C3 long drives
Thread Starter
Intermediate
Joined: Jan 2018
Posts: 40
Likes: 0
C3 long drives
i have a 77 corvette and heard they are not made for long freeway drives, I have also heard they are fine for the freeway. My 77 has a 4 speed transmission, brand new engine, along with new water pump, and new alternator. Are these 77’s with 4 speeds not cut out for 10 hour drives at 75mph? Are they made to cruise at 55mph?
Race Director
Joined: May 2006
Posts: 18,660
Likes: 2,562
when brand new there was no reason they couldnt go on a 10 hour drive at 75 especially a 77 which probably has a low numerical rear gear. Regardless of the new parts you mentioned having the car thoroughly checked would be a good idea including, pressure test cooling system, condition of all hoses, upper, lower, heater, condition of all belts, inspection of steering components and suspension bushings and ball joints, condition of all u-joints both axle and half shaft. Check wheel bearing play front and rear. Check all tires including spare. Check transmission and rear fluid levels and add/replace as necessary. Check all brakes for wear and signs of leaks.
Last edited by MelWff; Jan 17, 2018 at 01:31 PM.
Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
comfort level aside,
it could be about mph and engine rpm.
77 was after 55mph law i think?
where 55-60 mph would be @2000-2500
that gearing would be in the 3ks at 65-70mph.
now the debate comes in.
will the engine last? tolerate the heat?
maybe that is what was told you?
it could be about mph and engine rpm.
77 was after 55mph law i think?
where 55-60 mph would be @2000-2500
that gearing would be in the 3ks at 65-70mph.
now the debate comes in.
will the engine last? tolerate the heat?
maybe that is what was told you?
Racer
Joined: Apr 2015
Posts: 296
Likes: 30
From: Westchester NY
You can most certainly go on long-distance highway drives in your 77. I've done 500 a day on the highway in both my 71 and 80 Corvettes, the 80 is a 4 speed.
If you've never done distance in the car I would suggest tooling around town for a week or two staying within a tow radius, wait for those ready to break things to break, then set out without worry.
I do always carry a set of sockets an alternator belt a fuel filter and other miscellaneous tools, pliers duct tape etc. But, over 30,000 miles of driving I've yet to find a reason to use them.
If you've never done distance in the car I would suggest tooling around town for a week or two staying within a tow radius, wait for those ready to break things to break, then set out without worry.
I do always carry a set of sockets an alternator belt a fuel filter and other miscellaneous tools, pliers duct tape etc. But, over 30,000 miles of driving I've yet to find a reason to use them.
Race Director
Joined: Mar 2003
Posts: 11,608
Likes: 780
From: Eustis ( Area 51 Bat Cave ) Fl
What a crock, when new or if restored or well mantained c3s make good daily drivers on roads or highway,
I used all mine that way owned many, from 16 to 53
People who say no they dont either have non up to par c3s, are spoiled to their sedans creature comforts or are scared something will happen to the c3 while driving it...
I used all mine that way owned many, from 16 to 53
People who say no they dont either have non up to par c3s, are spoiled to their sedans creature comforts or are scared something will happen to the c3 while driving it...
Race Director
Joined: Oct 2000
Posts: 12,633
Likes: 3,100
From: Shamong, NJ
The two main limiting factors are your gear ratio, and your ability to pay for gas.
Assuming you have standard P225/70R15 tires, which are approximately 27" in diameter, with a 3:70 rear and a 4 speed, you'll be turning about 3500 rpm at 75 mph. A 3:55 rear will reduce your rpm to about 3300 at 75, and a 3:08 will drop your rpm to about 2800.
Turning 2800 rpm all day long, isn't to bad, but 3500 is pushing it a little. If your cooling and oiling systems are in good operating condition, 3500 all day long is certainly doable. But, as someone who's had their fair share of 3:70 and 4:11 rears, I can tell you that those sustained rpm's, can be somewhat disconcerting. This is why all modern cars have overdrive transmissions, and why a lot of owners of older Corvettes and muscle cars, are converting over to overdrive.
The other issue is that at 3000 rpm, these old cars tend to use a fair amount of gas. You can figure your probably looking at 14 mpg, at a steady 75.
Assuming you have standard P225/70R15 tires, which are approximately 27" in diameter, with a 3:70 rear and a 4 speed, you'll be turning about 3500 rpm at 75 mph. A 3:55 rear will reduce your rpm to about 3300 at 75, and a 3:08 will drop your rpm to about 2800.
Turning 2800 rpm all day long, isn't to bad, but 3500 is pushing it a little. If your cooling and oiling systems are in good operating condition, 3500 all day long is certainly doable. But, as someone who's had their fair share of 3:70 and 4:11 rears, I can tell you that those sustained rpm's, can be somewhat disconcerting. This is why all modern cars have overdrive transmissions, and why a lot of owners of older Corvettes and muscle cars, are converting over to overdrive.
The other issue is that at 3000 rpm, these old cars tend to use a fair amount of gas. You can figure your probably looking at 14 mpg, at a steady 75.
Drifting
Joined: Aug 2015
Posts: 1,939
Likes: 477
From: NSW, Australia
C3 of Year Finalist (track prepared) 2019
What a crock, when new or if restored or well mantained c3s make good daily drivers on roads or highway,
I used all mine that way owned many, from 16 to 53
People who say no they dont either have non up to par c3s, are spoiled to their sedans creature comforts or are scared something will happen to the c3 while driving it...
I used all mine that way owned many, from 16 to 53
People who say no they dont either have non up to par c3s, are spoiled to their sedans creature comforts or are scared something will happen to the c3 while driving it...
Last edited by Metalhead140; Jan 17, 2018 at 07:11 PM.
Race Director
Joined: Mar 2016
Posts: 14,297
Likes: 8,103
From: Napa Valley California
My 73 BB TH-400 with 3.36 rear gears runs at 3070 rpm @ 70 mph on the highway. The rpm is a little high for my liking for drives over 30 minutes, so I have a tendency to cruise in the slow lane at 60-65 on the highway of longer drives. Kind of embarrassing being America's sports car.
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Melting Slicks
Joined: May 2011
Posts: 2,753
Likes: 119
From: Springfield Missouri
NO, it gives people a chance to look at your car as they pass you!
I drive my 76 at 70 all the time on Interstates, and have no problem, like to St Louis(4 hours, or Kc, 3.4 hours) with no problem. This a stock 76 motor and transmission. The worst part is the seats, as you get older, your other car's seats are more comfortable. IMO. No heating problems etc, car gets about 19MPH, unless I have a little fun goosing it a little.
I drive my 76 at 70 all the time on Interstates, and have no problem, like to St Louis(4 hours, or Kc, 3.4 hours) with no problem. This a stock 76 motor and transmission. The worst part is the seats, as you get older, your other car's seats are more comfortable. IMO. No heating problems etc, car gets about 19MPH, unless I have a little fun goosing it a little.
Burning Brakes
Joined: Aug 2004
Posts: 1,115
Likes: 412
From: Washington State
Here is a thought,
My baby is a 69 and I too was concerned.
I have 373 rear end and ran very high rpms on the freeway.
Instead of worrying I simply swapped my th400 for a stage 2 2004R with od.
Problem solved! Locking torque converter and OD! Perfect!
Now I understand the th350 is better swapped with a 700R4. But really same diff!
Some folks even claim it is a better tranny! What ever.
Swap and end the concern AND get better mpg AND get lower rpms! Win Win Win!
Just saying!
Scott
Ps all this from a guy now stuffing an LS7 and 4l75e into the 69!
Heh heh! Swap? Me? Never? Oh how i’ve Changed!
My baby is a 69 and I too was concerned.
I have 373 rear end and ran very high rpms on the freeway.
Instead of worrying I simply swapped my th400 for a stage 2 2004R with od.
Problem solved! Locking torque converter and OD! Perfect!
Now I understand the th350 is better swapped with a 700R4. But really same diff!
Some folks even claim it is a better tranny! What ever.
Swap and end the concern AND get better mpg AND get lower rpms! Win Win Win!
Just saying!
Scott
Ps all this from a guy now stuffing an LS7 and 4l75e into the 69!
Heh heh! Swap? Me? Never? Oh how i’ve Changed!
Instructor
Joined: Jan 2012
Posts: 216
Likes: 16
From: Tanunda South Australia
The two main limiting factors are your gear ratio, and your ability to pay for gas.
Assuming you have standard P225/70R15 tires, which are approximately 27" in diameter, with a 3:70 rear and a 4 speed, you'll be turning about 3500 rpm at 75 mph. A 3:55 rear will reduce your rpm to about 3300 at 75, and a 3:08 will drop your rpm to about 2800.
Turning 2800 rpm all day long, isn't to bad, but 3500 is pushing it a little. If your cooling and oiling systems are in good operating condition, 3500 all day long is certainly doable. But, as someone who's had their fair share of 3:70 and 4:11 rears, I can tell you that those sustained rpm's, can be somewhat disconcerting. This is why all modern cars have overdrive transmissions, and why a lot of owners of older Corvettes and muscle cars, are converting over to overdrive.
The other issue is that at 3000 rpm, these old cars tend to use a fair amount of gas. You can figure your probably looking at 14 mpg, at a steady 75.
Assuming you have standard P225/70R15 tires, which are approximately 27" in diameter, with a 3:70 rear and a 4 speed, you'll be turning about 3500 rpm at 75 mph. A 3:55 rear will reduce your rpm to about 3300 at 75, and a 3:08 will drop your rpm to about 2800.
Turning 2800 rpm all day long, isn't to bad, but 3500 is pushing it a little. If your cooling and oiling systems are in good operating condition, 3500 all day long is certainly doable. But, as someone who's had their fair share of 3:70 and 4:11 rears, I can tell you that those sustained rpm's, can be somewhat disconcerting. This is why all modern cars have overdrive transmissions, and why a lot of owners of older Corvettes and muscle cars, are converting over to overdrive.
The other issue is that at 3000 rpm, these old cars tend to use a fair amount of gas. You can figure your probably looking at 14 mpg, at a steady 75.
Instructor
Joined: Dec 2011
Posts: 197
Likes: 27
From: New Jersey
I take my 80 automatic once a year on a 4 day weekend and put a 1,000 miles on it and it seems to get more comfortable as the miles pass. I’ll try to keep up with the others in their higher end cars with my rpm’s screaming at 3500 doing 65 to 70 mph. At times I’ll let them go and give the old girl a rest but I look cool going slower. Lol
My advice is go for it!
My advice is go for it!
Cruising
Joined: Nov 2015
Posts: 13
Likes: 5
I drove my 77 from MA to Indiana and back in a weekend during a heatwave. My tach wasn't reading correctly then, almost double what it was actually. That was a little scary as it looked like I was redlining. I was getting 14.4 MPG. New 350/290 crate motor with new 3:36 diff. I put new tach board in since.
Race Director
Joined: Aug 2004
Posts: 10,628
Likes: 132
From: Duvall, WA
My wife and I take our ‘71 4-speed convertible from Seattle down to Napa, about 800 miles each way. Speeds are usually around 80 mpg. I got 20 mpg on a couple of tanks, with a 420 hp roller cam build I did on a 350.
Race Director
Joined: Mar 2016
Posts: 14,297
Likes: 8,103
From: Napa Valley California
Thread Starter
Intermediate
Joined: Jan 2018
Posts: 40
Likes: 0
I drove my 77 from MA to Indiana and back in a weekend during a heatwave. My tach wasn't reading correctly then, almost double what it was actually. That was a little scary as it looked like I was redlining. I was getting 14.4 MPG. New 350/290 crate motor with new 3:36 diff. I put new tach board in since.
Pro
Joined: Feb 2017
Posts: 518
Likes: 365
From: San Diego
2023 C3 of the Year Finalist - Modified
I can't add to the C3 experience (yet) but I think it is all relative. When I take long trips in a 62 TR4 I look at the guys on motorcycles and think, man, what a luxury ride I am in.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
I haven't had my 69 really anywhere out of town, but right now it has 4.11 gears. Not a great thing for long highway drives for me. There are a couple other members here that has driven all over- like 6000 miles at a crack.