LT4 HotCam Shift Points?
Thread Starter
Racer
Joined: Mar 2002
Posts: 388
Likes: 0
From: Acworth Georgia
LT4 HotCam Shift Points?
Guys,
Here's the info, stock LT1 crate motor, LT4 HotCam, Crane 1.6RR's, K&N, MSD 6A, NGK's, Taylor wires, Hooker LT's, B&B TriFlo cat-back, 6spd.
What should I be shifting her at?
Here's the info, stock LT1 crate motor, LT4 HotCam, Crane 1.6RR's, K&N, MSD 6A, NGK's, Taylor wires, Hooker LT's, B&B TriFlo cat-back, 6spd.
What should I be shifting her at?
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
Re: LT4 HotCam Shift Points? (Hi-psi)
IMO you need stronger springs to go any higher then the 5800 rpm redline of the LT1. The LT4 has stronger springs and it has lighter valves. So to raise the redline you need springs.
Thread Starter
Racer
Joined: Mar 2002
Posts: 388
Likes: 0
From: Acworth Georgia
Re: LT4 HotCam Shift Points? (93 ragtop)
IMO you need stronger springs to go any higher then the 5800 rpm redline of the LT1. The LT4 has stronger springs and it has lighter valves. So to raise the redline you need springs.
Thread Starter
Racer
Joined: Mar 2002
Posts: 388
Likes: 0
From: Acworth Georgia
Re: LT4 HotCam Shift Points? (Hi-psi)
After roaming around over on CamaroZ28.com , it seems all the F-body guys with stock heads are shifting between 6300-6500. One guy posted a dyno chart showing the cam was still making constant power and not falling off up to about 6700-6800. Thoughts?
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
Re: LT4 HotCam Shift Points? (Hi-psi)
6400
FWIW, I shift mine at 6600 (and sometimes 6800 :D) but I have the lighter LT4 valves and swapped to Crane valve springs (~120# closed / ~340# open). On the dyno my hp peak is at 6400.
FWIW, I shift mine at 6600 (and sometimes 6800 :D) but I have the lighter LT4 valves and swapped to Crane valve springs (~120# closed / ~340# open). On the dyno my hp peak is at 6400.
Team Owner
Joined: Mar 2001
Posts: 30,847
Likes: 293
From: Boston, Dallas, Detroit, SoCal, back to Boston MA
Re: LT4 HotCam Shift Points? (96GS#007)
Don't go above 6200 with the stock LT1 the bottom end can't take it.
http://vette.ohioracing.com/majmods.html
That's one of the reasons I'm holding off on the hotcam.
http://vette.ohioracing.com/majmods.html
Gee what's that knocking noise?. The motor blew right at the finish line of an autocross event in the middle of nowhere Michigan. Of course right at the height of race season and one day after I had just spent big bucks on 4.09 gears. I broke my vette and Al Murrel, a fellow competitor, hauled me home. Thanks Al! You have an invitation to co-drive my car! Also, I owe thanks to John & Debbie Fessler, and Paul Wines for hauling my tire trailer home.
A word of warning, 6200 RPM is the Limit for a stock LT1. I set my rev limiter to 6400 RPM against the advice of Justin Vandersall (Superman Vette Mechanic). The motor lasted for maybe 10 revs at that limit. The LT1 rod caps can not take high RPMs. The cap on the number six cylinder stretched. The piston began to slap against the head when down revving. As soon as the engine cooled the bearing spun.
A word of warning, 6200 RPM is the Limit for a stock LT1. I set my rev limiter to 6400 RPM against the advice of Justin Vandersall (Superman Vette Mechanic). The motor lasted for maybe 10 revs at that limit. The LT1 rod caps can not take high RPMs. The cap on the number six cylinder stretched. The piston began to slap against the head when down revving. As soon as the engine cooled the bearing spun.
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
Re: LT4 HotCam Shift Points? (BrianCunningham)
Don't go above 6200 with the stock LT1 the bottom end can't take it.
http://vette.ohioracing.com/majmods.html
Gee what's that knocking noise?. The motor blew right at the finish line of an autocross event in the middle of nowhere Michigan. Of course right at the height of race season and one day after I had just spent big bucks on 4.09 gears. I broke my vette and Al Murrel, a fellow competitor, hauled me home. Thanks Al! You have an invitation to co-drive my car! Also, I owe thanks to John & Debbie Fessler, and Paul Wines for hauling my tire trailer home.
A word of warning, 6200 RPM is the Limit for a stock LT1. I set my rev limiter to 6400 RPM against the advice of Justin Vandersall (Superman Vette Mechanic). The motor lasted for maybe 10 revs at that limit. The LT1 rod caps can not take high RPMs. The cap on the number six cylinder stretched. The piston began to slap against the head when down revving. As soon as the engine cooled the bearing spun.
That's one of the reasons I'm holding off on the hotcam.
http://vette.ohioracing.com/majmods.html
Gee what's that knocking noise?. The motor blew right at the finish line of an autocross event in the middle of nowhere Michigan. Of course right at the height of race season and one day after I had just spent big bucks on 4.09 gears. I broke my vette and Al Murrel, a fellow competitor, hauled me home. Thanks Al! You have an invitation to co-drive my car! Also, I owe thanks to John & Debbie Fessler, and Paul Wines for hauling my tire trailer home.
A word of warning, 6200 RPM is the Limit for a stock LT1. I set my rev limiter to 6400 RPM against the advice of Justin Vandersall (Superman Vette Mechanic). The motor lasted for maybe 10 revs at that limit. The LT1 rod caps can not take high RPMs. The cap on the number six cylinder stretched. The piston began to slap against the head when down revving. As soon as the engine cooled the bearing spun.
That's one of the reasons I'm holding off on the hotcam.
I've always heard the LT1 is limited to 6100 due to valvetrain stability (with original springs/valves/etc vs the original poster's LT4 springs). Once one gets past the valvetrain issue, 6400rpm is the limit for '92-'95 LT1s due to piston ring flutter. Dan Parker did some research and the '96 LT1s have the same piston rings as the LT4. The later rings have twist to promote sealing at high rpms.
FWIW :)
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
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
Team Owner
Joined: Mar 2001
Posts: 30,847
Likes: 293
From: Boston, Dallas, Detroit, SoCal, back to Boston MA
Re: LT4 HotCam Shift Points? (96GS#007)
I know a couple of guys who have spun rod bearings.
are the rod bolts the same?
I've heard that's why the caps stretch.
[Modified by BrianCunningham, 10:56 PM 2/4/2004]
are the rod bolts the same?
I've heard that's why the caps stretch.
[Modified by BrianCunningham, 10:56 PM 2/4/2004]
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
Re: LT4 HotCam Shift Points? (BrianCunningham)
I know a couple of guys who have spun rod bearings.
are the rod bolts the same?
I've heard that's why the caps stretch.
[Modified by BrianCunningham, 10:56 PM 2/4/2004]
are the rod bolts the same?
I've heard that's why the caps stretch.
[Modified by BrianCunningham, 10:56 PM 2/4/2004]
Maybe the over-the-counter GM replacement parts are identical but factory installed pieces aren't?
Team Owner
Joined: Mar 2001
Posts: 30,847
Likes: 293
From: Boston, Dallas, Detroit, SoCal, back to Boston MA
Re: LT4 HotCam Shift Points? (96GS#007)
replacement vs original makes sense.
GM puts LT4 rods in thier crate motors, so that makes a lot of sense.
Need to find out what the original part #'s were.
GM puts LT4 rods in thier crate motors, so that makes a lot of sense.
Need to find out what the original part #'s were.
Team Owner
Joined: Mar 2001
Posts: 30,847
Likes: 293
From: Boston, Dallas, Detroit, SoCal, back to Boston MA
Re: LT4 HotCam Shift Points? (BrianCunningham)
From:
http://www.automotiverebuilder.com/ar/ar99928.htm
From:
http://www.grandsportregistry.com/lt1vslt4.htm
Wish I knew about the seal when I did mine! :crazy:
http://www.automotiverebuilder.com/ar/ar99928.htm
RODS
350 - The original LT1 came with regular forged 350 rods, that were shot peened for localized hardness under the head of the bolt and nut. Powdered metal rods were phased in for the Corvette around 1994 and used in all of the LT1 engines by 1995. GM made the change because the powdered metal rods were cheaper to make and were much stronger than the GM high performance "pink" rods. In fact, they are supposed to be good for up to 450 hp. They are machined at the parting line so they can be reconditioned.
350 - The original LT1 came with regular forged 350 rods, that were shot peened for localized hardness under the head of the bolt and nut. Powdered metal rods were phased in for the Corvette around 1994 and used in all of the LT1 engines by 1995. GM made the change because the powdered metal rods were cheaper to make and were much stronger than the GM high performance "pink" rods. In fact, they are supposed to be good for up to 450 hp. They are machined at the parting line so they can be reconditioned.
http://www.grandsportregistry.com/lt1vslt4.htm
SPECIALLY MACHINED CRANKSHAFT
The crank itself was improved via something called undercutting and rolling. Undercutting is the machining of a groove into the corner of a journal. Though this would seem to weaken the crank at that point, it actually makes it stronger where tensile stress is most likely to cause sudden failure. Rolling the undercut introduces compressive stress to the area. This makes it more durable, because potentially catastrophic tensile stress generated during high RPM operation must first overcome the compressive stress before that area of the crank is subjected to tension. Undercutting, a groove cut into the corner of a journal, looks counterintuitive, but makes a crankshaft stronger where tensile stress is most likely to cause failure. By undercutting and then rolling it, compressive stress is introduced. Tensile stress during high-speed operation first has to overcome the compressive stress before there's any tension on the joint. And as tensile stress is what breaks crankshafts, undercutting and rolling make the crankshaft stronger.
DUAL-MASS FRONT TORSIONAL DAMPER
Tuned for high engine speed, also helps reduce stress on the crankshaft. LT1 pt.# 10128489 and LT4 pt.# 12551486
NODULAR IRON MAIN BEARING CAPS
These LT4 components are considerably stronger than their LT1 counterparts and resist failure at higher RPM's.
TEFLON REAR CRANK SEAL
Offers improved durability over the standard LT1 crank seal.
The crank itself was improved via something called undercutting and rolling. Undercutting is the machining of a groove into the corner of a journal. Though this would seem to weaken the crank at that point, it actually makes it stronger where tensile stress is most likely to cause sudden failure. Rolling the undercut introduces compressive stress to the area. This makes it more durable, because potentially catastrophic tensile stress generated during high RPM operation must first overcome the compressive stress before that area of the crank is subjected to tension. Undercutting, a groove cut into the corner of a journal, looks counterintuitive, but makes a crankshaft stronger where tensile stress is most likely to cause failure. By undercutting and then rolling it, compressive stress is introduced. Tensile stress during high-speed operation first has to overcome the compressive stress before there's any tension on the joint. And as tensile stress is what breaks crankshafts, undercutting and rolling make the crankshaft stronger.
DUAL-MASS FRONT TORSIONAL DAMPER
Tuned for high engine speed, also helps reduce stress on the crankshaft. LT1 pt.# 10128489 and LT4 pt.# 12551486
NODULAR IRON MAIN BEARING CAPS
These LT4 components are considerably stronger than their LT1 counterparts and resist failure at higher RPM's.
TEFLON REAR CRANK SEAL
Offers improved durability over the standard LT1 crank seal.
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
Re: LT4 HotCam Shift Points? (Hi-psi)
I still believe it would be worthwhile to consider a different spring if you are going to rev to 6300 rpm. The LT4 may be able to do it with its lighter valves, but the LT1 valve would be better suited to a stronger spring. Springs are not that expensive, and a lot of damage could occur if it is too weak.
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
Re: LT4 HotCam Shift Points? (BrianCunningham)
Did some more digging thru the fiche last night. The rod bolts are the same p/n for the LT1 ('92-'96) & LT4.
No proof, but I buy in to the theory that the over-the-counter parts are LT4 (whether LT1 or LT4). Those that have had problems with rods and bearings, likely experienced them with pre-'94 original LT1 parts.
No proof, but I buy in to the theory that the over-the-counter parts are LT4 (whether LT1 or LT4). Those that have had problems with rods and bearings, likely experienced them with pre-'94 original LT1 parts.
