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#1
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Silly question
What is a ideal piston to wall clearance on a N/A motor?
Even with tape on the piston during mock up these babies seemed a bit loose....... Not gona say what I measure but I'm curious what you guys think is ideal.
__________________
"You have to evaluate the past,Focus on the future,and that tells you what you have to do in the present"--Lou Holtz “It’s the process it takes to get to goals that sets us apart, the execution on every single play, one play,one life” Notre Dame Head Coach Marcus Freeman 69 GTO NHRA Super Street Car 2860lbs 10.854@160.12 in Brainerd MN 7/2024 |
#2
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.006-.008
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EHTTFMF! Being dead, it is not hard on you. You don't even know you're dead. It is hard on everyone else that is not dead. BEING STUPID WORKS THE SAME WAY! The rest of us suffer. |
#3
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It depends somewhat on what the piston material is.
A Piston will always grow until it reaches its Thermal Stabilization Size (under load). The old California Pistons grew so much that sometimes you would have .009" piston to wall clearance when the piston was at room temperature. If you made it tighter the piston would scuff or seize. Some of the newer piston design people say you can run the things at .005" clearance. I have always been nervous of that deal and always had at least .006"-.0065" minimum. A engine like Mike's might need .008" to not scuff the pistons. JME Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#4
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LOL that's what I thought! I'll give someone a screamin screamin deal on a set of gas ported cv-1 Ross pistons! That have a. .043 .043 3mm ring pack. Set up for a 4.5 stroke and a 6.700 rod.these babies are brand spankin new
Actually anyone know how Ross is to deal with? Who's a good contact over there?
__________________
"You have to evaluate the past,Focus on the future,and that tells you what you have to do in the present"--Lou Holtz “It’s the process it takes to get to goals that sets us apart, the execution on every single play, one play,one life” Notre Dame Head Coach Marcus Freeman 69 GTO NHRA Super Street Car 2860lbs 10.854@160.12 in Brainerd MN 7/2024 Last edited by S/st 54; 02-04-2014 at 07:07 PM. |
#5
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It also depends on skirt design -- but a lot of the newer stuff is getting tighter -- the long stroke really causes piston rock with loose pistons upsetting ring seal -- the worst problem I ever had was with a set of Ross pistons, just saying.
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#6
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Running Ross Pistons right now. You have to measure them at the skirt across the pin. check the piston to find out exactly where they're supposed to be measured. If you measure at the very top of the piston they will measure way more than what you actually have.
__________________
EHTTFMF! Being dead, it is not hard on you. You don't even know you're dead. It is hard on everyone else that is not dead. BEING STUPID WORKS THE SAME WAY! The rest of us suffer. |
#7
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No issues with the local guys "Diamond Pistons" or the California Guys "CP Pistons" on either work or home projects.
Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#8
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x2.
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#9
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X 3
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#10
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Yup, you should hear the original LS1's on a cold start.
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#11
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That's why I prefer a shorter rod than the pontiac community thinks is ideal. I'd rather have a stable piston and lower the pin a touch. Helps with rock and is like coatings when it comes to power. No differance
__________________
EHTTFMF! Being dead, it is not hard on you. You don't even know you're dead. It is hard on everyone else that is not dead. BEING STUPID WORKS THE SAME WAY! The rest of us suffer. |
The Following 2 Users Say Thank You to mike leech For This Useful Post: | ||
#12
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X2. Again Mike is correct.
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The Following 2 Users Say Thank You to dda72 For This Useful Post: | ||
#13
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Did the machinist not have pistons in hand before boring the block? Any competent m achinest wants the pistons before taking the block to final hone...
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#14
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Jason how are you measuring the piston please describe.
__________________
EHTTFMF! Being dead, it is not hard on you. You don't even know you're dead. It is hard on everyone else that is not dead. BEING STUPID WORKS THE SAME WAY! The rest of us suffer. |
#15
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Sorry to hijack the thread, but this topic is timely... My new forged SRP piston instructions call for a minimum of .0025/.0030 wall clearance for a 4.2" bore (see attached). My local engine guy made the bore 4.185, which gives us about .0035 clearance.
Based on the instructions, i assume this will be fine for an aluminum head 455 street engine? |
#16
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Quote:
Quote:
The two materials have differing expansion rates thus different P2W specs. The pistons these guys are talking about are all 2618 I'm sure. And usage also comes into play,high CR,boost,nitrous all can require more P2W as SOP due to the additional heat the pistons "sees". My first thought when I saw the "What is a ideal piston to wall clearance on a N/A motor?" was .005" to .007" as a good "middle of the road" number for the bulk of applications,but then again I prefer the 2618 pistons as SOP as well,but yeah the 4032 pistons (and whatever material TRW/FM forgings are made of) can indeed run closer than that in many applications as well,they just are'nt as strong as a 2618 piston would be. HTH Bret P. |
#17
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My understanding:
Cold: clearance-spec tight Skirts, loose&oval slug heads. Warmed-up: slip-tight skirts, expanded heads that are closer to round & not scuffing. |
#18
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Ok measured them across the skirts..... Much better but still loose. That's with a cold block and a warmer piston. Thanks guys. It will be just like everything else on this motor. It will "probably"work but not what I wanted. Sure think I've spent way to much on this motor to not have exactly what I wanted.just my 2 cents. Thanks again guys for the help!
__________________
"You have to evaluate the past,Focus on the future,and that tells you what you have to do in the present"--Lou Holtz “It’s the process it takes to get to goals that sets us apart, the execution on every single play, one play,one life” Notre Dame Head Coach Marcus Freeman 69 GTO NHRA Super Street Car 2860lbs 10.854@160.12 in Brainerd MN 7/2024 |
#19
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Quote:
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#20
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Yeah but I really am looking for a specific HP. # and I know things have to be right to achieve that number..........the thing is I have already spent a healthy amount to try to achieve that # which shows I'm serious about obtaining it. Not the typical "I'm gona" that so many have said and NEVER FOLLOWED through with and do not even have a starting point let alone any kind of track results to get there feet wet...........just sayin.........I just don't want to wait 6wks to get a. "Correct " set of pistons.
__________________
"You have to evaluate the past,Focus on the future,and that tells you what you have to do in the present"--Lou Holtz “It’s the process it takes to get to goals that sets us apart, the execution on every single play, one play,one life” Notre Dame Head Coach Marcus Freeman 69 GTO NHRA Super Street Car 2860lbs 10.854@160.12 in Brainerd MN 7/2024 |
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