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Old 03-21-2012, 07:15 PM
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Fresh 383 burns up pistons

had a 383 stoker built for me a few weeks ago, iron vortec heads, 10:1 speed pro pistons and eagle crank etc. Well swapped it into my truck and put about 90 miles of driving here and there and started blowing oil out of the breathers severely. Checked compression and had two cylinders at normal around 175 and the rest were pretty much junk, around 30-80. Well sent the motor back under warranty and heres some pics of the damage. He first accused me of using NOS which I never have and probably never will. He believed me and is covering all the parts/labor but my question is what could cause this much damage?
engine never overheated
had consistent oil pressure
my spark plugs read normal
headers never got excessively hot
and I have a brand new holley 750 on top with 7psi supply giving it plenty of fuel

the only thing I did before it started blowing oil out the breathers was mess with the timing with a different timing light, cause ignition timing cause this much damage in such a short time?
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Old 03-21-2012, 07:36 PM
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What did you have the timing set at? Yes too much timing can cause issues that fast. Going by the looks of the damage with the cracks running through the ring lands it looks like it detonated itself to death.
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Old 03-21-2012, 07:37 PM
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Detonation. The severe enemy of hyper eutectic pistons..Ign timing wrong or terrible fuel..
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Old 03-21-2012, 07:40 PM
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fuel was fresh so it must of been timing when i screwed with it. can anyone think of other reasons for this?
I just want to run through all possible causes so it doesnt happen again

thanks for the quick responses
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Old 03-21-2012, 08:43 PM
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Quote:
Originally Posted by brad33478
fuel was fresh so it must of been timing when i screwed with it. can anyone think of other reasons for this?
I just want to run through all possible causes so it doesnt happen again

thanks for the quick responses

I would expect your plugs to show early signs of detonation (prior to piston damage).
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Old 03-21-2012, 10:03 PM
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Classic detonation, upper limit for compression on pump gas, too much timing. I did the same, even worse on my blower motor last year. I'm guessing the rings are tight in their grooves? Mine hammered bad enough I couldn't pull them out. I'm surprised you couldn't hear the death rattle.
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Old 03-22-2012, 01:40 AM
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Detonation Of Pistons

How Much Timing Did You Add When You Used That Timing Light? You Melted The Pistons.. Spark Plugs Should Have Looked Like Toast Also~! When You Drove It, Couldn't You Hear The Detonation?
That Is A Bummer Needless To Say....water Injection Might Of Helped With Methanol Added To The Water....maybe Next Time...good Luck With The New Motor...
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Old 03-22-2012, 09:52 AM
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Way to much timing and with Vortec heads we only need around 30 to 32 degrees of total timing.

Your balancer should be degreed with a 32 degree make and check it at the RPM where you have the most timing. And go from there. I don't use vac. advance on a performance engine. But do change the curve with springs.

Your tune up killed those pistons and your lucky the guy is standing behind this as its not his fault at all!!!!!
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Old 03-22-2012, 03:21 PM
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Quote:
Originally Posted by brad33478
had a 383 stoker built for me a few weeks ago, iron vortec heads, 10:1 speed pro pistons and eagle crank etc. Well swapped it into my truck and put about 90 miles of driving here and there and started blowing oil out of the breathers severely. Checked compression and had two cylinders at normal around 175 and the rest were pretty much junk, around 30-80. Well sent the motor back under warranty and heres some pics of the damage. He first accused me of using NOS which I never have and probably never will. He believed me and is covering all the parts/labor but my question is what could cause this much damage?
engine never overheated
had consistent oil pressure
my spark plugs read normal
headers never got excessively hot
and I have a brand new holley 750 on top with 7psi supply giving it plenty of fuel the only thing I did before it started blowing oil out the breathers was mess with the timing with a different timing light, cause ignition timing cause this much damage in such a short time?

The could be's from the pictures are:

- Detonation/preignition; but the spark plugs usually either have metal deposits on the insulator or are beat up like the pistons. Detonation tends to pound the piston apart where preignition tends to melt it. Like the piston detonation busts chunks off the insualtor, preignition tends to put melted metal blobs on the insualtor and rounds the edges of the electrodes.

- Running hot. The scorched oil and heavy carbon deposits indicate this. The combustion temps or piston temps can get out of line without the cooling system showing anything so gauge temp is not a clear indicator unless the engine runs low or out of coolant. This can also be a function of detonation or preignition.

- Inadequate bore clearance; this can be a cause of what you're seeing or a result. However, most damage seems to be in the ring lands and up to the crown rather than the thrust faces which leads be back to cooking the combustion chamber side of the piston or see below, inadequate ring gap or ring to groove clearance.

- Inadequate ring gap, I notice what appears to be a crack between the first and second ring land of one of the pistons in the first picture which leads me to this thought. Of course massive overheating of the crown could run the rings out of gap. when out of gap for whatever reason then they buckle and pop the piston ring lands apart. A similar situation can be associated with insufficient top to bottom clearance with the ring to ring groove.

Over-all for 90 miles these look more like what you'd see at a hard run 90,000 miles.

A question arises in my mind as to how dry you keep the sump and crankcase. The piston does depend upon oil throw-off from the crankshaft for lubrication and cooling. When you use a windage tray with a crank scraper you can contribute to pulling too much oil out of the windage, it gets to be a tricky line to walk in some cases. Keep in mind that many competition and industrial engines go to some lengths to put oil on the underside of the crown for cooling purposes. The Chevy, as well as many others, used to have a groove through the rod split to pass pressure oil off the journal/bearing to spray onto the cylinder wall and underside of the piston for lubrication and cooling. Since the advent of emissions restrictions this practice has been discontinued to reduce the oil pull over into the combustion chambers to reduce the octane contamination of unleaded fuels and reduce contamination of catalytic converters. The hypereutectic piston is also a response to this requirement, it is an attempt to get a more temperature stable piston that can be run at higher temperatures with tighter clearances and is cheaper than going to a forging for such a solution.

I rather think that 10 to one is a bit high for a cast iron Vortec head. This would especially be true with a fairly mild cam which will jack the DCR up and will be more susceptible to the problems you're seeing when in a heavy vehicle that has high gearing. This brings the engine into the lugging RPM range and dumps a lot of weight on it at the same time. The driver's response is to open more throttle which raises the temps in the combustion chamber which makes for detonation, preignition and other localized temperature related issues. You're running a carb, this has fueling problems that EFI doesn't have (there is no way around this), you need to consider that when using high compression EFI heads on a carb'ed engine. You just can't push these combo's as close to the edge, especially when an EFI engine is listening for detonation/preignition and will take steps to suppress it when it's present; it does not tell the driver it did that so the typical driver of a L31 pickup would be unaware that there was a problem as it's taken care of for him, however, not in your case with a carb unless you add such a circuit to the ignition which is done a lot with these things to head off these kinds of operating issues. MSD and others sell black boxes that do this for carbed engines running on the edge.

Bogie
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Old 03-22-2012, 06:45 PM
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Those pistons look like the ones I took out of my blower motor when the timing was over advanced. Burnt, broken and the ring grooves were crushed.
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Old 03-22-2012, 07:30 PM
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Just to break the numbers down so it's easier to see why so much damage occurred. Lets say you stood on it for 10 seconds. You say you drove it 90 miles "here and there", so i'm going to assume that you got on it at least once for a short bit. Let's pick 10 seconds of time, with full throttle and full load on the motor. For the sake or simplifying the math, we'll say you hit 6000rpm for those 10 seconds. You basically shifted from 1st to 2nd to 3rd and held third for a bit.

6000rpm= 100 revolutions per second
100 revolutions in one second= 50 firing sequences in one second
10 seconds of run time = 500 firing sequences on each piston

With a heavily advanced timing adjustment and/or poor tune and/or poor gasoline, you had yourself "marbles in a coffee can" type of detonation. Imagine the beating each one of those pistons took getting hit with 500 secondary flame fronts as they collided with the primary flame front. A hypereutectic piston simply cannot handle that type of abuse.
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Old 03-23-2012, 05:00 PM
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Brad,
What was the plug you were using E-3???

Small cam will kill an engine with vortec heads, even though 170psi is not that much on the compression tester. Most I have gotten by with 383" on pump gas with vortecs is about 10.5:1 CR = 200psi and a big cam at .050 230-240 narrow lobe separation 104*, intake on 100* and a fat carb, and timing at 25* full advance, this engine made about 475HP at the rear wheels. Plugs were marine R43LTS. I buy them 500 at a time if you need them as I use them in all of my crate engines. They retard timing and run cool with crappy fuel and they don't burn engines up unless folks get stupid with timing and lean jetting.

Anyway most folks don't know the spark plug can change the dynamic timing of an engine +/- 5*. That is why Cup engines used to run extended plugs for qualifying an retracted for the race. Most people say it is the heat range but these plugs had the same # heat range they just made combustion happen faster as well as heating up the cylinders super fast.

It also looks like the pistons were touching off on the heads as they are super clean in that area.

On the chassis dyno, I always check timing when cars come in the door. On 602 / 604 Crate engines I drop timing back to 25* after the initial baseline runs and start my tuning from there. I have found there is about 20-30 HP in getting rid of the extra timing that impedes the engine from working the way it was designed to. Once folks wake up and realize that timing advance is a tool for crappy fuel and PI$$ POOR engine design they will come to understand how to make an engine run efficiently.

If you need some good pistons for your engine I would recommend using Mahles HT piston as it is superior to most economy forged pistons on the market.

If you are running standard bore 350 I have some super nice ones coated up and everything that should work up to 500HP pretty easy, I use them in 550HP road race engines and get a year out of them. In a street application that should be 50,000 miles, if the timing and fuel is right.
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Old 03-25-2012, 10:36 PM
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When talking about poor fuel they do not mean fresh fuel necessarily. They are talking about octane rating. With a 10-1 motor you need AT LEAST 91 octane unless you have A LOT of cam. Fuel must match cylinder pressure. As mentioned earlier vortec heads like no more than and usually less than 34 deg TOTAL timing. This means 8 or less initial with most stock distributors which leads many people to overtime them. This motor appears to have been detonated or preignited to death which would be YOUR fault. sorry
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Old 03-26-2012, 05:04 AM
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Quote:
Originally Posted by Dixie23
I did before it started blowing oil out the breathers was mess with the timing with a different timing light.
Dixie? By way of Beijing, maybe.
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Old 03-26-2012, 11:12 PM
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Man that one piston top is bad. I can see where they thought Nos might have been used.but yes to high comp.with small of a cam is a nono that's why I hate hyper pistons. Plus cylinder to wall clearance might have been to tight. And ring gap also could have been tight and butted up.better luck next time I feel.your pain
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