crank shaft pulley

Randy N Connie

Registered User
My stock crank shaft pulley was 23.250 circumference.

I put a 23.875 aluminum pulley on the crankshaft to drive the blower jackshaft,
Would any one know how much this would speed up the blower with a
10% OD blower pulley.

randy
 
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I think what you meant to say is that the diameter of the new pulley is 6.2" rather than the stock 6.99".

Using that, I get an underdrive of about 2%. In other words it would spin slower than stock. In order to increase blower speed you would have to increase the diameter of the crank pulley.
 
Well I put the March UD pulley set on I was just woundering what
change I had with a 10% od blower plulley.

I though the blower would still be a little od. but not the 10%.
 
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The ASP set should not change your SC drive ratio at all. ASP only changes the accessory drive ratio as far as I know. Are you sure that it has changed the jackshaft drive pulley size?
 
Dave,I bought the aluminum UD pulleys from SCP.On the cranksfaft
pulley,both the front and back of pulley are a smaller dia. that stock.

T he circumference of 23.875 is the back part of the pulley (closest to the
motor.

I didn't notice at first, both crankshaft pulley surfaces diameter are smaller.
The jackshaft pulley drive part is a smaller dia. And the acc.drive portion
of the crankshaft pulley is also a smaller dia.

When I bought them I just thought that that acc. would be a smaller dia.

I was messin around with the water pump.when I noticed that the crankshaft pulley
was smaller on both sides.

So I need to figuar up what I have, then machine myself a new jackshaft pulley
to make up the differents.

I need to get the numbers of what I have.and maybe go with a jackshaft OD
pulley of maybe a 10% to15%.For the shootout may go with about 20%.

More bolt on's for my stock motor.That I have to run in the mod class.Since
I have to run in the mod class ,and if I have time to make them.I plan on
every bolt on mod I can design and come up with between now and the race.
Short on time so I am looking into getting a jackshaft pulley from BTM.

RANDY
 
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Randy,

Something is wrong with the pulleys you received if there is any change to the diameter of the pulley that drives the jackshaft. My ASP set was only smaller on the acces. drive portion of the crank pulley.

David
 
This is a ruff circumference measurement the third one.
Looking at the front of motor with pulley bolted on.

March..... FRONT 18.750....BACK..23.875

STOCK. FRONT 21.750....BACK.23.250

David N. I remember reading a post of yours.you and everyone
else that had a post, said they had a timing mark on there ASP
pulley.My ASP pulley did not have a timing mark.So I think maybe
now for sure I have a different ASP pulley.

I not whinnig,This may be good:p My pulley is lighter than every one
else's ASP pulley.:D

I will just have to add a aluminum jackshaft pulley.And make it lighter to.
I was going to due this anyway.I just didn't know it was a have to case.

My little stock motor is looking better every day,even the mistakes I have
had.

randy
 
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Have you tried your belts on that crankshaft pulley? Should be 8-rib for the accessory and 7-rib for the jackshaft. It sure sounds like the wrong pulley!
 
Well i made a mistake on posting my measurement all numbers needed 12 added.
And I did this.

And my pulleys are MARCH , NOT ASP.

but my MARCH pulley is still smaller on the crankhaft That drives the jackshaft..
than what the stock pulley is by .625

Sorry for the mistake it has heen one of those duuuuu! day:confused: :confused:

RANDY
 
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Randy, are all 3 of your pulleys aluminum then (crank, water pump and alternator)? Dont recall Bill ever carrying March underdrives.

Paul
 
Yes I got them from Bill E. he sells ASP now.
I called him he offered to take them back.
I have had them long enough,That I feel I
should keep them.Beside that, I think that
this size will work to my benefit.And I have
chucked the crank pulley up in the lath this
evening.Because I have seen a couple spots
that need to be lightin up,and i am going to do
that the first thing in the morning.

I have not ever ran the complete set of pulleys.
just the crankshaft and waterpump pulley.I have
never used the alternator pulley.I use the Alt. for
a ash tray. And yes they are aluminum.

With my new set up I am going to lightin up the
crank pulley and throw the water pump pulley away
and start using the aternator plulley ,and I am kicking
around buying the jackshaft pulley from BTM. I am waiting
to see how much the waterpump ,ac,& power steering
will cost me to delete.

And Bill E. is the best SC vendor I have dealt with.I don't
have a prolem with the pulleys.Just tring to make them better.
I am a racer,So I lightin parts up untill they break then back up
one step. Paul What kind of warranty would you have for me on
your parts.

RANDY
 
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1 year on the jackshaft if it is unaltered. I would still like to know if your water pump and alternator pulley are aluminum or steel?

Paul
 
Paul, Yes they are all aluminum March pulleys.

What I need to know is with this .625 smaller circumference crankshaft
aluminum pulley.And a steel 10% OD blower pulley,Then add your 10%
OD jackshaft pulley what kind of blower OD will I end up with.

I would like to figuar this out.

I want to over drive the blower but not 20%.This is why I think
that the smaller March crankshaft pulley will work for me.

But I would like to have some numbers so I know where I am at.
For future mods this coming month.For tuning to the max edge.

Are your quick change OD aluminum blower pulleys thick enough to cut down if I want
to shave a little off.

randy
 
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I have the March Pulleys from SCP. They are aluminum. I have yet to install the Alternator Pulley.


I measured mine Stock to March using a wasted belt cut in half. It appears that my rear section is the same as the stock roughly measured at 22 5/8. The front section is 20 1/4 for the March compared to 23 1/2 stock. Like I said roughly measured but it appears my set is ok.



I have another SC that I need to put pulleys on along with a BHJ balancer. What pulleys are preferred?
 
I have the the march underdrives and a BHJ with no complaints other than the fitment of the alternator pulley. I was on of the first deliveries in the group buy, so I had to massage my alternator pulley to get it to fit. Changes were supposed to have been made to fix this.

The BHJ damper is heavier than the stock unit, so I went with the March set to keep weight at the crank down.

Aaron
 
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