Under drive pulley?
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
You need to do some reading if you are perplexed. The alternator pulley is a overdrive (smaller) pulley so as to keep you output at spec. The third pulley is the waterpump pulley. The pulleys themselves are lighter being aluminum.
Race Director
Joined: Sep 2005
Posts: 10,878
Likes: 1
St. Jude Donor '07
What's the point of doing all three pulleys? Just changing the crank pulley will slow everything down. Unless you feel the need to slow the alternator down further, or just don't want to buy a new belt, I'm perplexed why the desire to spend all that money and time to swap the extra pulleys.
Same goes for decreasing the diameter of the crank (power) pulley.
It's like changing gears on a bike. When you use the smallest front gear and the largest rear wheel gear, it takes less forse to move the system. It also slows the speed of the chain. This will not increase any HP. It only salvages it from parasitic drag.
Fear not for overheating or low voltages. I made a 3,000 mile drive from MN thru the Tail and home in no less than 92 degree weather with the AC on 100%. Never a problem.
Race Director
Joined: Sep 2005
Posts: 10,878
Likes: 1
St. Jude Donor '07
Nope. It's larger to reduce drag. Alternators put out more than enough charging power at idle to charge a system. Very little time is spent at idle, so a 2 foot diameter pulley would still be enough to charge the system on the highway.
Tech Contributor
Joined: Jun 2004
Posts: 20,905
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Leverage. As a drag pulley, using a larger diameter pulley on the alternator increases me mechanical advantage of the system.
Same goes for decreasing the diameter of the crank (power) pulley.
It's like changing gears on a bike. When you use the smallest front gear and the largest rear wheel gear, it takes less forse to move the system. It also slows the speed of the chain. This will not increase any HP. It only salvages it from parasitic drag.
Fear not for overheating or low voltages. I made a 3,000 mile drive from MN thru the Tail and home in no less than 92 degree weather with the AC on 100%. Never a problem.
Same goes for decreasing the diameter of the crank (power) pulley.
It's like changing gears on a bike. When you use the smallest front gear and the largest rear wheel gear, it takes less forse to move the system. It also slows the speed of the chain. This will not increase any HP. It only salvages it from parasitic drag.
Fear not for overheating or low voltages. I made a 3,000 mile drive from MN thru the Tail and home in no less than 92 degree weather with the AC on 100%. Never a problem.
Race Director
Joined: Jun 2004
Posts: 13,961
Likes: 707
From: WI
Just a crank pulley:
http://store.summitracing.com/partde...540200&FROM=MG
ASP-540200 $74.39
Half the cost of the three piece March. But needs a new belt witch gets close to equalling the cost with steel instead of AL.
http://store.summitracing.com/partde...540200&FROM=MG
ASP-540200 $74.39
Half the cost of the three piece March. But needs a new belt witch gets close to equalling the cost with steel instead of AL.
Le Mans Master
Joined: May 2000
Posts: 7,033
Likes: 12
You took the time to respond to me, that shows somewhere deep down inside you do care, I'm honored.
Melting Slicks
Joined: Aug 2003
Posts: 3,401
Likes: 397
From: Lakeville MI
The March 3 pc. pulley sets come in two varieties, or at least they used to. Summit shows two versions for 84-87, but not for the later years IIRC
One with a smaller alt pulley called power and amp series recommended for auto trans cars, and one with a larger alt pulley called performance series or something like that.
On my 88, I have the old version that came with the larger alt pulley, and larger water pump pulley, which needs at least 800-900 rpm for decent charging.
The larger alt pulley version can also make use of a stock belt, which makes it attractive saving the cost of a new belt.
I ended up running a shorter belt anyway to put the tensioner mid-range.
One with a smaller alt pulley called power and amp series recommended for auto trans cars, and one with a larger alt pulley called performance series or something like that.
On my 88, I have the old version that came with the larger alt pulley, and larger water pump pulley, which needs at least 800-900 rpm for decent charging.
The larger alt pulley version can also make use of a stock belt, which makes it attractive saving the cost of a new belt.
I ended up running a shorter belt anyway to put the tensioner mid-range.
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