Chadborne

Since buying a 70 convertible w/454 HP recently, I have seen numerous times where it is referred to as LS5 and LS6. I originally thought it to be LS5. In overhauling the engine, I found that I had to replace one of the pistons. Hard to find just one, but finally did, but it was listed for a 1971 LS6 454 HP, model L2399F w/.095 Dome. Is it a LS5 or LS6 and why would the piston be shown for a 1971?

Durango_Boy

Is the car a numbers matching original? I wonder if maybe there was an engine change in it's past. Can you get the block numbers and we'll see if they match the car.

Chadborne

I already checked and the numbers do match.

MEAN72

The 450-horsepower, LS6 454 never made it into the Corvette for '70- , but was an option in the Chevelle. Then the LS6 showed up as an option for the '71 Corvette, but was de-tuned to 425 horsepower. Even more exotic was the LS7 454, rated at 465 horsepower. It never made it into any Corvettes officially.

The 1970 Corvette had an LS5 454 cu. inch engine ratred at 390 hp. It had hydraulic lifters. I believe the LS6 is a mechanical lifter engine.

BigBlockTank

I have a 1971 LS5 engine that has 365HP. Did a LS5 have 390HP in 1970? I ran the numbers on my motor and found it to be from a 71 4 speed Corvette. If you're right, I'm wrong, along with a bunch of documentation, and I'm lost.

Little Mouse

The 70 chevelle LS6 454/450 HP engine was a closed chamber rectangle port iron head, 11.0 compression. Only big block in the 70 vette was the 390 HP LS5, two bolt mains, iron closed chamber heads, hydraulic cam. 1971 vette had two big block options your 365 HP 454 compression was dropped on it for 1971 by using open chamber iron heads.Then there was the LS6 454/425 hp, 4 bolt block, steel crank, forged pistons, aluminum open chamber rectangle heads, mechanical cam. 1971was the only yr for it.

DARROW

What is the difference between the open and the closed chamber head. Or should I say what am I looking for, to tell the difference.

jnb5101

open heads have the area around the plug relieved, therefore the volume is increased and the cr is reduced (for unleaded gas). some say the open chamber promotes faster and more even flame burn. but to increase cr a domed piston must be used, and some say that interferes with flame burn.
jeff

Little Mouse

Closed chamber has a bathtub looking shape with a strait up and down
wall to the chamber close to the valves, open chamber has that same wall laid over angling away from the valves. open chamber helps unshround the valves better on that side of the valve allows the cylinder to pull air around the valves better.

shmoky

I have the same pistons and my motor is a 72 454 LS-5 (MKIV).

shmoky