Is it a Real C3 Big Block Car? What to Look For?

[Dave #45974]

I am a new NCRS member and am in need of some advice. I am looking for some tell-tale indicators that will help me determine whether 68-72 cars I am evaluating for purchase are truly original big block cars. From what I have read, only the '72's include this information in the VIN #. Without a tank sticker, what are some clues? I have heard the following: 1) check the U-joints on the IRS driveshafts (?) -- they are much more robust on a BB car, 2) only BB equipped cars had rear sway bars, 3) BB cars had larger capacity radiators.

Are these pieces of advice correct? Any help, pictures, etc. are greatly appreciated. Thanks much!

[Jim T.]

Re: Is it a Real C3 Big Block Car? What to Look Fo

Dave I am the original owner of a 70 350/300 with original turbo 400. The IRS driveshafts are attached to the differential with straps and not the regular type of U bolt, so some smallblock C3 Corvettes came with straps. Having the straps securing the IRS u-joints does not prove it is a big block car.

[Joe L.]

Re: Is it a Real C3 Big Block Car? What to Look Fo

Jim and Dave-----

Yes, the cap-type rear stub axles were used on small blocks as well as big blocks. However, I don't think that they were used for any small blocks prior to 1970. For 1970 onward, though, they were used on all big blocks and some small blocks. Prior to 1970, they were used for big blocks only. Of course, stub axles could easily have been changed over the years for any particular car.

The presence of a rear sway bar is fairly good evidence of an original big block car. Only big blocks received a rear sway bar in the years 1965-1974. After 1974, small blocks equipped with FE-7 suspension included a rear sway bar, albeit of smaller diameter than the 65-74 big block bars. Prior to 1975, small blocks did not receive a rear sway bar even if they were equipped with F-40 or F-41 suspension.

However, a sway bar could always be added.

[Harmon C.]

Re: Is it a Real C3 Big Block Car? What to Look Fo

Original stampings and broach marks would be one of the best ways to tell. Paperwork or stampings can be fake but with a little practice on the stamping you should be able to tell 90% of the time. The higher the horsepower you are buying the more chance you have of restamps. Any car over $50K you need to hire a person who knows Corvettes or you could make a bad deal.

Lyle

[Chuck S.]

JMHO...If You Need To Ask...

There is too much for the newbie to know, and too much incentive for fraud these days in high dollar cars. If you need to ask this question, then you need to spend a couple more years studying big block cars, observer judging, judging if possible to gain some experience such that YOU KNOW how to confirm a car is what the seller says. There is no way anyone can tell you in a few sentences how to know a car is right.

Even experienced Corvette judges can be at risk in this market IMO...Take the time, learn the cars, and then make an informed purchase. Otherwise, you should get someone knowledgeable to help you make any evaluation, or you may live to regret your haste. As I said...JMHO.

[Patrick H.]

Re: Is it a Real C3 Big Block Car? What to Look Fo

I think you could make a bad deal on Corvettes at any price. You just won't have as much to lose.

Seriously, Chuck is right. If he needs to ask, he needs to get local help.

Patrick

[Tim G.]

Re: JMHO...If You Need To Ask...

I believe that only big blocks and LT1's had caps on the half shafts. The code is different for the case on big block vs small block rear ends. Larger front sway bars, addition of rear sway bars, radiator, fuel lines, front springs, the list of clues goes on and on. Of course, the original engine and paperwork are the best ways to verify the engine that came in the car.

[Terry M.]

Re: JMHO...If You Need To Ask...

Sorry Tim, but in the early C3 era M40 transmission equipped small blocks also got the caps on the differential.
There is no ONE single litmus test to determine an original large motor Corvette in the C3 era. A combination of features, mentioned repeatedly in the other posts, will signal the original engine -- but those who are bent on fabricating these changes know the features also.

[Harmon C.]

Re: Is it a Real C3 Big Block Car? What to Look Fo

Patrick
Under 50K the hurt might go away faster!!!!!!!!

[Patrick H.]

Re: Is it a Real C3 Big Block Car? What to Look Fo

I dunno...

the extra $10k I'll have to put with my 71 to fix it after its "deer modifications" doesn't feel that great.

Patrick

[Dave #45974]

Thanks All! I Have Much to Think About.... *NM*

[Tim G.]

Re: JMHO...If You Need To Ask...

Terry, thanks, I didn't know that. It's good to have some new informaiton in the event I ever see a small block with caps on the half shafts.