lumij3

I am about to buy a COPO LS6 engine stamped with GM3963512. Can anyone give me some info about these engines?

Thanks

Luis

joewill

that is the block casting number that is cast and not stamped on the back of the block, find out the date code on the flange behind the distributor, and what is stamp on the front pad in front of the passenger side head? also confirm that it has 4 bolt main caps and square port heads.

other than that, as far as I know there is no such thing as a COPO LS6?

lumij3

Date code is K-12-9. No engine code pad. 2 bolt main block. Scat forged stroker crank (unknown stroke), SRP forged domed pistons. I was told this motor was 0.060 over. Comes with Moroso 7 qt oil pan, Edelbrock aluminum timing cover, and aluminum long water pump. Does have one collapsed lifter. Excellent cross-hatch pattern in cyls, no ridge. Bearings look like new.
So how much would it resonable to pay fo it.?

Mike Ward

The 512 block was used for just about everything, not just LS6. What makes you think it's a 'real' one?

lumij3

I do not know much about COPO engines or engine blocks. The seller mention that this is a COPO block. I just want to know what to ask for to verify that it is a COPO block. And actually, what is a COPO block?

gbvette62

COPO LS6???

The 512 block was used from 69-71, as both a 427 and a 454. The 512 came in both 2 and 4 bolt versions. The LS6 version of it would have had 4 bolt mains.

K-12-9 was cast on Nov. 12, 1969, so this block could potentially be a 427 or 454.

What's reasonable for this engine, I don't know. It doesn't sound like an LS-6 to me, and even if it is (was?), with all of the mods to it, it no longer is one. So in the end, I guess that it comes down to how much is a broken, hot rodded big block worth to you?

Mike Ward

No such thing.

gbvette62

Central Office Production Order. Orders for vehicles with equipment outside of what was normally available as a Regular Production Option (RPO), had to go through the "Central Office" for approval for production. These orders were COPO's.

The only COPO use of the 512 block that I'm aware of, would have been the 69 Chevelle and Camaro 427 COPO cars.

scottyp99

I don't think there is any such thing as a "COPO LS6". Unless they mean it is an LS6 that came in a COPO car. COPO stands for Central Office Production Order. All it was, was a way of ordering something that didn't come as a RPO (Regular Production Order) kind of a back door way of ordering a car with an option that didn't exist. For instance, if you went into the Chevy dealer in 1970, and said "I want an Impala station wagon with the L88 engine." the dealer would say "They don't come with that engine, it's not an option." Then you open a suitcase full of 100 dollar bills, and the dealer says "We can do a COPO!" meaning, of course, that you can have your car built however you want if you have the money. This may not be EXACTLY how it works, but it is how I understand that it generally used to work.

joewill

you don't know the numbers on the engine code pad, or the pad is blank? if blank and factory broach marks then it is worth alot to someone looking for that date LS5.. add 1000$, someone will pay alot for a factory broached blank pad. I expect the real truth is that it was wiped by a rebuilder and not worth any premium.

with 2 bolt mains, it is not a LS6 and the 69 copo camaro cars were all 4 bolt main 427s and probably were not built that late in 69.. that engine could have gone in a real late 69, but most likely it is a 70 model year. either way, it is not a COPO and is not a LS6. the internals of the engine may indeed put out more HP than a factory LS6..

a factory LS6 had square port heads, 4 bolt mains and would have been stamped with a chevelle stamp.

look on EBAY, the bare blocks are going to about 1500 and complete engine maybe 2500. as said above, it is probably worn out and the owner is either ignorant ( most likely ) or trying to defraud you. the bigger engine houses try to sell bare blocks for 3500, don't know if they get that much though.

if you don't know the stroke, then you don't even know the displacement?

d555

It's a 2-bolt .060 over used MK4 block, the rest are all used aftermarket parts. A LS6?... only in someones dream.:

What heads? or is this a short block only? Put your wallet away, nothing good here. The only one who will be smiling after the transaction is the seller. Buying BS never turns out well.

That said... the parts all have value to the right person. Now if you had the correct LS6 rect. port heads and Intake!? Soooo...what heads? What does he want for the motor?

Dave

lumij3

No heads. Short block only. He wants $1500.

Easy Mike

Tell him he can keep it.

Mike Ward

Fixed it for you.

69 Chevy

At .060" over bored already, used up is right. Even if I had 1500 bucks just burning a hole in my pocket, I'd look elsewhere. Saying a 2 bolt block is a COPO '69 tells me he thinks you're a newb who will believe anything. Pass.

BOSTONCAMARO

I agree, if it was a clean block i.e. was usable at .60 over and was say $300-$500 it could be worth it for a street motor, but .60 over is at end of its long life...unless you have it sleeved etc, which of course would kill its dollar value as something to resell...but again could be good for a nice street car

69 Chevy

Check your decimal placement, dude.

joewill

yes, read this carefuly.. DO NOT buy a .060 used block unless you are desparate for that particular date code and have been looking for years. you will have maximum build costs, much higher likelyhood of other issues ( cracks, line bore out, needing heli coils, needing all sleeves, etc...)

anything that is already .060 over has lived a very long and hard life..