Technical 350 Chevrolet Water Pump Bolt size?

Probably a simple question, if you know. I'm changing water pumps on a mid-70s 350. The old one had three different lengths of bolt among the four bolts holding it on. I want to use polished button head bolts, so I just can't buy a kit, so please, what is the correct length(s) of bolt? Thanks.

 

Is it a short pump? or a long pump? if you can't tell the difference by looking at it, post a picture

 

Long

 

I only have a short pump to measure....it uses several different bolt lengths.

but looking at the internets, it looks like on the long pump, they should all be 2" long?

also, button head bolts are at the very bottom of the list of bolt head types I'd use on anything, ever.

 

If you want polished, here's probably your best option. If you have to have button-heads, this product page tells you the lengths.

CHEVROLET ARP 430-3202 ARP Water Pump Bolt Kits | Summit Racing

Here are all ARP options for long water pump on a SBC.

ARP Water Pump Bolt Kits CHEVROLET Chevy small block Gen I - Long Water Pump Style (application) - Free Shipping on Orders Over $109 at Summit Racing

 

2.0 inches, which is what I found, too

 

What happen to getting out the tape measure? Is it all tap tap get an answer now and day’s?

 

Polished button heads would indicate SS?
Not my first choice of water pump bolts.

 

Four at 2.0 and one at 2.5 are what come from ARP.

 

He said he had 3 different lengths of bolt. What happened to reading?

 

Thanks, What's the 2.5" for?

 

Way more socket heads on the motor than not so I'm trying to match with less work. Call it a custom?

 

The ARP kit with the 2.5" bolt also fits big blocks, which use one long bolt

 

A socket head would be OK

A button head screw would be worthless in a couple years .

Jaguar V12’s had button head screws on the water pump as it was to close to the crank pulley for anything else .
Doing a water pump was a complete nightmare !!!

we would call it the 10 and JD job

10 hours labour and a bottle of jack daniels !!

 

Measure the water pump then add for threads is what I’m say’n. It’s not rocket science to see which of the 3 bolts would work best then measure that one. And if it’s a diameter and thread count issue, use the thread gauge that most hardware stores have for one’s convenience.

 

Or just ask those who have done it if you're unsure.

 

Jim is right, I just checked a long water pump I have in the garage and all four need the same length.

 

Why would a button head be so much worse? If both are the same material, what makes the button head so much harder to remove?

Genuinely curious.

 

Look at the size of the "hex" on a button head 3/8" bolt, compared to the 9/16" hex on a normal hex head bolt. Or even the 5/16" internal hex on a normal Allen head bolt.

They really like to strip, because the tool size is so much smaller than the thread size.

It's just a really bad design.

And stainless button heads have the bonus of being a softer material.

 

Button Head and Flange Head bolts can exert higher clamping loads without a washer underneath cupping

ARP make a stainless steel accessory bolt kit for Chevy's.
They also make a small hex flanged bolt option in polished stainless

A whole kit is a nice way to keep the engine looking nice.
I had them on my Big Block race engine and they didn't look shitty after using 2-3 times like normal bolts.

@5window my Trailer uses Zinc button head cap screws throughout [just to class it up a bit] They are cheap!!
I didn't want to weld the coupler to the trailer [so I glued it ]