Print Page - Do you have to drill the oil passage on a 79 shovelhead

Title: Do you have to drill the oil passage on a 79 shovelhead
Post by: jvall1201 on February 23, 2019, 06:56:43 PM

Is it absolutely necessary to drill the relief passage on a 1979 engine when installing a newer style oil pump. What will happen if you don't drill it?

Title: Re: Do you have to drill the oil passage on a 79 shovelhead
Post by: Ohio HD on February 23, 2019, 07:21:24 PM

Never tried it, I always drilled the case. I imagine the oil pressure may be erratic without it.

Title: Re: Do you have to drill the oil passage on a 79 shovelhead
Post by: Burnout on February 24, 2019, 08:13:30 AM

I think you are talking about the vent hole for the pressure relief valve.
I always drill this because if/when the passage fills with oil it will hydrolock the pressure relief valve.
Bad things happen to pumps with a malfunctioning pressure relief valve.
I could rattle off a list, but ask yourself how long you want your motor to run with no oil pressure.
And how good are you at replacing sheared keys beside the road?

Title: Re: Do you have to drill the oil passage on a 79 shovelhead
Post by: jvall1201 on February 25, 2019, 08:29:26 AM

Thank You for the reply. Really appreciate it.

HarleyTechTalk

Technical Forums => Shovel Head => Topic started by: jvall1201 on February 23, 2019, 06:56:43 PM