[Bob_Myers]

Nope, nothing, bolted on

[Just Add Boost]

That is odd. When I first got the Essy pump I had to enlarge my stock pulley to fit the center pump shaft. After reading that they should be the same size I figured maybe I just had an older Essy pump with a larger shaft.
Fast forward to now and buying the Essy pulley that looks like Bob's, it fits the Essy pump perfectly but the center hole is definitely too big for the stock pump.
No idea what the deal is. Stock pump can't be an off the wall incorrect part or the stock pulley would not fit.

[TurboRay]

Well.....that pic sure had me fooled, Bob (not that hard to do, apparently). It must be an optical illusion:



:headscratch: <font color=navy>

[Bob_Myers]

Nothing there, that pump is sitting on my shelf and I looked before replying. My parts history is

1) stock type pump is a parts store replacement that went on my new at the time shortblock 6 years ago. Started out with a factory single serpentine factory pulley on it.

2) Esslinger pulley was likely pretty early in their production. Like Brian said they was available and I bought one. I’m certain at the time it was sold for stock type stuff as I think I was the first to show them it was smaller diameter than a stock pulley.

3) Esslinger pump was bought lightly used, but as I understand it from an older race engine that was parted out.

I was actually prepared to drill the center bore on the pulley when putting my new bullet together but it slid right on. That’s why I tried assembly before dropping it in. It fit, bolted it down, moved on, lol.

Some mysteries will never be solved

[88TurboBird]

I know I’m reviving an old thread here but I just took delivery of an Esslinger billet water pump and the center bore on the stock pulley is too small as some others have noted on here. I do have their pulley on the way though. 

My question for those who have the billet water pump. What are the thread sizes for the four pulley holes? I’ve tried m8 1.0 and m8 1.25 (stock bolt) and neither will thread in all the way. I’ve checked the threads on the pulley “snout” and everything looks good

[88TurboBird]

Found out the thread size is 5/16 - 24 for anyone who needs it in the future.