L92's Turbo & blown Copper head gaskets...
Thread Starter
TECH Senior Member
iTrader: (6)
Joined: Jul 2005
Posts: 5,276
Likes: 0
From: Decatur, AL
L92's Turbo & blown Copper head gaskets... Ok, the specs on this engine at the time of failure is:
370 ci
9.0:1 comp, 223/218 114 cam
front mount PT76-gts FMIC
L92 heads stock
6psi
16* timing
10.5:1 afr
ARP studs tqed to 70lbs with arp moly lube
Only about 1000 miles on engine, O-ringed block, and SCE solid copper .040" gaskets. From the markings it looks like they have been blowing by more than once.
Heads and block were checked flat and hand stoned before assembly and oringing.
As a note, previously I had 317 heads with all the same specs above but 13psi and 11.7:1 afr and when I pulled the heads they factory MLS gaskets had been blowing by on the center two cyls as well with ARP bolts.
Does this look like a common problem with factory heads that only have a 3/8" deck? Is the only fix for this aftermarket heads with a 3/4" deck? I'm plum fed up.
370 ci
9.0:1 comp, 223/218 114 cam
front mount PT76-gts FMIC
L92 heads stock
6psi
16* timing
10.5:1 afr
ARP studs tqed to 70lbs with arp moly lube
Only about 1000 miles on engine, O-ringed block, and SCE solid copper .040" gaskets. From the markings it looks like they have been blowing by more than once.
Heads and block were checked flat and hand stoned before assembly and oringing.
As a note, previously I had 317 heads with all the same specs above but 13psi and 11.7:1 afr and when I pulled the heads they factory MLS gaskets had been blowing by on the center two cyls as well with ARP bolts.
Does this look like a common problem with factory heads that only have a 3/8" deck? Is the only fix for this aftermarket heads with a 3/4" deck? I'm plum fed up.
Thread Starter
TECH Senior Member
iTrader: (6)
Joined: Jul 2005
Posts: 5,276
Likes: 0
From: Decatur, AL
My prognosis is they are a great NA head, so that is what I will make them. I'm not spending $2500 on AFR's. Anyone want a front mount turbo kit for a truck?
Looks like there were a couple of things i would be weary of, it looks like those heads still have the swirl marks from the decking, if so they dont have a smooth enough finish for the gaskets to seal. Second did you retorque those head gaskets after the first heat cycle? Those kinds of gaskets should be retorqued. Other than that everything looks right but those are the most common spots for any head gasket to blow i wouldnt chalk it uo to just an l92 problem.
Trending Topics
Thread Starter
TECH Senior Member
iTrader: (6)
Joined: Jul 2005
Posts: 5,276
Likes: 0
From: Decatur, AL
The factory facing marks were somewhat noticable. I stoned the hell out of them and the divits or waves you may see I would estimate to be no more than .0005" deep if that. There is just enough there for discoloring and you can't hardly feel them with your nail. I doubt they affected the seal of the oring. There is more variences in the oring from dinks or marks when the wire was installed.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Gifts Neither Your Dad Nor Grad Will Shove Into the 'Trinket Drawer'
Brett Foote
Topdon ONE vs. Artidiag 800 BT2: Which is the Diagnostic Tablet For You?
Pouria Savadkouei
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Ill even pick it up from your
Thread Starter
TECH Senior Member
iTrader: (6)
Joined: Jul 2005
Posts: 5,276
Likes: 0
From: Decatur, AL
Originally Posted by cncbird
head surfaces really do look too rough--you can even see swirl marks from the heads on the gaskets
Thread Starter
TECH Senior Member
iTrader: (6)
Joined: Jul 2005
Posts: 5,276
Likes: 0
From: Decatur, AL
Originally Posted by LASTLS1
Did you re torque the heads after the first heat cycle?????
Thread Starter
TECH Senior Member
iTrader: (6)
Joined: Jul 2005
Posts: 5,276
Likes: 0
From: Decatur, AL
Originally Posted by black98ws6ta
How much does the wire protrude ? Did the gaskets blow on both side of the gasket or just one(block/head side)
The wire should only be protruding no more then 25% of the total thickness of the copper gasket. If your boost/timing is where you say it was and there arent any backpressure issues or anything I cant understand why your old or new set-up should be blowing. If you have a .015-.020 and a .040 gasket, you need to go to a thicker gasket for them to be used correctly.
Originally Posted by TurboGibbs
I spot checked a few I could get to and none of them budged at 70lbs. ARP recommended 65 with their lube, I torqued to 70 initially.
If you mark each nut before you loosen it you will be suprised how much further they will turn.
