Problems with srp pistons breaking

[firebird_1995]

Anyone else had issues with srp pistons?


I picked up a 383 golen engine from a guy (great guy btw) and he had a lot of blowby and low compression on #1 and #4. Faces of the pistons looked fine, but after removal was another story...
http://tapatalk.imageshack.com/v2/14/08/22/9a36aeabd71d6050d6a157258a75c985.jpg
With the rings removed...
http://tapatalk.imageshack.com/v2/14/08/22/0785ff3bea1328479b997454fea919ca.jpg
http://tapatalk.imageshack.com/v2/14/08/22/c468640d7c34b00b4807243fed5e3085.jpg
#4 piston. I didn't remove the rings but I'm sure the damage is similar. ..
http://tapatalk.imageshack.com/v2/14/08/22/01e63bc69ecbeca5b64eb2a25c3d2c68.jpg
He had this issue one before with the #8 cylinder and replaced it. Now, there was an issue with the tune. He was unfortunately at the mercy of a 73 year old tuner that refused to run anything other than a 1 bar map and maf sensor. His afr was right around 13.5 at 5600 rpm and 11# of boost on pump gas. Prior to the damage he was running on a pcm for less tune on low boost. When the "tuner" got a hold of it and he changed pulleys is when problems started...
I checked the ring gap and both rings are at .022. It was running lean for sure and that very well could have been the only issue, but here's my problem..
It obviously needs a new pair of pistons at the least. I happen to have a set of the exact same (would have get them checked for weight and possibly weight matched to avoid rebalancing) of the pistons golen used, sitting on my shelf. In the research I've done I see that these 4032 srp pistons are pretty well limited to 100 hp per cylinder (at the crank). On his last dyno run he was at 605 hp to the tires through an m6 with the 60# injectors maxed out around 5600 and 11# of boost. (Its got a d1sc with pullies capable of 16#) It's a safe assumption to say the engine is capable of cresting 100 hp per cylinder so, do I
A) replace the pistons with what was in it
Or
B) upgrade to a 2618 alloy piston and get the bottom end rebalanced.

I intend to run e85 this time around with a set of 80# Siemens injectors (base pressure bumped up if necessary).



Thoughts?

[popo8]

Wow man.. that sucks... hut still ahead of the game.

Now...Will u be satisfied with 800 crank hp? Guessing thats 600 to the wheels...

[firebird_1995]

Well I'm running the power robbing 4l80e and a Ford 9", but yes, I would be satisfied with 800 at the crank. I honestly believe that golen has the gap wrong. Most things I read regarding ring rap leads to the second ring needing to be LARGER than the top ring to allow any escaped gasses to pass through into the crankcase as opposed to creating pressure on the backside of the top ring, which would cause the top ring land to crack. I'm going to hit golen up Monday to see what they set the ring gaps up at assembly, and then I'm going to contact je/srp and see what their recommendation is for the power level of that piston. If the current setup is capable of running the ragged edge of being safe, why not upgrade to something that will take everything you can throw at it. I just know if I stick with these srp pistons my butthole will pucker up every time I get into it. I'm sure the e85 will help, maybe enough to give me a large enough margin of error to feel comfortable running the 4032 alloy piston.

[popo8]

Well if ud be happy with that... correct the ring issue and use what u have... thats my OPINION only. However if u think ur gonna wanna go bogger than that... then handle it now so u dont have to open the motor again to upgrade. Post up what Golen says when u call.

[Fastbird]

I just know if I stick with these srp pistons my butthole will pucker up every time I get into it.

This right here tells me you have already partially made up your mind to upgrade. Given the option, it's what I'd do. Peace of mind at least.

[firebird_1995]

I'm just very wishy washy right now. I know to upgrade is going to be $$$ and time. And with running the e85 (or even running a proper tune) with the correct ring gap I may not have a problem. With the srp's. I guess a better question to ask would be, for the guys that are putting out over 600 at the tire, what pistons are you running, and what alloy is it?

[Fastbird]

I don't know the alloy but mine are custom diamond pistons.

[firebird_1995]

They are 2618 then. That's all diamond makes. Looking at a set on sale now for 750 bucks. I just need to cc my heads to make sure the compression ratio is copesetic

[shownomercy]

Thats a weird/tight ring gap, and the motor I got to build my current bullet up with had a similar issue. SRP pistons and the one had melted the ringland pretty bad, that was a nitrous build in its previous life though.

I run a JE extreme duty piston, which I think are 2618 material, they survived with my car pushing I would guess over 800 crank.

[zraffz]

Most ring manufacterers suggest a tighter compression ring gap and looser 2nd ring gap as you stated. You are correct on your theory that it will allow exhaust gases to exit easier and the term they use to describe the issue is called "ring flutter". I've used rings before that went against this rule and double checked by calling the company to verify they wanted a tighter 2nd ring gap.

However, I'd imagine a ring land would break due to excessive heat, a poor quality piston (which will break at any thin inconsistently casted sections of the pistons) or an improper final cylinder wall diamater. Generally speaking, a piston will crack in the flycut/valve pockets because they are the thinnest part of the casting. Another issue could be the depth of the top ring land on a nitrous or forced induction motor; generally you want the top ring as far away from the crown as you can get it... With three being broken I would honestly think the final hone was severely undersized and isn't allowing for proper expansion.

A ring will usually break and relieve pressure way before a piston will crack if the ring gap was wrong. If the gap was that far off you should be able to notice the ends of the rings getting chipped or misshaped from them touching.

[firebird_1995]

Well I thought the same on the ring gap and looked up JE's (srp's baby momma) ring installation manual and they call for .0050 per inch of bore on the top ring which shakes out to .020 and .0055 on the second ring (.022). This is the chart for their recommended rings (assuming that's what golen installed) for "street moderate turbo/nitrous".
http://tapatalk.imageshack.com/v2/14/08/23/8d0c558f344d9e29dda0079b3e020d93.jpg
Keep in mind this engine has 25k on it and while I wouldn't expect there to be a LOT of wear to the rings, the current gap leads me to believe they may have been installed even tighter. I just got some pics from him in the #8 ring failure, check this out..
http://tapatalk.imageshack.com/v2/14/08/23/2c830e201c2e504b54a07172f2a010b9.jpg
Identical failure.
I wouldn't consider this a "blown race only" application but that would put the ring gaps at .024/.026 which is more along the lines of what the last set of rings I installed (Mahle I believe) called for.
I know there has to be some guys running the 4032 alloy above 800hp. The 2618 alloys didn't hit the scene until recently (last 5 years maybe). Something else has to be going on.

[firebird_1995]

With three being broken I would honestly think the final hone was severely undersized and isn't allowing for proper expansion.


I would totally agree with you on this except there is little to no scuffing on the piston skirts, sidewalls, bores.... anywhere. Not even the crown. But it is definitely something worth checking and I will mic the bores today and see what I come up with.

[firebird_1995]

Interesting pictures on the three failures and their location....
#8 (previous failure)
http://tapatalk.imageshack.com/v2/14/08/23/a99e1d51bbebf9ddcfc76d988e8a2da7.jpg
#1
http://tapatalk.imageshack.com/v2/14/08/23/a07173d4a349171afe6947348d3ce5eb.jpg
#4
http://tapatalk.imageshack.com/v2/14/08/23/63a2218c8209f5d4b0906cd3c73eee4e.jpg

The location of the damage is in the exact same spot on all three pistons.
On the quench pad area of the piston favoring the intake side of the chamber.
Block is zero decked, and was running a felpro 1074 head gasket (.039 thickness)


Heres an up close of the #4 showing the 3rd ring land getting ready to dislodge
http://tapatalk.imageshack.com/v2/14/08/23/e24d96bb7b21412b2ec1b80878f2f8c3.jpg

Ring gap on this hole was .025" top ring and .022" second ring. And I promise I'm not getting these backwards, unless they were installed that way....

[BIG CAT]

listen to what mark says about the alloy's.


https://www.youtube.com/watch?v=t51oPTg5lrI

[firebird_1995]

listen to what mark says about the alloy's.


https://www.youtube.com/watch?v=t51oPTg5lrI
Well that just about sums it up then. This golen engine has eagle h beams with arp 8740 bolts. Since I'll have to get it rebalanced anyway, I think I'm going to pull my scat h beams with arp 2000 bolts out of my 355, buy a new set of 2618 pistons and be done with this bottom end mess. Do you run probe pistons BIG CAT ?

[BIG CAT]

Well that just about sums it up then. This golen engine has eagle h beams with arp 8740 bolts. Since I'll have to get it rebalanced anyway, I think I'm going to pull my scat h beams with arp 2000 bolts out of my 355, buy a new set of 2618 pistons and be done with this bottom end mess. Do you run probe pistons @BIG CAT (http://ltxtech.com/forums/member.php?u=3572) ?

no we run j&e pistons with manley h beam rods and 7/16 8740 bolts.

[firebird_1995]

Ok. I wasn't sure if you were endorsing probe pistons or just the use of the 2618 alloy. Pretty bad when a piston manufacturer says he doesn't see any place for a 4032 alloy in today's market.
Well I guess I'll see cc my heads and find out what chamber volume I have and find a piston to match. I need to get the specs off this cam and find out if it's worth hanging on to. If I'm changing things up I might as well go balls deep. Thanks for the help!

[zraffz]

I would totally agree with you on this except there is little to no scuffing on the piston skirts, sidewalls, bores.... anywhere. Not even the crown. But it is definitely something worth checking and I will mic the bores today and see what I come up with.
I just took another look at the pics from my computer rather than my phone and can see them much clearer now. The skirts defiantly don't indicate any improper expansion rates between them and the cylinder walls BUT let's not forget about Keith Black's line of pistons and the issues they had due to improper cylinder wall clearance. They weren't showing much wear and were cracking.

It never hurts to call SRP and ask them what their tolerances are supposed to be. Regardless of what material was used, they still shouldn't be breaking like that. With them all breaking in the same spot between the ring lands, I'd 100% agree with you that it is more than likely caused by ring flutter. Basically what is happening is the pressure is getting caught between the two rings with more entering than what is bleeding down (a forced induction motor will make this even worse) and ultimately pushing the two rings apart... but I'd still imagine the rings would be weaker than the ringlands on the pistons! With regards to why they are breaking where they are, it appears like it's right in the area (on the backside) right at the end of the wrist pin housing... where the casting thins back out and gets weaker again. I'd assume this would also be an exteremely high pressure area caused by the forced on the piston from the rod on the combustion stroke.

4032 might be significantly more brittle than 2618 but this issue isn't the pistons fault... the more I think about it, a 4032 piston calls for a tighter tolerance and that's mainly due to it not expanding or being able to expand like a 2618 (due to the higher silicone volume in the 4032 alloy). Using a 2618 piston might have bought you more time but eventually something would have broken between the rings or ringlands. I've pushed 4032 pistons with a 200+ shot of nitrous for quiet a while and am getting ready to do it again on my 94 z28.

If you do switch to a different alloy just remember that your final hone will need to be slightly larger. I also think it's safe to assume you've figured out the reason why they are breaking and have some idea of why it's in the same spot on all three pistons.

[firebird_1995]

Yea I agree. I believe the ring gap is what has done these pistons in. That's a question to ask golen as to why they are set up that way. If i didn't think the engine was capable of cresting 800 (or I didn't intend to push it that hard) I would consider using the ones sitting on the shelf with the right gap. But like I said in the beginning, every time I'd mash that peddle I'm going to pucker up tight wondering if it's the last time.... I think if I can get lucky and find a set slightly lighter than what I have I should be able to get away with just having to have the crank drilled for balance instead of adding metal... ugh

[BIG CAT]

Ok. I wasn't sure if you were endorsing probe pistons or just the use of the 2618 alloy. Pretty bad when a piston manufacturer says he doesn't see any place for a 4032 alloy in today's market.
Well I guess I'll see cc my heads and find out what chamber volume I have and find a piston to match. I need to get the specs off this cam and find out if it's worth hanging on to. If I'm changing things up I might as well go balls deep. Thanks for the help!

probe makes a good piston and mark is a straight shooter. i would not hesitate to use his stuff. we went j&e because of there established long history of performance and durability. as for the cracks i would investigate the ring gap and tune. i have had a few diesel pistons come out looking like that from improper use of ether. the shock from it igniting can break them pretty quick. its very similar to detonation.

[firebird_1995]

Well I feel really sorry for the guy I bought this off of. His "tuner" had the max knock retard set to zero and you could see the knock count racking up pretty good. But there were no signs of detonation on the plugs. No specks, nothing. They all looked the same. I know it went really lean. Max timing was around 26°. But, again, the guy tuning it had the injectors maxed out. One log showed a 99.6% duty cycle at 5800 so I'm sure it was a combination of being too lean even for 26° of timing.

And the probe piston will most likely be the way I go if my heads haven't had the snot milled out of them. They are trick flow 195's but who knows what all was done to them

[dawdaw]

Have em coated and some gas ports put on them :)

[firebird_1995]

They had gas ports lol. That's one of them in the chunk you see me holding.

[BIG CAT]

They had gas ports lol. That's one of them in the chunk you see me holding.

:laugh:

[Ryan Stout]

Heh....'gas ports'

[Catmaigne]

I tried to steer clear of Probes when piston shopping after hearing about how they lack forced pin oilers. They have little broaches instead and are oiled by the crank flinging shit around. Some say to open up the pin clearance a bit more to help out... but more expensive piston brands like Mahle, Ross, Wiseco, JE all have forced pin oilers and are used in countless high HP builds for a reason. I recall seeing some some pics floating around the web of a Probe from a motor that failed with visible score marks on the pin and piston pin bore. The broaches just seem bad for longevity and a bad idea in general. I'm sure the Probes will take a lot of abuse but they're still a cheap piston with a shorter lifespan.

I wouldn't attribute the piston failure to the alloy type being that the tune was crap. Here's a ZR1 with factory 4032 pistons laying down 752rwhp on pump gas.


https://www.youtube.com/watch?v=TCagvEFJUiY

Granted, it isn't fair to compare this to the ole LT1 but you can still see that 4032 pistons can hold a lot of power without disintegrating with proper tuning and piston design. Maybe the SRP 4032 piston alloy and design is crap... Wouldn't be surprised being that it's the "budget" branch of JE. For reference, the ZR1 has factory Mahles. I've been meaning to email them and ask for specs (out of curiosity).

If you're going for a dedicated race car and you don't want to sink a whole lot into the top end then get a nice set of 2618 pistons. Otherwise, you could probably get the job done with a nicer 4032, less boost, and head porting. I chose the 4032s because I knew the wear characteristics of a 2618 weren't as good (short lifespan) and the slap would drive me up a wall in a mostly street car.

[firebird_1995]

Verbally told in a phone call made to je that their srp 4032 line is only good to 10# of boost. The je extreme 2618 is good to 20#, conditional on tune of course. Was offered the 2618 pistons for a jobber price (which I thought was a very generous gesture). Then I received a reply to my email stating the pictures indicated the tune was off and could have contributed to the failures. And that there was no consistency with the failures (although they were all in the same place) then offered the pistons for full price lol. shownomercy did you know about this 20# limit?
I'm going to call probe and see what mark has to say

[Catmaigne]

10 psi, another way of saying "our pistons suck." Both the ZR1 (10.5#) and 2013+ GT500 (15#) run 4032 Mahles with roots blowers from the factory.

Check out this guy's truck. He ran Mahle Powerpaks (very similar to mine, same .197" crown thickness and 4032 alloy) for many miles with more boost than what I'm aiming for. The pistons survived for 107k until a lifter broke apart.
http://ls1tech.com/forums/forced-induction/1317176-107-000-boosted-miles-comes-end.html

[firebird_1995]

I see what you're saying as far as the 4032 alloy not to be counted out as being capable, but the design of the pistons we are making a comparison to are not exactly apple to apples. Case in point, stock ls pistons have been shown to tolerate 1k hp. Maybe it's the sbc design in particular that's hard to work with. I'm in no way trying to defend je/srp (and to be honest, to hear that their top of the line piston is only capable of 20# is a little disappointing) but I would prefer to compare what others running an SBC piston are using for boost as opposed to to other engine platforms.

[JPack]

CP bullet pistons. Got them in mine and will handle what you need.

[firebird_1995]

I checked them out as well jim, unfortunately they only offer a -16 dish in an off the shelf piston which would put me into the mid 10's on compression ratio. I'm sort of limited on whats available with the 5.7" rods.

[JPack]

I can get any size you need made. Mine were custom made by my builder making a call. He has custom pistons made all the time to his specs. You wont find them online. They are specific to his specs and they wont make them for anyone else.

[shownomercy]

The boost number is plain silly for them to even reference..

10psi on a stock unported heads with a tiny inlet restricting boost is way less power than a 10psi on massive flowing heads and big bore...

That being said, I know mine survived fine with my 10-15psi and I believe blackbirdWS6 runs JE extreme duties in his and his F1a hits way more than 10psi. Both are over 700whp cars.

[Catmaigne]

Well yeah, not all pistons are created equal but I think it's safe to assume that a piston with a quality alloy and design should hold a good amount of power assuming the tune is on point. Stupid things a short compression height (thinner in general w/ shorter ring pack and less heat dissipation), big dishes or valve reliefs (makes the area behind the top ring groove dangerously thin), and gas ports in a boosted motor are obviously bad news. But I think the common points of failure between a SBC and Gen 3+ piston in a boosted app are pretty much the same. Cracked lands and holes in the crown. A good design, alloy, tuning, ring gap, meth/water, intercooling, etc. can prevent all of this.

I don't think there's any magic behind the factory LS pistons that aftermarket SBC pistons can't touch. Bores are different, pins are a little bit thicker, but both pistons types have similar structures and seem to fail in the same ways I listed above so I doubt those tiny differences matter. The only real advantage I can think of that the Gen 3+ motors have off the top of my head is a better head selection to drop compression and a wider/less shrouded chamber b/c less valve angle (although less quench area). Not sure how much of an effect the LS valve angle has on the depth/location of the valve reliefs, but it looks like the same sort of deal on Gen 3+ aftermarket FI pistons that you see on Gen 1/2 aftermarket stuff where the reliefs are cut pretty close to the edge. Maybe the reason the stock LS pistons take a beating is because they're pretty flat up top despite having a thin top land. There's no reliefs to make things between the top ring groove and piston head too thin and break chunks off

The ZR1 and GT500 pistons both have full dishes w/o reliefs (barely any quench area). This is understandable in the 4v Ford, but the pushrod ZR1 is a real oddball. The ZR1 piston also has a raised portion in the center of the dish which is supposed to help stir things up. The big question: Is quench the enemy or is it still necessary? I've heard both opposite arguments. I understand that a super tight quench on a boosted motor is going to create nasty hot spots and too loose will result in an inefficient burn. Some say FI eliminates the need for quench because of more turbulence but I think there has to be a happy medium between too much and too little for an old 23* motor with a big quench pad. I really wish there was some real R&D out there for an FI app that we could check out.

That's definitely not the first SRP to fail in a LT1... but the fact that the tune was bad throws any speculation about SRP design/quality out the window unfortunately. However, I find their 10# limit hilarious and think that says something. So who has SRPs in their boosted motor and hasn't broken them yet???

[firebird_1995]

That's definitely not the first SRP to fail in a LT1... but the fact that the tune was bad throws any speculation about SRP design/quality out the window unfortunately. So who has SRPs in their boosted motor and hasn't broken them yet???


That's probably the best question to ask. I'll admit the tune being off is most likely the biggest contributor to the failure. I've read ENDLESS articles on the need or lack thereof for quench in a boosted engine. I can tell you that the 355 that I just melted down all 8 pistons in had no quench (-16 cc piston .095 in the hole). The ones I'm seeing set up from the big name builders don't have more than .045 quench, speaking about sbc's here. So who knows.

[BIG CAT]

the best parts in the world will not survive a bad tune or improper assembly.

[firebird_1995]

the best parts in the world will not survive a bad tune or improper assembly.
I'm with you 100% on the tune.

You run a lot of boost, what's your take on quench in forced induction engines?
If you do a search on yellow bullet you'll have guys talking about running two hundreds in the hole all the way at the guys running what normal na guys would run.

[BIG CAT]

I'm with you 100% on the tune.

You run a lot of boost, what's your take on quench in forced induction engines?
If you do a search on yellow bullet you'll have guys talking about running two hundreds in the hole all the way at the guys running what normal na guys would run.

(imo) on a forced induction setup its a gray area. as for it making more power i have not seen any real hard evidence one way or the other. but i think you could run into trouble if its to tight
on mine i run down the hole just a bit.

food for thought.
http://www.yellowbullet.com/forum/showthread.php?t=307207

[firebird_1995]

So it seems that they are basiclly creating a "ramp" where the quench pad would be. I can see the benefit of this. First, there's no sharp edge where the untouched quench pad would be that can create a hot spot, plus it still creates turbulence because it's still got squish towards the end of the chamber. Lot of sharp guys over there. Not going to lie, it's given me a headache, but I've read pages and pages and pages on boosted engines in particular regarding quench. This seems to be the best comprise between the two and just goes to show that making the piston work with the head to create good ignition and burn is more important than saying "run x amount of quench".

[shownomercy]

I have an absolute crap quench when talking NA or N20 land, but, it seems to work just fine.

Now, granted I have my hands tied cause I forced myself to use stock heads and off the shelf slugs.

[firebird_1995]

Well that's what I did on my 355 build. I had no problem with it until I tried going to a tr6 plug. Ran great on a stock heat range plug for whatever reason.

[Catmaigne]

You could effectively "soften" the quench area by running a full dish instead of the usual D-shape. I know the transition isn't as smooth as a ramp, but this seems to be working out for the ZR1, ZL1, CTSV, and even the GT500. None of those motors have D pistons with valve reliefs and there are plenty of hot rodders out there swapping pullies without blowing things up.

What is strange about the GM pushrod motors is that the area between the piston dish at TDC and the chamber itself isn't very concentric. There are more hard edges than I'd expect out of a stout motor because of the quench pads on the heads (although, they're not very big). Some pics:
LS9 on the left, LSA on the right.
The LSA piston isn't even forged.
The LS9 head also has less valve shrouding and less quench area than the typical 23* SBC head.

So it seems like too much quench could become a problem but there has to be a point of diminishing returns with reducing overall squish. I doubt running a d-shaped piston is going to have that much of an adverse effect on the motor assuming the distance between head and pad isn't really really small. I doubt it becomes a problem until you get into astronomically high power numbers or extreme conditions. I was planning on running around .050" in my motor which isn't super tight. Can't say I've seen a failure caused by quench alone.