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Discussion Starter #1
Dammit. I am seriously 2 seconds away from ditching the mod motor shit and putting a pushrod in this thing. Maybe this was simply mechanical failure, or perhaps caused by something else. Any input is greatly appreciated as I am not the best at diagnosing these things, but I am learning.

Bit of background. Car was on a low 8 sec pass and it let go at about 1000'. 28psi in the logs and A/F was good 11.3-11.5, 17* total timing on e98, BR9 plugs (not extended tip), A/F didn't even change much when the motor let go which is kind of frightening in itself. Only lost 1psi when the shit hit the fan, lol. I get to about 1000' and the motor let go, blew the oil baffle lines off the oil can, and lines off the head, oil everywhere, so that was fun just slowing down. Motor still ran so I quickly limped to the return road and shut it down. Car never over heated, this was at a race so we had plenty of cool down time, etc. Obviously the crankcase was pressurized so oil everywhere.

Get it home, start the teardown, and here is what we see. This is cylinder #4 by the way.





The top of the piston is wavy, like it started to collapse, and the chunk is missing out of the top. It's hard to tell if the head got hot and started to come apart, or if the piston let go damaging the head. These are Manley flat tops with upgraded wrist pins. Stock cobra crank, Oliver billet rods, Teksid block, rings are all hand-filed, not sure of the brand or gaps off the top of my head.

Observations from teardown:
  • Plug #4 tip destroyed, obviously
  • Oil breather lines blown off, oil everywhere.
  • Intake port #3 was 100% completely filled with fuel when Sullivan was removed!
  • DS bank plugs all oil fouled, oil seen in intake as well
  • Oil dripped out DS header, waste gate on that side had oil in it as well
  • PS header and waste gate very white on the inside. Evidence of bad heat or ?
  • Cylinders/pistons #1 - #3 look 100% fine
  • Still have to pull DS head #5 - #8
Like I said, #3 intake port was completely filled with fuel when the intake was removed - does that mean the injector is stuck open and all the fuel from the rail drained into there? Or bad coil, bad wire? The thing is that #3 looked fine and #4 was wrecked next door.

Any thoughts ? Detonation, heat, something else? The fuel filled intake port was pretty concerning to me lol

I have a pair of new heads on the way, but I'm seriously considering dropping the mod motor shit, even if I have to not race next year to change my stuff over to SBF.
 

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Discussion Starter #4
head gaskets blown everywhere?
Nope. I believe the head gasket is fine. I didnt see anything that jumped out at me, but I'll look at it closer when I get home

Guess Hans was right, he guessed that the head would get fucked before a Cometic lets go on these motors
 

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1-877-MOD-POWR
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What ecu is this FAST???
 

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How many low 8sec passes.
 

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1-877-MOD-POWR
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hmmm
 

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We recently had a similar issue but with a FAST, and EVERY SINGLE piece of data was the same before and after it let go....in fact nothing had changed since the prior runs where it ran perfect, did you change anything, also what battery? Hoping to link a common problem.
 

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Pull out the piston, I am gonna go ahead and guess this block had no fill in it ? Also, find out where the ring gaps are. I saw this happen a few years back with similar power. the cylinder wall was so wobbly that it literally shook the rings till they lined up and then oil got by, which of course burned the slug down exactly like that one.
 

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Discussion Starter #12
No fill in the block.

I will check to find out what the rings were gapped at.

One piece of info I forgot to add. This motor is 30 over. [Flamesuit on]
 

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No fill in the block.

I will check to find out what the rings were gapped at.

One piece of info I forgot to add. This motor is 30 over. [Flamesuit on]
Not what the ring gaps are, but where the ring gaps ARE on the piston is the key question.I bet they lined up.

Welcome to big power mod motor country.
 

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Discussion Starter #14
Not what the ring gaps are, but where the ring gaps ARE on the piston is the key question.I bet they lined up.

Welcome to big power mod motor country.
Oh jesus, you mean the gaps on the actual rings were rotating around the piston so much that the gaps lined up. Interesting. I'll be sure to take it apart slowly so we can check that

Big power mod motor country...this place kinda sucks :eek:
 

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How many hours were spent on the engine dyno dialing in the individual cylinder temps? Playing with timing, fuels, spark plug heat ranges? How many 330' and 1/8 mile hits were made with good data? How many passes were made with no or low boost? This thing looks like at one time this thing was rattling apart.at one point it puddled fuel under the rings and the explosion only has on place to go. UP! you can't tell from the pics is that head gasket, spark plug or piston all over? That crack to the seat is for an excessive amount of heat. From what limited info is here...you would have failed a pushrod motor just as fast. looks like this thing rattled at one point leaned out and one point and overfueled at one point. typical signs of a guy creeping up on a tune up or someone new to a particular injection system or combo of both. You didn't put this thing on 1200hp tune and go try to make clean passes did you? Please keep in mind very little info so this is an educated guess.
 

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Oh jesus, you mean the gaps on the actual rings were rotating around the piston so much that the gaps lined up. Interesting. I'll be sure to take it apart slowly so we can check that

Big power mod motor country...this place kinda sucks :eek:
Yes, and it can and does happen. Though rare, it happens more when the cylinder walls are flexing due to cylinder pressure. I've seen it happen with dyno mules at the big 3.
 

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Discussion Starter #17
How many hours were spent on the engine dyno dialing in the individual cylinder temps? Playing with timing, fuels, spark plug heat ranges? How many 330' and 1/8 mile hits were made with good data? How many passes were made with no or low boost? This thing looks like at one time this thing was rattling apart.at one point it puddled fuel under the rings and the explosion only has on place to go. UP! you can't tell from the pics is that head gasket, spark plug or piston all over? That crack to the seat is for an excessive amount of heat. From what limited info is here...you would have failed a pushrod motor just as fast. looks like this thing rattled at one point leaned out and one point and overfueled at one point. typical signs of a guy creeping up on a tune up or someone new to a particular injection system or combo of both. You didn't put this thing on 1200hp tune and go try to make clean passes did you? Please keep in mind very little info so this is an educated guess.
We didnt tune individual cylinders on this motor. Tuner definitely crept up on it on the dyno - I think we only made 6-7 passes on the dyno and only went to 26psi on the dyno. Tuner doesnt like beating on cars on the dyno.

We crept up on it at the track too. First day was 15psi, then 18, 22, 25, then finally 27-28. I did not modify the original tune at all, never changed the timing once, etc. Plenty of good 330' & 1/8 mile hits with good data.

I did have an issue with a fuel pump a month back. Car would idle, go on the brake just fine. I would put it on the brake, launch, and as soon as it came under load would go dead lean and miss. The car honestly never moved more than 20' under power but it was lean on 20psi. Tried fixing a few things before narrowing it down to the fuel pump. It was lean for 20' in first gear then I'd lift. Didn't think that could do much damage but I suppose it could have rattled the motor.

Plugs have always been 8 & 9 range plugs to fight off detonation with the ethanol fuel. Sounds like most have good success with colder plugs and ethanol fuels.

The shit on the valves I'm assuming is a bit of everything lol. Small piece of the head is burned off, chunk of piston is missing, and the plug was trashed too, so it all went somewhere.

Perhaps mid 11's A/F is too lean for 28psi ?
 

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We run e98 non-intercooled and shoot for .7 lambda above 30psi, which is 10.25:1 on gas scale. I do not think it was a lean problem though, will be interesting to see the piston once it is pulled out.
 

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We didnt tune individual cylinders on this motor. Tuner definitely crept up on it on the dyno - I think we only made 6-7 passes on the dyno and only went to 26psi on the dyno. Tuner doesnt like beating on cars on the dyno.

We crept up on it at the track too. First day was 15psi, then 18, 22, 25, then finally 27-28. I did not modify the original tune at all, never changed the timing once, etc. Plenty of good 330' & 1/8 mile hits with good data.

I did have an issue with a fuel pump a month back. Car would idle, go on the brake just fine. I would put it on the brake, launch, and as soon as it came under load would go dead lean and miss. The car honestly never moved more than 20' under power but it was lean on 20psi. Tried fixing a few things before narrowing it down to the fuel pump. It was lean for 20' in first gear then I'd lift. Didn't think that could do much damage but I suppose it could have rattled the motor.

Plugs have always been 8 & 9 range plugs to fight off detonation with the ethanol fuel. Sounds like most have good success with colder plugs and ethanol fuels.

The shit on the valves I'm assuming is a bit of everything lol. Small piece of the head is burned off, chunk of piston is missing, and the plug was trashed too, so it all went somewhere.

Perhaps mid 11's A/F is too lean for 28psi ?
Once oil get in the cylinder, all hell breaks loose.
 
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