A&E piston direction

[aeronca65t]

I just asked this question in the "Racing" section, but maybe someone here might know the answer:

I have a new set of A&E 21253 pistons (.0400 over) I'm putting in my 1275.

Is there a "front" or "back" or "thrust side" to these pistons?

I don't see any markings to indicate direction of fit.

They do have "A&E 21253 +.040" on the top of the piston. Do I use that to orient the pistons?

Thanks!

 

[BlueMax]

I believe the AE- 21253’s are non directional. I’ve always said if they are not marked they can go either way, some have the .040 to the front, others to the rear.

 

[Spridget64SC]

The AE21253 pistons have centered pins, so there is no set orientation. Being an ACD engineer, I like to have all the nice AE part number etchings show up on the same side of the engine. Also, with the LPHP engines I've built, I add some extra volume into the top of the piston with valve reliefs and this necessitates a fixed orientation for the 1/3 and 2/4 pairs.

The pins for these pistons are not unique to each piston. So, when weighing for balancing, I will move the pins from one piston to another to reduce how much material has to be removed from a piston.

Also, double check how much room you have inside the pin bosses for the rod little ends. Sometimes, the offsets of the rods are enough to cause binding against the pin boss from the side of the little end. I'll usually remove about 0.080" to 0.090" from the offending side on the rod to help with this situation.

Mike

 

[aeronca65t]

Excellent! Thanks!

I'm balancing them today, so I'll be sure to use your method with the piston pins. And I'll check the pin boss for clearance too.

Again, thanks to both of you.

 

[Gerard]

I just asked this question in the "Racing" section, but maybe someone here might know the answer:

I have a new set of A&E 21253 pistons (.0400 over) I'm putting in my 1275.

I need a set of these for a 1275 I plan to build. Can you tell me who you sourced them from?

P.S. I tried to PM you on this, but message says you are over quota.

Thanks

 

[aeronca65t]

BPNorthwest

https://www.bpnorthwest.com/

They are a supporting vendor here, which is nice. They also sell tri-metal engine bearings and other good stuff.

 

[Gerard]

Thanks, I'll check them out.

 

[smaceng]

Aeron,
What compression ratio are trying to achieve with those 21253s?
Scott in CA

 

[aeronca65t]

These are 9.75 to 1, but I'm running a slightly trimmed head, so probably close to 10:1.

I'm running mild cam with stock porting and stock SUs. Race gas, of course. I'll be quite happy if I end up with 80 HP.

 

[Trevor Jessie]

Is this for the teapot?

 

[aeronca65t]

Right now, it's going in the little green car below.

But as soon as the A35 is done, this engine will go in it (sometime this year).

I have another 1275 to build for the Spridget next Winter.