Two pistons .005 larger?
Thread Starter
Joined: Dec 2001
Posts: 3,915
Likes: 0
From: Panama City, Fl
Two pistons .005 larger? I recently had an incident where my #1 and #2 pistons (Wiseco 4.030, -11cc dish, pn 6444H3) made contact with the cylinder walls and scuffed up the pistons and wall pretty good. I took my block (2006 iron 6.0) to the machine shop and he thinks he can get #1 & #2 smooth with a .005 overbore (4.035 final bore). Wiseco is the only manufacturer I have found with a 4.035 off the shelf piston. According to Wiseco the new pistons are the same as the ones I have with the exception of a new ring pack and coated skirts. Should I just buy two new 4.035 pistons and put the other 4.030 pistons back in or do a full 4.035 set? Would .005 larger on #1/#2 make that much difference in rotational force and cause vibrations? This engine will be run with ~15lbs of boost.
Launching!
Joined: Jan 2008
Posts: 225
Likes: 1
From: Fargo, ND
i feel like im missing something here.
why did the skirt get skuffed in the first place?
was everything measured correctly before being put into place? i know they usually advise .005" clearance on their pistons soo...
just asking obvious questions. if it was built correctly in the first place it shouldnt have happened.
why did the skirt get skuffed in the first place?
was everything measured correctly before being put into place? i know they usually advise .005" clearance on their pistons soo...
just asking obvious questions. if it was built correctly in the first place it shouldnt have happened.
TECH Apprentice
Joined: Oct 2007
Posts: 301
Likes: 20
It is possible, but will need to be rebalanced. Weight can be added to counterweights or removed from counterweights (or preferrably pistons) to get it spot-on. .005 oversize isn't going to add but a few grams anyway.
Been done for years on the old school stuff, not a big deal.
I'd probably opt for a full new set of .005's, coated, bores will only need a torque plate hone, no boring. Get everything perfect this time around, you'll sleep better.
Been done for years on the old school stuff, not a big deal.
I'd probably opt for a full new set of .005's, coated, bores will only need a torque plate hone, no boring. Get everything perfect this time around, you'll sleep better.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
It is possible, but will need to be rebalanced. Weight can be added to counterweights or removed from counterweights (or preferrably pistons) to get it spot-on. .005 oversize isn't going to add but a few grams anyway.
Been done for years on the old school stuff, not a big deal.
I'd probably opt for a full new set of .005's, coated, bores will only need a torque plate hone, no boring. Get everything perfect this time around, you'll sleep better.
Been done for years on the old school stuff, not a big deal.
I'd probably opt for a full new set of .005's, coated, bores will only need a torque plate hone, no boring. Get everything perfect this time around, you'll sleep better.
Trending Topics
TECH Enthusiast
Joined: Feb 2007
Posts: 625
Likes: 0
From: Raleigh, NC
What you are asking about has been done before. Is it the "correct" way to do it? No, but it can still work. You just need to make sure the engine is rebalanced using the correct bob weights on the crank journals in question for the new piston weights in those two cylinders.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Five Reasons the Camaro Was the Most Pivotal Player in the Pony Car Wars 2.0
Brett Foote
Thread Starter
Joined: Dec 2001
Posts: 3,915
Likes: 0
From: Panama City, Fl
Thank you for the input gentlemen. It has been my intention all along to change all 8 but I wanted to know "if" it would work with two new slugs on a tight budget. Now I am just awaiting a call from the machine shop to let me know if .005 cleaned up the scratches in 1 & 2.
Thread Starter
Joined: Dec 2001
Posts: 3,915
Likes: 0
From: Panama City, Fl
i feel like im missing something here.
why did the skirt get skuffed in the first place?
was everything measured correctly before being put into place? i know they usually advise .005" clearance on their pistons soo...
just asking obvious questions. if it was built correctly in the first place it shouldnt have happened.
why did the skirt get skuffed in the first place?
was everything measured correctly before being put into place? i know they usually advise .005" clearance on their pistons soo...
just asking obvious questions. if it was built correctly in the first place it shouldnt have happened.
http://www.performancetrucks.net/for...ebuild-522509/
Anyone here ever balanced a crankshaft assembly ???? The factory tolerance
is within 30 grams and most machine shops try for within 5 or 10 grams.
The difference between .030" and .035" pistons is maybe 8 grams. Also
this being a boost application means the rpms don't need to be high where
the higher order (4th & 5th) harmonics become more pronounced. I'm tellin'
ya in all seriousness, two pistons out that much at under 6500 rpms....you
will never know the difference; Especially with a quality harmonic dampener.
is within 30 grams and most machine shops try for within 5 or 10 grams.
The difference between .030" and .035" pistons is maybe 8 grams. Also
this being a boost application means the rpms don't need to be high where
the higher order (4th & 5th) harmonics become more pronounced. I'm tellin'
ya in all seriousness, two pistons out that much at under 6500 rpms....you
will never know the difference; Especially with a quality harmonic dampener.
TECH Enthusiast
Joined: Feb 2007
Posts: 625
Likes: 0
From: Raleigh, NC
Anyone here ever balanced a crankshaft assembly ???? The factory tolerance
is within 30 grams and most machine shops try for within 5 or 10 grams.
The difference between .030" and .035" pistons is maybe 8 grams. Also
this being a boost application means the rpms don't need to be high where
the higher order (4th & 5th) harmonics become more pronounced. I'm tellin'
ya in all seriousness, two pistons out that much at under 6500 rpms....you
will never know the difference; Especially with a quality harmonic dampener.
is within 30 grams and most machine shops try for within 5 or 10 grams.
The difference between .030" and .035" pistons is maybe 8 grams. Also
this being a boost application means the rpms don't need to be high where
the higher order (4th & 5th) harmonics become more pronounced. I'm tellin'
ya in all seriousness, two pistons out that much at under 6500 rpms....you
will never know the difference; Especially with a quality harmonic dampener.
Last edited by usdmholden; Oct 18, 2013 at 08:47 AM. Reason: fixed mistake
You wouldn't have to rebalance the engine anyway. Just weight match those two pistons to the rest.
When balancing any engine, all pistons are weighed and matched to the lightest one by removing material.
Like AR said, even if you didn't match them, you would never know the difference.
It is kind of ghetto, but you know what? Once it's together and you are banging gears, you won't care one bit.
Ron
When balancing any engine, all pistons are weighed and matched to the lightest one by removing material.
Like AR said, even if you didn't match them, you would never know the difference.
It is kind of ghetto, but you know what? Once it's together and you are banging gears, you won't care one bit.
Ron