I was on my way home last night, while on a freeway on-ramp I rolled into the throttle in second gear, held WOT til' the beginning of 3rd (low 70's MPH)...my brother happened to be following me home (we had been visiting family)...anyways he said he saw me get on it, soon as I did tons 'n tons of blue smoke started to pile outta the car. I looked in the rearview soon as I lifted, saw the smoke, and pulled over at a "Park-n-ride" about a 1/4 mile away. As soon as I got out of the throttle the smoke cleared up.

Well, this was on a low-mile stock shortblock I had just put in the car. This same thing happened to me 3 months ago on my high mileage stock shortblock. The first one lasted about 3weeks at 7 psi...this one lasted about 1 week. This newest shortblock leak-down tested between 3%-8% @100psi about a week ago. And it ran super super healthy up until last night...never missed, never hesitated. Now it acts just like the old one, you can hear it miss, has a horrible case of the Chug-o-death, and I'm pretty certain it'll have chipped or broken ringlands just like my last one.

So, the car is still drivable...it has a horrible case of the chug-o-death, worse than before...my only saving grace i think is my crankcase evac system...I'm assuming it's the only thing keeping oil from blowing past main seals like crazy right now...so I'm not totally sunk...Here's where I need some help figuring this out...My scanmaster datalogged the WOT run that blew the motor...it showed a lowest avg 02mv of 999, and 0 degrees of timing retard at ZERO MPH...this was the first I've ever seen it display this...all other WOT runs I have done displayed high 800's low 900's mv, and 7 degrees of Retard. My ECU was tuned by PCMForLess for the exact mods on my car, I havn't changed a thing...(this was the same tune I had when the first shortblock blew)...I have an e-mail saying they tuned for 5-7psi...my setup would peak at 7psi...so I was under the assumption it was pulling roughly 1 degree of timing for every pound of boost...(i have a crane cams 6AL, it does not have boost retard...I made this known to the tuner, so I assuming they generically expected to see boost at certain RPM's and retarded timing accordingly). I was reading "InjuneerZZ" write-up about the scanmaster,

he says, "Be careful. I have seen sudden transitions screw up the recorded values, and give you the max possible value of 999mV. This will usually be accompanied by a corresponding MPH value of "00"."

Can anyone elaborate on this for me? I'm basically just trying to figure out what is causing me to get the pre-ignition/detonation that is blowing my motors so fast...as far as gas goes I've been running the highest octane available 92-93, along with a full bottle of Lucas Octane Boost with every fill up...previous to the Lucas I was running Amsoil octane boost. I emailed PCMForLess requesting information on the tune they did...what all should I ask for, Timing maps, etc? I'm not neccessarily trying to point fingers, I'm ultimately trying to gain understanding so this never happens again...I couldnt' afford for this to happen this soon, let alone a 3rd time. I'm paying my way through college while working full-time, blowing these motors is killing me...

My plan is to pull the supercharger setup, which has less than 2K miles on it, selling everything I can...prolly here on the board, or ebay(whichever is fastest)...hoping I can limp around with this chug-o-death until everything sells...I have my old motor on an engine stand in the garage....so soon as my **** sells, I will be able to piece together a new rotating assembly and I'm just gonna go back to N/A to get the car healthy and back on the road again.

Sorry for the long post, just need some Ideas on what I should do next to try to get to the bottom of this...

Thanks,

Andrew

 

Supercharger and stock LT1 pistons and compression = blown motor. IF the boost is kept quite low it might last quite a while though.

Rich

 

Yes, this I've learned the hard-way...but I had a healthy shortblock...It should have lasted longer than it did. I think i've got it narrowed down to too much timing. Bryan said if he knew I was seeing any KR he would have wanted to pull timing, mentioned something about maybe my local gas station is running too much ethanol...this is all very concerning to me, since I was registering 7 degrees retard apparently when I should have been seeing zero...

I was under the impression they'd be able to program a safe tune for 7psi...or well, safe in relative terms. I by no means expected this engine to last long...but I DID however expect it to last longer than 300miles...and to have 2 shortblocks fall dead because of too much timing programmed into the ECU leaves me bitter...I'd like to compare the programming on my ECU to what "should" have been programmed and see if there are any discrepencies.

 

how much total timing were u running ?

 

Take it and get it dyno tuned next time.

 

Bryan just emailed me back. Says he had programmed it for 26 degrees. Yeah, I see no point in risking this happening again. The nearest dyno is damn near 60 miles away...I'll get there one way or another come 'round 3...

 

Post a little more about the setup. Were you using the stock injectors with an FMU, that kinda stuff. Generally though, Rich has the right of it, LT1 + boost is a crap shoot. Sometimes you roll snake eyes.

 

Stock shortblock, Stock heads, Stock Valvetrain. Bosch 42lb Fuel Injectors, T-Rex Inline Fuel Pump, NO FMU, Vortech V-1 A-Trim @ 7psi, Hooker LongTube Super Comp Headers, Tayler 10.4mm Wires, NGK TR-6 plugs, Crane Cams 6AL Ignition Box, MSD BlasterII Coil, relatively New OEM Opti-Spark, ARP Head bolts, LT1 Scanmaster, EWP, 160* stat, Mr. Gasket Crankcase Evac, 1074 headgaskets, lots of other lil' stuff that is irrelavent (1LE a/c Delete pully, SLP airfoil, etc...)

The maf was running as blow-through, as opposed to the regular vortech location, I also got rid of the "dryer ducting" and made a hard-pipe.

 

26 timming seams a lot for a stock compression shortblock.
I think i am only running round 22 myself.

 

yeah, something seems arry. 7 degrees retard when they're should be zero is a big red flag. How can/who can I have check the ecu and make sure the programming is where they say they put it (26*), and not something else?

 

I ran a stock long block with stock timing and an FMU with a P600B at 8 lbs. of boost for 20,000+ miles, no problems. I did however, keep the set screw on the FMU closed so it would run rich under boost, used SVO injectors not the factory GM ones. The factory injectors can "lock up" under high fuel pressures. Also, the Procharger boost is intercooled thus reducing IATs.

Also, you should be running NGK TR6s. And its not just the timing, you need to know where your air-fuel ratio is at.

 

My mistake...TR-55's was a typo...I am running the TR-6's

http://web.camaross.com/forums/showt...hlight=NGK+TR6

Brainfreeze...I was in a debate about the IX's and got my numbers mixed up...

As far as the A/F i kept a close eye on the 02 mv's via the scanmaster. This is the only means I had to monitor. I realize stock 02's should be used merely as a guideline, it's my understanding past 600* as they get hotter and hotter they can become less and less accurate; Nonetheless they're were consistently high 800mv's, low 900's before this mishap.

 

Forged slugs is the only way to go.

 

I'm just relating my own experiences and what I've heard and learned from others experiences but in general:
6 psi is max non-intercooled boost on a stock LT1
8 psi is max for intercooled boost on a stock LT1
Forged pistons would help BUT, I know specifically of one person with a forged rotating assembly and a mail order supercharger tune that experienced detonation so bad he put a hole in the piston. His reply was, "But its forged". So what. It was a bad tune, he detonated, and that was it.

 

Don't sell the supercharger just yet. I've replaced many pistons with the engine still in the car. You can fix a $1000 problem for $300.

Other than that I agree with you shoulda' never run it with 7 deg of knock retard and you shoulda' put forged pistons in it when you had the chance.

Don't feel too bad, though. I've blown an engine in less than 5 miles after fixing a broken piston.

Mike