edwardzracing

iTrader: (59)

Doing first ever LS1 rebuild with stock parts... block was not decked, but after assembling bottom end, the pistons are out of the hole .025. Can anyone tell me why this may be? Wrong bearings??? I'm ultra confused. I tried calling Race Engine Development to see if they might have a little insight, but was not able to reach them so I left a message and thought I'd hop on here to see if anyone else could share a little info.

This is a stock 98 block with 2004 LS6 rods and ls6 pistons (floating setup) and arp 2000 rod bolts. What could possibly make the pistons stick out that far? If anyone can lend a little insight, I'd greatly appreciate it. Excuse my ignorance... I admit I'm a newbie with all of this. At least I was smart enough to measure first right? Thanks, guys.

Brad

JRENIGAR

iTrader: (37)

did you have the block line bored?

edwardzracing

iTrader: (59)

Yes, but not dramatically. Would a line bore change things that much? I figured it would end up somewhere between 8 and 10 thousandths. But wow, .025 just seems crazy high. I appreciate the response.

Just adding a little more info here:

Stock LS6 crank (used with the same rods and pistons that are in the motor).
ARP Main Studs.

Thanks again to all those willing to share a little info.

JRENIGAR

iTrader: (37)

yeah, Id think your on track about 8 to 10 thousanths. Im assuming your sure about square decking then, as in it wasnt done?

Midnite Magic

How are you measuring this? Stock connecting rods are 6.098" and stock LS6 pistons should come out of the hole .007-.010" depending on the deck height of the block and machine work

A.R. Shale Targa

iTrader: (2)

I thought most ls family engines have a .007-.010 positive deck height
which is why GM uses .056-.060 thick head gaskets. If a machine shop
decked the block fron 9.024 down to 9.010 then you could easily see
about .025 out of the hole. No worries though because bringing the primary
compression ring closer to the deck surface reduces "dead" quench, cleans
up emisions a bit, and a factory .060 head gasket will put the piston to head @ about .035.....A pretty desireable figure

edwardzracing

iTrader: (59)

Block was not decked. I measured using a dial indicator similar to this:



Like I said, stock 2004 LS6 rods and pistons. 6.098 length, 3.622 stroke. Block had no deck work done at all... a line hone and a cleanup hone on the cylinders. What could possibly cause the pistons to be more than 15 thousandths too far out of the hole? Would a line hone have messed things up that bad??

Even with the .051 head gasket on it, claying the piston top shows obvious contact with the head after turning it over. Valves aren't hitting, but the head definitely does.

At this point I can only assume something has been assembled incorrectly or the line hone has completely changed things... but have any engine builders here ever seen a line hone throw the deck height that far out of whack??? I know it's a dumb question, but would the wrong size of bearing have an effect on anything?? Again, excuse my ignorance; I'm just trying to figure out what could have changed things this dramatically on what is mostly a stock rebuild.

Big thanks to everyone for chiming in. Feel free to add more comments and/or ideas.

gtotoocool1

iTrader: (6)

something isn't right,that's for sure.
if your gasket is .051 thick,and your out of the hole .025,the piston shouldn't be hitting the head?(although that is damn close)
maybe a little too much metal was taken off when line honed,and/or the wrong bearings are being used?
you could use a thicker gasket to add clearance,assuming the rotating assembly is ok..
obviously the people to talk to is the machine shop who did the work.

KCS

iTrader: (20)

How are you measuring the piston again? Are you rocking the piston and finding the average?

edwardzracing

iTrader: (59)

Motor is still at the shop... this is the first LS1 assembly the shop has done and things are on hold as I'd like to figure out why the pistons are out of the hole this much. Rocking the piston changes things a little, but it's not going to rock down to 10 thousandths. That'd have to be 15 thousandths worth of rocking. Even if it rocks between say 15 and 25, my average is still crazy high and way off.

I suppose it's possible the line honing took off more metal than average, but I have a hard time believing the mains were roughly 15 thousandths out of round. I do know that the shop had to send off the block to another shop for them to finish the line hone so perhaps the other shop really did have to take off that much metal. I'm going to try and find out today.

I'm still curious if incorrect bearing sizes would move things this much.

THANKS AGAIN to everyone who has chimed in. It's greatly appreciated.

KCS

iTrader: (20)

Usually they rock more than .010". You need to measure.

The way you're supposed to do it is you first zero out the indicator on the deck and then set the tip at the edge of the piston perpendicular to the pin. From there, you rock the piston so that you can measure how low and how high the piston rocks.

So if the piston rocks .025" above the deck and .005" below, that means the piston rocks .030" total. Divide .030" by 2 and you get .015". Add that number to the low (which will be -.005" since it was below the deck) and you see that the piston is actually only .010" out of the hole.

I think thats way more likely than bearings or the line hone.

edwardzracing

iTrader: (59)

I appreciate the information. I will try that method and see what I end up with. Unfortunately that still doesn't explain why there is not even 30 thousandths worth of clearance between the head and piston with the .051 gasket installed and the heads still not completely torqued down. Maybe I'm just being paranoid, but sadly I think there is still a problem. Thanks again, KCS.

Keep the thoughts coming guys.

S10xGN

iTrader: (11)

Have you tried running in the main cap side bolts? If they won't thread in correctly, then the line bore might be the issue...

A.R. Shale Targa

iTrader: (2)

Typically if a machine shop raises the crank NORTH by line honing the crap
outta it the timing chain wil be sloppy loose even if it's new.

JRENIGAR

iTrader: (37)

true... some companies actually make a shorter chain to correct this...

edwardzracing

iTrader: (59)

Very good point. The side main bolt caps went in without a problem. We did use a new .005 smaller chain and it's good and snug; definitely not sloppy. Beginning to wonder if it might indeed be an incorrect bearing or something.

Thanks for all the responses guys. I sure appreciate the help, thoughts, and ideas.

Brad

heykw

G Atsma

Read the title of the thread- piston .025 out of the hole.

CattleAc

iTrader: (7)

I think he means, what was the final solution/outcome/fix to the ".025 out of the hole" problem...

(but...since this is a 2011 thread...chances are slim he will reply...)