Your right..... 71 ls6 was open chamber lower compression 425hp. I'm pretty sure 71 was the last year for the ls6. The ls7 was open chamber, rated at 465 hp and was only offered over the counter well into the 80's possibly into the 90's. I know someone who bought several ls7's over the counter throughout the mid to late 80's

yes,my moms 71 vette has a ls6,,i think the tag was like 435 hp and 500 ft lbs of tq..ill have to look at it again..

yep,,i put a ls7 crate motor in my 78 trans am...that thing would carry the rt front tire when you wacked 2nd gear..i hear the engine was way over 500 hp..

I cant see how those pistons, with a 108cc head, and 4.25 stroke in 4.25 bore, would net only 9:1. Without knowing the deck height or gasket thickness, Id say they are probably closer to 10:1.

Actually I believe those pistons had 14cc domes. If the heads been surfaced, and block been surfaced, you might have a 10.25-10.5:1 engine there. That piston was originally meant for the 1971 LS6, but to be used with the open chamber head. The 1970 LS6 used the closed chamber heads, but an even larger dome than the pistons you have, which netted around 11.25:1.

I wouldn't be surprised if you listed those heads on fleabay, and get some good money out of them to a guy doing a restoration on a Chevelle or Vette. Then get some aluminum heads, better modern rods and pistons. Those are some heavy rods and pistons you have there.

I would have to check the number on mine but that piston looks like the same dome (hard to tell exactly) which is an L2349F which has a volume of 30.6cc. depending on if the block is decked, head cut, etc it would run 11.5 to 12:1 or so. the same piston was used in a lot of them with the open chamber head which brings it down to around 10:1 depending on the head used. as we all know chevy head cc is all over the place. mine was probably equiped with open heads when new but had a set of closed heads from a 1965 425hp 396 corvette. I sold the heads and paid for my entire engine rebuild so that worked out pretty good.

I think those are like the 2399 speed pro /trw with smaller dome

What I have found after sifting through a hundred Chevy forums is, a replacement for the LS6 piston (in over sizes too) is like you all said, TRW/Speed Pro 2399 / .095 tall dome. If I remember right they fill something like 13cc.
All I can really say is someone put a lot of time and effort into this motor and then ran the piss out of it so there has to be something there. I spun the motor over a few times before I took it apart and nothing hit. When I got it apart I also inspected to see if anything made contact and couldn’t find anything. Something did happen one time to a valve cover. Looks like one of the pushrods tried to come through it at some point but again there is nothing inside that looks like it did the damage to the valve cover so maybe it was old damage.
Anyone know how far down the oil in the pan is below the pan rail? Need to make a dip stick and need the full level.

M/T, hate to say it but I’m not a fan of aluminum heads in a boat. I see what the water around here does to my intakes and want no part of it when it comes to heads. Not only that but if this motor didn’t come like it was I may have stroked it but I would have not nearly done all the stuff that’s been done to it. The boat is lite and small enough that it doesn’t require the same hp for say an offshore. It’s even a little scary now. But like I said before, I can’t let this motor go. If for just the cool factor alone. I was almost prepared to accept a Hp loss to keep it after just reading the run #’s off the block. If I can get this one together I will then have a Mark IV 454 (496 stroker) and a 427 (stroked to who knows what at the moment) complete roller motors from the floating wrist pins to the roller rocker. This is stuff I dreamed about only 20 years ago.
I know some of you guys have unlimited budgets and this is old news but to me when I started to open up this motor and finding out what was inside it was the best Christmas I ever had. I took 5 years to go from a Mercruiser 330mei 454 to a 420hp 454 then to a 4 bolt main 496 stroker roller motor. After all the rebuilds the only thing left from the original 454/330mie is the oil filter mount. The gen V 454 in the Biese now is a great motor and in perfect condition. I have a note pad in front of me now of all the things I wanted to buy for it over the winter so I could stroke it and a couple other things. After totaling up the money I didn’t think it was going to get done this year. Then to have this motor basically fall in my lap I’m more than happy to get it back together just like it was raced and drop it in the 54 year old drag boat. I’ll just have to accept that the wife will never get in it even if it’s on the trailer. The kids will love it though even though the wife will only let me take one out at a time just in case. LOL.

[I]What I have found after sifting through a hundred Chevy forums is, a replacement for the LS6 piston (in over sizes too) is like you all said, TRW/Speed Pro 2399 / .095 tall dome. If I remember right they fill something like 13cc.[\I]

See, and your answer was right here on oso waiting for you!

True but I'm kind of an information slut and I've been known to slum a little to get what I need.

Block has been taken off the machine shop. Has to be done. They used gapless rings the last time and it looked like the ring and the support ring under it, the gaps lined up and dug into the cylinder wall is the best I can come up with. I didn’t want to have it cut and damned if I can afford it but now is the time to do it. While there Ken (the owner of the shop I take my blocks to who knows me by name like you know your neighbor ….scary how many times I’ve been there) confirms that one of the cylinders has been sleeved. He also mentions that back in the day the big thing was to have the longest rod you could fit in a motor. Not necessarily for stroke either. Wasn’t positive why else they did it besides getting the piston to the top of the cylinder.
The more and more I get into this motor the more it’s starting to look like it should be a museum piece on old school bad ass.
Today I spent 5 minutes looking over the intake and heads. Everything is ported and polished. Double springs with a damper spring on the valves. Heads have been cut for nylon valve seals (when I have 4 packs of umbrella seals in stock, go figure).
Just when I think I got this motor figured out it throws me another curve ball. I was starting to think that someone built this motor in their garage for a strret rod or race car and they still may have at some point but…. When I took it apart it looked like it has never been taken apart before. Gaskets and RTV were perfect and there was not a single mismatched bolt or nut on the whole motor and for the most part they were all allen heads (intake, oilpan, fuel pump). Even the intake has 7-11-69 (July 11 1969) stamped on the inside. Then ……… I notice the flywheel. It’s an inboard flywheel that the starter mounts to the bellhousing. Thought about flipping the ring gear over on the other side but it’s not cut for a gear and there would be almost nothing left for a shoulder for the ring gear (.024”) to be centered on. And even if done according to the 454’s flywheel (pictured on left) the ring gear still won’t be in the right place.