FAQ: Smaller SC pulley? What Size?

chitown_riv98 wrote:

I agree with Matt, I installed a 3.4 pulley a while back and neglected to scan. I was fine for a while but on a hot day last year I abused the rivi racing a ricer on i55. I mean pedal to the metal like 3-4 miles. Well ended up spinning a bearing. Make sure your oil is nice and fresh, premium gas, and I'd say make sure your intake gasket is in good shape. I suspect mine failed. I had been having fun for a while with my car tho. 10 years of abuse . I won the race , but coasted off the expressway with the warning lights on and the chime going off

Your choice of pulley size was not the reason you spun a bearing. It was just waiting for the right time to happen. A spun bearing can happen for quite a few reasons, but NOT a choice of pulley size. It's probably not what you meant, but I just wanted to clarify. Too small of a pulley results in a completely different type of engine failure...like chipping a piston or blowing holes in the top of the piston (result of Knock). Now, SERIOUS knock could potentially put more stress on the bearings, but lack of oil, heat, or worn out oil is the main culprit.

Just sayin.....

Yes abaddon, I agree. I think worn out oil was probably the main reason.

Detonation will take out a rod bearing.  We call it knock, but it is detonation, and if it is severe enough at WOT, it will do damage. I believe that is what happened to Aarons engine.

LARRY70GS wrote:

Detonation will take out a rod bearing.  We call it knock, but it is detonation, and if it is severe enough at WOT, it will do damage.  I believe that is what happened to Aarons engine.

Wonder if it was lack of (or bad) oil that killed Charlie's engine or if it was knock....... Maybe he can chip in.

LARRY70GS wrote:

Detonation will take out a rod bearing.  We call it knock, but it is detonation, and if it is severe enough at WOT, it will do damage.  I believe that is what happened to Aarons engine.

Sever enough, yes. It would have to be beyond the limits of the PCM to compensate for. Chances are, though, with a 3.4" pulley, it was an oiling issue. Nobody ever really knows. It's one of those things that can just happen. By the time the bearing spins, the damage is beyond what an inspection can verify as the cause.....unless of course there isn't any oil in the damn thing, or the last oil change was 10k ago.

Abaddon wrote:

LARRY70GS wrote:

Detonation will take out a rod bearing.  We call it knock, but it is detonation, and if it is severe enough at WOT, it will do damage.  I believe that is what happened to Aarons engine.

Sever enough, yes. It would have to be beyond the limits of the PCM to compensate for. Chances are, though, with a 3.4" pulley, it was an oiling issue. Nobody ever really knows. It's one of those things that can just happen. By the time the bearing spins, the damage is beyond what an inspection can verify as the cause.....unless of course there isn't any oil in the damn thing, or the last oil change was 10k ago.

I can tell you that with the 67-76 big block Buick, lack of oil pressure is the biggest reason for engine damage. Detonation is a close second.  These engines have a huge crankshaft to stabilize the light weight casting block.  They have 3.25" mains, and oil pressure is critical with the front mounted pump in the timing chain cover.  The timing cover is aluminum, and internal pump clearances increase as the engine heats up.  That lowers the oil pressure as the engine heats up and the oil thins out.  To make a BBB live at higher RPM, you must have 11-12 psi per 1000 RPM of operation.  If you don't, what typically happens is the  #7 and #8 rod bearings get scorched from lack of oil pressure at the rear of the engine.  Detonation will typically pound the hell out of the rod bearings even with adequate oil pressure.  That is why I ALWAYS add leaded race gas to the unleaded fuel in my tank at the track.  Cheap insurance against detonation as I see it, but you would be surprised how many guys think they should run with pump gas at the track because that's what the engine was tuned with.  There is a huge difference between punching it wide open on the street for a few seconds at a time, and going wide open at the track through all 3 gears at maximum load.  I see guys with destroyed engines all the time.  Sometimes, they luck out with just a blown head gasket.  The GN guys blow head gaskets all the time.

None of that is true of the 3800 though.  The oil pump in our engines is light years ahead of the pump in my big block.  I have mechanical pressure gauges in all my cars.  On my 70 GS, after a long highway run, my oil pressure can get down to about 22-24 psi at an in gear idle.  At 5500 RPM, it will be 75 psi +.  In the Riv, on the hottest day after a long highway run, I've never seen it lower than 35-40 at an in gear idle.  Breathe on the gas and it goes up to 60-65 and stays there, and it will max out at 70 at WOT.  That is plenty for that engine.  Oiling is excellent on the 3800, so I have a hard time believing any bearing problem is oil pressure related.  I think it is much more knock related.  All you need is one injector that's a bit clogged. Even though the PCM commands full enrichment, you can go lean, and then it detonates more than the PCM can compensate for.  Then, you either chip a piston or pound out a rod bearing.

Aside from the usual LIM leaks, and an occasional head gasket job, 99% of every single 3800 that rolls in here knocking (or the ever so fun squealing) has a spun bearing. BONE STOCK cars. 3800's don't generally fail internally, but when they do, you've probably spun a bearing. Why? I don't know. We get N/A, and S/C 3800's alike. It makes no difference. Lucerne, Lacrosse, PA, LeSabre, GP, etc etc. For some reason, it's the common internal engine failure of a 3800. As I stated in my first post, severe enough knock will help it along, but it isn't the cause.

EDIT: Let's not forget about a bad Harmonic Balancer too, or anything to toss the engine out of balance for that matter.

EDIT #2: If you guys read the first response on HPTuners when Charlie posted about his spun bearing, the guy says "non tune related", and it's just the "nature of the beast". Just trying to back up my claims here. Don't know the depth of this guys experience, but he sure sounds like he's been there before.....
http://www.hptuners.com/forum/showthread.php?47927-3800-Series-II-L67-spun-bearing-Whatever-it-is-it-s-not-good

Type 3800 spun bearing into Google, see what pops up!

Abaddon wrote:

Aside from the usual LIM leaks, and an occasional head gasket job, 99% of every single 3800 that rolls in here knocking (or the ever so fun squealing) has a spun bearing. BONE STOCK cars. 3800's don't generally fail internally, but when they do, you've probably spun a bearing. Why? I don't know. We get N/A, and S/C 3800's alike. It makes no difference. Lucerne, Lacrosse, PA, LeSabre, GP, etc etc. For some reason, it's the common internal engine failure of a 3800. As I stated in my first post, severe enough knock will help it along, but it isn't the cause.

Having a shop, I'm sure you see what you're seeing.  I'm just wondering if the bearing spins first, or whether it is pounded out and then it spins.  There is really no way to know unless you take each engine apart to do a careful inspection.  What do you do most of the time with these engines?  I would imagine it's easier to just replace the engine than repair it.

One of our club guys had a 2000 Lesabre with a N/A 3800.  One day, he went full throttle passing someone on the highway, and there was a big bang and the motor was seized.  I have about 159,000 miles on my Riviera.  It's my daily driver so I treat it well.  I very rarely have any need to floor it in normal driving.  Let's face it, you really don't have to step on them much to make them go and I don't. I'm thinking some guys here are bound to find the limits.

Two scenarios come to mind:

1) Oil not maintained -or- LIM gasket failure permits coolant to contaminate oil, causing bearing failure.

2) Knock causes chipped piston, leading to bearing failure. Should be evidenced by missing portion of piston(s).

I got 246k miles out of my original, modded 3800 SC (with orig plastic LIM gasket). The cause of failure was chipping piston #1 from knock, leading to bearing failure. All the other bearings were in great condition; the engine had a lot more life in it otherwise. No reason to believe the bearing would have failed from any other cause, imo.

AA,
I know I haven't been on the forum in a long time but I'm very surprised you had an engine failure due to Knock.
I know you have engine management software and have been tuning your drivetrain for a long time. I thought you, of all people would never had experienced a chipped piston due to knock.
Just saying I'm surprised.

Rick, I understand your take on it. We all like to think tuning is sure thing, and if done correctly, nothing bad will ever happen. But tuning is only one part of the equation. Other factors will cause knock: heat, fueling, driving style, carbon build-up to name a few. It's really not possible to tune around all of these variables. Since you were away, I'll share what happened, and you can decide if you still feel the same.

After the incident (which occurred at ~100 MPH, on a racetrack, at 5800 RPM, after dozens of hot laps) the engine was sent out for rebuild. I was surprised to learn that only piston #1 was chipped, and only that bearing was spun. I decided to send out the fuel injectors for analysis and cleaning.

The report showed fuel injector in cylinder #1 was partially clogged causing the cylinder to run lean. Not bad enough that any significant KR showed with normal daily driving, spirited driving, even a 1/4 mile run. But under the extreme conditions of racing many miles of constant WOT, it became a problem. Reviewing video footage after the event, early laps showed mild KR on the Torq scan tool. I saw 0-2º at first, then 4º, then as high as 8º. I wasn't aware of the alarms because I had a helmet on and couldn't hear them. The radio comm broke that day, so copilot CharlieRobinson couldn't really warn me, either.

What happened? I raced without knowing injector #1 was lean. What normally wasn't a problem became a problem after 20+ laps of built up heat. The chipped piece of piston compressed against the head and transmitted a lot of force down through the con rod, destroying the bearing. Makes perfect sense after seeing the parts and getting the injector analysis. This was a learning experience.

What would I do differently, or what would I tell someone who doesn't want the same result?

#1. Run high-octane fuel for race events. Not premium gas - 100 or 110 octane race gas. The stuff that costs $8/gal. It won't make your car any faster, but it could help tame the detonation from a lean condition + added heat, just enough to maybe save a piston.

#2. Use gauges rather than scanning/data logging tools at the track. I run an Aeroforce Intercepter gauge everyday. It's mounted to my steering column in plain view. If anything is wrong, like KR or trans temperatures, some very bright red LEDs come on to warn me. They're really hard to miss. The day I blew the engine, I disconnected the Aeroforce so I could plug in the interface for the Torq scanning app. I did this because I was confident the engine was running in good order. I was wrong. If the Aeroforce were running, it would have warned me and probably saved the engine that day. Hindsight is 20/20.

#3. Have the injectors cleaned if they haven't been in a long time. Change the fuel filter. Eliminate the chance for a lean condition.

#4. Understand that racing cars causes them to wear and break, especially if you go to the track in the middle of June with 246k miles on the engine. To play this game, many racers rebuild their engine every season. It's like brakes or tires - they'll last a long time if you're gentle, but abuse these parts, they will wear and fail much sooner than the average.

Did I adjust in my tune or change my SC pulley after reinstalling the rebuilt engine?

Nope, not at all. Current tune is same as it was that day in 2012. I still run the same 3.4" pulley I've been running for the past 5 years. Don't think I've seen more than .2º KR in the last 30k miles, and usually it's tough to see any at all. If I ever track the car again, I'll run race gas and I'll have my Aeroforce gauge connected. I'm not too worried about the injectors, but the most important thing: I will accept that even taking every precaution there are no guarantees when abusing a daily-driven car on a hot track.

matt270avian wrote:

LARRY70GS wrote:

Detonation will take out a rod bearing.  We call it knock, but it is detonation, and if it is severe enough at WOT, it will do damage.  I believe that is what happened to Aarons engine.

Wonder if it was lack of (or bad) oil that killed Charlie's engine or if it was knock....... Maybe he can chip in.

Nice pun...
I think it was a terminal intake gasket but I'll never know the exact truth. One inconspicuous day, wheeling the grocery cart out to the Riv, cause it's only a grocery getter after all , I started 'er up and what seemed from outta no where...knck knck knck knck

Well AA, I guess you it explained everything elegantly. Hope your new/rebuilt engine is running well.

Rick

On the bright side, having a 3800 V-6 rebuilt costs roughly the same as replacing the thermostat on an Audi S4, or a brake job on a Lexus IS300.

It was also a nice opportunity to clean up the engine, install the updated LIM gasket, and wrap the headers. You can read more about it here if you like:

https://rivperformance.editboard.com/t9354p30-write-up-3800-series-ii-sc-engine-removal-installation#146213

I've always thought Lexus SC300s were cool.
Riv is cooler, tho

IS300 > GS300

Bonus:

charlieRobinson wrote:

Nice pun...

I didn't even mean to do that

If you run race gas Aaron the possibility of detonation goes way down. I tell everyone I know to do the same. I would never go down the track without. Like the old Fram commercials use to say, "Pay now, or pay later"

I intended to run it, but ran out of time that morning. At the time, I didn't see knock as a risk, but you're right. Good insurance. One of a few things I could've/should've done differently.

charlieRobinson wrote:

I've always thought Lexus SC300s were cool.
Riv is cooler, tho

It's not a brown Miata wagon so the internet disagrees.

It's amazing how important getting those injectors cleaned and flow tested is. Good detective work! I should send out the injectors on our 455 before we drive it much further, they've been given a diet of poor quality fuel and lots of sitting for many years.

AA, can we please have over sized tensioner and idler pulleys on the front page post of this thread?

Page 1 has been updated with part numbers and updated guidelines.

AA wrote:

Page 1 has been updated with part numbers and updated guidelines.

Thank you! Also:
3.5" smooth tensioner pulley: INTENSE Racing #STP-635; ZZPerformance #ZZ-6R35SM

Gates '3.5"'/90mm smooth tensioner pulley: 38001

This is what I'm using now!

Added the Gates #, thanks!