A little help

[wipeout]

Hi,

Just a few questions for you guys, when my car does about 70-80 mph its reving at around 3500rpm. Is this where it is supposed to be for a small block 350.

Its a l-48 all original except for the hooker sidepipes. Also my car revs really high in park and in drive. In park its at 1500-2000 rpm.

in drive if i let the brakes go it stays at about 1200 rpm and iwth the brakes on it goes to about 900-1000rpm.

Just wondering to see what steps I should take to resolve this problem before I jump into it.

Save the Wave. (I think its extinct cause nobody does it here)

 

[AKRAY4PLAY]

sounds as though your idle is turned way up. i believe a stock car with an auto should idle around 700-800 rpm in neutral and about 600-700 rpm in gear. try backing off on the idle adjust screw, lower idle rpm is a lot easier on the rear end when you pop it into gear. the highway rpm is normal if you have around 3:70 rear gears and close to stock tires. you may want to look and make sure your throttle cable is free and returning all the way. disconnect the cable at the carb, that will tell you if the cable is hanging or the idle screw needs adjusting.

 

[jon79flavette]

Yup, you got it AKRAY, your idle (adjustable) screw will give you true idle, and take the guess work out of a binding or sticking cable. I have never run the numbers on that rear, but isn't 3500 still high at 70-75 or so. Are you running a shorter or low-profile tire than factory stamped at the door jam??? JOn

 

[wipeout]

Yeah,

I think my tires are smaller then the original or what is supposed to be there. I will have to check tomorrow since its dark out.

Just wondering what other people where getting.

 

[Bob Chadwick]

You may have a fast idle/choke issue. Mine revs at 1500 cold and 7 - 800 when hot.

3500 is normal for 80 mph with the stock gears on a 77, which I think are 3.08.

Bob

 

[rpounds]

Assuming a 1:1 final transmission ratio, a 26" tall tire and a differential ratio of 3.70:1, you should be running 3348 RPM at 70 MPH and 3588 RPM at 75 MPH. Theoretical top speed with a 5300 RPM red line is 110 MPH.

Sounds like you need to upgrade to a 700R4.

With the same differential ratio of 3.70:1 and the same tire size, you would be running 2575 RPM at 70 MPH and 2759 RPM at 75. Top speed (theoretical) would be 144 MPH.

 

[wipeout]

great thanks guys,

man you would think they would of had designed it so it woudnt rev so high at those speeds.

Oh well maybe in the future im gonna change the transmission or maybe just get me a big block engine. Oh yeah.

Gonna go check my Idle screw today and let you know what happens talk to you later.

 

[page62]

The later C3's had high rear end gear ratios -- perhaps to compensate for the lack of HP caused by smog equipment. But also remember the national speed limit was 55 mph. But at 75 mph, it feels like the engine is going to tear itself apart...

In 1982, the first 4-speed auto overdrive transmissions were installed in Vettes. Quite frankly, it makes all the difference in the world -- I know, because I installed one in my '79. Not cheap, but definitely worth it!

Learn more at www.700r4.com

 

[wipeout]

Yes i always found that quite strange my cavalier revs at 2800 at 80mph and my corvette revs at 3500-4000. Guess im gonna have to change it to and overdrive transmission like the one you said.

Im dont really care about 1/4 mile times, im more into top end speed. What kind of changes would you have to make to a 77 corvette to get more top end power.

Like my speedometer goes up to 160mph I would like to be able to reach that or at least pass it.

Man that would be sweet.