So my l26 3800 died. I was getting on the expressway and as soon as I got up to speed It just went out on me. It made a terrible sound, I looked back and could see smoke and debris coming from my car. There is about a 3 mile drive to the expressway, 35mph all the way there. I took it easy getting on the expressway I never went over 5psi. Turbo was basically just spooling from accelerating. I was still able to start it and pull it on a trailer, but it sounded terrible and vibrated badly.

Now the day before I was beating the piss out of the car. I had just got some new tires put on the back so I could actually have some fun. Drove it around for about 2 hours, racing some friends and what not.

It seems like something like this would happen while I'm beating on it. Not when its making 150hp. I took the engine down and found a broken rod. The piston was sitting sort of crooked in the cylinder. There was no scratches on the walls. The bearings and the tops of the pistons looked perfect. The piston skirt was all broke. I don't know if that was a cause or an effect of the broken rod. Maybe these l26 engines can't take as much power as I want to believe. At least these engines are cheap and plentiful... I took some pictures with my cell phone.




L67 rod on the left




------------------
Turbo 3800 E85 5spd spec5
11.53@126.7

[This message has been edited by Justinbart (edited 03-31-2011).]

I've been really torn about keeping the bottom end l36 or going for l67,.... this makes me want to go l67 lol.

Sorry Justin, that sucks. Those n/a rods are tiny compared to the sc rods. I would like to see a side-by-side of the L67 vs the L32 rods.

quote Originally posted by 1fatcat: Sorry Justin, that sucks. Those n/a rods are tiny compared to the sc rods. I would like to see a side-by-side of the L67 vs the L32 rods.

you just did

I guess what I want to know is if, its normal for the piston to look that terrible when a rod breaks? Or did the rod break because the piston skirt broke and it turned sideways in the cylinder? I am thinking the latter because I wasn't under any serious load when this happened.


------------------
Turbo 3800 E85 5spd spec5
11.53@126.7

[This message has been edited by Justinbart (edited 03-31-2011).]

quote Originally posted by jasonfox: I've been really torn about keeping the bottom end l36 or going for l67,.... this makes me want to go l67 lol.

L67 bottom end's only issue is if you're using a manual transmission. If you're wanting turbo instead of Eaton, use L36 heads on L67 short block assembly.
Those powdered-metal rods have insufficient beam cross-section. PM itself is not inherently weak. Howards makes some great PM rods for SBC up to 800 HP. But they have beefy beams. Still, they're lighter than traditional rods.

Ok, I need a refresher. The series3 sc is L32, right? The series3 n/a is L26, right?

quote Originally posted by 1fatcat: Ok, I need a refresher. The series3 sc is L32, right? The series3 n/a is L26, right?

yep;

this is a zzp picture of a L32 rod.

quote Originally posted by Justinbart: I guess what I want to know is if, its normal for the piston to look that terrible when a rod breaks? Or did the rod break because the piston skirt broke and it turned sideways in the cylinder? I am thinking the latter because I wasn't under any serious load when this happened.

The rod may have failed under combustion, that may have pushed the piston into the bob-wts in addition to what the loose end of the rod swinging around could do to it to make it look that way. I'd expect to hear piston slap characteristic of an undersized piston when the skirt starts to give way, which I did in my 3100.

I agree. I think your boost may have pushed the piston into the crank after the rod broke.

quote Originally posted by Isolde: L67 bottom end's only issue is if you're using a manual transmission. If you're wanting turbo instead of Eaton, use L36 heads on L67 short block assembly. Those powdered-metal rods have insufficient beam cross-section. PM itself is not inherently weak. Howards makes some great PM rods for SBC up to 800 HP. But they have beefy beams. Still, they're lighter than traditional rods.

Def going turbo. I've got l67 rebuilt heads and an l26 uim & l36 lim with 3/8 tapped injector bosses fitted with 1/4 push to connect nickel plated brass fittings currently plugged but available for nitrous or water/meth. The only thing I haven't finished is the bottom end. Taking my block to the machine shop for a hot tank and hone this month and then sourcing the l67 parts. I didn't realize just how much beefier those l67 rods were till I saw that picture!!

wow man thats got to be the worse place i have seen a block crack. Glad the rod or block debris didn't lodge into the starter solenoid and catch the car on fire.

quote Originally posted by Justinbart: I guess what I want to know is if, its normal for the piston to look that terrible when a rod breaks? Or did the rod break because the piston skirt broke and it turned sideways in the cylinder? I am thinking the latter because I wasn't under any serious load when this happened.

It doesn't really matter that you were "not under any serious load" when it happened because the metal could have been fatigued already from being subjected to previous overloading and just decided to fail later when it did. (Look up "metal fatigue" if you want to know more about it.) That rod could have failed the next time you went to full boost, but instead it failed before you even got that far.

The damage the piston suffered could have been done when the rod failed. I've seen much worse when rods fail (I've seen the pistons damage or break the cylinder heads). Just depends on the nature of the failure.

I would like everyone to also note the thickness difference of the piston pins used on the N/A parts vs. the SC parts in those pictures posted earlier. The piston pins used in the SC applications are much thicker (as are the rods) than what the N/A engines use.

I know you guys hate hearing this but this is why I don't recommend anyone put boost on N/A internals. It may work for a while, but there is just no telling for how long. Trust me, as cheap as GM is, if they could have gotten away with using cheaper/lighter parts in the supercharged engines - they would have used them to save money.

Granted, Justin's engine was making a lot more power than most of the top-swapped L26/L36 engines out there. But still, you are living on borrowed time if you ask too much of these N/A parts no matter how much power you are making if you are putting boost on them. It is just a matter of time. Replacement L36/L26 engines may be cheap, but for how long will they be cheap and how many times do you want to be changing engines (and how much money and time is it going to cost you to change engines)?

Worse yet, do you want to be hundreds of miles from home on a road trip when this happens?

-ryan

------------------
OVERKILL IS UNDERRATED

Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com

[This message has been edited by Darth Fiero (edited 04-01-2011).]

at 500+whp, I dont think that I will be running away from L26/L36 bottom ends.. Justin already said he wont.

I'll give the L26 another shot so I don't have to rebalance my flywheel again. If I break another rod, then I'll go back to L67 or L32. Time really isn't an issue since it only takes a Saturday to swap out blocks. The few hundred dollars for a long block is sucky though.

I never realized how much difference there is between the n/a and supercharged engines. Its a learning experience to say the least. I wonder if the cast L36 rods are any stronger? Still better than spending 10's of thousands of dollars for a shop to work on the cars like some of our buddies around here.

------------------
Turbo 3800 E85 5spd spec5
11.53@126.7

L36 vs L67 rods.

quote Originally posted by darkhorizon: at 500+whp, I dont think that I will be running away from L26/L36 bottom ends.. Justin already said he wont.

What are you running in YOUR car? A L32/L67 bottom end?

Keep on telling people to run the L26/L36 bottom ends with boost. The junkyards will be happy you are giving that advice.

quote Originally posted by Justinbart: I never realized how much difference there is between the n/a and supercharged engines. Its a learning experience to say the least.

I've been saying it for years but I guess nobody believed me (or listened)???

quote I'll give the L26 another shot so I don't have to rebalance my flywheel again. If I break another rod, then I'll go back to L67 or L32. Time really isn't an issue since it only takes a Saturday to swap out blocks. The few hundred dollars for a long block is sucky though.

Hey, that's cool. Do what you need to do to get it back on the road. Just hope that next time it decides to give up you are close to home so you don't have a huge towing bill.

Good luck!

Lol, I've wanted to chime in a few times about this (boosting the n/a engines), but everyone doing it seems so certain that there engine will take it. I haven't said anything because I felt it would just start an arguement.

In all honesty, I'm prertty suprised that the n/a engines hold up as long as they do with boost. I guess that's why it's done and will continue to be done.

The n/a pistons are not ideal for boost either. They have a somewhat high comp ratio and the ring lands are not in an ideal location for boost. Also, the tiny wrist pins look like a ticking time bomb to me.

The l26 and L67 piston ring lands looked the same to me. I liked the higher compression better than the lower. 9.4:1 is still not that high in the scheme of things. But maybe I'll break a piston next time

------------------
Turbo 3800 E85 5spd spec5
11.53@126.7

quote Originally posted by Justinbart: The l26 and L67 piston ring lands looked the same to me.

I've always heard they are different. Not by much, but it doesn't take much. I have never measured the two, so I'm just going off what I've read.

Yeah i've head that too. I put my eyeball on them and couldn't see anything that stuck out to me. Maybe if I put a mic on it or took the rings out then I would see...

I think what I had read was that the top ring is farther away from the piston top, increasing the thickness of the top land, which helps the piston handle knock better, should it occur. The thinner the land, the more prone it is to breaking if subjected to knock. But now I don't know what to say if they have the same specs?
It would be nice to get confirmation on this if you have both pistons and a caliper. But the specs might have changed from series2 to series3 stuff too? Many times I wish I had more 3800 parts laying around for this sort of thing

[This message has been edited by 1fatcat (edited 04-02-2011).]

quote Originally posted by darkhorizon: yep; this is a zzp picture of a L32 rod.

What about series II? I thout L32 was na and L67 was sc no matter what series

Someone correct me if I'm wrong, but I believe it goes like this:

Series II n/a = L36
Series II s/c = L67

Series III n/a = L26
Series III s/c = L32

All these build codes are giving me a headache.

[This message has been edited by 1fatcat (edited 04-02-2011).]

quote Originally posted by 1fatcat: Someone correct me if I'm wrong, but I believe it goes like this: Series II n/a = L36 Series II s/c = L67 Series III n/a = L26 Series III s/c = L32 All these build codes are giving me a headache.

this is correct........

quote Originally posted by 1fatcat: Someone correct me if I'm wrong, but I believe it goes like this: Series II n/a = L36 Series II s/c = L67 Series III n/a = L26 Series III s/c = L32 All these build codes are giving me a headache.

You are correct.

quote Originally posted by 1fatcat: I think what I had read was that the top ring is farther away from the piston top, increasing the thickness of the top land, which helps the piston handle knock better, should it occur. The thinner the land, the more prone it is to breaking if subjected to knock. But now I don't know what to say if they have the same specs? It would be nice to get confirmation on this if you have both pistons and a caliper. But the specs might have changed from series2 to series3 stuff too? Many times I wish I had more 3800 parts laying around for this sort of thing

Moving the top compression ring down further on the piston helps shield it from the heat of combustion; which will help it in the event there is detonation or a lean running condition. Top piston ring lands usually break because of lean conditions, and that is usually because the lean condition causes combustion temps to rise so much the top ring expands to the point the already small factory ring end gap closes and causes the ring to deform and break the ring land on the piston. Detonation is usually harder on the rod bearings (as well as the connecting rod, piston pin, etc) but can have an effect on the piston as well. Aftermarket forged pistons usually have the top compression ring moved down farther on the piston to protect it more from the heat of combustion. We also run wider ring gaps when doing turbo-specific builds than the factory does. The factory runs the top ring close to the top of the piston and runs a tighter ring gap to improve emissions.

quote Originally posted by Justinbart: I liked the higher compression better than the lower. 9.4:1 is still not that high in the scheme of things.

It all depends on the octane of fuel you are running and how much boost you are wanting to run. Generally, higher static compression ratios mean you have to run less boost for a given octane of fuel. Yes, higher static compression ratios do give your engine better off-boost performance and make it more efficient, but the compression/boost game has been played over and over again. Ultimately, you get the most power from more boost and less compression than you do from less boost and more compression. The reason why people like running the L26/L36 bottom ends and higher compression with the blowers is because the M90 blower is a very inefficient design which doesn't work that well when you start cranking the boost up. If you're running a good turbo (or a more efficient supercharger), you can run more boost without having this issue.

-ryan

[This message has been edited by Darth Fiero (edited 04-02-2011).]

I think what helped Justin's engine last this long was the intercooler and E85. You can run higher boost and compression if the charge temp is lowered and/or the octain is raised. This is hard to do with an M90 supercharger, and the method of cooling the charge with a blower is less efficient than with a turbo (small water to air cooler vs. larger air to air cooler). And the E85 should help due to it's high octane. IDK? Just my thoughts. I have no real world experience with this sort of stuff, just going off what I've read. I do enjoy learning about this sort of stuff though.

Look at that Justin, you destroy an engine and your the center of attention! Everyone loves destruction (when it isn't their engine)

quote Originally posted by 1fatcat: I think what helped Justin's engine last this long was the intercooler and E85. You can run higher boost and compression if the charge temp is lowered and/or the octain is raised. This is hard to do with an M90 supercharger, and the method of cooling the charge with a blower is less efficient than with a turbo (small water to air cooler vs. larger air to air cooler). And the E85 should help due to it's high octane. IDK? Just my thoughts. I have no real world experience with this sort of stuff, just going off what I've read. I do enjoy learning about this sort of stuff though.

Yes, higher octane fuel will allow you to run more boost / more compression. Lowering the charge temps will lower combustion temps which can allow you to run more boost/compression. But the act of compressing the cylinder charge creates heat. The more boost and/or the more compression you run, the higher your combustion temps (and pressures) are going to be. And there is a limit to what you can run before you have issues with detonation and other things depending on the fuel octane you are using. I think what happened in Justin's case with the broken connecting rod was he simply overloaded the part(s) he was using.

-ryan

If anyone is looking for L67 or L32 rod & piston assemblies, this guy has a least two sets for sale. $10 each ($60 for a set of 6)!

https://www.fiero.nl/forum/Forum4/HTML/056346.html

quote Originally posted by Darth Fiero: What are you running in YOUR car? A L32/L67 bottom end? Keep on telling people to run the L26/L36 bottom ends with boost. The junkyards will be happy you are giving that advice.!

I have always ran L67 lower ends.... I am more paranoid than most though.

I am currently thinking that maybe the L36 will offer more strength over the L26 rods, which will probably keep me a high compression fan for a bit longer... the pistons/pins are IMO never going to be a weakpoint in a L36/L26.

The most confusing part about Justins failure... was the fact that I knew there was no issues with the setup. The car never saw less than 105 octane, ran low timing, and fairly conservative boost... with massive intercooling to boot.

quote Originally posted by darkhorizon: the pistons/pins are IMO never going to be a weakpoint in a L36/L26.

Not sure why you would feel that way after seeing side by side pictures of the two?

quote The most confusing part about Justins failure... was the fact that I knew there was no issues with the setup. The car never saw less than 105 octane, ran low timing, and fairly conservative boost... with massive intercooling to boot.

It's not all about what's happening on top of the piston. The parts underneath it need to hold up to the force it comes down with too.

quote Originally posted by darkhorizon: I have always ran L67 lower ends.... I am more paranoid than most though. I am currently thinking that maybe the L36 will offer more strength over the L26 rods, which will probably keep me a high compression fan for a bit longer...

I will agree with you there - the L36 rods certainly look beefier than the L26 rods. (And the L67 / L32 rods look even beefier yet - but this was already a known fact).

quote the pistons/pins are IMO never going to be a weakpoint in a L36/L26.

I disagree. Thinner is weaker no matter which way you cut it. The question is how much power can the thinner N/A pins/pistons endure and for how long???

quote The most confusing part about Justins failure... was the fact that I knew there was no issues with the setup. The car never saw less than 105 octane, ran low timing, and fairly conservative boost... with massive intercooling to boot.

Doesn't matter. I've seen engines suffer failures with perfect tunes and perfect running conditions. The problem may not be with the fuel octane, the tune, or the intercooling. The problem may be the parts he (Justin) was using. They simply were not designed to handle the amount of power being run thru them. Sure, they worked for a while, but their days were numbered running that kind of power. It would be no different if we were to take a stock 2.8, bolt a huge turbo on it, and run a lot of boost thru it. Even if we used 150 octane fuel and made sure the tune was very conservative; you would have to admit at some point something is going to fail in that motor because the parts in it simply aren't designed to process that much power. What would fail first would depend on where the weak link is. In Justin's case, it was the connecting rod (this time).

For his next build he may use "stronger" L36 rods but that could move the weak link to the lighter piston pins if he uses them. Or perhaps it could be the pistons next time. Who knows. It depends on a lot of factors. If it were my car, I would put the strongest parts in there I could afford. L67/L32 shortblocks are not that much more expensive than L26/L36's.

-ryan

[This message has been edited by Darth Fiero (edited 04-03-2011).]

If a gasket failed, it's possible that the cylinder hydro locked and broke the rod, but I think the rod just let go.

Remember that seriesIII rods are powdered metal, so L26 rods might be stronger than L36 rods, even though they are lighter and thinner. I don't know this for sure? It's my understanding that if the rods were arranged by strength, it would be like this (strongest to weakest): L32, L67, L26, L36.

quote Originally posted by 1fatcat: if the rods were arranged by strength, it would be like this (strongest to weakest): L32, L67, L26, L36.

Correct, in theory. PM is stronger, IF the cross-sections remain identical. But because PM is stronger, this allows for reduction of the cross-section, to save weight and material. So, GM may have reduced the cross-section too much, leaving the PM rods unable to take as much abuse.

I'm really curious to know what the load testing results were on all these rods. The series II stuff was cast iron, big and heavy. The series III is powdered metal, thinner and lighter. I was reading this and "Mr. Intense" from intense-racing stated that they run L32 rods in 700+hp 3800's with 40-60 passes (at time of posting) and no problems. He said they have never had an L32 rod failure, and that an insider from GM told them about the rods a couple years before they went into production and that they were at least 20% stronger than L67 rods. This is comparing L32 to L67. No info on L26 or L36 rods.

Well I picked up an L32 today. I'm hoping that I can sell the blower and LIM to make up the difference of buying another L26.

------------------
Turbo 3800 E85 5spd spec5
11.53@126.7

Well Golf has been getting in the way of finishing up my car. It should be back on the road tomorrow. (fingers crossed)
I took some better pictures today of the difference from the L26 piston and l67 piston. Hopefully I wont be taking any picture of the L32 anytime soon.


^^^L26

------------------
Turbo 3800 E85 5spd spec5
11.53@126.7

quote Originally posted by Darth Fiero: It doesn't really matter that you were "not under any serious load" when it happened because the metal could have been fatigued already from being subjected to previous overloading and just decided to fail later when it did. (Look up "metal fatigue" if you want to know more about it.) That rod could have failed the next time you went to full boost, but instead it failed before you even got that far...

That is so true. Coud have failed just when you fired up the engine. I have a SC Harley F-150 and most of the rod failures I have heard on them happened just cruising at highway or light load.

Wrist pin seizure what happens is every thing gets hot when your beating on it then you slow down piston cools faster then the pin seizes just for a bit to bend the rod then rod breaks or crack piston pin boss and rod breaks latter just my 2cents

[This message has been edited by engine man (edited 04-14-2011).]

quote Originally posted by engine man: Wrist pin seizure what happens is every thing gets hot when your beating on it then you slow down piston cools faster then the pin seizes just for a bit to bend the rod then rod breaks or crack piston pin boss and rod breaks latter just my 2cents

I could believe that