PDA

View Full Version : Alum Crank Pully



kenewagner
04-20-2006, 01:41 PM
Does replacing an existing steel crank pully with a Alum one require that the alum one be balanced? I still have the stock balancer.

Ken

90coug
04-20-2006, 03:35 PM
You might be able to get away with it but I wouldn't risk it, get it balanced and know it's done right.

68COUGAR
04-20-2006, 04:10 PM
Does replacing an existing steel crank pully with a Alum one require that the alum one be balanced? I still have the stock balancer.

Ken
I assume that you're talking about the alum. pulley ONLY, and not the whole rotating assy. (Crank, Rods, Pistons, Flywheel, Balancer, & new alum. pulley)?

Our engines are Zero-Balanced. So if you're using an SC crank pulley, just bolt it on & it'll work fine. Remember that ONE of the 4 bolt holes in the pulley is off center. If the holes don't line up with the threads, turn the pulley 90 degees & try again. Repeat until ALL the holes like up with the threads.

How long do you think a company would stay in business, if their SC crank pulleys were unbalancing engines? I would guess that ANY aftermarket crank pulley is more balanced than the OEM pulley. Remember that the some of the OEM pulleys had to have weights ADDED to them, to bring them into balance. I believe that the quality control on aftermarket pulleys is much higher than OEM.

68COUGAR

68COUGAR
04-20-2006, 04:24 PM
You might be able to get away with it but I wouldn't risk it, get it balanced and know it's done right.
Your statement implies that all aftermarket crank pulleys are made WRONG or BADLY?

Do you know of ANY instance where an aftermarket Supercoupe pulley has unbalanced a motor? Considering the number of happy people using the 3 aftermarket crank pulleys avail., I'd say that your fears are groundless.

68COUGAR

Mike8675309
04-20-2006, 05:02 PM
If you're not sure, you may want to have it checked. Since Aluminum pullies are typically made from Billet blocks of forged aluminum, and since they must be perfectly uniform, they are inherently zero balanced. If there is a lack of balance it would be due to an error in machining or if it was dropped.

FredSC
04-21-2006, 07:59 AM
I think the balancer and the pulley were zero balanced as a unit when bought from FORD. Putting a zero balanced pulley on a regular SC balancer would probably need to be balanced. I agree with 68cougar, don't risk it.

XxSlowpokexX
04-21-2006, 08:33 AM
Maybe someone else will chime in on this but teh balancer and pulley from what I know are zero balanced from ford as a unit. HOWEVER I would hope that the balancer itself is not the reason they do that but that big steel pulley.

Perhaps March or ASP has tested this being larger companies but I highly doubt anyone else producing aluminum pulleys has done so for our cars. Perhaps they checked their own pulley but I doubt they checked them with a balancer. And even if they did, each balancer would be different if that is part of the reason ford balanced balancers and pulleys as a unit.

With all that said I dont worry about it.

David Neibert
04-21-2006, 08:54 AM
I and several others have installed underdrives onto a stock balancer and ran them for several years without any problems. IMO, Removing the balancer just for balancing it with the new crank pulley will do more harm than good, because of the aluminum inner hub of the stock balancer deforms slightly and won't fit as tightly when reinstalled.

If your really worried about it, replace the stock balancer with a BHJ unit.

David

Paul93SC
04-21-2006, 08:54 AM
Does replacing an existing steel crank pully with a Alum one require that the alum one be balanced? I still have the stock balancer.No. As others have stated, you just bolt it on and go.

The OEM harmonic damper is neutral-balanced, as is the OEM steel-stamped crank pulley. They are NOT balanced together as a unit.

The steel crank pulley usually has one or more weights welded on the inside surface for balance (which BTW can rust and fall off: I've seen this happen several times). The harmonic damper has a series of holes along the outer rim for balance pins, however the factory used these for a final "dynamic engine" balance, not for pulley/damper balance.

In the "early days" Bill Hull made a mistake and assumed they were balanced as a unit (probably because Ford sold them together as a unit).

kenewagner
04-21-2006, 09:45 AM
I have talked to Victor at Spinningwheels who is providing me the pully. He said bolt it on and go which is what I am hearing here as well. I have a dyno day comeing up in a week so this is just one more thing I have to get done to be ready

Ken

lilredstang
04-21-2006, 03:04 PM
Some Shops, Like The One I Use, Charge Nothing Just To Check It. Odds Are You Will Be Fine, But I Figure Better Safe Than Sorry.

XxSlowpokexX
04-21-2006, 03:12 PM
In the "early days" Bill Hull made a mistake and assumed they were balanced as a unit (probably because Ford sold them together as a unit).


Thats good to know. But makes you wonder though. I assume they had to dynamically balance teh motor after installation fo that pulley because its a bahemuth!

I did have a balancer failure a week after installing aluminum puilleys on my 94. Was most likely a coincident though. I never worried about it

Paul93SC
04-22-2006, 09:26 AM
Thats good to know. But makes you wonder though. I assume they had to dynamically balance teh motor after installation fo that pulley because its a bahemuth!That stock steel pulley IS heavy isn't it! Installing a lighter aluminum pulley has got to help take some of the strain off of the harmonic balancer, even if it's only stock diameter (no underdriving). Because our OEM dampers are somewhat weak, I believe everyone should get an aluminum version for this reason alone.

With regard to the little harmonic damper balance pins, my understanding is that Ford was concerned with engine vibrations due to the fact we don't have a separate balance shaft like the N/A 3.8's do. When you rebuild the engine all of those pins should be removed (mine are gone now - I did have 3 on one side when the motor was OE).

XxSlowpokexX
04-22-2006, 11:46 AM
Not only that Paul but the extra rotating mass on the crank snout. I have run roots tye blowers on SBF's with nodular iron cranks and dam near twisted the snout of the crank off from the stress of the blower and teh extra weight of the pulley assembly. I believe this is one reason ford went with a steel crank as well as a jackshaft system.