Piston dish
Thread Starter
Racer
Joined: Jan 2009
Posts: 393
Likes: 14
Piston dish
I'm in the middle of chosing pistons to my LS1. Is the zero dish stock flat top? I mean those dish sizes +2 or -2, are those compared to stock when flat top piston visits deck height?
Do Wiseco and Diamond pistons come with hone instructions? Or do I have to choose rings separately and figure the honing details that way?
I was planning to use stock rods.. I seem to have smaller amount of pistons to choose from because of the smaller piston pin than aftermarket rods have.
Do Wiseco and Diamond pistons come with hone instructions? Or do I have to choose rings separately and figure the honing details that way?
I was planning to use stock rods.. I seem to have smaller amount of pistons to choose from because of the smaller piston pin than aftermarket rods have.
Le Mans Master
Joined: Aug 2002
Posts: 8,472
Likes: 38
From: Houston TX
St. Jude Donor '11
>95% of the pistons out there are going to use the 6.125" rod. If you're swapping pistons it would be a good idea to swap rods too. True flat tops are hard to find as most of the forged ones come with valve reliefs which are typically -2 to -3cc's. The stock bore will limit your piston choices even more. Most say a .005" hone is needed to make sure the bore is round. I'm not sure how true that is. The Wiseco catalog calls for a 20-25 degree cross hatch and 400 grit stones.
Thread Starter
Racer
Joined: Jan 2009
Posts: 393
Likes: 14
I am not sure about that "round bore" either.. when it comes to LS1. Head bolts pull from the main bearing area and I can not see how the bore would change due to stress from bolts. I quess some people bore and hone these blocks with stress plates and have measured the difference..?
I will hone the block anyway, so I quess I'm going to that .005" size.
Pro
Joined: Feb 2009
Posts: 651
Likes: 33
From: North Port Florida
Thanks, that's the info I'm looking for. I'm looking for -4 cc pistons and I was confused not to see many "0 cc dish" ones out there..
I am not sure about that "round bore" either.. when it comes to LS1. Head bolts pull from the main bearing area and I can not see how the bore would change due to stress from bolts. I quess some people bore and hone these blocks with stress plates and have measured the difference..?
I will hone the block anyway, so I quess I'm going to that .005" size.
I am not sure about that "round bore" either.. when it comes to LS1. Head bolts pull from the main bearing area and I can not see how the bore would change due to stress from bolts. I quess some people bore and hone these blocks with stress plates and have measured the difference..?
I will hone the block anyway, so I quess I'm going to that .005" size.
Racer
Joined: Mar 2009
Posts: 312
Likes: 11
From: Cleveland Ohio
There is a variance in 24mm "ish" pin diameters from the factory that make it hard to build a proper line of forged pistons (multiple stroke/c.r.) around them. Enough difference that loose press-fit would be a problem if you install the pistons in the wrong LS engine code connecting rods. The factory rods are good up to a point, but .927 pinned forged H beam aftermarket rods in 6.125 are plentiful, stronger, and pretty inexpensive nowadays. Look for rods with the correct LS beam offset and s.e. width.
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
Wiseco and all the ring manufacturers don't have a clue. Forget about all that 20-25 degree stuff. Just get a scotchbrite pad and rub it a little.
You're suggesting to measure the piston to bore clearance with feeler gauges?
Last edited by BLOWNBLUEZ06; Jan 25, 2012 at 02:55 PM.
Racer
Joined: Mar 2009
Posts: 312
Likes: 11
From: Cleveland Ohio
Borrow a nice micrometer and someones dial bore gauge. Take your time and do it right so it doesn't use oil, smoke, and piston slap from to much piston to wall clearance. Lot less expensive in the long run.
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Thread Starter
Racer
Joined: Jan 2009
Posts: 393
Likes: 14
..why not do it right when you're at it? I'm planning to use my car on street and various track events for many seasons to come. I'm not building a dyno queen or planning to open the bottom end every winter.
I have a good selection of measuring tools on hand and honing the block while it's stripped off any parts isn't very pricey. Now I need to get pistons before I give the instruction to honing shop so the clearance will be what piston manufacturer wants.
BTW, smallest diameters were
#1 top: 99.015 mm
#5 top and middle: 99.015 mm
#6 top: 99.015 mm
#6 bottom: 99.010 mm
and the largest one was
#3 top: 99.035 mm
I have a good selection of measuring tools on hand and honing the block while it's stripped off any parts isn't very pricey. Now I need to get pistons before I give the instruction to honing shop so the clearance will be what piston manufacturer wants.
BTW, smallest diameters were
#1 top: 99.015 mm
#5 top and middle: 99.015 mm
#6 top: 99.015 mm
#6 bottom: 99.010 mm
and the largest one was
#3 top: 99.035 mm
Racer
Joined: Mar 2009
Posts: 312
Likes: 11
From: Cleveland Ohio
ok, good mindset. Cleanliness is a big deal for long life. Most shops don't do it, so ask them to spend extra time sanding/polishing the bottom of the cylinder sleeve so they don't have sharp edges. The bores are worn .0013" already, so that would have turned a skirt coated piston to wall from .0035" to .005"... woulda run ok if the rings took a seat, but not the best way to start off. It would have made more cold piston slap that way. Some of the aftermarket pistons are meant for bores between 3.903 and 3.905, so once the pistons are in hand, you can take everything to the shop for them to balance the assembly and hone. Even when it comes back to you, grab a can of brake-kleen and spend maybe 10 minutes a hole (maybe more) for the white papertowels till is comes up clean. That's your job, not the machine shops 
