76-cj7
Bought a Underdrive pulley from the E-store and went to install and noticed it doesn't line up correctly with the rest of the pulleys.......seems as if its too "tall" and the groves are about 1/16" to 1/8" off.....can't figure out how to measure it correctly :-| ....anyone else experience this before? and would it be ok if i just use warshers to space out the rest of the pulleys to make them align?
jeepsr4ever
Hmm thats very strange! I have heard and have witnessed a couple of 1980 360s that had differetn crank pulley lengths but not on any 304s. I would send it back in for inspection!
76-cj7
MC....can you give me some measurements to check to see if mine is in fact machined wrong? and if so i do believe i have some parts that have yet to be shipped from you and just bill me for another correct pulley and then i'll ship this one if it is wrong back and get a refund???
jeepsr4ever
1.905 from mounting surface to the first groove. You could also send us your steel pulley as a model.
76-cj7
Ok.....i'll get mine measured and measure the old one to check it.....my stock pulley on the motor was just a 2 groove but i had a 3 groove layin around so i tossed her on to run dual p/s belt and they both had lined up ok......
76-cj7
Stocker measures aboot 1 7/8" and the Underdrive measures 1 15/16"
76-cj7
SO...if the crank pulley comes to be 1.9375" and the stock one comes to 1.875".these are "about" answers......then that means im going to have to use spacers behind the rest of the brackets?
jeepsr4ever
I wouldnt mess with it. Send in both pullies and we will make a nice accurate pulley for you. You must have a 1972 motor.
76-cj7
Well.....from what i under stand the heads that came off of it are from a 71' or 72' so im not sure exactly what year it is......but the rest of my bottom crank pulley i have all seem to measure the same size........ :-|
tufcj
AMC changed the water pump in 1973, going to a taller pump. The pulleys changed that year too, to match the pump. As long as you have a matched set, you're good, but you can't mix the short and tall pieces.
Bob
tufcj
76-cj7
Its got a oil pump housing from BullTear and a FlowKooler water pump on it......so im not too sure wut exactly im dealing with but i do know i need to take my to an over all height of 1.905" down to 1.85"......got a buddy that has lathe and a mill so ima just alter the one i have.
Patf10
just a question, what is the purpose for underdrive pulley?
76-cj7
Spins everything at a slower rate than stock......your alternator and power steering pump will be much happier spinning slower..........i know 6k RPMS ain't that high..but for stock accessories it is haha :t:
tufcj
Spinning the accessories (P/S, alt, water pump, fan, even A/C) slower takes less horsepower, so the engine has a little more, maybe 10-20 HP to put to the rear wheels.
The down side is that at low RPM, like idle, all the accessories put out less. They work great for a race car where you're trying to squeeze every bit of power to the rear wheels, but not so good on a rock crawler where you need every bit of accessory power (particularly cooling and P/S) at right around idle. Remember that a belt powered fan will turn slower too. If you use an electric fan, you're alternator is turning slower and has less output.
Bob
tufcj
76-cj7
I have a High flow water pump that i think spins a bit to fast and cirrculates faster than it cools....alternator is a 93 AMP AC Delco, and my P/S pump is a AGR High flow pump.......got a deal on the Rock Ram kit.......the one for 40" tires or bigger so i think i gots everything covered....but theres only one way to find out i guess
tufcj
Alternator output is generally rated at about 6000 RPM alternator shaft speed, about 2000 RPM engine speed, not at idle. The alt turns 2.5-3 X as fast as the crank. At 600-700 RPM idle, some factory alternators don't put out enough voltage to keep up. Underdrive pulleys will slow it down even more.
I've got a 100 amp Bosch on my CJ with stock pulleys, if I don't rev it slightly on start-up, it won't turn out my charge warning light (aftermarket).
Bob
tufcj
76-cj7
Hmm......at bout 600-700 RPMs with the stock pulley my gauge always read at 14 volts.......if it don't work out right then i'll just swap it out for a stock and save it for later i guess.... :-|
76-cj7
Well it worked out great....cirrculates the w/p enough so i wont overheat, spin p/s pump enough to steer awesome and spins alt. good enough to supply 13 volts!
