Underdog1993

Hey everyone! I recently bought at 81 c3 and on the way back home i notice that at 70mph she runs at 5500 rpm which seems a little high. I will admit im not super knowledgable about cars but im wanting to learn. I do know it has a zz4 crate engine and a performance intake. It is the 3 speed auto transmission as well. I havent had any heat issues and the car seems to run really strong.

resdoggie

Is your tach working properly?

Kevin68

Scatter shooting here. Are you sure it is shifting into 3rd gear? If so, somebody may have put a racing gear set in the differential although 5500 is approaching red line for that engine. It won't last long driving like that. Can you jack up the rear end (both wheels) and put a piece of tape on the tire and one on the driveshaft. With the car in neutral, rotate the tire one revolution and count how many times that makes the drive shaft turn. This will give us your final drive ratio. Report back. And when you do this make sure you are on a firm level surface and you chock the front tires well, you don't want the car rolling off the jack or jack stands.

Another possibility is the electronic tachometer is bad.

I've got a ZZ4 and can't imagine driving for any distance at 5500 rpms.

C3 Stroker

I would suspect the tach accuracy.........if you're running at a true 5500 rpm's, it will seem a lot more than just a "little" high.

gleninsandiego

L-46man

Shift from 1 to 2nd to 3rd....do you feel the steps?
Running at redline (almost) will make that (valvetrain) engine very short lived.

I think you'd know if your car was SCREAMING at you!

TACH WHACKED

Unkahal

Underdog1993

Unfortunately i wont be able to get it out until sunday cause it will be raining until then. Also monday i will be taking it to have some minor work done. If i do have to drive on the highway should i drive slower to stay at low rpm?its 3 inch pipe all the way to the headers and its loud It only screams super loud when you get on it. On my tack it starts at yellow 5500 rpm and readline starts at 60

derekderek

Make a video with the engine sound when you're on the highway.

C3 4ME

I'd put money on it being a tach reading wrong. Mine did on my 79 when I first got it, and it read way high.

derekderek

Go on youtube. Dyno run videos. Those motors are at 5500 a lot. See if your note is lower than that.

Underdog1993

okay the rain might die iff a little tomorrow and ill take it out for a ride

carriljc

Borrow or buy an aftermarket tach. It's a lot cheaper than blowing up the engine.
Do you happen to have an old tach/dwell meter?

Al T

What does the tach read at idle?

F4Gary

As already posted, just listen to hear if it shifts from 1st to 2nd and then to 3rd.
What rear end do you have?

Underdog1993

after it warms up it idles at around 1 to 1.5 K rpm

Underdog1993

I honestly don't know I do plan on taking it to a friend who is a certified mech to look at it this weekend so i can see exactly what everything is. I can report back to you then. Like i said its pouring down rain here and i dont want to take it out in the rain and its not suppose to let up until sunday.

Underdog1993

I dont have a old tach but i can get a aftermarket one. How would that stop from blowing the engine though?

gunnerja

It would tell you if your really pushing over 5grand rpms. If so don't put it on the highway or sooner or later you will blow the motor.

Al T

Assuming a warm idle of 700, your 5500 at speed reading could actually be south of 3000. As previously asked, what does the engine sound like at speed. 5500 would be extremely noticeable with or without the tach reading.

Underdog1993

ill have to take it out tomorrow for another drive. The rain will let up for a few hours and i will also record it. Its so loud its hard to tell. When i drove it home from buying it i noticed the tach and just cruised at 55 mph. Took a little longer to get hone but i wanted to be on the safe side