Problems with srp pistons breaking

**firebird_1995** · 08-23-2014, 12:31 AM

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...

With the rings removed...

#4 piston. I didn't remove the rings but I'm sure the damage is similar. ..

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*** · 08-23-2014, 12:46 AM

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** · 08-23-2014, 01:49 AM

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*** · 08-23-2014, 03:14 AM

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*** · 08-23-2014, 03:54 AM

Originally Posted by firebird_1995

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** · 08-23-2014, 05:02 AM

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*** · 08-23-2014, 07:06 AM

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

**firebird_1995** · 08-23-2014, 07:18 AM

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** · 08-23-2014, 08:32 AM

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** · 08-23-2014, 08:54 AM

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.