Vortec head accessory bolt holes

[Jim K]

Hi guys. I am trying to figure out the bolt pattern of the accessory holes on my 97 L31 vortec. I am pretty sure they are metric. If anyone has input I would greatly appreciate it. Thanks

 

[PlayingWithTBI]

I'm not sure about the Vortec but, the TBI head is all SAE, the ancillary equipment can be both.

 

[Jim K]

Thanks much

 

[L31MaxExpress]

Hi guys. I am trying to figure out the bolt pattern of the accessory holes on my 97 L31 vortec. I am pretty sure they are metric. If anyone has input I would greatly appreciate it. Thanks

Should be 3/8" x 16. Smaller bolts on the side for the wire looms are 1/4" x 20.

 

[Jim K]

Thank you. Yes you are correct. I chased the threads with a 3/8 tap. What had me confused was the intake bolts holes are metric. Thanks again