I was looking at a few web sites last night for some under drive pulleys, those that I found for an '89 noted "recommended for automatics"

My question is why and does anyone know where I can get a set for a manual trans?

Thanks.

 

I see no diff between an A4 and a stick so far as underdrive pulleys are concerned...

For example, my March folder lists the same P/N for '88-'91 Vettes, with no mention of transmission type.

 

Thats the web site I looked at, the "disclaimer" was at the bottom.

Another question, steel or aluminum?

 

Both materials are fine for street use. IMHO just the crank pulley is all thats necessary for the street. If you also use the alt pulley, the reduced speed will cause the system to draw on the battery at lower engine speeds. For general street driving, this is not recommended. Unless you carry jumper cables...

 

I run the March Power & Amp series steel pullies but only the underdrive crank and overdrive alt pullies.

In retrospect I feel the Al would be the best choice for reducing parasitic drag due to lower rotating mass.

 

That's a good point. it sure would be a drag to find that out after.

 

No need to ask me how I know.....

 

L-98 is a known alternator eater. You wouldnt want your alternator turning slower than it already is.

 

That's why the overdrive alt pulley is needed to maintain charge at idle.

 

Does anyone know the correct belt size or part number if I use the crank pully only?

 

65Z01,

what part numbers are the pulleys you use?

 

Sorry but I don't have those numbers now and their worn off the belt.

I had to go back to Auto Zone several times to get just the right belt even though I did a rougn estimate by measureing with a piece of string once the new pulleys were in.

BTW, first I had only the underdrive crank pulley installed as I couldn't remove the alt pulley. When the alt died I took the ovedrive (smaller) alt pulley to the AC Delco store and had them install it onto the new alt.

Of course after the overdrive alt pulley went on I had to once more get a slightly smaller serp belt.

 

Here's my "review" of my underdrive crank pulley...
http://forums.corvetteforum.com/show...ght=underdrive

The belt number for Mid America underdrive crank pulley only is:
DAYCO 5060865 or
GATES K060865

Obviously, if you add the smaller (OVERdriven) alternator pulley, this number may not be correct any longer. My car charges fine without it, but I have stick car that idles slightly higher than an auto car does in drive. I'll know this Spring if mine becomes an issue, since I am doing an automatic transmission conversion over the Winter...

 

I have a brand new belt, 20 + shipping

 

I think I can pretty much guess that one
Was the mod worth the time and money?
Bryan

 

from my post linked above...

I have no charging system issues.
I have no cooling system issues.
I have no regrets buying this part.

I'm actually kind of surprised that more people don't use them.

 

Honestly its not. Yes there are claims from March pullys that they add 10 horsepower WHICH THEY DO, but its only relieving the power steering pump and alternator from going so fast. Its not worth having your alternator wear out faster. If you really want to spend over a 100 dollars on some pulleys that add that little horsepower have at it. Now, I thought about getting them but then I learned its a waste of time. You wont feel the performance gains, so not worth my time. Id rather save up for something better.

 

Yes there is a definite SOTP feel and throttle response is quicker.

I have no data to back up my claim.

 

Hey, thanks guys.
Bryan

 

B!@cK 86 V3tt3:

I don't know of anyone who can honestly "feel" 5-10rwhp difference...but that doesn't mean it isn't there.

Not sure why you claim they are a waste of time, but they do what they claim to do, which is slow down the accessories to free up some horsepower stolen from parasitic drag. The theory that you'll wear out an alternator prematurely from slowing it down isn't accurate.

If the C4's are known for "eating alternators", then why do they do it with stock pulleys? Slowing them down as slight as an underdrive pulley does isn't going to make that happen any sooner or later than it was going to happen anyway.

I've owned at least a dozen 5.0 Mustangs over the last 12 years, and underdrive pulley sets are one of the first mods done...on mine, or anyone else's. Why? Because they make (or should I say, free up) horsepower. Usually 5-10 horsepower at the wheels, sometimes a tad more. Never once have I had to replace an alternator on any of those cars. My point is, if the Corvettes have an issue with alternator life, it has nothing to do with the pulley. It's a problem that's already there.

When you put the price of a pulley set into perspective, it's a very cost effective mod. You figure if you pay $100 for 10hp...and most say that headers give you 20-25hp at a price of $600-$1000+....which really is the wiser, more cost effective mod? Parasitic losses that are eliminated or reduced, have been proven over and over again to free up hidden horsepower. No different than air pump removal. Some say it doesn't cost any power, but I've personally made 8rwhp on my last car by bypassing the air pump with a shorter belt. The same car went .5 second quicker and 4mph faster by replacing steel driveshaft with an aluminum one, an electric fan, and a set of underdrive pullies. That was $300 worth of mods had I bought the stuff brand new.

The less drag you have on an engine/drivetrain, the better it will run...that's a given. The little things add up and are just as important as the big things.