Any way to tell the difference between an 1970 LS5 and an LS6, if the original motor is no longer available and there are no known build sheets or docs. of any kind? I have a friend who has a 70SS he might part with. He has owned the car for about fifteen years and says he has no idea what the original motor was and doesn't care. It probably doesn't matter at this point, but was just curious. It may have been a 396 for that matter. Thanks

One thing that would guarantee it was not an LS6 or L78 is air conditioning. A/C was not available on those 2 engine options. Is it a tach equipped car? If so what is the red line?

Thanks for the reply. I will have to check the tach red line, or ask him. What would the red lines be for those three options?

What would the red lines be for those three options?

Redline for all low horse 396-350HP and LS-5 are 5,500RPM. Redline for all High Horse 396-375HP L-78 and LS-6 is 6,500RPM. Some of these cars had no tach, and at that point, inconclusive as to which engine you had, unless you can find the build sheet in the car. Good Luck!!!!

Jeff Dotterer
Dated Components
Diamond Restored Judge

Check how many fuel lines there are and when the car was built on the cowl tag.

Check how many fuel lines there are and when the car was built on the cowl tag.

What number of lines should it have? Different for the low horse and high horse cars?

No, but if it has an early build date, 12A or earlier, it's not an LS6, with 1 exception of an LS6 that has a November build date. A build date of 12C or later will pretty much garuntee it's not an L78 as that RPO was cancelled Dec. of 1969 and replaced with RPO LS6.

What number of lines should it have? Different for the low horse and high horse cars?


This can get complicated. First, we are assuming it is an SS454, Right? The LS5 will always have the return line for the longer #40768 fuel pump. So there will be two lines in the frame. An LS6 started production with a #40727 Short pump, which would not have a return, and therefore only one line in the frame. The LS-6 switched over to the #40768 and added the return line in most plants by Feb 1970, and Atlanta sometime in March. This would make it more likely it is an LS-6 if it has no return line, but not help settle the difference if it has the return line. Additionally, the 396-350HP also used the return line pump for the full year, and the L-78 used the one without the return untill the option was cancilled in favor of the LS-6.

Jeff Dotterer
Dated Components
Diamond Restored Judge

If the original motor is gone and you have no documents, how do you know you even have an orignal SS, more less a 454 SS?

If the original motor is gone and you have no documents, how do you know you even have an orignal SS, more less a 454 SS?


Oviously, you cannot know for sure. There are only things that will lead you to believe what it was, but definately no "smoking gun" without documents or a motor. The rear axle codes can also tell the difference between SS396 and SS454. You would also have to check this date against the production date of car, and still have the possibility that someone switched a correctly date coded rear in years ago. It can get very involved, and still only be a guess. Still worth checking the car, if only to know what is there.

Jeff Dotterer
Dated Components
Diamond Restored Judge

John,
I fully understand and appreciate your interest in determining which engine was installed in the car when it was built.
But, consider a couple of things.
First of all, for every car ever built, there is ONLY one original engine! If the original engine is gone, it's gone. Consider your options for a future engine and move forward.
Next, as time goes by, you will likely discover that a complete, unbutchered, solid, rust free car is more important. It will provide a better foundation to build on.
Also, does it have the original tranny? If not, then you also will have to locate another tranny.
Trying to return the car back as closely as possible to its original configuration may cost you more than to just build a nice engine and tranny. If it was a BB car, especially a 454 car, and you locate and build a nice, dependable 454 with all the correct brackets and hardware, you will have a VERY nice car that won't wreck your budget.
Last, if you can acquire the car (and its in solid condition) for a very good price, considering what it will cost to get it back on the road, BUY IT! These classic Chevelles just are not getting any cheaper and the 70 model is one of the most desireable versions!

Talk about some oddities, I would not expected that an LS-6 would have a CRU axle combination. It's an open rear end 3:31 from the factory. What a horror to drive with that rear end around with the 2:20 first gear M-22. I don't think that would of been much fun! Jeff, I assume a posi would of been the standard regardless the gear? What have you found to be the usual?

That is what my build sheet shows it came equipped with, weird combo for a performance car.

Jim

If the original motor is gone and you have no documents, how do you know you even have an orignal SS, more less a 454 SS?

Not to sound like a smart azz, but that is basically my original question. The current owner has owned it for 15 years. The previous owner had it for approximately the same amount of time. So there is ball park of 30 years, which takes us back to the late 70's. It may be a 4 or 5 owner. The current owner has no interest in weather it's a true SS, only that is the way he bought it and was told by the previous owner that is way he bought it. So to his knowledge it has been an SS for at least 30 years. Sure it could have been cloned then and probably would have been alot easier then with available wrecks and such. Anyway he has never looked for a build sheet and didn't really know what I was talking about when I asked him about it. He is not going to let me gut his car looking for one either. I would have to buy the car and then look. So I'm trying to gather all the info I can, because if I'm going to pay 15k for the car, I at least want a 15k car. Thanks for all the help. It is much appreciated.

You could not clone a Chevelle for that price now, if it is solid buy it and try not to break his hand giving him the money!!! jmo

Talk about some oddities, I would not expected that an LS-6 would have a CRU axle combination. It's an open rear end 3:31 from the factory. What a horror to drive with that rear end around with the 2:20 first gear M-22. I don't think that would of been much fun! Jeff, I assume a posi would of been the standard regardless the gear? What have you found to be the usual?

That is what my build sheet shows it came equipped with, weird combo for a performance car.

Jim

RPO G80 Positraction was only mandatory on 4.10 geared equipped LS6 cars. 3.31 geared cars were standard with a peg leg 3.31 unless RPO G80 was checked off on the order ticket.

I know of an Atlanta built Red/white LS6 M22 that has no posi.
Does the car have side terminal battery cables?
Do you have the VIN of the car handy? If so where was the car built?
Most Atlanta cars have a buildsheet on the back side of one of the front door panels. Easy to see with just a few screws removed.

RPO G80 Positraction was only mandatory on 4.10 geared equipped LS6 cars. 3.31 geared cars were standard with a peg leg 3.31 unless RPO G80 was checked off on the order ticket.


Tom,
I do not know that this is necessarily the case, as almost every LS-5 or LS-6 seems to have G80 positraction. I do know there were some other ratios and combinations available as non-posi, but they are extremely rare. Either almost everyone ordered the posi, and I do mean almost all of appox 9,000 SS454 cars, or they came standard with the posi, while the non-posi could be ordered. I kind of think the latter, but I have no documentation to support it, only a theory at this time. Anyone have any further info?

Jeff Dotterer
Dated Components
Diamond Restored Judge

I owned a 70 ls5 convert that was baltimore built,turob 400 car with the cru rear. Rick nelson is restoring a misty turqoise ls6 convert,m-22 cru rear baltimore built. these cars were 80 units apart built on the same day documented with builsheets.

I think I have 3 CRU rear equipped LS-6's in the registry and just heard from another LS-6 owner on the east coast with yet another CRU.

The convertible is an odd duck to say the least. The car is equipped like most every other LS-6 yet has the CRU rear which still rides in the car. Both this car and Chad's were 6A cars.

This can get complicated. First, we are assuming it is an SS454, Right? The LS5 will always have the return line for the longer #40768 fuel pump. So there will be two lines in the frame. An LS6 started production with a #40727 Short pump, which would not have a return, and therefore only one line in the frame. The LS-6 switched over to the #40768 and added the return line in most plants by Feb 1970, and Atlanta sometime in March. This would make it more likely it is an LS-6 if it has no return line, but not help settle the difference if it has the return line. Additionally, the 396-350HP also used the return line pump for the full year, and the L-78 used the one without the return untill the option was cancilled in favor of the LS-6.

Jeff Dotterer
Dated Components
Diamond Restored Judge

My car is a 1st week Feb car from the Arlington, TX plant and it has a 727 short pump (build sheet confirms it). Sorry for robbing the tread but I know that Jeff keeps track of this stuff as a judge.

Jim