I have a 382 stroker with a forged crank and forged pistons that would make tapping noises when the car was cold and I cranked it up. After a few minutes the noise would go away. I was told by a guy who used to race and build older 350ci motors that since I have forged pistons this is normal. Recently the tapping noise seems to just stay even if the car has been warmed up. The new motor has 1300 miles on it. Anyone else with forged pistons have this issue? Does your car always have slight piston tapping even after it's warmed up? Does anything in the list below stick out as being done wrong or wrong parts?

382 cid stroker LS1 (3.900x4.000 bore x stroke)
Brand New LS6 Block
Eagle Forged 4340 stroker crank
6.200 H-beam rods
Forged pistons, dished, 8.85:1 compression ratio
Comp 130-330 lb. valve springs
Comp Cams 1 pc. .080 wall push rods
1 pc. stainless intake and exhaust valves
ARP head bolts
Comp hydraulic roller lifters
Fully balanced/blueprinted

NEW BLOCK LS-6 $750.00
DE-BURR BLOCK/BLEND ALL OIL GALLYS/AND CLEAN BLOCK $100.00
CLEARANCE BLOCK (ASSEMBLE, CLEARANCE, CLEAN AND RE-ASSEMBLE TO CHECK)
$200.00
HONE WITH TORQUE PLATES (NEW BLOCK) $100.00
INSTALL CAM BEARINGS $35.00
BALANCE $350.00
CUT RODS TO FIT PISTONS (PIN END) $80.00
FIT BUSHINGS/DEBURR RODS/CLEAN AND ASSEMBLE PIST. TO RODS $80.00
INSTALL VALVE GUIDES (16) $75.00
PERFORMANCE VALVE JOB 8 CYL. $175.00
SURFACE V8 HEADS $70.00
ASSEMBLE LONG BLOCK PERFORMANCE $850.00
EAGLE 4340 STEEL NEUTRAL BAL CRANKSHAFT 4.00 STROKE/6.200 H-BEAM RODS
$1,318.12
PROBE S/C 9.0:1 FORGED PISTONS $599.10
3.902 RING SPACERS (OIL) $71.90
3.905 FILE FIT PLAZMA MOLY TOTAL SEAL RINGS (METRIC) $165.50
RACE ROD AND MAIN BEARINGS (NARROWED TRI-METAL) $138.71
MELLING OIL PUMP (WE BLUEPRINTED) $139.00
FEL-PRO RACE HEAD GASKETS $66.36
FEL PRO FULL SET (LESS HEAD/INT/VALVE COVER) $151.06
FEL PRO INT. SET $22.43
G-M VALVE COVER GASKETS $16.00
CAM BEARINGS GEN 3 2ND REVISION $55.00
ROLLMASTER H-D TRU ROLLER (DUAL ROW) WITH TORRINGTON BEARING $148.00
OIL DIVERTOR/PLUG $9.50
COMP HYD. ROLLER LIFTERS $147.96
FERREA 1 PC. STAINLESS INT. VALVE $125.00
FERREA 1 PC. STAINLESS EX. VALVE $125.00
COMP LS-6 130 330 LB. VALVE SPRINGS $197.43
COMP CAMS 1 PC. .080 WALL PUSH RODS $138.55
G-M LOCKS $20.00
INT. SEALS $17.55
EX. SEALS $19.88

 

Yeah, from what understand from the explaing is forged pistons need more sidewall clearance then Hyper..... so, they tap a little when cold... Ain't it grand? oh, and I don't have expierence with this, my forged piton engine is in the garage being assembled

 

My old forged motor did it all the time when cold.

 

Like 87calais said: it's normal when cold. Forged pistons need more clearance because forged aluminum have a greater coefficient of expansion than cast aluminum when temperature rises.

My 382 (3.901 x 4.000) will make some tapping noise like your's when it's cold (sounds like a diesel engine), but the noise will gradually fade off and completely go away after 5-7 minutes. Mine have 4500 miles.

I don't know however why your's is starting to make that noise all the time. Did you used a mineral oil during the break-in period and have you switched to synthetic recently? Did that gradually begin or did that happen overnight? I don't know, thats the first time I heard about that. Hopefully, someone more knowledgeable than me will chime in on this one...

 

Well, there's a lot of "I don't knows" coming from me because I just bought the car recently. I've had it for almost 3 weeks now. It always did it when it was cold but after it warmed up it was fine. Now it still does it when it's cold but quiets down a tiny bit when warm but easily heard when the car is warmed up. The diesel sound like Blue Hawk said is exactly what I'm talking about. The guy who sold me the car mentioned using 20-50w oil since the engine was clearanced/built for use with thinker oil such as 20-50w.

Maybe I should go get the oil changed with some 20-50w synthetic? The oil looked very new when the car arrived here so I didn't change the oil.

 

Yup, that's perfectly normal with a set of forged pistons. Mike is pretty loud when its cold

 

I just went through the very same thing that you did only kept the stock bore. The pistons that I used were Mahle Forged. By the time I honed with torque plates I was .002 over the stock sized pistons that I had ordered. When I called Tech support they said it would be no problem. The skirts were coated he said. I now have 650 miles on the motor and when I start it up it is noisey and calms down a little after it is warm. I rebuilt the motor myself with close tollarences. I have got to the point where I like the sound as if the is something lurking under the hood. Going with a 111.5 233-239 600-603 is hard to hide the sound of power. Good luck to you.
C5JIM

 

Well c5jim I think that's good news for me. I was getting a little worried that I could still hear some tapping noise even after it warmed up. It's definitely louder when the car is 1st started up in the morning but does quiet down after it warms up. I was worried because I can still hear the noise when I give it a little more gas but I guess I'll just see if it gets louder. If it gets much louder then I guess I'll yank the motor out, otherwise it could be very normal. This is the first car I've owned with forged pistons so it's new to me.
Thanks for all the replies

 

Mine makes a racket when cold. There is always a noticable amount of noise even when warm. Not a lot, but noticable. My motor now has 15Kmiles and it is running as strong as ever. With all the slap the slugs make, the bores looked pristine both times I changed the heads. (Last time was at 13.5Kmiles)

 

The only way to know for sure what is going on is to measure your piston to bore clearance and check it against the piston manufacturers specifications. There is no way it should tap when warm (My stock LS1 does because GM messed up their own manufacturing). I am guessing your engine was bored slightly beyond spec for the piston and it taps. As we all know a minor tap will not kill your engine, its just annoying, it also probably releases a couple of extra hp.

If running a thicker oil helps its one thing to do but the service manual specifically recommends against running 20W50 (it of course assumes proper bearing clearances are used). Its an old school mentality to run big bearing clearances and try to "float" everything on a thicker oil. If that is what the engine builder did then you are stuck at this point. I would just run the thicker oil and be done with it though. If you ever have the engine apart set it back to proper clearances. Chances are the tapping will be worse with synthetic versus dino oil regardless of viscosity choice.

 

I run forged pistons in my H/C 360 Marine engine and as stated above they do make noise when cold. Tis the reason the new LS7 will not come with forged pistons. GM doesn't want owners bitching about cold start noise problems with their $60+ Vette.

 

(The only way to know for sure what is going on is to measure your piston to bore clearance and check it against the piston manufacturers specifications. There is no way it should tap when warm (My stock LS1 does because GM messed up their own manufacturing) QUOTE

I have owned more cars with forged pistons and a forged bottom ends than most. Forged piston for an alum block tend to be noiser than most engines There is a way for them to be noise even built by the best. It is the nature of the beast. If mine gets to noise I just turn the radio up a little louder and pass whatever is in front of me. I base my findings on what I have done myself, not on something I read or heard.
JIM

 

I have JE forged pistons in my motor and they are dead quiet even cold. Stock bore. 35 degrees out not a single noise from them. My old motor however was just the opposite, it was noisy cold.

 

Thanks for the replies, I feel better at least knowing some of you have similar issues that are considered normal.