down. I will be swapping the rods and pistons around. Luckily everything else looks good. I am going to contact the machine shop and let them know what's going on, try to get them to send me a gasket set or something.

 

[happyjackdaddy54]

that is an old super stock trick .Don't know why they did it. But, its not that rare in the old days

 

[Mike67]

Never seen that before to be honest, but it it makes me wonder how the valves didn't hit the piston???...might need to check the push rod lengths.
The 184s have a 1.992 Comp Ht, a 1.094 pin, & a .140 quench pad
The 236s CH 2.057, 1.094 pin & a .075 pad....

 

[451Mopar]

Looks like the builder thought they were "Dome" pistons for compression?
Often called "Reverse Dome" for reducing quench distance.

 

[lewtot184]

that is an old super stock trick .Don't know why they did it. But, its not that rare in the old days

they used stock type flat top pistons with off set pins. different scenario.