How would I know if my car was originally a big block?

was rebuilding the brakes over the weekend and noticed the rear sway bar?

By the look of it it seems to match the front one. But could have been added later.

Any other obvious ways of knowing?

 

I think the VIN will tell you, I'm not 100% sure about that, but it's worth looking into.


Scott

 

What year??? VIN is useless, just if it was coupe or conv, not engine size...........

 

As more "knowledgeable" people on here can tell you, if you originally had a BB and a small block was transplanted, check engine pad first for matching numbers, and also the redline on the tach is different, someone will be able to tell you the actual redline numbers for engine displacement and horse

 

Hi

The cars a 69. The current engine isn't the original one.

4 speed manual, think the speedo show 160mph top speed ( does this differ from small to big block?)

 

They all had the same speedo.

I don't think there's any way to tell and be 100% sure unless you have the original documentation. Besides that, if you don't have the original engine, it really doesn't matter what it used to be because it'll never be that again.

 

True, but might be of some benefit if i'm to change her back to a big block.

 

If you're talking about parts that must be changed to do the swap, the exhaust and the hood are the major ones.

Which hood do you have?

 

I dunno. I think the VIN will give you the original engine size. Try using this classic VIN decoder: http://www.vinwiz.com/ Just type in your VIN.

 

No, it won't.

 

VIN definitely a NO-GO for engine size. What is the red line on the tach???? Most people don't replace the tach in an engine swap................

 

As was stated before, without the original number matching engine and documentation there is no way to tell for sure. This can all be forged anyway depends on how much effort is made and how much money is spent doing it.

At a glance the rear sway bar (factory style of course not aftermarket) and the presence of differential stub axles with caps and bolts instead of straps are both good indicators of a big block car. Then it gets into a particular redline on the tach and placement of some emission stickers in the engine bay I beleive.

 

Starting in '72, the engine option was included in the VIN, so that's good for knowing original big blocks on '72-'74 cars, it doesn't help you with a '69.

Are you sure it isn't the original engine? What does it say on the engine pad?

There are actually a dozen or more differences between big block and small block cars. To "upgrade" a small block car to a big block car is quite doable. As far as I know, all of the pieces to do the conversion are bolt-on type mods with the parts readily available. Sadly, fake documentation is available of sufficient quality that weekend hobbyists like myself are unable to distinguish it from the real thing.

So, where does that leave you? If you aren't talking about an original car, and just want to do some sleuthing to see if your car was originally a BB car, do some searching here on this site on the differences between BB and SB cars. There is a lot of information readily available here. If you run into specific questions, there are some real experts that post regularly that will chime in and help out. Have fun!

 

It will never be what again?
Never be original, obviously.
Never be a big block Vette again ???

 

Original.

I thought that was quite clear.

 

No, it wasn't. Some feel once a car is no longer original it will never be --- optioned again. Never made sense to me.

 

When you say "it seems to match the front one", do you mean the 2 bars are of similar diameters? A factory rear bar is about half the thickness of the front bar.

As others have said, it's pretty tough to identify a real big block car, but there are some hints.

If the car has it's original rear, or rear end housing, the identification code on it will indentify it as a big block rear. This code is stamped into a machined surface, but is very hard to see with the rear in the car. As mysixtynine said, the BB rear also used different stub axles. BB stub axles have caps and bolts to attach the u-joints. The small block rear uses atub axles that secure the u-joints with bands.

The radiator and core support, are unique to the big block, and the big block didn't use an expansion tank.

Is the rear spring a 7 or 9 leaf type? The BB uses a 7 leaf. The BB also uses the domed hood. What engine is indicated on the engine data plate attached to the console? Though easily changed, it could be original.

Of course, if the tank sticker is still on the gas tank, this would be positive proof of a big block car.

 

This makes no sense to me.

 

Doesn't make sense to me either. Any car can be restored to whatever configuration it had originally. I agree, can't be original.

 

Radiator, hoses, and hood..... a BB Vette will have a copper radiator and related parts not aluminum....... and the chances of a car being switched from a BB car is too remote....the tach has nothing to do with engine size but would reflect whether it was a HP car as opposed to a hydraulic cammed low HP Vette,