has anyone added underdrive pullies, and then install a high output alt. I know/believe the police versions came with a 140 amp alt. If so did the higher ouput eliminate the charging probs at idle??? For those that haven't tried it yet does the theory sound right??? thnx to all

------------------
'89 SHAGGY IROC
L98 7r4, all free stuff,T.E.S.,HOOKER CAT BACK,KYB,ACCEL8.8,JET fan sw. etc.
so much to do , so little money

 

irocnroll89, I have underdrive pullies and had charging problems too. I found out that basically you need a custom chip to make it work properly. I had this problem till I did a cam and heads replacement and then had to get a custom chip then no more problems.

But alot of poeple had no problems with the pullies, mostly the ones by "MARCH". Mine were by TPIS.
Also some people put back the original alternator pully on and drove the car that way, but I don't like that. But to each their own.
But you may be able to reset the idle a little high by readjusting the IAC and the TPS voltage. Also double check your timing before you do this.
As for the police alternator I don't know for sure if will fit but I don't think having more potenial current will solve the problem if the underdrive pully is used and the idle is not right.
Also check with the guys in the PROM board if special programming is needed on the chip if you use underdrive pullies. They may be able to help you or steer you in the right direction.

Good Luck

 

I have an underdrive crank pulley and I don't have any charging problems at idle, except if I have ALL my accessories on including the rear window defroster. And even then, it only drops a bit under 13 volts. The minute the engine gets over 1,000 rpm, it back to charging over 13.5 volts. After 6 years with an underdrive pulley, I haven't killed any batteries or alternators.

Be careful of an underdrive alternator pulley though. It is larger than the stock alt. pulley. You want an overdrive alt. pulley with the underdrive crank pulley if you want to compensate for the slower turning speed.

 

I put on the march underdrive pulleys and haven't had any problems in the year or so I have had them. If you get the two piece power and amp set you won't have any charging problems. I have a 110 amp altenator so you probably don't need to upgrade.

------------------
'91 Z28 305, Auto trans, K&N filters, power pulleys, ported plenum, hypertech chip, hooker cat back, kyb shocks, STB, 14.7@ 93 mph.

[This message has been edited by Casey'91Z28 (edited November 20, 2000).]

 

I'VE ONLY HAD PROBLEMS WHEN IDLING FOR A LONG TIME, LIKE AT THE TRACK IN LINE.
ONCE ABOVE 1,000 RPM IT IS CHARGING JUST FINE. I'D IMAGINE THE BETTER ALTERNATOR WOULD HELP THE PROBLEM, I NEED TO GET ONE.
SUMMIT MAKES REBUILD KITS FOR 140 AMP.
THEY ALSO HAVE A 200 AMP ALTERNATOR MADE FOR OFF ROAD TRUCKS, BUT ITS STILL A SMALL BLOCK SO THAT WOULD REALLY WORK!

------------------
88 CAMARO RS
87 IROC-Z DRIVETRAIN
305 TPI, 700R4, 3.73s
ported plenum, performance resource chip,edelbrock TES Headers and cat-back, K&Ns, AFPR, rest is stock.
15.0 @ 92.5 (bald tires)

 

Small pullies, great marketing. BUT.
they slow down the Water pump. Well, the=is lessens the the operating pressure in the block (not to be confused with the system pressure). At high HP you need the high pressure to prevent localized overheating.
Meaning in small areas around the exhuast valve seats and guides the heads can run to hot. then they are more prone to detonation.
Then EFI cars are very voltage sensitive. Also, remember that even a 1v drop at high rpm drops your available firing voltage about 3,000 volts.
Use a small alter pulley with the oem pullies, and if you can a smaller water pump pulley, if your serious about making HP

 

ok before you guys go off and spend the dollars on a new alternator. get an over drive alternator pulley from march it is like 20 bucks and speeds the alternator to the rpms it would have been if you did not have a crank pulley. as for the cooling i put i high flow watter pump on my car and it actualy cools better than before the pulleys. I get no voltage drop what so ever at stop lights either. I have no overheating problems and after the over dirve alternator pulley my car feels stronger (g-tech confirmed).

------------------
90 iroc l98
last season best corected 13.62 @102
mods
full exhaust, AFPR, pulley, jet stage 1 chip, billet servo, 52mm throttle body and a few other little things.