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Old 10-16-2012, 05:01 PM   #1
fastblueufo
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Default ptw clearance with 99.5mm forged pistons and factory bore.

I'm looking to see what different brand forged pistons at stock 99.5mm bore wind up with ptw clearnance on a factory bore. I read that 99.5mm CP pistons have .005 ptw clearance on a factory bore. What do some of the other brands have like wiseco, JE, mahle, etc etc?
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Old 10-16-2012, 05:51 PM   #2
04ScoobyWtf
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Dont do drop ins your asking for a disaster. Have someone disassemble and hone it and you want about .003-.0035 any more any you'll be slapping a lot and your rings will wear out faster
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Old 10-16-2012, 05:54 PM   #3
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Quote:
Originally Posted by 04ScoobyWtf View Post
Dont do drop ins your asking for a disaster. Have someone disassemble and hone it and you want about .003-.0035 any more any you'll be slapping a lot and your rings will wear out faster
No *****? I'm specifically looking to see if there are any forged pistons I can use and only do a hone to achieve ptw without doing 99.75 over bore.
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Old 10-16-2012, 06:16 PM   #4
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I am also curious. A friend recently "dropped in" some Manleys...but he was in such a hurry he did not even use the bore gauge I loaded him on the bores or mains, mic the pistons, gap the rings or any of that other "racing stuff" In other words I would know but he decided to build an oil burner
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Old 10-16-2012, 09:18 PM   #5
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You need to get the 99.75 to get that perfect p/w you and i are going for. Im using a new s.b. case too. So it hurts a little to jump up. But worth it and the only way. You wont be happy using drop ins (99.5)
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Old 10-16-2012, 09:38 PM   #6
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I am no builder but I have measured several blocks as I work on my build, and I have no idea how people claim they are getting .0035 PWC with 99.50 pistons. I see three alternatives besides going with 99.75:

Thicker coating, like Swantech/Embee
Abradable Powder coating, creates the perfect PWC. http://www.line2linecoatings.com/techgeneral.html
Or
Have Wiseco custome build you a set of ever so slightly larger pistons, call Tech support and talk to Jeff.

Also, Wiseco is now stocking the 99.75mm piston.
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Old 10-16-2012, 10:13 PM   #7
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You can order custom pistons.
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Old 10-16-2012, 11:15 PM   #8
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Any reason you don't want to go 99.75 specifically?
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Old 10-16-2012, 11:27 PM   #9
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Quote:
Originally Posted by Irv Weissmanhowerton View Post
You need to get the 99.75 to get that perfect p/w you and i are going for. Im using a new s.b. case too. So it hurts a little to jump up. But worth it and the only way. You wont be happy using drop ins (99.5)
Not at all.. I've built a ton of motors using 99.5 ots pistons and just did a hone to get a 30-45 clearance. Some motors no. Just built one last week out of a Forester with 150k on it. The cylinders were so egg shaped the pistons didn't want to budge. With the way the cylinders were, "dropping" 99.5's in would have yielded a .0020 PTW......at the loosest marker.. Honing brought them out to a perfect 32... Right where I wanted to be. HOWEVER some blocks are infact waaaaay to large for a standard 99.5 without risking issues. But some can be fixed without boring to 99.75
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Old 10-17-2012, 02:06 AM   #10
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my stock bore 99.5 low compression cosworth pistons spec'd out .003. im not having any issues...cars kickin ass.
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Old 10-17-2012, 12:05 PM   #11
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For about $15.00 <estimate> more per piston, you can order custom pistons that are the exact size you need them to be brother. JE will do it and it should only take them a couple of weeks to get them ready to ship for you. Just make sure they have a ring pack for the pistons you spec. That (rings) is the only "hang up" to ordering non "shelf" sizes.
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Old 10-17-2012, 12:10 PM   #12
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^^^ So can Wiseco. BTW, where the heck have you been TeamScream?
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Old 10-17-2012, 12:44 PM   #13
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^^^ So can Wiseco. BTW, where the heck have you been TeamScream?
LOL, sorry gotsugg, it is work season and I am on the 14-16 hour per day schedule now.... sucks... and it keeps me from spending lots of time online.... ugh..
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Old 10-17-2012, 03:20 PM   #14
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I was hoping to buy a brand new factory 257 block and have it rehoned to fit 99.5 forged pistons. From what I've read above here that might not work. Are the factory blocks that far out of spec or are the forged pistons built slightly smaller to hopefully get the proper clearances dropped in a standard bore?
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Old 10-17-2012, 04:45 PM   #15
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Quote:
Originally Posted by ripman View Post
I was hoping to buy a brand new factory 257 block and have it rehoned to fit 99.5 forged pistons. From what I've read above here that might not work. Are the factory blocks that far out of spec or are the forged pistons built slightly smaller to hopefully get the proper clearances dropped in a standard bore?
^^ This

If JE would make their shelf pistons .001" larger it would be so much nicer to do drop in upgrades
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Old 02-05-2013, 03:47 PM   #16
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Bumping this because I am curious whether anyone out there has measurements for various brand 99.5mm pistons. Specifically Manley and JE
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Old 02-06-2013, 12:20 AM   #17
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Quote:
Originally Posted by aboothman View Post
Bumping this because I am curious whether anyone out there has measurements for various brand 99.5mm pistons. Specifically Manley and JE
JE fsr are 3.9125" for stock bore pistons and 3.9225" for the 99.75mm bore pistons.

On the 99.75 je, I get the machine shop to hone the block out to 3.9255". That gives me a .003" ptw clearance and they work out great and are quiet for such a short skirt.

The stock bore je would leave way to much ptw clearance unless its a racing short block.
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Old 02-06-2013, 01:29 AM   #18
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Thanks!! Any measurement for Manleys? Might be buying a new oem block, but upon review of old threads, I am realizing I pretty much need to go 99.75 to do it right. Unless I get a tight oem block that is...

I have a set of Manley high CR that I measured at 3.914" earlier. If That is a consistent measurement they would be a lot better for "drop ins" than JEs
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Old 02-06-2013, 11:16 AM   #19
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Quote:
Originally Posted by aboothman View Post
Thanks!! Any measurement for Manleys? Might be buying a new oem block, but upon review of old threads, I am realizing I pretty much need to go 99.75 to do it right. Unless I get a tight oem block that is...

I have a set of Manley high CR that I measured at 3.914" earlier. If That is a consistent measurement they would be a lot better for "drop ins" than JEs
ehh. They are still louder than je's due to the design of the piston. All we run are je's at MPS and I ran manley 99.5 HC pistons on my new block and they are louder than drop in jes on new blocks. And the manleys have a slightly tighter PW than the je's do.
But to me its just piston slap.... who cares. your trying to make power arent you. if you want quite get the mahle 4032 and a good set of rings.
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Old 02-06-2013, 12:05 PM   #20
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I have manleys and they are loud . Stroked 2.1
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Old 02-06-2013, 03:06 PM   #21
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whats your PTW clearance?^
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Old 02-06-2013, 03:34 PM   #22
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Sorry i wont share my build specs. Per builders request
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Old 02-06-2013, 04:26 PM   #23
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Quote:
Originally Posted by NW2TONE View Post
ehh. They are still louder than je's due to the design of the piston. All we run are je's at MPS and I ran manley 99.5 HC pistons on my new block and they are louder than drop in jes on new blocks. And the manleys have a slightly tighter PW than the je's do.
But to me its just piston slap.... who cares. your trying to make power arent you. if you want quite get the mahle 4032 and a good set of rings.
I care more about good PTW than noise. I am still going to throw a plate on it and hone, or at least check it, regardless. My last engine was too loose and burnt **** tons of oil as a result, but it was not plated.

Probably going to suck it up and bore it to 99.75. Reason i asked is because I was looking at a new block and it seems silly to bore a new block to 99.75. If I can find a good used block I will probably just go that route and spend the extra coin on machine work and extra bearings. Hopefully the mains don't need a line bore...that is the hold up on my sleeved block.

Main reason I am looking at the Manleys is the 26cc dish on the stroker piston. That gets my CR and quench right where I want it with +2mm rods, oem HG, and D25 heads...on 91 octane

Last edited by aboothman; 02-06-2013 at 04:35 PM.
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Old 02-06-2013, 08:19 PM   #24
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Sorry i wont share my build specs. Per builders request
Lol, are you serious :-\
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Old 02-06-2013, 08:50 PM   #25
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Sorry i wont share my build specs. Per builders request
will you say if they are tighter or looser than .0035?
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