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forged vs. stock 95 pistons

JET

Proven Member
223
0
May 20, 2002
Minneapolis
I can't say enough about the Wiseco's. I know there was another happy user up farther. I have NEVER heard anyone unhappy with them. They have a much smaller piston to wall clearance than most other pistons because of a better sidewall design (I am sure I will get some flack for this). Their skirts are thicker and longer than JE's and the alloy is slightly different. They are slightly heavier, but DSM's have strong rods anyways. The JE's are a ton noisier than the Wiseco's when cold. I have heard both of them in person. You cannot tell the difference from the Wiseco's and stock. The Wiseco/Eagle combo is the way to go unless you are going over 600 hp.
 

chrisAWD

Proven Member
129
1
Jan 17, 2003
Clinton, New_Jersey
after doing my motor i realize how "inaccurate" i was in alot of things.

My dad is now building an injected/blown 392 hemi and he is using a machine shop in eastern PA that is way expensive, but very good. I know that with his ross pistons, Ross actually specifies the piston to wall clearance that there pistons need....its not just a .030 overbore for example....also even the rings(total seal gapless) require a special cylinder wall finish to seat properly. these were just some of the things that made me realize how much more accurate some of these processes need to be.

sometimes though you can get into trouble and really get OVER informed and then just get paranoid and think its impossible to ever get everything perfect. there are still alot of opinions and sometimes a manufacturer might say one thing and the machinist another and you don't know who to go with, even though both might be acceptable. oh well....i thought i had a point but....
 

UndergroundR32

Proven Member
664
0
Jun 6, 2002
NY
Originally posted by Suparata
It's natural for all forged piston to slap . They are supposed to have 4-5 times bigger clearence compared to stock.
For how long during warm-up they slap I would say it depends of the clearence and manufacturer. But don't expect to have a quiet engine that will produce 600 HP!
About trusting the machine shop it should be your responsability to have the specs for the parts you walk in with. You are the one who knows how you will drive the car , what modifications you have, what boost, ... .

It's not necessarily natural to have piston slap with all forged piston jobs. Yes, if you plan to make 600 HP with your DSM, chances are you're going to need a fair amount of clearance to allow 30+ psi and nitrous to spool whatever rediculously large turbo you get. BUT with a street car with forged pistons, It's not something you should hear with the right machinist.
 

JET

Proven Member
223
0
May 20, 2002
Minneapolis
You are right. I hear almost no slap with mine. The more clearance your have, the more pressure you have on the rings. When running high boost or nitrous, this is a big deal. Most built DSM engines that die are from a broken ring or a siezed bearing.
 

UndergroundR32

Proven Member
664
0
Jun 6, 2002
NY
Just because it's not as tight as stock doesn't mean it's going to slap. It's about clearance, and how well it's bored, and if you use a torque plate. If the bore isn't perfect of course it's going to slap. Do you think it doesn't matter who does the work?
 

JET

Proven Member
223
0
May 20, 2002
Minneapolis
The machinist does make some difference in piston slap. It is not cake to bore a cylinder (I am a machinist). You need the right speeds and feeds to prevent taper. Also dialing in the size between all of the cylinders. As long as you have a competent machinist this is not a problem. The biggest thing that causes piston slap is the skirt design. Wiseco seems to be the best, with Ross just behind and JE is way back in the dust.
 

BryanK

Proven Member
133
0
Jun 25, 2002
Iowa
Suprata... I understand what you're saying, but I do think it makes a big difference who you go to for machining. With 2.0 DSM's, you usually won't hit 30 psi until well after 4K, so going down the highway at 80 mph shouldn't be pushing those crazy boost levels. But obviously, any moron who drives their car for more than 10 seconds on 30 psi deserves to have their engine sieze. A lot of it has to do with how you treat your car. If you drive it like to stole it on a daily basis, and really beat the sh*t out of it, than you have to expect to do a lot of rebuilds, thats just common sense. I don't care how well you build an engine, or if you use frigging titanium on everything, its going to break if you beat it to hell. I realize that there isn't any way you can get clearance the same as stock if you're going with forged pistons because the expansion rates are different, but its my opinion that if you're machinist knows what they're doing that they usually can get it close enough to not have piston slap to the point that it scores the cylinder walls. I think thats the only issue here... if slapping didn't cause any damage to the cylinder walls than I'm pretty sure everyone and their mom would have forged pistons in their car. The point, and what I believe is the reason why a machinist makes a huge difference, is to eliminate slapping to the point that it won't cause damage or score those walls. You are right, the manufacturer should provide you with the correct specs to get the clearance close, but those are usually just estimates. There isn't any way the manufacturer can tell you exactly what those specs are because they don't know how much boost/nitrous you're going to be using. Thats where, I believe, the machinist comes into play. If you've got a good machinist, who has a lot of experience doing 4G63 build ups, they should have a pretty good knowledge of how the different pistons (JE, Ross, Wiseco, ect) tend to behave under different circumstances. Not to mention they ability to do all the things that JET just described, and do them VERY, VERY well. Looking back at your post it looks like I pretty much just reiterated what you said, but I disagree that your machinist shouldn't make a difference.
Don't get me wrong... if you get piston slap its not automatically the machinist's fault (unless, of course, they fukt up in a big way). If you're planning on beating the hell out of your engine than you've got to accept the consequences (that you are GOING to have slap). But, if you're just planning on using it as your daily driver that you take out to the track/beat on V8's (ie not going over 25psi of boost... ever... and even then at 25psi keeping it at 10 second sprints) than I don't think its unreasonable for your machinist to get piston slap down to a VERY Minimum. Just a difference of opinion I guess.
BryanK
 

UndergroundR32

Proven Member
664
0
Jun 6, 2002
NY
Originally posted by Suparata
all Diesels run forged and they slap A LOT and they run for ever.
Scuffing and wear are not a result of slap.

Diesels don't rev out to 8k. How can you say slap doesn't cause scuffing and wear with a straight face?
 

BryanK

Proven Member
133
0
Jun 25, 2002
Iowa
Nah suprata... I think you took my post in the wrong context. I guess, what it boils down to, is DSM's simply cannot push 500+whp on a daily basis without breaking or needing rebuilt. Reminds me of unrealistic kids asking "I wanna run 10's and still have my thumpin stereo and all the creature comforts that the car came with stock... where can I get some nos to do this?"

I don't know crap about deisel... but 4G63's aren't deisels so that argument isn't really valid. Thats comparing apples to oranges.

The only thing I was arguing is that it does (once again, in my opinion) make a difference who you have do the machining. To me, when it comes to 4G63's and engines in general, knowledge is secondary to experience. Knowing how to do something doesn't mean crap as compared with having done it many many times.

BryanK
 

JET

Proven Member
223
0
May 20, 2002
Minneapolis
I don't disagree with too much of what you are saying. I agree the machinist doesn't matter IF they do it correctly. A poor machinist is not going to do it correctly though. I think we agree on that. I have forged pistons. I live in Minnesota. Do I have slap? No more than stock. I can only hear anything if I lift the hood and get right down by the engine when it is cold. Do JE's slap? Yes, like crazy. That is what happens when Wiseco's are gapped at .003" - .0035"and JE's need .0065"+. Stock is .0015" - .002", so the Wiseco is barely over stock gap. So in summary the PISTON is the cause for slap, not the machining job as long as it was done correctly.
 

Tevenor

Supporting VIP
1,786
11
Mar 18, 2002
Rochester, New_York
Originally posted by Suparata
Thanks for your help and I hope everybody will get the point I'm trying to make.
So you run .0035 on the Wiseco's and the JE's at .0065 . What about Ross? The manufacturer ask for .006 . Are you guys using that or what?

We would get your point a hell of a lot more if you could spell and use proper sentence structure.

1) Who the machinist is does matter. If he is a shitty machinist, you get a shitty job. You get a good machinist, you get a good job. How much deeper do we really have to delve into this?
2) Piston slap is mismatched clearances. Mismatched clearances lead to scuffing and wear. This too is really that simple.

I am not sure what your deal is. From trying to read your posts you looking like you restate the same thing most of the people in this thread have alread said.
 

Tevenor

Supporting VIP
1,786
11
Mar 18, 2002
Rochester, New_York
Originally posted by Suparata


My apologies for misspelling and using improper sentence structure but I'm trying to do my best if that's really important for you.
Why don't you just go to Europe and see if in less than 4 years you will be able to express yourself better than I did in a language other than English.

My first 12 years were in Europe. I didn't hit the states until into my early teens. And it is important to this forum, as the rules state.

You have made your point. I have made mine. Let's move on. :)
 

tominatortwo

15+ Year Contributor
99
4
Jan 5, 2003
Indianapolis, Indiana
Does any body know of a way to upgrade my rods on a 2g and keeping stock pistons. All after market rods are for floating pistons. I did not want to have my motor punched out for floating pistons and I cant find any after market pistons in stock bore sizes?????????
 

Big Woo

DSM Wiseman
458
18
Sep 9, 2002
Grand Rapids, Michigan
First not all diesel's run forged pistons, but they do run a larger piston to wall clearence, which is where the slap comes from (large clearence, cold motor, 20:1 compression). lets keep in mind that we are talking about a 20:1 compression ratio, and a max of roughly 3000RPM's. Not compairable to spark ignition engine.

95 pistons are good for about 450 to 500 HP as long as detonation and EGT's are kept in check. The 95 piston 6-bolt rod combo is a good proven economical set-up. If you want to use the 95 pistons and the eagle rods, first I would ask why, but it can be done. A: the 95 pistons could be modified for spirol locks, and the wrist pin shortened to fit. Or B: the eagle rods could be modified for press fitting the wrist pin. Either way is costly, so you might as well buy the forged pistons, and be done with it.

Yes you need a good machinest, because he or she could mistakely set the piston to wall clearence incorrectly. Especially if they have not worked on many hi boost turbo motors. What you don't want is somebody who thinks they know it all. However you also need to provide that machinest with good info. I.E. many turbo piston manufactures vary piston to wall clearence depending on the intended maximum boost pressure for each application. For example Brand X piston may reccomend .003 piston to wall clearence for a maximum of 18 psi of boost, but would reccomend .0045 piston to wall clearence in the same engine if the intended maximum boost was said to be 25 psi. So you can't have your cake and eat it to. Jest remember if you say your going to run 30psi of boost, and get the extra clearence for it, you may also get a little slap when your motor is cold. The same people that are complaining of piston slap would be screaming bloody murder if the clearence was to tight , and scraped a set of $500 pistons in the driveway. There is a tendency by "(some)" machinest's to loosen things
up a bit. This is because sometimes loose pistons make a little noise, but tight ones junk parts quickly.
 

ho chi inn

Probationary Member
27
0
Jan 13, 2003
denton_texas
i sell parts for a living. one of my accounts builds a lot of high performance bmw motors, and is a metallurgist by trade. he has a full blown machine shop in his basement. he talks a lot about modern piston design, and follows bmw piston changes. he also gets all of his pistons custom made. one of the things he has said is that because of the different rates of expansion forged pistons have versus cast, much larger clearances must be run. this problem has been solved by using forged pistons with a high silicon content, which makes the rate of expansion very close to cast. also, just ordering a set of forged pistons is negating one of the big advantages of forged over mass produced cast, in that you can change the design of the piston; for example, recent bmw pistons have gone to much shorter skirt design, some of the oil rings now actually cover part of the pin opening. also, the #1 ring is now a LOT closer to the top of the piston. nascar was one of the first to go to this, they discovered that a lot of unburned fuel collected in that area, and then was pushed out with the exhaust gasses. if you burn ALL of the fuel mix, you get more power, and better fuel economy. just my 2 cents.
 

ShapeGSX

Proven Member
698
10
Jun 13, 2002
Worcester, Massachusetts
Moving the #1 ring closer to the top of the piston also has been a great way to reduce vehicle emissions for the reasons that you mentioned. However, it makes for a horrible forced induction piston. This is a big part of the reason that Hondas with forced induction or a big hit of nitrous end up cracking their stock pistons. The ring lands are simply too thin and weak to support that much pressure. Then add a tiny bit of detonation on top of it, and you will end up with a piston that comes out in a few pieces. Same goes for LS1 and LT1 pistons.
 
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