New motor gone...

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chargd72

chargd72

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The motor **** out on me while giving it some test pulls. Trying to figure out what went wrong. What are the chances my Mallory 685 isn't pulling timing correctly? Engine is 408 with 9.1:1 compression. Was only at 8 psi boost with air/fuel around 11.5. 93 pump gas running air to air intercooler. Complete forged bottom end from MRL Performance. It all of the sudden started running like crap so got is towed home. Started pulling plugs and the #1 piston is beat all to hell. Not sure if it's cracked or a completely blown apart yet. I was pulling 1.5* per psi with the Mallory 685. I don't see how I could've had pre det as that should be more than conservative if timing was pulled correctly. I know some guys on here run the same ignition so perhaps someone can give some ideas. I still need to pull the head to make sure something didn't drop into the cylinder but I'm confident that isn't the case. I've been building this motor for a year and have less than 3 hours on it.
 
sorry to hear this but it sure sounds like detonation im no expert but 93 octane seems borderline but you never said your c.r.
 
It is mentioned above but c.r. is 9.1:1. Nothing radical for 8 psi.
 
My magic internet crystal ball says we need more pics.
 
I only have a pic of the plug that ended up getting flattened for now. I could see the piston got hammered through the plug hole. I'm hoping to pull the head tonight after work.

IMG_2707fabo.PNG
 
Pulled valve covers last night. All valves and springs are where they should be.
 
Curious what your initial timing was? The numbers don't sound too off theoretically (I'm building one right now as well), but 8 psi at 9:1 your FCR would be close to 14. Not sure what 93 octane is good to but I've always been told to stay under 12. I don't have any experience to share but definetly trying to learn so I don't end up in the same boat.
 
Could be flat out detonation damage. It happens.
 
i feel for ya man, been there done that. mine was #8 that got ate up from detonation. rebuilt and changed from bt and msd 6530 to full on efi.
 
canadian duster said:
Curious what your initial timing was? The numbers don't sound too off theoretically (I'm building one right now as well), but 8 psi at 9:1 your FCR would be close to 14. Not sure what 93 octane is good to but I've always been told to stay under 12. I don't have any experience to share but definetly trying to learn so I don't end up in the same boat.
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Timing was locked out at 35*. With 8 psi the Mallory should have pulled timing to 23*. Without running lean that should have been safe. That's why I'm thinking the box failed.
 
clv22p said:
Have you checked any other cylinders?
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Couldn't get the heads off last night. I need a 12 point socket to get the rockers off. I don't see any other damaged to plugs. Just fouled as all hell.
 
70wayfarer said:
i feel for ya man, been there done that. mine was #8 that got ate up from detonation. rebuilt and changed from bt and msd 6530 to full on efi.
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Yep. I see FiTech 8 in my future. Who did you go with?
 
chargd72 said:
Yep. I see FiTech 8 in my future. Who did you go with?
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i went with the Link G4+ Storm, love the tune ability. like the Fitech. guys are making great hp with these. a lot cheaper option than what i went for.
have to agree with others that the plug looks more beaten than burnt.

P1010897.JPG
 
70wayfarer said:
i went with the Link G4+ Storm, love the tune ability. like the Fitech. guys are making great hp with these. a lot cheaper option than what i went for.
have to agree with others that the plug looks more beaten than burnt.

View attachment 1714991649
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That looks like a great setup! Did you ever determine why you detonated using the MSD box? Do you think it wasn't pulling timing correctly or did you just push it too hard?
 
chargd72 said:
That looks like a great setup! Did you ever determine why you detonated using the MSD box? Do you think it wasn't pulling timing correctly or did you just push it too hard?
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electrical fault caused the water meth to fail at wot on the dyno.
 
8 psi on 93 with an air to air, I wouldn't pull any timing at all.



What are you reading air fuel with? what do the plugs look like? I'm betting on lifted ring land/ butting rings.
 
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