Water pump hardware question

[Slyclone]

I just had a idea to replace the hardware that fastens the water pump pulley to the pump. I removed the oem stuff measure it with a micrometer. I checked threads and they appeared to be 5/16-18. The threads are coarse. a 5/16-24 would be very tight threads visually

I purchased some new hardware to change things around in the engine bay and the 5/16-18 are not threading in but 1/4 a inch. I did not have a tap handy to clean out or check the threads.

I have a standard edelbrock waterpump which is like brand new. Not sure why the threads are so tight. I do not want to force anything on if it is not going to allow me.

Just checking to see if anyone actually knows what the thread pitch is.

 

[0966Sy]

They are metric, I can not remember off the top right now but if you have a metric thread gauge you should be able to figure it out. 5/16-16 is close but incorrect

 

[DaveP]

Re: Water pump hardware question

I also recall they're metric. M8-1.25

 

[Syclone#892]

Re: Water pump hardware question

5/16-24, the water pump is for a small block and they dont put metric bolts on small blocks. Check out the instructions for the tru-trac
http://www.billetspecialties.com/tr.../tru-trac-serpentine-system-small-block-chev/
On the 3rd page it shows the size of the bolts and says water pump pulley, length may not be correct for a stock pulley but thread size is.

I haven't had factory studs on the water pump for years but I thought one side of the stud was fine thread and the other was coarse, again its been a really long time but thats what I remember.

Good luck with the project

 

[DaveP]

Re: Water pump hardware question

No More Guessing. I just went out and checked an original, OEM, take-off 4.3 waterpump

M8-1.25 For both the holes in the waterpump flange, and the nuts that hold the clutch on.

the water pump is for a small block and they dont put metric bolts on small blocks.

You're kind of close, but not correct. Only the holes drilled into the block and heads are SAE. Accessories and other components that were not produced in the engine plant are metric. The engine plants never re-tooled to metric threads for the smallblock/V6.

If its a hole in the head or block, it's SAE. If it's not, it's metric.

 

[Slyclone]

Re: Water pump hardware question

I was going to say M8X 1.0 must be something else.

I checked a few things I can get M6 in the 1.0 pitch but not the M8.

So it must be the M8X1.25

It does not look like a fine thread it is rather coarse.

 

[Syclone#892]

Re: Water pump hardware question

From what I can tell they made studs for sae and metric, Dorman 23737 and 23733
One is 5/16-18 on one end and the other end is 5/16-24, the other set of studs is m8x1.25. It's been a while since I have had a stock part on my sy but I know for a fact mine are sae and I have an edelbrock pump. You have an edelbrock pump so it's possible they went sae or metric, I even found a tech bulletin for Cardone where they have the identical pump with 2 part #s, one is sae one is metric.
5/16 fine isn't much different than m8x1.25 in appearance so double and triple check so your fan doesn't come loose!
It sounds like Dave P found a stock setup where it was metric so hopefully that is the case for the guys with stock parts.
I do not believe the talk about only the block and heads are sae, there are very few metric threads on a syty engine and I will stand by that. I have replaced every bolt on my sy's engine with sae arp.

Good luck with the bolt search

 

[DaveP]

Re: Water pump hardware question

.
I do not believe the talk about only the block and heads are sae,

Believe what you want. But don't confuse others.

If the threaded hole was made at the engine plant, it's SAE. If the threaded hole was made elsewhere, like the P/S pump, Alternator, A./C compressor, Intercooler mounting bolts, turbocharger, coil bracket, the entire transmission, and the entire transfer case, it's Metric.

Find an SAE threaded hole in something other than the block, heads, and intake manifold, on a STOCK as-produced SyTy I'll eat crow. But you won't find any. You admit your recollection is hazy. Mine isn't. I know every fastener and wrench size in a SyTy by memory. I missed the pitch on the waterpump hub, but I got the metric part right, because I know it's a 13MM wrench; 1/2" is too tight and doesn't work.