ranwalk

iTrader: (1)

Need some input. I'm currently working on building up a 6.0 for my truck.
Going to run diamond pistons. I will be running a supercharger around 10-12 psi. On the spec sheet with the pistons it says to install with .0035 clearance.
Should i go with more clearance since I will be running a supercharger?

BLUEBALLS ZZ

iTrader: (2)

.0045 is where you want it at. i would also call Diamond to confirm it.

T/A Medic

iTrader: (1)

APE said pistons come with the proper clearances built into them...

i ordered pistons for a 4.03 bore... so made the bore 4.03

BOWTIE

Pistons come with the recomended clearance built in (at least all the ones I have seen), that said many engine builders prefer to add a little more for insurance. This would become even more critical in heavy demand applications such as supercharged, turbo'd, or heavy nitrous use. As mentioned earlier, call Diamond and find out if they recomend more clearance for a forced induction set up. A lot of lousy builders will run the bores with a lot of extra clearance and this is not the way to go. For one it allows the piston to rock in the bore causing several problems. First it will affect your ring seal, second it will cause the piston skirts to collapse causing even more clearance and multiplying both of your previous problems. Another thing, you only want to run the minimum recomended clearance if the bores are honed with a torque plate and the main caps torqued down. If you are not doing this you need to add clearance or find a better builder. The reason is those things distort the cylinder bore and will cause tight spots on final assembly. Also keep in mind, the final bore size will affect ring gap unless you are using file fit rings. So unless you are using file fit rings, an increase of .001 in bore size will increase the ring gap by .00314. So if the standard rings come pre-gapped at .018 on a 4.030 bore then if you increase the bore to 4.031 to gain that extra .001 of piston clearance, you have just increased your ring gap to .021. Food for thought. I will usually hone my blocks with a plate and main torqued to actual size, maybe a .0005 over, and then run my smallest pistons in the front holes (water comes in from the pump and tends to keep those cylinders from expanding as much) so they have more clearance and next smallest in the next holes, largest in the 3rd set of holes, and the others in the last holes. I have not done any scientific testing to determine those piston placements, but from years of practice, observation, and guessing, those made the best sense to me. Hope this helped confuse you some
(jk). In short, you want the bore as small as possible without the risk of galding a piston to make the most and most reliable power, so as close to nominal as you can get would be my recomendation.

Chris@AP-Engineering

iTrader: (-2)

Run the clearance that is listed on the sheet. If you feel the need to open the clearance up i would only go about .0005 bigger. If you have any other questions I can help.

Thanks,

BLUEBALLS ZZ

iTrader: (2)

friend did a motor with 0035 clearance and scared the cylinder walls and the piston skirt when he sprayed the car. didn;t allow enough room for piston expansion. i used the 0045 on my car and on Mech's car with out any problems and thats clearance came directly from Diamond when i called them and explained that i am spraying. the clearance they give you is for all motor. call them and let them know. they make the piston, they would know.

ScatStroker

Forced induction applications ALWAYS require greater piston to wall clearance than NA applications. It simply makes more heat, has greater expansion and needs to have clearance to allow for it. Your ring gaps will also need to reflect a forced induction application.

Most piston manufactures will include a spec sheet, listing a bore diameter and a recommended piston to wall clearance, along with a specification for forced induction or marine applications.

If they do not list a recommendation then I would contact them directly. If it were my engine I would recommend more than .0035 piston to wall clearance in a boosted application.

$.02

Brian