Piston to Wall Clearance for AEB Forged Piston

**A4 TSCHUSS** · 08-24-2008 09:52 AM

Does anyone have a bentley or something they can look up what the clearance is supposed to be for the AEB piston. Forged pistons require more clearance than cast since they expand but I cant seem to find a constant number.

Some say that .008 is the max and that .004-.005 is the optimum range for a forged piston but then others say that JE and Wiseco use a spec of under .003, so I guess the perfect way to know would be to see what the factory spec is for the AEB piston since all forged pistons are made with different material which in turn will cause them to expand more or less than the next.

**Audi Skate Snow** · 08-24-2008 10:45 AM

.001 per inch of bore is a good start. :) however usually with a forged piston minimum is .0045

**Don Supreme** · 08-24-2008 11:14 AM

AEB piston is a low expansion piston (different alloy), not like JEs, etc... I think .0045 would be WAY too much clearance.

**F16HTON** · 08-24-2008 11:28 AM

AEB=.0006, measure 3/4 way up the piston 90 degrees from the wrist pin. Clearance at the top should be slightly greater.

**RLB6** · 08-24-2008 02:44 PM

Originally Posted by Don Supreme

AEB piston is a low expansion piston (different alloy), not like JEs, etc... I think .0045 would be WAY too much clearance.

Agreed. Even .004 is too much. I just don't know what grade aluminum was used for the AEB pistons. generally, forged pistons need about .0050 of clearance and this is dependent on the material used to produce them.

IMO, I would have them coated, via Swain Tech, then have the bores honed to meet the minimum or even slighty under. The coat will definitely stop the pistons from expanding as much. Too much piston slap is not cool.

**Don Supreme** · 08-24-2008 02:50 PM

I have the MAHLE tt225 style 9:1 piston going into my motor and Bob Q said clearance should be .0015" PAST THE COATING.

**A4 TSCHUSS** · 08-24-2008 04:39 PM

Ok so I just read like 5 different clearances in this tread once again! Nobody can agree. Does anyone have a bentley they can look up and give me the exact number I need instead of a bunch of opinions/guesses?

**Audi Skate Snow** · 08-24-2008 04:41 PM

Originally Posted by A4 TSCHUSS

Ok so I just read like 5 different clearances in this tread once again! Nobody can agree. Does anyone have a bentley they can look up and give me the exact number I need instead of a bunch of opinions/guesses?

sorry man I wont have one untill tomorrow...
tomorrow at 6am ill have it.