Cracked block @ 27psi - Time to step up
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From: Tennessee Tech
Cracked block @ 27psi - Time to step up setup - kytp front mount w/billet pte76
Forged LS1
1/8: 6.5 @ 111mph
made 620 on 11psi
stock suspension / 10 bolt
Racing a terminator last year
Long story short, raced a busa from a roll going to a dyno meet and when I pulled into the meet antifreeze was spewing out. Initially thought it was a head gaskets but later found a crack across number 7, after checking the data log it showed a total of 27psi, I was shooting for 11 so something went fubar with the controller. Good thing atleast was when we tore the block down nothing was messed up internally, pistons, rods, rings, everything looked normal so after talking with my builder, sam daffron, he says it was caused by the motor mounts, the block torqued so vilantly under that much boost with no motor plate causing the crack. If I had known the internals were salveagable I wouldn't have decided to go bigger but oh well, I ordered everything before we tore it down because i was sure there would be problems.
The engine will be done this weekend and we're setting it off in the car to hopefully have some tune time before lsfest next weekend.
402 ci LS2 (4.005" bore)
4" Stroke Eagle Crank
Diamond -31.9cc Dish Pistons (ceramic coated, teflon skirts)
Manley Billet Rods
Total Seal Stainless Steel Rings (ms3906-5)
Same cam - 22x/23x .61x/.62x 115+2 LSA
Block
Pistons
Mock Up
Forged LS1
1/8: 6.5 @ 111mph
made 620 on 11psi
stock suspension / 10 bolt
Racing a terminator last year
Long story short, raced a busa from a roll going to a dyno meet and when I pulled into the meet antifreeze was spewing out. Initially thought it was a head gaskets but later found a crack across number 7, after checking the data log it showed a total of 27psi, I was shooting for 11 so something went fubar with the controller. Good thing atleast was when we tore the block down nothing was messed up internally, pistons, rods, rings, everything looked normal so after talking with my builder, sam daffron, he says it was caused by the motor mounts, the block torqued so vilantly under that much boost with no motor plate causing the crack. If I had known the internals were salveagable I wouldn't have decided to go bigger but oh well, I ordered everything before we tore it down because i was sure there would be problems.
The engine will be done this weekend and we're setting it off in the car to hopefully have some tune time before lsfest next weekend.
402 ci LS2 (4.005" bore)
4" Stroke Eagle Crank
Diamond -31.9cc Dish Pistons (ceramic coated, teflon skirts)
Manley Billet Rods
Total Seal Stainless Steel Rings (ms3906-5)
Same cam - 22x/23x .61x/.62x 115+2 LSA
Block
Pistons
Mock Up
Last edited by 273sunsetZ; Aug 29, 2012 at 11:04 PM.
Thread Starter
10 Second Club
Joined: Aug 2005
Posts: 567
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From: Tennessee Tech
your telling me... but the cr will be around 8.5:1 with the ls9 head gaskets. We should be able to squeeze 25psi through it with no problem. Still need a different turbo though, this 76mm isn't going to cut it with the extra cubes.
Why such low compression for the new motor, from everythign ive seen the general consensus is those days are over and 9-9.5:1 was better suited. I also have 8.5:1 on mine and wish it was a tad higher to help spool the turbo quicker.
Thread Starter
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Joined: Aug 2005
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From: Tennessee Tech
Funds... I'm using 100$ trunk heads. I'll have them decked before long to bring it up a few tenths but I'm really not too concerned about it. I'll eventually get a nice set of heads to finish the build and bring the cr to around 9:1
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Thread Starter
10 Second Club
Joined: Aug 2005
Posts: 567
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From: Tennessee Tech
Lol without going into too much detail I had total timing pulled down to 6* as a safe mode if it overboosted, and the data log showed 13.x afr at those boost levels due to my single pump setup so it didn't exactly feel real fast, I should have walked the busa but it was more less an even race.
I don't buy the stock mounts killed the block story. I have several cars making more power constantly being beaten on not cracking the block, using either rubber, poly, or solid mounts in the stock location.
Your camaro sounds killer, and you will really like the extra cubic inches even if the compression is pretty low.
Your camaro sounds killer, and you will really like the extra cubic inches even if the compression is pretty low.
I don't buy the stock mounts killed the block story. I have several cars making more power constantly being beaten on not cracking the block, using either rubber, poly, or solid mounts in the stock location.
Your camaro sounds killer, and you will really like the extra cubic inches even if the compression is pretty low.
Your camaro sounds killer, and you will really like the extra cubic inches even if the compression is pretty low.
Exactly. I don't buy the motor mounts story either, not even for a second. For added insurance, iron block all the way!
Isn't that deep of a dish in a piston disigned for 6.125" rods and a 4" crank gonna leave little room between the crown and where the pin is?? I would much rather keep the stock 317 combustion chamber and get a thicker piston. Just an observation. I also don't quite agree with the mount breaking the block.
glad to hear something about Sam...
i tried calling him and emailing him a few times a few months back and never heard from him and didnt know what happened.
good luck with the new build!!
i tried calling him and emailing him a few times a few months back and never heard from him and didnt know what happened.
good luck with the new build!!
when i was scared to go above 12psi when i first finished my turbo build i set my VE table to pull all fuel at anything above 190kpa. when i put a cheap boost controller on there i was able to test that function many times.... not intentionally. It would cut all fuel and keep from overboosting. Now that i have my 2 bar map sensor maxed out i lost that safety feature but when i go to a 3 bar sensor i will do it again. it could have saved your motor instead of just pulling timing.
Im really curious why more people dont implement this. Its not like its gonna run lean and melt **** with no fuel, or an extremely small amount of fuel going in... i see no downsides and having hit that cutoff probably 10 times at WOT on a stock motor i am not worried one bit. Ill tell ya one thing... you know it when it reaches that point on the map and instinctively lift off the gas. your talking less then half a second in most instances. Its basically like hitting the rev limiter... motor has no fuel and falls on its face. One important thing to try and remember is to have some room in your normal boost range and the cutoff as i think the VE table blends the cells.. i liked to keep the cutoff 15kpa above my peak boost.
Im really curious why more people dont implement this. Its not like its gonna run lean and melt **** with no fuel, or an extremely small amount of fuel going in... i see no downsides and having hit that cutoff probably 10 times at WOT on a stock motor i am not worried one bit. Ill tell ya one thing... you know it when it reaches that point on the map and instinctively lift off the gas. your talking less then half a second in most instances. Its basically like hitting the rev limiter... motor has no fuel and falls on its face. One important thing to try and remember is to have some room in your normal boost range and the cutoff as i think the VE table blends the cells.. i liked to keep the cutoff 15kpa above my peak boost.
Last edited by got-a-ls1; Aug 30, 2012 at 11:29 AM.
Thread Starter
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Joined: Aug 2005
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From: Tennessee Tech
Can someone explain why all cylinders, pistons, Rods, and crank check out at the machine shop? The only problem with the engine was a hairline crack just above the engine mount location on the passenger side.
How is it that detonation caused the crack on the outside of the block across the cylinder wall, and the inner sleeve looks fine?
How is it that detonation caused the crack on the outside of the block across the cylinder wall, and the inner sleeve looks fine?