rebuilding my LS6 - Chevelle Tech
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  • 3 Post By Chris27
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post #1 of 8 (permalink) Old Apr 27th, 17, 4:13 AM Thread Starter
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rebuilding my LS6

going to start pulling engine this weekend. engine is using a lot of oil and is not running good. I hate to do it but I need to maintain the car. thinking about lowering compression for todays gas and possibly going to a solid roller instead of flat tappet. what are your thoughts on lowering compression and going to a solid roller? i want the car to sound correct. This car gets driven and enjoyed, thats why i'm thinking about lowering the compression to around 10 to 1 or so. thanks for your thoughts. Jim

1970 LS6, unrestored, 4 speed,special ordered orange

1972 Nova, 557ci, Legend 5 speed, FiTech EFI 8, lemons Headers, 723hp/690tq
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post #2 of 8 (permalink) Old Apr 27th, 17, 10:29 AM
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Chris
 
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Re: rebuilding my LS6

I'd almost build a different 454 for the car and leave the LS6 alone. If you do rebuild it make sure if the block has to be decked that the numbers don't get "erased". Assuming it's a numbers matching car. It's only original once.
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post #3 of 8 (permalink) Old Apr 27th, 17, 10:52 AM
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JIM
 
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I doubt it truly measures 11.0 now. So I wouldn't lower it. I'd just get the right cam to make it work the best.

Jim.
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post #4 of 8 (permalink) Old Apr 27th, 17, 11:45 AM
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Mark
 
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Re: rebuilding my LS6

I think you really need to take it to a shop and tear it down to see what you have. I would look at it as a freshen up. I'm a fan of roller cams, and I would change to one. I wouldn't go too heavy on the machining if it isn't truly needed, and of course a valve job. That way you would feel better about not voiding the original LS6 feel.
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post #5 of 8 (permalink) Old Apr 27th, 17, 12:03 PM
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Tony
 
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Re: rebuilding my LS6

for something as cool/rare as a real LS-6 that needs a freshening up/basic maintenance for a 47 year old car, i'd look into a custom cam from Chris Straub or Mike Jones.

you should be able to bleed off enough compression to run on 91ish octane pump gas....and get a cam custom matched to your heads/engine/drivetrain.

going roller obviously decreases the risk of FT cam failure on break in. I don't fear breaking in a FT cam today like many do.....but I don't have an original LS6.

just my two cents.....
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post #6 of 8 (permalink) Old Apr 27th, 17, 12:21 PM Thread Starter
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Re: rebuilding my LS6

thanks guys. the engine is going to a builder to be disassembled and inspected. Not sure what they will find but it has to be fixed. The block will not be decked. Possible bore? Dunno. I just hope this doesn't hurt the value of the car too bad, but it is still the born with engine. JIm
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1972 Nova, 557ci, Legend 5 speed, FiTech EFI 8, lemons Headers, 723hp/690tq
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post #7 of 8 (permalink) Old Apr 27th, 17, 6:51 PM
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Re: rebuilding my LS6

Jim, Chris Straub has a solid roller cam that will sound just like the original. I used one in a customer's car, and Albert put one in his COPO 427. THe lift is mild, like .540/.560 so it's easy on the valve train. You'll need matching springs with good retainers and locks, new pushrods, and roller rockers. I used Scorpions on the LS6 I did, I think... You'll need longer rocker arm studs, and short polylocks for the exhaust side, but it will clear the stock valve covers. You'll also need to remove the pan from the bottom of the intake as the number 3 exhaust lifter won't clear with it on. Not a big deal.
Let me know if you have more questions. I'm sure Straub can put together a whole package for you.

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post #8 of 8 (permalink) Old May 6th, 17, 10:39 AM
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Ole
 
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Re: rebuilding my LS6

Quote:
Originally Posted by Chris27 View Post
I'd almost build a different 454 for the car and leave the LS6 alone. If you do rebuild it make sure if the block has to be decked that the numbers don't get "erased". Assuming it's a numbers matching car. It's only original once.
I recently pulled the "numbers" L78 block from my '69 SS Chevelle and replaced it with another JD-coded ('69 396/375 hp/4 spd) block with matching 840 heads and 163 intake. I fired the new engine off on Thursday with stock Speed Pro (11.0:1) L2242+.060 pistons, dimple rods, .010/.010 cross-drilled GM steel crank, Howards flat tappet solid lifter cam (stock L78 grind + .020 lift) and freshened heads with Milodon stainless valves and NOS GM valve springs. Short block was balanced and honed with torque plates. The block was not surfaced, thereby leaving the numbers intact. Quench is in the .035-.045 range using steel shim head gaskets.

The (Speed Pro) rings seated quickly and the engine sounds strong. A peek under the valve covers reveals all rockers opening at what appears to be full valve lift.

But the best part of this story is that the "numbers" block and date matched 291 heads are now getting a well-deserved rest.
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