85 Corvette Engine Questions!
Thread Starter
Advanced
Joined: Feb 2005
Posts: 77
Likes: 1
From: zanesville ohio
85 Corvette Engine Questions!
LATELY I'VE NOTICE A LOT OF CONFLICTING INFO ON THE 85 CORVETTE ENGINE PARTS SUCH AS WHETHER OR NOT THEY HAVE FORGED PISTONS AND THE MATTER OF EITHER BEING A 2 BOLT OR 4 BOLT BLOCK. I WAS WONDERING IF ANYBODY KNOWS FOR SURE. THANKS MIKE 
Melting Slicks
Joined: Mar 1999
Posts: 2,830
Likes: 20
From: Las Vegas Nevada
When I rebuilt the engine in my last '85 the pistons were original and they were forged. From everything I've heard they are exclusive to the '85. I can't remember if it was a 2 or 4 bolt main.
Last edited by VtVette; Jan 9, 2006 at 03:19 AM.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Sounds like you've been getting free info from the corvetteforum. 
Forged, yes.
Exclusive to 85, I don't think so, but not sure.
2-bolt mains, yup (and because I saw for myself, not because someone told me so.)
Forged, yes.
Exclusive to 85, I don't think so, but not sure.
2-bolt mains, yup (and because I saw for myself, not because someone told me so.)
Melting Slicks
Joined: Mar 1999
Posts: 2,830
Likes: 20
From: Las Vegas Nevada
It seemed strange that GM would decide on forged pistons for one year but I know I've heard that and it seems I've hear it more than one place.
Can someone elaborate on this who knows for sure?
Can someone elaborate on this who knows for sure?
Melting Slicks
Joined: Mar 2001
Posts: 2,149
Likes: 303
From: Timra, Sweden
The block is 2-bolt.
The stock pistons are forged TRW #464664. They were used on the 1984, 1985 and a lot of C3 corvette engines too. At least the 1982 L83 engine and I think also the 1971-1980 L82.
The stock pistons are forged TRW #464664. They were used on the 1984, 1985 and a lot of C3 corvette engines too. At least the 1982 L83 engine and I think also the 1971-1980 L82.
Last edited by JoBy; Jan 9, 2006 at 08:01 AM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Team Owner
Joined: Sep 2001
Posts: 62,137
Likes: 1,727
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
They have TRW forged pistons in a 2-bolt block, the pistons were leftover parts from the GM parts bin carried over from the Sharks. It is the only L98 year to have forged pistons.
It is also the only L98 year with a 2-piece rear main seal.
It is also the only L98 year with a 2-piece rear main seal.
Last edited by vader86; Jan 9, 2006 at 10:54 AM.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Originally Posted by vader86
They have TRW forged pistons in a 2-bolt block, the pistons were leftover parts from the GM parts bin carried over from the Sharks. It is the only L98 year to have forged pistons.
It is also the only L98 year with a 2-piece rear main seal.
It is also the only L98 year with a 2-piece rear main seal.
Melting Slicks
Joined: Mar 2001
Posts: 2,149
Likes: 303
From: Timra, Sweden
Originally Posted by CFI-EFI
The only difference between a 1984 and a 1985 long block is the camshaft, and THAT isn't a big difference. Forged pistons, two bolt mains.
RACE ON!!!
RACE ON!!!
Melting Slicks
Joined: Mar 2001
Posts: 2,149
Likes: 303
From: Timra, Sweden
Originally Posted by CentralCoaster
Do the iron head motors from first half of 86 production have 2pc rear mains? Are the early 86 motors exactly the same as the 85?
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by JoBy
Are you sure? According to my book 1984, 1985 and 1986 has the same cam specification, at least the same lift.
1984 Camshaft GM# 14088843
1985-1986 Camshaft GM# 14094728
I imagine aftermarket, replacement parts, suppliers might use the same cam for all three years. By now, GM may also. That is ONE advantage of old literature. It would not surprise me to see both of those part numbers superseded by the same, third, replacement part number.
RACE ON!!!
PS. All 1986 SBCs have one piece rear main seals. All L98s are 2 bolt mains.
Team Owner
Joined: Sep 2001
Posts: 62,137
Likes: 1,727
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Originally Posted by CentralCoaster
Do the iron head motors from first half of 86 production have 2pc rear mains? Are the early 86 motors exactly the same as the 85?
We have cast pistons.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Then I suppose the early 86 EGR system is also the same as 85.. and therefore, the shorty headers also the same (no external tube).
Is the rest of the early 86 exhaust the same as 86-up though? IE, has precats, and 2-bolt flanges for the cats?
Is the rest of the early 86 exhaust the same as 86-up though? IE, has precats, and 2-bolt flanges for the cats?
Team Owner
Joined: Sep 2001
Posts: 62,137
Likes: 1,727
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
We do have an external tube from #8 to the back of the intake manifold on 86E.
Exhaust is all the same from 86E-91, neglecting muffler changes.
Exhaust is all the same from 86E-91, neglecting muffler changes.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Interesting, so you've got egr heads and external egr. So if you ever upgraded to headers you could put an 85 base, or just 85 egr valve on there, and not worry about the ugly tube.
