Thread: For Don Shilady

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36Sedan,

Here is some good news. I am attaching a picture of my previous pulley setup to run the RayLoc 13-8283 alternator. I am also attaching a picture of the solution to the problem of insufficient amperage when running in OD 4th gear of the 700R4. The second picture shows the new 5" pulley from Jones Racing Products (Ottsville, PA, 610-847-2028). What is shown is for a 1" diameter mandrel which was exchanged for the pulley on the engine now which uses a 1 1/8" mandrel, not shown but the outer diameter is the same 5" deep groove for a single v-belt. The T-shirt was free and offset the shipping cost. Without worrying over (pi x diameter) =circumference you can easily see the first pulley is only 3.5" diameter compared to the new 5" diameter which gives an increase in rpm at the alternator of (5/3.5)=1.428571429 for about 42 % increase in the alternator rpm. It turned out that the little pulley for the alternator would have given about 11% more rpm but there was just not enough clearance due to a cone on the back of the small pulley so the shop put the original 67 mm pulley back on the alternator. Once again Bruce Orlandi of Performance Transmission in Ashland/Hanover Air Park was a big help installing the new pulley in a very tight space between the harmonic balancer and the bottom of the radiator. Since he has experience with the mandrel drive for his drag car he finished the job in about two days in between other tasks while I would have certainly taken much longer using a floor jack to get under the front end. I learned several things about alternators which might be worth mentioning here. First, the amp curve for an alternator is generally shaped like a hockey stick rising up rapidly with rpm and then gently leveling off but still working up to about 12,000 rpm. In my case driving around town and on local blacktop roads my engine rpm seldom gets above 1900 rpm so the pulley ratio of about 1.8955 keeps the alternator at about 3600 rpm. Even at 3000 engine rpm (roughly 67 mph in OD) the alternator is still turning at only about 5686 rpm. The alternator specs say 44 amps at 2000 rpm (alternator) and 69 amps at 6000 (alternator rpm) so most of the time I will be running at about 60 amps which seems to be enough to charge at 13 volts even with the head lights on. Now I can run at night and still have enough amps to run my electric water pump and the two electric fans, although I think the whole system is marginal. However at a stop the engine idles at about 950-1000 rpm and amazingly I have 14 volts on my dash meter where before the voltage would drop to 10 or 11 volts at idle indicating a battery loss. Previousy I could generate all the time if I would run in third gear at 1.0 ratio instead of the 0.7 ratio of the 700R4 OD. I suppose the 3.55 ratio rear gear does not help much but now at least I am only running the alternator at an rpm that would be typical of running in 1.0 trans gear. I think the combination of my 3.55 rear and the 700R4 4th gear of 0.7 is on the ragged edge of a high ratio but it was chosen to give reasonable mpg and even then only comes out to about 16 mpg on average. The second thing I learned is that an alternator does not turn on until about 1500 alternator rpm BUT once you rev the engine to get above that value you can let the engine slow down and the alternator will still charge. Well now I have lights for night driving and can idle without running the battery down. I did a search on this Forum under "alternator" and found very little but other Camaro sites had a number of entries on the Jones pulley for increasing amperage, especially at idle. Maybe most of the folks here just put a 100 amp alternator on their engine and have no problem but cars that use an electric water pump, especially on the Moroso mount, may need to use a Jones 5" pulley to increase amps at engine ide speed so I am documenting my experience here.

Don Shillady
Retired Scientist/teen rodder