I had a new alternator installed on my 87 5.7 TPI Iroc-Z. Its was a AC-DELCO alternator. Ever since I had the car and even now with the new alternator, the voltemeter jumps a lot. It seems sometimes when the car is stopped in gear the meter goes down to like 8-10 volts but soon as you rev it up the meter goes up to 14 volts. What gives???

------------------
1999 Camaro SS LS1 m6 12.6@112mphw/1.9 60ft
1987 Iroc-Z 5.7 TPI best et. 14.24 @95mph w/1.99 60ft.
1984 Camaro

 

check your belt

------------------
87 IROC-z 305 TPI 5spd 10-bolt 3.73 posi ,8.8 Accel wires , bosch platinum +4 plugs,MAF sensor screens removed, gutted air box, ram air, K&N air filters,TB coolant bypass ,polyurethane tranny and torque arm mounts, K&N oil filter,Mobil 1 synthetic oil 20w50, futura GLS super sport tires 265/50/15 rear and 235/60/15 front mounted on 86 monte carlo SS rims ,

400 sbc and a 6 spd in the works

 

Does it have a set of power pullys on it?

 

No power pulleys on the car. The belt seemed to be ok.

 

The stock idle speed on an L98 is pretty low, like 500-500rpms. Couple that with the possibilty of both fans being on (+whatever other accessories are on), and the notorious inaccuracy of factory guages and what you are seeing is not necessarily abnormal. At idle RPMs the charging system won't put much out, and both fans alone is enough for my LB9s volts to drop below 13, and my idle speed is higher than an L98s, plus i'd venture i may have a better alt than you as well.

You need to verfiy with a DVM on the battery what your alt is putting out when the dash guage is reading low to see how bad it really is. Other than that, it's a matter of balancing what accessories you're running. You can't idle around all day with the fans on, AC on, fog lights on, rear defrost on, etc.
If it is giving you a real voltage problem even with none of the above listed big draw device on, then perhaps you have a bad alternator. Even a new out of the box one can be bad sometimes.
...ed

------------------
Ed Maher - Moderator @ The TPI & Carb Boards
92 Z28 Convertible - Quasar blue / Tan top
305 TPI A4 2.73 - 14.8 @ 93.1
Stock except ported plenum and dual cats
-=ICON Motorsports=-

- Definitely prototypes, high powered mutants of some kind. Too weird to live, too cool to die

 

Can I raise the idle rpm like on a carb, or do I have to have a chip burned with that info?

 

It's in the PROM. If you turn the curb idle screw, the IAC will simply compensate down.

 

Just get an alternator with a higher amp rating. If they didnt give you the right one, you could have an 85amp and your application could call for a 105. Personally, I use a 108amp with an OVERDRIVE pulley, not underdrive, and I do ok at idle with everything running.

------------------
Mike Metzler (Desert86Roc)[*] Check Out:SpeedWorldMotorplex.com[*] Check Out:Chevrolet F-Body Online Part & Illustration Manual[*] My 86 IROC 305 TPI Page (406 build in progress)

ET's @ 1250 ft[*] 14.28 @ 95.461 mph (uncorrected, NOS, no headers)[*] 15.362 @ 88.238 mph (uncorrected, headers, no NOS)
<><