Which way should my Pistons/rod point?

[Lil Demon]

Getting ready to start assembling my 340 soon and as I visually inspected my rods and Pistons I noticed I couldn't find any indicators to show which way they should be pointing once installed in the block. Can anyone point me in the right direction? Pistons are new SRP 142068 and rods are stock 340 that have been balanced so I don't know if an indicator was machined off during lightening process.

 

[RustyRatRod]

The rod bearing locks on the inside of the big end of the rods face the outside of the engine. We will need to see the pistons in order to tell which way they need to face.

 

[Lustle]

When you say pistons "point" I assume you're talking which way the valve reliefs face? On A engines the exhaust valves are the two centre-most valves and the two end valves in each head. So the middle two pistons the small reliefs should face each other. And on the outer two pistons they should face to the outside of the block.

 

[krazykuda]

The squirt holes in the rods should point to the opposite cylinder (or toward the center of the engine).

If the pistons are to be installed one way, there should be a mark on the side that goes to the front. If they are not marked, they may be able to be installed either way.

 

[Lil Demon]

Thanks for the quick reply I already put everything away but will get a picture up sometime tomorrow.

 

[Mrmopartech]

On most pistons you have a notch or arrow or some type of printed ID numbers to show direction.Other ways are valve notched which should be one small and one larger for the vavles.This type of piston only has one way to be installed.If one is using a flat top piston which has NO indication at all,one must look at the wrist pin offset location.All piston are offset to allow a better angle to push the crank to rotate.If you check the pin location and measure the pin location to the side of the skirt, you will find a offset,this offset is to be on the lower side on the passenger side,and the on the top side of the drivers side to allow a much easier push of the rod to the crank to rotate.So please check and post pictures of the piston/rod assembly,so we can see what you have for the 1,3,5,7 assembly,s and the 2,4,6,8,assemblies,as you may have to remove and re-install some rods and pistons,mrmopartech:burnout:

 

[67Dart273]

And to make things worse, in the seventies there was a big fad to reverse OEM pistons in the bores to supposedly produce more top end power. No idea if this was a "good idea."

 

[Double M]

And to make things worse, in the seventies there was a big fad to reverse OEM pistons in the bores to supposedly produce more top end power. No idea if this was a "good idea."

It was a great idea. The only engines that I know of (which means less than nothing LOL), that reversing the pistons and swapping cylinder banks to gain different wrist pin offsets was the 10.5-1 273 Commando engines and the D Dart 273. I've built myself a couple of them. Depending on how you build it, you can get another 1,000 RPM. You also get piston slap. The L2222NF TRW powerforged pistons (273 10.5-1) are ZERO pin off-set, probably not even made anymore. I know nothing about other MOPAR engine pin off-sets.

Old school way to know how rods are installed:...Numbers/locks to the outside, pee-hole to the cam. Real easy to remember.

Russ.

 

[nm9stheham]

The SRP eyebrows go to the top like any other 2 valve relief piston in the SBM. Like the pix below of these KB's.

Unless they are marked left and right banks, these can go anywhere; I don't think they don't have a pin offset; the website does not say. If there is no notch or arrow or similar mark on either side of the piston top above the pin holes, then that also says no pin offset. Most, or any, of the KB's, as well as the Speed Pro's IIRC don't have offsets.)

 

[famous bob]

The SRP eyebrows go to the top like any other 2 valve relief piston in the SBM. Like the pix below of these KB's.

Unless they are marked left and right banks, these can go anywhere; I don't think they don't have a pin offset; the website does not say. If there is no notch or arrow or similar mark on either side of the piston top above the pin holes, then that also says no pin offset. Most, or any, of the KB's, as well as the Speed Pro's IIRC don't have offsets.)

not familiar w/ small blocks, but u better have the right valve notches in the right correlation w/ the bigger in take valves.

 

[toolmanmike]

not familiar w/ small blocks, but u better have the right valve notches in the right correlation w/ the bigger in take valves.

Yep. show us a photo of the top of your pistons and we'll see what you need to do.

 

[nm9stheham]

not familiar w/ small blocks, but u better have the right valve notches in the right correlation w/ the bigger in take valves.

So far the flat top ones I have seen have equally sized reliefs on both sides. The KB's are all that way as are Speed Pro's....flat tops, that is. The mfr's pix looks that way for this, but may be a stock photo. So, yes, you and TMM are right; a pix from the OP is for sure the best.

 

[krazykuda]

So far the flat top ones I have seen have equally sized reliefs on both sides. The KB's are all that way as are Speed Pro's....flat tops, that is. The mfr's pix looks that way for this, but may be a stock photo. So, yes, you and TMM are right; a pix from the OP is for sure the best.

You are correct that when there are two valve reliefs, they go to the top of the bore.

Funny how the manufacturer's web site does not post a picture, but other ones show that they are two valve pockets on the top of the piston. But you are correct that those could be a generic stock photo...

Then he needs to make sure that the squirt hole points toward the center of the engine and the anchor slots go to the outside. So you would pin the rod so the squirt hole is on the same side as the valve pockets and the anchor slots go toward the side of the piston without the valve pockets... Then when you install them in the bore, they will point to the center of the engine, or opposite bore...

Always make sure that the anchor slot on the rod and cap mate up on the same side. Not opposite each other, they work together...

 

[Lil Demon]

Ok guys I barely got home and catching up with thread. I was gonna take th pic but the Pistons do have top valve reliefs and yes they are equal size. Of course once I saw the explanation of making sure they are to the top I laughed and realized of that logical reasoning, explaining the reason why there are no typical notches,dimples,arrows etc.. Assembly is balanced and machinist numbered top of pistons. I guess that is enough indicator. Another case of overthinking perhaps? Thanks nm9stheham for the pic and everyone's advice. I'll post a pic either way

 

[krazykuda]

Ok guys I barely got home and catching up with thread. I was gonna take th pic but the Pistons do have top valve reliefs and yes they are equal size. Of course once I saw the explanation of making sure they are to the top I laughed and realized of that logical reasoning, explaining the reason why there are no typical notches,dimples,arrows etc.. Assembly is balanced and machinist numbered top of pistons. I guess that is enough indicator. Another case of overthinking perhaps? Thanks nm9stheham for the pic and everyone's advice. I'll post a pic either way

It's better to ask before making a mistake, than to not and make one...

Make sure that the oil squirt holes in the rods are oriented properly to the piston valve pockets. They point toward the opposite cylinder.

 

[Lil Demon]

I hope this picture comes out bigger than the last one I uploaded

 

[Lil Demon]

Krazykuda I didn't understand what you were talking about when you mentioned oil squirts. As I grabbed the assembly to take the pic I saw what you were talking about. I'd never seen that on any Chevy or fords I'd ever put together, learning the Mopar way now.

 

[toolmanmike]

Better to be safe than sorry especially if you are not familiar. Yes the valve reliefs are equal and the machine shop marked the pistons to their respective bores. The probably finish honed each cylinder to its specific piston. Good work there. Keep us posted on your progress. Tmm

 

[RustyRatRod]

There could also be markings in the piston pin area as to which way the pistons face.

 

[krazykuda]

Krazykuda I didn't understand what you were talking about when you mentioned oil squirts. As I grabbed the assembly to take the pic I saw what you were talking about. I'd never seen that on any Chevy or fords I'd ever put together, learning the Mopar way now.

Yes, it's a groove in the cap so oil will squirt onto the opposite bore.

View attachment Pist rod A09 B.jpg

Here is the Oil Squirt hole labelled in red:

View attachment Pist rod A09 B2.jpg

Here is the anchor slot that is opposite the notch for the squirt hole. Always butt the anchor slots together as they keep the bearings from spinning, so they must be on the same side on the rod and cap.

View attachment Pist rod A13 B3.jpg


Here the anchor slots for the cap and rod are circled in red, and the anchor slot in blue. Keep the anchor slots together when you put the cap on the rod:

View attachment Pist rod A17 B3.jpg


Here is how they should go into the engine. Notice how the oil squirt holes (labelled OS in blue) point toward the center of the engine when installed, or to the opposite bore. The anchor slots go on the outside when installed:

View attachment Pist rod A23 B3.jpg

 

[nm9stheham]

I hope this picture comes out bigger than the last one I uploaded

Actually if you look at the pix in post #16, the reliefs are indeed NOT the same size. Being this piston is numbered 8, the large relief will end up under the intake.....which makes sense. Maybe that is why the pistons were numbered.... to help you sort them properly. My hat is off to Famous Bob for mentioning this.