Hello,

I recently had my 1980 350 L48 upgraded to fuel injection and installed a four speed automatic transmission with overdrive. Currently going through the, "break-in," period and not exactly sure how I should be expecting my car to perform. Some of my initial observations are as follows:

Idle Speed: 1200 rpm
Second Gear: 1500 rpm
Third Gear: 2000 rpm
Fourth Gear: 2000 rpm

At highway speeds, the car seemed to cruise well at 75 mph and 2500 rpm.
At the lower speeds around 25 - 35 mph, the car seems to jump between second and third gear and rev towards the higher end of the range.

Temperature ranges between 195 and 220 deg F; fairly stable.

Oil pressure ranges between 45 and 55 psi; looks higher than i remember operating before fuel injection was installed.

From what i read about the components installed, during the, "break-in," period, the controller will auto-adjust for a smoother ride; even so, im just looking for some advice on what to expect. I was assuming with the four speed / overdrive that i would be able to cruise around 75 - 85 mph, at a lower rpm than usual; approaching 80 on the highway started approaching 3000 rpm. How high would be too high for a cruising speed?

I this description might be incorrect in some areas, but that is why im reaching out for some recommendations / suggestions on what to expect / what is, "normal," for a configuration like this.

Thanks!

Ed

 

Need more info. What auto trans is it, does it have computer control or TV cable? What is your differential ratio? Do you have lockup on the torque converter?
I would have expected the idle speed to be much lower than 1200, how far have you driven the car since the upgrade? Does the engine have a non standard cam in it?
Second third and fourth RPM's are at what road speed?
2/3rds of you maximum torque RPM is usually the most economical max cruising RPM but you can "cruise" at what ever you like under the red line.

I have a 4 speed auto with lockup on 4th gear, with a 3:55 diff ratio the engine is revving at 1800 rpm at 62 mph.

 

Appreciate the advice; let me answer your questions as best i can at this moment:

- Transmission: I think its an R7 mechanical with overdrive
- Differential: 3:55
- Torque Converter: Not sure; car does not perform as if it has lock up (rpm rises as speed increases at cruising speeds)
- Car has driven about 350 miles since being modified
- Cam: Not the original cam; i believe they referred to it as a light cam
- 2nd (1500 rpm): 15 - 20 mph
- 3rd (2000 rpm): 35 mph
- 4th (2000 rpm): 45 mph
- Here is some of the rough data i recorded while driving today:
* Speed: 76, Rpm: 2500, Gear: 4
* Speed: 67, Rpm: 2000, Gear: 4
* Speed: 48, Rpm: 1500, Gear: 3
* Speed: 25, Rpm: 1500, Gear: 2/3

Ed

 

Okay, I'm not familiar with a R7 auto, the two most common used are 700R4 and 200R4.
The car would cruise a lot better with a lock up torque converter, do you know the stall rpm of the one fitted?
RPM's seem okay at the speeds you list, I would expect the trans to stay in 3rd most of the time around town, the most common issue is the trans upshifting into 4th at low speeds and then into lockup. Many fit a lockout switch to the lockup solenoid circuit to give manual control of lockup, you can buy a kit to control this automatically linked to road speed.
Your cam has a a big influence on how low your cruising rpm can be. The cam has an operating rpm range for example say 2000 - 6000 rpm. You don't want your open road cruising rpm to be much lower than the operating range of the cam otherwise your engine is not operating very efficiently. All this is my personal opinion, some of our forum gurus may chip in with more help

 

The Automatic gear box issues, well, I'm no help.
when it comes to your EFI this I may be able to give some advice. Not knowing what EFI system you are running doesn't help. But by no means should you be idling that high. Where is your IAC set? I would think around 800 with car in drive, foot on the brake. Would be good. IAC should be around 5 give or take with air off and no electric fans running warmed up.
180 - 200 degrees Should be normal for a gen 1 Chev V8. 220 is a bit Hot. I'd be working on the cooling system.