piston side clearence and ring end gap

[JamesD]

i'm building a 383 and i was wondering what the piston side clearence should be. they are hypereutectic pistons. also what ring end gap should i run, The motor will probably be about 350 to 400 HP, and it will never see nitrous or forced induction. any ideas?

[camcojb]

You really need to go by the manufacturers recommendations on both of those. Different brand hyper pistons will likely have difference clearances they want; same for the rings.

Jody

[JamesD]

yeah i kinda figured that. it has it on the side of the box, i think it was about .001". the rings are moly rings, but the paper in the inside just tells how to install them not what the clearence should be.

[ProdigyCustoms]

Basically, if they are not "file and fit rings", they are pre fit if you use the proper bore size.

Frank

[camcojb]

yeah i kinda figured that. it has it on the side of the box, i think it was about .001". the rings are moly rings, but the paper in the inside just tells how to install them not what the clearence should be.

.001" is too tight I believe, double-check that!

Jody

[JamesD]

ok i rechecked it it said a minimum of .001,

[camcojb]

Wow, shows what I know about hypers! The tightest clearances I've run were about .0035, but those were custom forged pistons. Most of mine want .0045 to .0055". I know forged need more clearance but would never have thought you could get away with that small of a number.

Jody

[JamesD]

every thing i've read about hypereutecitc says that they are run pretty tight. heres the side of the box

[Novacane]

.001" is definately too tight! Because of the silicon content of the hyper. pistons they done grow as much when they heat up, which is why they run them tighter. I would not go any less then .0035-.0040". GM went to this style piston to get rid of the "cold engine piston slap" they they have had with the newer motors. That is tight compared to my 427 LS1 Twin Turbo that has a piston to wall clearance of .0065"!

As far as ring end gaps; the rule of thumb is .00042" x the bore diameter. 4.030" x .0042= .017". That would be the tightest you can run. I suggest between .018-.020 for the top and .020-.022" 2nd ring. If you do decide to spray the motor you should open those gaps to .022 and .0024 respectfully.