1971 LS5 Engine Recreation
Thread Starter
Racer
Joined: Aug 2011
Posts: 493
Likes: 217
1971 LS5 Engine Recreation
I was contracted by a customer to build a mild 454 for his 68 Vette, I came across a 512 block 1970 vintage along with a set of 820 heads, there was a Vette pan pan also but it was just to rough to use. So i built a .030 454 with a cast crank, factory 3/8 rods with ARP bolts, Speedpro pistons, a mild hyd cam, came in around 9.3 compression, LS6 rocker arms, factory 1973 cast iron intake, Harold Bettes Q-Jet. I enjoy these stock type builds its a nice change. Excellent idle with lots of vacuum. I ended up with 462 HP @ 5600 RPM with 532 TQ @ 3500.
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
When I saw your title I went
Why would anybody want that low compression 365 hp pig, but with your higher compression and cam you made @ 50 -100 hp over stock depending on who you talk to.
The 365 might have actually been as much as 50 hp higher because of rating changes in the early 70's.
Last year I also rebuilt a Vettes 454 and I went to @10.0 c/r and I think that the final installed cam was h-flat in the 238/248 with headers and free flowing exhaust. 4 speed car. The owner wanted all forged and we also went internally balanced. It was a night and day difference from when I drove it to the shop to when we finished it
Why would anybody want that low compression 365 hp pig, but with your higher compression and cam you made @ 50 -100 hp over stock depending on who you talk to.
The 365 might have actually been as much as 50 hp higher because of rating changes in the early 70's.
Last year I also rebuilt a Vettes 454 and I went to @10.0 c/r and I think that the final installed cam was h-flat in the 238/248 with headers and free flowing exhaust. 4 speed car. The owner wanted all forged and we also went internally balanced. It was a night and day difference from when I drove it to the shop to when we finished it
Melting Slicks
Joined: Jun 2003
Posts: 2,802
Likes: 241
From: Niles, MI
Very cool! This engine is going into my buddy's '68; which was originally a Tuxedo Black over Medium Blue L-71. It's an L71!
This engine is going into my buddy's '68; which was originally a Tuxedo Black over Medium Blue L-71. It's an L71!
Thread Starter
Racer
Joined: Aug 2011
Posts: 493
Likes: 217
When I saw your title I went
Why would anybody want that low compression 365 hp pig, but with your higher compression and cam you made @ 50 -100 hp over stock depending on who you talk to.
The 365 might have actually been as much as 50 hp higher because of rating changes in the early 70's.
Last year I also rebuilt a Vettes 454 and I went to @10.0 c/r and I think that the final installed cam was h-flat in the 238/248 with headers and free flowing exhaust. 4 speed car. The owner wanted all forged and we also went internally balanced. It was a night and day difference from when I drove it to the shop to when we finished it
Why would anybody want that low compression 365 hp pig, but with your higher compression and cam you made @ 50 -100 hp over stock depending on who you talk to.
The 365 might have actually been as much as 50 hp higher because of rating changes in the early 70's.
Last year I also rebuilt a Vettes 454 and I went to @10.0 c/r and I think that the final installed cam was h-flat in the 238/248 with headers and free flowing exhaust. 4 speed car. The owner wanted all forged and we also went internally balanced. It was a night and day difference from when I drove it to the shop to when we finished it
Race Director
Joined: Jan 2000
Posts: 13,011
Likes: 2,250
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Very cool! This engine is going into my buddy's '68; which was originally a Tuxedo Black over Medium Blue L-71. It's an L71!
This engine is going into my buddy's '68; which was originally a Tuxedo Black over Medium Blue L-71. It's an L71!Your buddy is going to be in for a nice surprise once he stuffs his foot in it.
Mark...you just keep knocking out the hits! Congratulations!
JIM
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Racer
Joined: Aug 2011
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Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I'd also want to know what cam he used. because the customer is always right we ended up with this crane cam, but the ci was 468 with an over bore.
Performance usage, good mid and upper RPM torque
and HP, bracket racing; Heavy, Pro ET, Super ET, etc.,
auto trans w/3000+ converter, oval track; Street
Stock, Enduro, Hobby, etc., 3/8-1/2 mile,10.0 to 11.5
compression ratio advised.
Saturday Night Special 3000-
6600
134551* 236/246 110 .553 .571
Performance usage, good mid and upper RPM torque
and HP, bracket racing; Heavy, Pro ET, Super ET, etc.,
auto trans w/3000+ converter, oval track; Street
Stock, Enduro, Hobby, etc., 3/8-1/2 mile,10.0 to 11.5
compression ratio advised.
Saturday Night Special 3000-
6600
134551* 236/246 110 .553 .571
Le Mans Master
Joined: May 2006
Posts: 9,993
Likes: 1,136
From: League City Tx
Solid power from such a mild combo.... (basically stock components)
That's more then we were able to make with our stock appearing/resto 396(408)...10-1 comp, 237/245 hyd roller, square ports, 163 intake... And we had a ton of money in that motor.
No doubt, yours is making twice the HP per dollar. No doubt it will scoot in a C3 if the car is setup right. Customer should be very happy.
That's more then we were able to make with our stock appearing/resto 396(408)...10-1 comp, 237/245 hyd roller, square ports, 163 intake... And we had a ton of money in that motor.
No doubt, yours is making twice the HP per dollar. No doubt it will scoot in a C3 if the car is setup right. Customer should be very happy.
Last edited by ajrothm; Sep 9, 2015 at 03:09 AM.
Thread Starter
Racer
Joined: Aug 2011
Posts: 493
Likes: 217
Solid power from such a mild combo.... (basically stock components)
That's more then we were able to make with our stock appearing/resto 396(408)...10-1 comp, 237/245 hyd roller, square ports, 163 intake... And we had a ton of money in that motor.
No doubt, yours is making twice the HP per dollar. No doubt it will scoot in a C3 if the car is setup right. Customer should be very happy.
That's more then we were able to make with our stock appearing/resto 396(408)...10-1 comp, 237/245 hyd roller, square ports, 163 intake... And we had a ton of money in that motor.
No doubt, yours is making twice the HP per dollar. No doubt it will scoot in a C3 if the car is setup right. Customer should be very happy.
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
What are the exact specs (primary rods, jets, power piston spring, size of idle down tubes, secondary rods and hanger, any extra air bleeds and anything else you can find out) on the carb? Do you have a graph of the A/F ratio?
Last edited by jnb5101; Sep 9, 2015 at 10:34 AM.
Thread Starter
Racer
Joined: Aug 2011
Posts: 493
Likes: 217
My air turbine doesn't fit on the Q-Jet, so we never dialed the carb in, the carb is highly modified, I didn't build the carb and have not opened it up so I can't answer your questions. I will ask the builder.
Melting Slicks
Joined: Jun 2003
Posts: 2,802
Likes: 241
From: Niles, MI
Racer
Joined: Jun 2009
Posts: 409
Likes: 3
From: St. James, NC
I was contracted by a customer to build a mild 454 for his 68 Vette, I came across a 512 block 1970 vintage along with a set of 820 heads, there was a Vette pan pan also but it was just to rough to use. So i built a .030 454 with a cast crank, factory 3/8 rods with ARP bolts, Speedpro pistons, a mild hyd cam, came in around 9.3 compression, LS6 rocker arms, factory 1973 cast iron intake, Harold Bettes Q-Jet. I enjoy these stock type builds its a nice change. Excellent idle with lots of vacuum. I ended up with 462 HP @ 5600 RPM with 532 TQ @ 3500.
I also choose Mark to build an engine for my 71. The engine will be replacing my numbers matching LS5, which is going into hibernation. It’s going to be a little hotter build that follows Mark’s 570hp recipe plus a roller cam. We’re going with a factory intake manifold and a Q-jet setup. It should look very similar to the LS5 that is coming out, but have monster torque and HP, can’t wait till it’s finished.
Take Care
Pat
Racer
Joined: Feb 2010
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