BBYSTWY

So I have found a way to run a cog belt on my 256 blower if I end up running this blower...my question is for pulley sizing...

blower pulley sizes available....

28,30,32,34,50 tooth sizes available

From what I've read on the conversion this allows you to run a standard cog pulley on the crank like a 6-71 would have...

What size crank pulley should correspond to 5-8 lbs of boost or more?? just kinda would like to get in the ballpark if anyone can offer insight so I don't have stacks of unusable pulleys

Thanks!!

Stewart

Griff

Not sure why you would want to do that. Cogs are way more expensive and not as readily available as serpentines..
Its all math. Calculate the how much its overdriven now.
If its a 6" lower and 4" upper, then its 50% overdriven (6 divided by 4 = 1.50 or 50% overdriven)

BBYSTWY

Well...here's my issue...I have v-belt accessories and the 575 sci lower pulley uses serpentine accessories...I have researching this swap more after I started this thread and it may not be as simple as I thought...trying to come up with a lower pulley solution that will net me 5-8ish lbs boost..I was thinking the cog would be an easy conversion but come to find out 256 shafts are splined not keyed like the 177 so the swap will take a little more enginuity than I thought...so maybe lower pulley solutions may be a better way to go??

I had a 525 sc to start with

Stewart

JRider

The 256 pulleys are getting tough to find, you may have some luck posting in the wanted part of the swap shop. That being said converting to a cog system wouldnt be a bad way to go. You could take the stock 4" 575 upper pulley and machine it into an adapter for the standard 6 bolt roots pulleys, although there may be some alignment issues to work through. Nothing spacers couldnt solve. That is assuming you have access to a lathe.

Mohavvalley

I have a 3.25 splined 575SC upper pulley if that'll work $70 shipped.

I'm pretty sure TBS has keyed shafts for the 250's, if you want to go that way also.

Also, you said you said you started with a 525sc. I assume it had 177 blowers on it, and from your comments they had keyed shafts? If so do you have a keyed shaft for the 177 OR any upper splined pulleys for it? If so I could use either in my build, I have a splined shaft and need to swap to keyed shaft & keyed pulley OR get a splined 10 rib pulley in the 3.25" to 3.5" range.

Pm me

Thanks

JRider

After rethinking this it may be smart to keep the grooved pulley, the 250/6 blowers are not very stout. If the motor backfires with the cog belt the belt cannot slip and there is the possibility of throwing the blower out of time due to the bevel cut gears. You may be farther ahead finding serpentine pulleys for your accessories. You need one for alternator, power steering and water pump?

I thought you had found a 671 series blower? If you can use that it is a lot more blower than the 256. I think I might have a snout laying around for a 71 series.

Also, the 3.25" pulley would put you at 6 to 7 psi depending on cam and heads.

BBYSTWY

Mohav...I don't have anything left from the 525..already sold the blower and everything...sorry..I'll let you know on that pulley whats I figure out what I'm gonna do thanks!!

As far as the 6-71..thats ideally what I'd like to do..I have a standard GMC 6-71 that I need to get converted through dyers...unfortunately I don't have the funds for that unless the 256 setup sells which its been listed for awhile with minimal hits

I was thinking however today before bed(I'm on nightshift lol) has anyone tried putting a blowershop or any other snout on a 256?? from pictures it looks like it will bolt up just unsure on the inside couplings and what not??

I was also thinking the same thing about backfires with a cog setup...that's why I was curious about the snout swap and if that's the case I could run blower shop 250 pulleys and be done

Hopefully this thing will sell soon and all of this won't matter but until then I have to prepare and plan to run the 256 as its what I have and its like new

As far as swapping to serpentine accessories...I think I would have a small fortune in that??? I would need all the brackets too I assume to make everything line up right?? I am also running a crossover no water pump so I would have to buy the crossover with the pulley delete on it and that thing is outrageous priced lol

thanks for all the help so far guys!!

BBYSTWY

As far as heads and cam on my build...I have dart iron eagle heads and the cam is still up in the air...I bought one that came with the heads but not sure if it will work for me..I think I need to start a dedicated thread on that and see what people say...My engine builder said he's gonna check it out but the numbers are ground off as it was a custom grind for the guy I bought the heads from so he suggested just spending the couple hundred bucks and buying one that I know what it is and know it'll work but I have no idea what to get lol

indysupra

BBYSTWY

Will do thanks!! need to do wome measuring when I get home from work..i think the blower pulley is smaller than stock to compensate for the chiller..looks like it was bought as a kit