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I have a '79 vette and im new to these kinds of cars.
I know that they dont have overdrive transmissions, but ive noticed that when i drive on the highway with it at 70 mph or so, the RPM's are around 3000.
Is this okay to drive at for extended periods of time? Im worried this while harm the engine if i do it for too long. I am unsure if the high RPM's for this kind of car is okay or not
The standard rear axle ratio in the 79 Corvette was a 3.55, so 3000 RPM at 70 MPH is about right. It's hard to get used to when your use to modern vehicles with overdrive transmissions, but cruising at 3000 RPM was normal for those of us that were on the roads 45-50 years ago. My 62 has a 4.11 rear and turns 3000 at 60 MPH!
I've put many, many miles on mine travelling cross country at speeds well above 75 mph. Yes I rebuilt the engine at about 90 thousand miles. Oh well.
still run my 4 speed, doesn't hurt it one bit spinning 3,500 RPM down the highway. Been doing it for 48 years now!
It is getting easier for me to look at my tach while cruising also. I went from a 1982 to a 1975. I understand your concern.
It gets easier, and in fact, I am liking the sound and feel of the 3000-ish at cruising speeds.
I like the sound, but not watching the fuel gauge go down in real time.
Changing to an overdrive transmission has a number of benefits, from improved fuel economy, reduced noise in the cabin while cruising, and powertrain longevity from not having to work as hard.
If you have a TH350 right now and want to stick with the automatic but want overdrive I would look into a 200-4R.
I've been driving my 79 for 19 years for hundreds of miles at at time road trips and on the interstate I'm turning between 3500 and 4000 rpms, so hours at a time. I've never had a problem. As others have said, that's what these cars did when they were new. That said, I did just complete a tremec TKX conversion on mine and am looking forward to the first road trip. I love the lower noise level, yes, of course lower rpm, and hopefully noticeable better gas mileage, (although gas mileage has never been a consideration, we drive these cars for FUN!)
I've been driving my 79 for 19 years for hundreds of miles at at time road trips and on the interstate I'm turning between 3500 and 4000 rpms, so hours at a time. I've never had a problem. As others have said, that's what these cars did when they were new. That said, I did just complete a tremec TKX conversion on mine and am looking forward to the first road trip. I love the lower noise level, yes, of course lower rpm, and hopefully noticeable better gas mileage, (although gas mileage has never been a consideration, we drive these cars for FUN!)
I have to admit this is my first corvette , but owned many other muscle cars .. there are so many things wrong with these cars .. can’t drive on the highway , brakes won’t bleed , can’t jack up the car without opening all doors and hood, constant overheating, etc etc…. Doesn’t seem these cars were built for longevity maybe a fast buck for GM sounds more like it .
interesting thoughts about rpm.
I haven't really picked a max sustained rpm I am happy with.
all I know is the lower number without lugging the better.
side worry, my nephew's ford 289 recently broke a dist oil pump drive rod while
cruising @ 3500 rpm on freeway.
his dad thinks oil was not draining back from the top end.
I don't know myself but 3500 makes me cringe
If your engine turns at 3000+ rpm when at highway speeds and you don't want to install an overdrive transmission, the BEST thing you can do for the engine is to start using FULL synthetic oil. Every mile you drive on the highway with organic oil causes wear on the cylinders and bearing journals of your engine. The higher the revs, the faster the wear. Full synthetic oil is SOOOO much better than organic oil, that engine which will last 90K miles on 'dino' oil will probably last twice that long (or longer) with proper maintenance and use of synthetic oil.
I was recalling this thread while working on my 1989 Sea Ray with a carburated small block Chevy 5.7. The Mercury factory stated wide open throttle range is 4400-4800 for these engines and is where we run them for long periods of time while underway. I typically cruise comfortably at 3500.
I would think the internals are mostly the same for all 70’s - 80’s small block Chevys whether installed in a car or marine use adapted by Merc?
If so, cruising our C3’s at 3000-3500 at today’s interstate speeds should be pretty easy on them. Am I correct?
1975 L48 all original 3:36 rear diff.... 3000 RPM at 70 MPH, verified with GPS. Bought the car a month ago and have already done 1000 Miles on it, mostly freeway driving.
Totally normal for a SBC to sustain this kind of RPM.
A friend of mine has a '66 427 with 4.11 gears in the diff. Can't pass a gas station when driving on the interstate, but man does that thing scoot.
I would think the internals are mostly the same for all 70’s - 80’s small block Chevys whether installed in a car or marine use adapted by Merc?
If so, cruising our C3’s at 3000-3500 at today’s interstate speeds should be pretty easy on them. Am I correct?
Yes, and yes. Not much load at all, especially considering the weight (or lack of), and a slippery vette silhouette. I bet your Sea Ray would benefit from a crank scraper and good windage tray/oil pan combo considering it's normal rpm range. May help fuel mileage some (I know - boat sore spot), and oil life. Wish I would've thought of such things as a teen with a '70 chevelle and 4.56 gears!!
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