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

maybe i should have just bought from FM

 
Old 04-02-2010, 12:30 PM
  #1  
:(
Thread Starter
iTrader: (7)
 
Join Date: Jul 2006
Location: nowhere
Posts: 8,254
Total Cats: 2
Default maybe i should have just bought from FM

i just pulled my weisco pistons and am happy to see no real signs of detonation(aside from alil on #1 yeah tunning), however i am disheartened by the sight of what looks like latteral wear on the piston and the cylinder walls adjacent so i geus i was getting abit of piston slap. There is no evident damage but i can definetly see where the stuff had worn alil. So all you engine builders on here with real solutions what would you do? Keep in mind i am a cheap bastard and if i can get 50-60k miles out of the motor i will be more than happy with it. pics to come later
magnamx-5 is offline  
Old 04-02-2010, 03:06 PM
  #2  
Elite Member
 
Join Date: Dec 2008
Location: Colorado
Posts: 1,644
Total Cats: 36
Default

These engines have crappy rod ratios so forged pistons will oval cylinders over time. How many miles did you get and was the comp still good?
Sparetire is offline  
Old 04-02-2010, 04:24 PM
  #3  
Junior Member
iTrader: (2)
 
Join Date: Oct 2007
Location: Lisle, IL
Posts: 294
Total Cats: 0
Default

What sort of piston to cylinder clearances were you running with the Wisecos?? Are the Wiseco's a 2618 alloy or a 4032 alloy?? FM lists their pistons (custom made for them by Wiseco) as being a 2618 alloy. Forged 2618 pistons are generally accepted as being stronger than 4032 forged pistons but they have a higher coefficient of expansion and require more piston to cylinder clearance. You are going to get more cold piston slap with 2618 pistons than 4032 pistons but this shouldn't be a problem if they are properly clearanced and you are not beating on a cold engine. Did you actually mic the pistons and cylinders and verify that they are "oval"??
sn95 is offline  
Old 04-02-2010, 05:16 PM
  #4  
Elite Member
 
Join Date: Dec 2008
Location: Colorado
Posts: 1,644
Total Cats: 36
Default

Good point. I still have a block that shows some wear (no more visible cross-hatch) on the cylinder walls, but the cylinders are near-as-darn-it perfectly round still, and it had great compression when tested before removal. This was with Wisecos (not sure what alloy).
Sparetire is offline  
Old 04-03-2010, 12:18 AM
  #5  
Junior Member
iTrader: (2)
 
Join Date: Oct 2007
Location: Lisle, IL
Posts: 294
Total Cats: 0
Default

Yeah, I doubt that the Wiseco pistons are the problem (I think most Wiseco's are 2618). What can be a problem is if someone uses stock Miata piston to cylinder bore clearances with 2618 pistons (2618s require more clearance than 4032s which require more clearance than stock cast pistons). Once the pistons warm-up (and fully expand), the piston to cylinder wall clearances become too tight and scuffing can result.

Edit:

Some piston slap is normal on a cold engine at startup with high coefficient of expansion forged pistons. It should not cause any abnormal wear if the clearances are "right" and the motor is not put under boost/strong load when cold. On a properly "clearanced" forged piston motor, there will be no piston slap once the engine is warmed up. Piston slap on a warmed up motor is sign of very loose piston to bore clearances.

Last edited by sn95; 04-03-2010 at 12:23 AM. Reason: Added piston slap
sn95 is offline  
Old 04-03-2010, 12:47 AM
  #6  
Junior Member
 
Join Date: Jun 2005
Location: Huntington Beach, CA
Posts: 354
Total Cats: 0
Default

Originally Posted by sn95 View Post
Forged 2618 pistons are generally accepted as being stronger than 4032 forged pistons but they have a higher coefficient of expansion and require more piston to cylinder clearance. You are going to get more cold piston slap with 2618 pistons than 4032 pistons but this shouldn't be a problem if they are properly clearanced and you are not beating on a cold engine. Did you actually mic the pistons and cylinders and verify that they are "oval"??
2618 is stronger than 4032, not generally accepted, just look at the fatigue strength at elevated temperatures...I can also tell you that the pistons are oval, just measure at the same height up the skirt and you will find that the difference between the skirt axis and pin axis is probably .0125''.

Magna, take a pic of the wear, if you're seeing scratches up and down the bore, then it's most likely ring wear and tension. If you're just seeing darkened areas on the cylinder over the skirt face, that's typically just the peaks of your cylinder honing wearing slightly.
iWeasel410 is offline  
Old 04-03-2010, 10:46 PM
  #7  
Former Vendor
 
Join Date: Dec 2007
Location: Texas Hill Country
Posts: 271
Total Cats: 12
Default

Forged piston slap at cold and low speeds drove me crazy for a couple years. I don't waste emotions "hating" anything. With a firm hold on my lightening rod, I admit to fudging the truth; I do "hate" piston slap.

I cured the problem in every case in which I used forgings by the old/old/old knurlling of the piston thrust faces and then baking on a Dow Corning molycote bond on dry film lubricant in the knurl.

The piston will prove reluctant to push down the bore on assembly, but bash it soundly with something soft and it will shear off all the stuff that it needs to in order to slide down the bore. When the engine is cranked up it will establish the absolute minimum clearance that it can live with in the range of temperature induced expansions.

Presto, forged pistons, no cold slap, and no hot idle slap. Easy 60K durability. This procedure is right in there with the absolute best margarita formulas.

Corky
On second thought, its just close.
Corky Bell is offline  
Old 04-04-2010, 01:11 AM
  #8  
Elite Member
iTrader: (17)
 
Join Date: Apr 2009
Location: Atlanta, GA
Posts: 2,799
Total Cats: 0
Default

i feel stupid after reading your post Corky cause there is a lot of big words in there that i have no clue as to what they mean! lol damnit, i should of went to college or paid more attention in high school!


this thread is really making me 2nd guess using forged pistons in my engine build and just sticking with OEM pistons and having the Tri-coated like Rotornut did!
WonTon is offline  
Old 04-04-2010, 02:57 AM
  #9  
Junior Member
 
Join Date: Jun 2005
Location: Huntington Beach, CA
Posts: 354
Total Cats: 0
Default

The big question in deciding whether you want cast or forged comes down to tuning. How are you going to tune it? Keep in mind you can run 4032 forged pistons and keep piston to wall clearance at a minimum to prevent piston slap. Crack resistance due to detonation changes from the type of material too, so if you can get a good tune from the get go maybe cast pistons are down your alley...
iWeasel410 is offline  
Old 04-04-2010, 08:30 PM
  #10  
:(
Thread Starter
iTrader: (7)
 
Join Date: Jul 2006
Location: nowhere
Posts: 8,254
Total Cats: 2
Default

Name:  Photo-0009.jpg
Views: 53
Size:  85.0 KB
Name:  Photo-0008.jpg
Views: 56
Size:  70.0 KB
Name:  Photo-0007.jpg
Views: 58
Size:  76.6 KB
ok here is a pic of #1 for reference overall after not looking at it for a day it looks alot better than i was thinking. there is a interesting defect about an 1/8th of an inch or so wide going down the bore wich i suspect was from dirty assembly at the machine shop or something last time. 12k miles fwiw anyway what do you guys think? will i be ok to just slap in my new rods and bearings and pwn some face or what?
magnamx-5 is offline  
Old 04-04-2010, 11:57 PM
  #11  
Junior Member
iTrader: (2)
 
Join Date: Oct 2007
Location: Lisle, IL
Posts: 294
Total Cats: 0
Default

Originally Posted by magnamx-5 View Post
ok here is a pic of #1 for reference overall after not looking at it for a day it looks alot better than i was thinking. there is a interesting defect about an 1/8th of an inch or so wide going down the bore wich i suspect was from dirty assembly at the machine shop or something last time. 12k miles fwiw anyway what do you guys think? will i be ok to just slap in my new rods and bearings and pwn some face or what?
Those vertical scratches in #1 aren't good, do all your cylinders have vertical scratches?? Vertical scratches like that are usually caused by dirt/debris getting caught between the piston and cylinder wall. Do you remember what the piston to bore clearance was when the motor was built?? At a minimum, I think you are going to need to hone the cylinders and see if you can eliminate the vertical scratches (may be able to do this with a bottle brush style hone) to be able to get a good ring seal.

Assuming you don't have a dial bore gauge or inside micrometer to check the bores, it's probably a good idea to take the block to a machinist/machine shop that has one and get the bores checked for taper and out of round. You can also have the piston dimensions checked vs. new Wiseco specs and make sure that nothing is drastically worn (which seems unlikely given the picture of the #1 piston). Once you have piston and bore specs for each cylinder, you can calculate the piston-to-bore clearance and make sure if it is within Wiseco specs for 2618 pistons (you don't want clearances too tight with forged pistons).

Hopefully, a cylinder hone, some new rings (file fit to TURBO end-gap specs) and lot of meticulous cleaning (clean everything twice, keep clean parts in sealed ziplocks until you install them, assemble in a clean dust-free area and seal up the shortblock with plastic bag anytime you are not working on it) will be all you need.
sn95 is offline  
Old 04-05-2010, 02:17 AM
  #12  
:(
Thread Starter
iTrader: (7)
 
Join Date: Jul 2006
Location: nowhere
Posts: 8,254
Total Cats: 2
Default

nah its just on that one cylinder and yeah i was gonna atleast brush those out cause they arent deep but ima take care of em.
magnamx-5 is offline  
Old 04-05-2010, 09:14 AM
  #13  
Elite Member
iTrader: (8)
 
Join Date: Jun 2009
Location: Albany, NY
Posts: 1,470
Total Cats: 4
Default

Originally Posted by Corky Bell View Post
...I cured the problem in every case in which I used forgings by the old/old/old knurlling of the piston thrust faces and then baking on a Dow Corning molycote bond on dry film lubricant in the knurl.
...
The piston will prove reluctant to push down the bore on assembly, but bash it soundly with something soft and it will shear off all the stuff that it needs to in order to slide down the bore. When the engine is cranked up it will establish the absolute minimum clearance that it can live with in the range of temperature induced expansions.
...

Corky
For realz? Makes sense, but sounds brutal, and sounds like THIS will scratch the bores.
webby459 is offline  
Old 04-05-2010, 01:27 PM
  #14  
:(
Thread Starter
iTrader: (7)
 
Join Date: Jul 2006
Location: nowhere
Posts: 8,254
Total Cats: 2
Default

Name:  Photo-0010.jpg
Views: 52
Size:  130.6 KB
well i dont geus it is a myth about our rods being weak atleast 2 of my stockers are bent i wondered where my hp was going. maybe i didnt need cops etc after all.
On a side note where the hell do you get new circlips i had a few spring on me on disasembly reasembly and they went pretty damn far and i am unable to refind them.
magnamx-5 is offline  
Old 04-05-2010, 02:36 PM
  #15  
Junior Member
iTrader: (1)
 
Join Date: Sep 2007
Location: Nor-Cal
Posts: 78
Total Cats: 3
Default

[QUOTE=webby459;550653]For realz? Makes sense, but sounds brutal, and sounds like THIS will scratch the bores.[/QUOTE

Isn't this just shearing off molycote which should be softer than anything you have to worry about scratching?
1drum is offline  
Old 04-05-2010, 02:42 PM
  #16  
Elite Member
iTrader: (8)
 
Join Date: Jun 2009
Location: Albany, NY
Posts: 1,470
Total Cats: 4
Default

Originally Posted by magnamx-5 View Post
On a side note where the hell do you get new circlips i had a few spring on me on disasembly reasembly and they went pretty damn far and i am unable to refind them.
Mazda Motorsports, p/n 0221-11-205, at least for '97. Prolly find them from Rosenthal for you dumbfucks that don't have a motorsports account.
webby459 is offline  
Old 04-07-2010, 11:39 PM
  #17  
:(
Thread Starter
iTrader: (7)
 
Join Date: Jul 2006
Location: nowhere
Posts: 8,254
Total Cats: 2
Default

i ordered some from fastenal if this dont work i geus i will have to hit up rosenthal or some other random dealer
magnamx-5 is offline  
Old 04-08-2010, 12:33 PM
  #18  
:(
Thread Starter
iTrader: (7)
 
Join Date: Jul 2006
Location: nowhere
Posts: 8,254
Total Cats: 2
Default

ok fastenall=fail luckily rosenthal has em for 1$ apeice lol god i hate ky so much at times it nvr has what i want or need.
magnamx-5 is offline  
Old 04-08-2010, 12:44 PM
  #19  
Elite Member
iTrader: (8)
 
Join Date: Jun 2009
Location: Albany, NY
Posts: 1,470
Total Cats: 4
Default

Originally Posted by magnamx-5 View Post
ok fastenall=fail
Fastenall=always fail, in my experience.
webby459 is offline  
Old 04-20-2010, 01:39 PM
  #20  
:(
Thread Starter
iTrader: (7)
 
Join Date: Jul 2006
Location: nowhere
Posts: 8,254
Total Cats: 2
Default

ok well i put the oilpan and head back on and proceeded to try and prime the oiling system only to find i had low flow and oil pressure. hmm. on a hunch i pulled my oil squirters and geus what i found on #2
Name:  Photo-0013.jpg
Views: 57
Size:  41.3 KB
Yep so how much is this bad boy and where can i get one? Or should i just cap it off and be done with it pros cons anyone?
magnamx-5 is offline  

Thread Tools
Search this Thread
Quick Reply: maybe i should have just bought from FM


Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.