Oversize Pistons - How big would you dare? - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Engine Performance This section is for discussion on all engine building related questions.
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 07-12-2011, 04:01 AM   #1
Junior Member
Thread Starter
 
Join Date: Sep 2007
Location: Brisbane, Australia
Posts: 112
Total Cats: 0
Default Oversize Pistons - How big would you dare?

I am looking at some time in the future, building a 1.8. On my list of things to do is oversize pistons. I am looking at increasing the displacement as much as possible on the stock stroke so I was thinking 1.5mm oversize (84.5mm) JE pistons as you can buy them off the shelf. I see that you can buy up to a 2.5mm oversize piston from Supertech and am curious to know if anyone has taken a stock block out that far? I want to do this to a stock block ie. I don't want to sleeve it.

So how far has anyone taken out a stock block without troubles and does anyone know the limit?

Cheers,

Tim
zoomzoom is offline   Reply With Quote
Old 07-12-2011, 06:05 AM   #2
AFM Crusader
iTrader: (18)
 
olderguy's Avatar
 
Join Date: Oct 2004
Location: Wayne, NJ
Posts: 4,438
Total Cats: 84
Default

olderguy is offline   Reply With Quote
Old 07-12-2011, 06:34 AM   #3
Senior Member
 
Join Date: Dec 2004
Location: Brisbane, Australia
Posts: 1,272
Total Cats: 32
Default

I remember seeing this recently, it was 1mm oversize on 23 pounds boost:
https://www.miataturbo.net/engine-performance-56/cracked-engine-block-d-58823/
timk is offline   Reply With Quote
Old 07-12-2011, 06:51 AM   #4
Junior Member
 
Join Date: Mar 2011
Location: Tallahassee, FL
Posts: 279
Total Cats: 3
Default

Quote:
Originally Posted by olderguy View Post
spitefulcheerio is offline   Reply With Quote
Old 07-12-2011, 08:24 AM   #5
Junior Member
Thread Starter
 
Join Date: Sep 2007
Location: Brisbane, Australia
Posts: 112
Total Cats: 0
Default

Wow, thanks for the useful responses. I think I might stick to 1mm after seeing that. Maybe 1.5. Sleeved block is a bit outside my budget.

I am sure I have seen a couple people on here running 1.5 over, can anyone own up to having gone 1.5 over? And has anyone else seen any issues like the one in that other linked thread?

Cheers,

Tim
zoomzoom is offline   Reply With Quote
Old 07-12-2011, 11:03 AM   #6
Senior Member
iTrader: (2)
 
Join Date: Nov 2007
Location: Saint Paul, MN
Posts: 1,296
Total Cats: 22
Default

Sleeves... how much is THAT going for? I'd legitimately be interested if/when I kill my block..
Der_Idiot is offline   Reply With Quote
Old 07-12-2011, 11:17 AM   #7
Elite Member
iTrader: (9)
 
Join Date: Sep 2008
Location: Bloomfield, Michigan
Posts: 5,682
Total Cats: 10
Default

Click the link and read Anyhooters, add says price is not finalized, but it will be in a $3-4k range. Not bad really
buffon01 is offline   Reply With Quote
Old 07-12-2011, 11:42 AM   #8
I'm Miserable!
 
Join Date: Jun 2009
Location: albany, ga
Posts: 1,869
Total Cats: 3
Default

sonic test the cylinders
Techsalvager is offline   Reply With Quote
Old 07-12-2011, 11:58 AM   #9
Supporting Vendor
iTrader: (31)
 
Savington's Avatar
 
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 14,366
Total Cats: 1,327
Default

If you're serious, you sonic test.

I wouldn't bore a stock block 2.5mm over for forced induction use.
Savington is offline   Reply With Quote
Old 07-12-2011, 12:35 PM   #10
Elite Member
iTrader: (12)
 
Join Date: Aug 2006
Location: Central-ish VA
Posts: 4,449
Total Cats: 16
Default

Quote:
Originally Posted by buffon01 View Post
Click the link and read Anyhooters, add says price is not finalized, but it will be in a $3-4k range. Not bad really
I'd assume that's for an assembled engine. Not just getting the block sleeved. If I'm wrong then it's a terrible price. Reading the description though it sounds like it includes rods and pistons, etc... assembled. The price isn't all that bad if you consider that it normally costs at least $1k to sleeve other motors where it's more commonly done in addition to the cost of the core and the other parts involved.
neogenesis2004 is offline   Reply With Quote
Old 07-12-2011, 12:38 PM   #11
Elite Member
iTrader: (9)
 
Join Date: Sep 2008
Location: Bloomfield, Michigan
Posts: 5,682
Total Cats: 10
Default

Quote:
Originally Posted by neogenesis2004 View Post
I'd assume that's for an assembled engine. Not just getting the block sleeved. If I'm wrong then it's a terrible price. Reading the description though it sounds like it includes rods and pistons, etc... assembled. The price isn't all that bad if you consider that it normally costs at least $1k to sleeve other motors where it's more commonly done in addition to the cost of the core and the other parts involved.
They refer to a "drop-in" short block for that price. I assume, yes, it is assembled. I'd like to see a list of part...
buffon01 is offline   Reply With Quote
Old 07-12-2011, 01:38 PM   #12
Elite Member
iTrader: (7)
 
samnavy's Avatar
 
Join Date: Apr 2006
Location: VIRGINIA BEACH, VA
Posts: 6,020
Total Cats: 175
Default

WOW! If they can deliver a $3500 2.0 sleeved built motor, that sounds like a helluva deal.
samnavy is offline   Reply With Quote
Old 07-12-2011, 07:39 PM   #13
Junior Member
Thread Starter
 
Join Date: Sep 2007
Location: Brisbane, Australia
Posts: 112
Total Cats: 0
Default

If they can deliver a built short block for 3500 I agree that it would be a pretty good deal. Unfortunately living on the other side of the world has it's drawbacks and I am sure freight would blow that right out of the water even if I could stretch my budget for the block.

Think I have to try and find someone here that can do sonic testing.
zoomzoom is offline   Reply With Quote
Old 07-12-2011, 11:48 PM   #14
Senior Member
iTrader: (3)
 
Join Date: Jun 2008
Location: Port Orchard, WA
Posts: 620
Total Cats: 4
Default

I sonic checked a 2001 block that was at 85.5mm, had less than .050 wall thickness in one spot and was under .070 on every cylinder. Thin spots were near the top of the bore right under the deck (worst possible place). I will say that the fronts of the cylinders were much thinner than the backs, which could have been bad machining, or equally likely to be core shift in the casting process.

Unless I sonic checked the block, I wouldn't go over 84mm.
Rennkafer is offline   Reply With Quote
Old 07-13-2011, 01:01 AM   #15
Senior Member
iTrader: (18)
 
Join Date: May 2008
Location: Big Bear Ca
Posts: 990
Total Cats: 8
Default

^^^ This was my block. It's now taking up space in my garage, along with some supertech 85.5mm 11.5:1 pistons. I went with 84mm per Rennkafer and Savigntons suggestions.
dstn2bdoa is offline   Reply With Quote
Old 07-13-2011, 01:36 AM   #16
Elite Member
iTrader: (3)
 
Join Date: Feb 2008
Location: Huntsville, AL
Posts: 1,881
Total Cats: 45
Default

One of my buddies has built several +2.5mm NA motors that have been pretty successful. He has the local marine machine shop that we use sonic check the blocks before punching them that big, but he's never had will thickness issues. I'm thinking your block had some serious core shift, Rennkafer. The bore centers are located based on the mains during manufacturing, not the other way around, so if the cylinder section of the block mold shifted rearward, they would just all be thin at the front.
vehicular is offline   Reply With Quote
Old 07-13-2011, 12:34 PM   #17
Senior Member
iTrader: (3)
 
Join Date: Jun 2008
Location: Port Orchard, WA
Posts: 620
Total Cats: 4
Default

Quote:
Originally Posted by vehicular View Post
One of my buddies has built several +2.5mm NA motors that have been pretty successful. He has the local marine machine shop that we use sonic check the blocks before punching them that big, but he's never had will thickness issues. I'm thinking your block had some serious core shift, Rennkafer. The bore centers are located based on the mains during manufacturing, not the other way around, so if the cylinder section of the block mold shifted rearward, they would just all be thin at the front.
As I said before, could have been core shift or could have been mismachined.

The block front walls were ~.060" and the rear walls were ~.220", if you had that perfectly centered you'd end up with ~.140" wall thickness which would be fine. That's why I'd suggest sticking with 84mm unless you have the block sonic checked and KNOW what you're dealing with. If we'd built Dstn2bdoa's block and boosted it, it would likely have failed in short order, an NA engine "might" have lived for a while depending on how you built it (ie what kind of cylinder pressures you're seeing).
Rennkafer is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 58 12-13-2017 10:04 PM
Need help - Stock Balancer and Fastforward overlay pulleys Frank_and_Beans Supercharger Discussion 13 09-12-2016 09:17 PM
OTS Bilstein to motorsports ASN conversion stoves Suspension, Brakes, Drivetrain 5 04-21-2016 04:00 PM
WTB Stock NB Pistons pdexta WTB 0 09-28-2015 12:18 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 08:16 AM.