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cometic lsx reseal question

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Old Nov 15, 2011 | 09:54 PM
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Default cometic lsx reseal question

if you push some water on a pass due to the timing being jacked up are the gaskets toast? i had my BS3 put 20* in my motor when i wanted 10*. the plugs dont show signs of detonation and the timing strap on the plugs is half way between the bend and the threads. it was a new setup and the boost creeped from 18 to 24psi on the pass.

additionally i made a pass after it pushed and had to get out of it, the pass it pushed water it started at 180* coolant temp and was at 215* by time i was back in the pits. i started the next pass 45mins later at 190* and it rose 15* to 205*, but it wasnt a full pass.

lsx block 6 bolt, 1/2 studs torqued to 105lbs.
cometic gaskets
E85, 24psi, 11.8 a/f
101mm turbo
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Old Nov 16, 2011 | 01:18 PM
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I would not re-use them.
1. you pushed water
2. they were torqued to 105lbs.

if you were to tear engine down to make some changes and hadnt had any water issues and were torqued at a lower rate than I would say yes.

I have re-used them, but only cause I was pulling heads to replace some bad valves. Originally torqued at 80lbs. so......
cleaned and inspected gaskets for defects
heated gaskets up w/ propane torch to get them to expand a lil bit
re-assembled and torqued to 85lbs. ran it for 2yrs. w/out any problems
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Old Nov 16, 2011 | 03:03 PM
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Do you think it's possible the cometics just didn't seal? Somethings up if you are pushing with a 6 bolt setup. I have made a ton of hits on 22-24* - 20+lbs of boost on 4 bolt heads with LS9 gaskets. Skinnies has also done the same and never pushed water on a stock 5.3 with LS9 gaskets.
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Old Nov 16, 2011 | 03:24 PM
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20psi on this setup makes around 1200rwhp, im wondering maybe if it was thermal expansion of the water, i did have the radiator full and overflow got clogged so it popped the line off as soon as the water expanded. one thing i remember is it did it at the top of the track not during the run which makes me think it could of heated the water.

i wouldnt think the 6 bolt would push water at 1200ish hp. but with a bad tun anything is possible.

automagicls1- what fuel are you running?
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Old Nov 16, 2011 | 03:42 PM
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Have you checked your timing at max rpm with a timing light?

20* would not scare me on that setup with an intercooler as long as there was plenty of fuel. I would be targeting in the .72 range.

Run a compression and leak down on it, at least get an idea of the shape the gaskets are in.
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Old Nov 16, 2011 | 03:43 PM
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How did the ecu give you 20 deg when you should have 10 ?

That has to be caused by whoever has programmed the ecu.

As for seeing 24psi when you wanted 18psi, why no overboost protection ?


And generally speaking. If a gasket lets go due to excessive timing, which often will cause some detonation, although depends how much leeway you have with fuel/CR etc, then yes the gaskets will have warped like a banana and must be replaced.

it's handy to add a pressure sensor into the expansion tank on the cooling system to monitor HG integrity during/after racing to see if they are leaking at all.
Or in the most simplest form, stick a boost gauge onto it so you can see it.

Having big studs to clamp everything down can almost mask a blown head gasket with MLS gaskets, but they will still be blown.
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Old Nov 16, 2011 | 04:34 PM
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Originally Posted by cjg454ss
20psi on this setup makes around 1200rwhp, im wondering maybe if it was thermal expansion of the water, i did have the radiator full and overflow got clogged so it popped the line off as soon as the water expanded. one thing i remember is it did it at the top of the track not during the run which makes me think it could of heated the water.

i wouldnt think the 6 bolt would push water at 1200ish hp. but with a bad tun anything is possible.

automagicls1- what fuel are you running?
E85. My car made just under 1100rwhp on 25lbs/24*
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Old Nov 16, 2011 | 04:46 PM
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This is my question. Is this a new motor and new head setup? If so did you end up re torquing the heads after running the car for a bit? I know this can happen. It doesn't really sound to me that you pushed water.
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Old Nov 16, 2011 | 04:57 PM
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i had some boost creep thats why the boost rose so high. i shifted at 7400 on the 1-2. anything over 6800 and it would rise from 18psi.

as for the timing, bs3 was set at 353* for the crank trigger reference, verifed it with the timing light, went to the track and made a pass, checked the plugs and it looked hot. went through the tune and the reference was at 343. it was odd, its happend twice before and i caught it once.

ill make some passes next weekend to see, the new 106 will be here
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Old Nov 17, 2011 | 02:30 AM
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If you arent prepared to use an overboost cut to protect, at least run the map cells higher than normal in such a manner as it can only be safe with regards to fuel and timing should it overboost.
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Old Nov 17, 2011 | 06:03 AM
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Originally Posted by stevieturbo
If you arent prepared to use an overboost cut to protect, at least run the map cells higher than normal in such a manner as it can only be safe with regards to fuel and timing should it overboost.
understood, how low of boost can you run with a 60mm gate and a pt106, i ran on a light wastegate spring and im not sure if the 60mm can get rid of the air.
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Old Nov 17, 2011 | 07:02 AM
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I would be concerned more with the crank trigger reference moving around on its own!
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Old Nov 17, 2011 | 07:26 AM
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yea tell me about it, i think something similar happend to fireball, BS3 through a bunch of timing in and caused a meltdown, believe me i would never run BS3 again.........never,

im not the only one that has issues. id like to sell the BS3, and go with a distributor and carb. then i know i have control over the fuel and spark.
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Old Nov 17, 2011 | 08:33 AM
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I often run key on and off then back on in the pits to double check everything after making changes in the tuneup. I have caught little bugs here and there too, nothing this big though.
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Old Nov 17, 2011 | 09:12 AM
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^ good idea, ill start doing that.
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Old Nov 17, 2011 | 09:46 AM
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Originally Posted by cjg454ss
understood, how low of boost can you run with a 60mm gate and a pt106, i ran on a light wastegate spring and im not sure if the 60mm can get rid of the air.
I cant answer that question. But it should be very easy to set up overboost failsafes same as any aftermarket ecu.

Be they a full on boost cut if the limit is exceeded, or heavily overfuel/retarded timing so it goes totally flat should your normal safe boost be exceeded.

Obviously the first method is preferred, although the latter means the engine will still run and make decent power as opposed to cutting out
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Old Nov 17, 2011 | 10:33 AM
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Originally Posted by stevieturbo
I cant answer that question. But it should be very easy to set up overboost failsafes same as any aftermarket ecu.

Be they a full on boost cut if the limit is exceeded, or heavily overfuel/retarded timing so it goes totally flat should your normal safe boost be exceeded.

Obviously the first method is preferred, although the latter means the engine will still run and make decent power as opposed to cutting out
i run Big stuff 3, if i wanted to run 20psi, and at 22psi i put the timing at 2*, would that hurt anything?
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Old Nov 17, 2011 | 10:39 AM
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Originally Posted by cjg454ss
i run Big stuff 3, if i wanted to run 20psi, and at 22psi i put the timing at 2*, would that hurt anything?
2 would be quite low. But drop back say 5-10deg over previous row, and increase fuelling. Obviously not by silly amounts, but enough that the engine will go flat and you can feel yourself that something has gone wrong.

But would be better to drop in stages, as interpolation will take place between load cells.

So if 20psi was the absolute max you see on a safe run, and not a bit more. You could do a row at 21psi just in case, and then at 22psi have it as the failsafe.

Not much odds over 20-22psi though

But a full overboost cut at say 23psi would still be a wise precaution if the engine is tuned on the very edge.

As pulling timing and adding fuel would struggle for example if the w/g failed and caused overboost. Or a w/g pipe came off and caused overboost. No amount of safe overfuel or safe retarding of the timing will save that.
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Old Nov 17, 2011 | 11:26 AM
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yea thats how i lost my last motor, 35psi spike and compustar rods went through the block,
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Old Nov 17, 2011 | 02:54 PM
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Originally Posted by cjg454ss
yea thats how i lost my last motor, 35psi spike and compustar rods went through the block,
Then you need to do two things.

Sort out your boost control system, and sort of some safety features so it cannot happen again.

Ive never used BS3, but every aftermarket ecu I have used has a safety overboost cut feature that totally cuts fuel in the event of an overboost. Virtually all OEM turbo car makers operate in the same way.

Well, 3 things....pull the heads and check/replace the head gaskets.

And as said, it can be helpful to monitor pressure in the cooling system as well.
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