I've looked at a number of cars, but have always been in love with the styling of the C3. I have done some reading, but still havn't found a few answers. Assume the car in these instances was well maintained (solid compression, etc). On a side note, I found a few cars I am going to check out. All 74-79 autos. I plan on modding and daily driving it if at all possible.

1) What kind of fuel mileage can I expect? I've built an 89 Supra and own a 97 trans am so I'm fairly used to 10-15 city, but more like 20-28 highway. My guess is lower but how much lower? Let's assume the base 350ci motor in a 73+ car, since I know a big block will get worse mileage. Also, will 'basic' mods (intake, full exhaust, cam, heads, carb) help the mileage any? It did on my buddy's 78 stang.

2) How well does the (l48?) 350 hold up to top-end engine mods without touching the bottom end?

3) How well does the 4 speed hold up to power? How about the auto? The differential?

4) Where should I look for rust? I've never bought an older car. (The body panels! haha bad joke)

5) Is it more cost effective to build a 400hp NA motor out of the (l48?) or buy a crate motor?

6) What is the base rear gearing? Is a stock auto geared for 90 mph cruising or ***** out acceleration (well not with a stock Smallblock)?

Sorry for any style/spelling errors. My right hand is broken from a bar fight on Saturday. Well, more specifically, some guy went for my head with a bar stool and I blocked it with my hand and beat him senseless with the broken hand. Was just trying to enjoy a few beers and a game or two of pool.

 

OK - I'll take a few shots...

1) Probably about the same as your TA without ever getting into overdrive. A lot of folks here have added OD transmissions (not so much for mileage but more for cruising).
2) Pretty well - except for power adders, the bottom end should hold up to anything you can bolt on (assuming that they are in good shape to start with)
3) The are pretty stout - but you didn't ask about the half-shafts and U-joints (there are 6 of them). Stock stuff should be good to 450hp unless you drag race...
4) Look for rust on the frame just ahead of the rear wheels where it kicks up over the rear shafts. If it's good here, the rest is probably OK too...
5) ???
6) This varies and would have to be checked on the differential.

Good luck -

 

Take a look at www.corvettefaq.com they have some good info about
buying a Vette. What to look for and once you pick it up.

 

The L48 holds up well, but if you get a car with the optional L82 it will have a 4-bolt main block. This might be nice even though the L48 bottom end is probly fine at 400hp. I think the L82 heads flow better too, if you are not going to change the heads immediatly.

 

My stock '70 350/350hp 4 speed was getting 17.8 mpg on the interstate at 70-80mph and about 3000-3500rpm.

Me? I stay home and drink now

 

1) Honestly, if you are looking for anything above 18, you will have to get an '82 with the 4 speed auto, or swap in an overdrive transmission yourself. Adding go fast parts will help with mileage a little, but the temptation to put your foot into it quickly does away with any benefits.

2) Good, not great. But that all depends on how much power you want.

3) That really depends on how well they've been maintained or abused. The years you have mentioned all have the steel rear end carrier, so that holds up to more power than the aluminum ones found in the '80-'82 cars.

4) Bird Cage and frame

5) crate motor

6) Again, depends on the trans that you put in the car or if it's stock. The top gear for both the three speed autos and the 4 speed manuals is 1:1. There is no over drive. I turn 3000 rpm at 70 mph in my 4 speed manual. Keep in mind, most SBC V8's don't rev freely like a Japanese v6 and they tend to make more of their power at rpms lower than 5k, like your T/A.