aluminum Pistons ?

[markmullins]

Hey guys im having a machine shops rebuilt my 4g63t 7bolt, and he replaced the pistons with an alluminum compsotie mix, im not sure of the brand i just stopped by the shop and saw the pistons in the block. Has any one ran on possibly generic alluminum pistons before , or knows if their going to hold up like stock ones ? im alittle worried and its too late to pull out from the deal.. running a small 16g , ported head, 15 psi, will be adding 750cc injectors , and 255 fuel pump , then uppping the boost ... help need to know dont want to lose another engine

 

[No_Skillz]

http://www.dsmtuners.com/forums/showthread.php?t=213902

http://www.ffwdconnection.com/rods.shtml

Find out what company your rods are made of.

 

[ChicksDigBoost]

Hes talking about the pistons those threads are about rods. Find out what company there from. Your saying that there not a forged aluminum piston like ross or wiseco? Or are they just a brand you've never heard of forged piston?

 

[underradar92]

To No Skillz; he seems to be referring to pistons. Mark; most pistons for MOST engines since a long tine ago, are some form of aluminum alloy. Your shop should have some idea who made your pistons, your engines life depends on these kind of details.

 

[No_Skillz]

feel like an idiot right now. Sorry, woke up and just skimmed it.

 

[SlowSpyder]

Ask your builder what kind of pistons they are. Most likely they might be your stock replacements "cast aluminum pistons". There is a small possibility that your engine builder is using hyperutectic pistons.

 

[markmullins]

Thanks alot guys that helps i will ask , yeah im sure their just stock replacements, im trying to figure out though if theses replacements hold up like stock or are going to be more prone to melting down or causing any kind of future problems. i will find out what brand pistons and rods are.

 

[Turbocharged]

Generic pistons are prone to slapping the cylinder walls.

 

[SpoOLxExO]

Generic pistons are prone to slapping the cylinder walls.

Not only is this statement (Among the other things in this thread, "I don't know if my engine will hold up, Planning on 750's and turning the boost up") Vague but also carries uneducated presumption.

ANY piston can slap. Mattering not what kind, or construction.

What matters is what honing process is used, what the clearence between the piston and bore, and ring gap inside of the bore. If these things are within spec, or even a little tighter, then this will not be an issue.

I have put together a 4g with the topline rebuild kit, and it makes not a noise. This is because I knew all the clearences were in spec.

POINT: Definately find out what pistons are being used, and what honing process was done, with or without a torque-plate.

Then, and only then can you even think about turning the boost up, there Marcmullins.

What you were asking in the first place makes me cringe
(AKA: I have no idea if this motor will last, should I blow it up now?)

Get back to the board on that.

 

[dsm-onster]

POINT: Definately find out what pistons are being used, and what honing process was done, with or without a torque-plate.

Well for the masses to know: bores are not honed with a flaxplate at the factory and me and many, many others have seen 25+ psi with out a trouble.

Hell I'm running an RS60T to 25 psi, fp2x cams maxing my 650s at 97% idc and I swapped in new rings with out even honing at all. See this. I've done this with 2 other turbo cars and have had zero blowby or any ill effects at all. And, thousands of miles have been put on these engines since the replacement.

 

[kottyking]

Also if I may chime in, why not rebuild a used 6 bolt block??

 

[92awddsm]

Well for the masses to know: bores are not honed with a flaxplate at the factory and me and many, many others have seen 25+ psi with out a trouble.

Hell I'm running an RS60T to 25 psi, fp2x cams maxing my 650s at 97% idc and I swapped in new rings with out even honing at all. See this. I've done this with 2 other turbo cars and have had zero blowby or any ill effects at all. And, thousands of miles have been put on these engines since the replacement.

First off, its not a flaxplate, its a torque plate. No one ever said it wouldnt run fine, its just the fact that you get a better seal between the piston rings and the cylinder wall if it was honed with a torqueplate. The stress of torquing the head will distort the block slightly and compromise ring seal. This issue is then aggravated when the engine is heated. With a plate hone, you actually simulate the head being bolted on during the honing process. Once the plate is removed, the cylinder might(and usually will) measure slightly out of round. Once the head is torqued, all of a sudden, the cylinder measures round again. The factory doesnt do this because it is not cost effective on a mass produced engine. But then again, how many high horsepower dsm's did they hand build between 1990-1999? None.

On topic, most all automotive pistons and made of some sort of aluminum alloy. As long as they are for the right application, they should hold up as good as an oe piston for a stock rebuild. As everyone has stated, find out what brand they are and let us know.

 

[sweet97]

I would have chosen the pistons and rods of any motor I was having rebuilt before the work was started. Did you get a quote on price before the work was started? Mark

 

[dsm-onster]

First off, its not a flaxplate, its a torque plate. No one ever said it wouldnt run fine, its just the fact that you get a better seal between the piston rings and the cylinder wall if it was honed with a torqueplate. The stress of torquing the head will distort the block slightly and compromise ring seal. This issue is then aggravated when the engine is heated. With a plate hone, you actually simulate the head being bolted on during the honing process. Once the plate is removed, the cylinder might(and usually will) measure slightly out of round. Once the head is torqued, all of a sudden, the cylinder measures round again. The factory doesnt do this because it is not cost effective on a mass produced engine. But then again, how many high horsepower dsm's did they hand build between 1990-1999? None.

On topic, most all automotive pistons and made of some sort of aluminum alloy. As long as they are for the right application, they should hold up as good as an oe piston for a stock rebuild. As everyone has stated, find out what brand they are and let us know.

Oops. "flex" plate. Freudian slip? yea torqueplate. I know the process. I just typed the wrong set of letters. Yes I still am off topic, but I have to add this link, again.

Honing and Deglazing

I am a high horsepower dsm running around with not even a hone job (only hone job was what was left of the non-torqueplate hone job that came from the factory 190,000 miles ago; along with the glazed over) when I reringed several thousand miles ago. Results of compression test as of last week: 165 accross the board.

On topic. yep, I agree. For a stock rebuild, as long as they are for your car and the are to oem-like specs, then they should be just fine.

 

[Turbocharged]

Hell I'm running an RS60T to 25 psi, fp2x cams maxing my 650s at 97% idc and I swapped in new rings with out even honing at all.

Is this why you had to replace the rings. 97% idc is VERY high. Never go over 90% unless you are looking to cook your rings...

 

[dsm-onster]

Is this why you had to replace the rings. 97% idc is VERY high. Never go over 90% unless you are looking to cook your rings...

I ran this AFTER installing the new rings. Before, I was running an 18g. I am fully aware what IDC I should be operating at. Operating over even just 80% IDC is hard on your injectors.

My A/F ratio never logged over 11.0:1. So I wasn't running lean enough to worry. No matter what IDC you have (under 100%), if you're not running lean, then running lean is not the reason why you've burned a ring. But I am not running this boost level now, regardless. I will be purchasing a set of 950-1000cc injectors rather soon. I'm retuning for higher base fuel pressure right now.

 

[Baron4406]

I've always wondered about using a torque plate when honing. All big time engine builders says its an absolute MUST. However a few years back a buddy and I actually played around a little bit with a Dodge 2.2 motor. With a VERY accurate dial bore guage we got ZERO, NADA, NO differance at all in the bores with a torque plate on, and with it off. We heated the block to 225 degrees in an over for 1/2 hour then remeasured. I actually got about a 1/10 thousandth out of round, then when the block was cooling it went out of round less and less. I just don't see how a high nickle cast iron block and distort massively with the head bolted up, it actually distorts alot more with heat- but because of the construction of the block it tend to distort unevenly. Keep in mind this was VERY unscientific, in fact both me and my buddy kept our results to ourselves. Why stir up a hornet's nest. Food for thought the last 4g63T I rebuilt I didn't even take measurements, I just did a cheapo ball hone job and the piston ring gap was perfect. The car had 160 PSI compression and after a year of abuse was still right there. Maybe if you are building a high dollar , massive horsepower motor you need the right hone job. However people keep mentioning that their 200k mile motors still have crosshatching on them, well its because modern turbo motors use low tension piston rings (compared to older V8's that beat the bores to death in 100k miles)