Drill / Tap front engine mount hole - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**chev-obsession** · 01-25-2023, 11:29 PM

I am needing to drill and tap this hole to add a factory GM serpentine belt system. Block is a 327 from a 65 impala This boss is on the passenger side between the timing cover and fuel pump. The hole needs to be 1/2” to 3/4” deep at the most.

Any tips or advice before I start drilling?

**Getter-Done** · 01-25-2023, 11:44 PM

Yes, I have Advice

I would make a drill template plate/ jig.

One that you can use the timing cover bolt holes that are beside to Bosses.

Then use a Drill stop on the drilling process.

RustyPile · 01-26-2023, 05:18 PM

Quote:

Originally Posted by chev-obsession

I am needing to drill and tap this hole to add a factory GM serpentine belt system. Block is a 327 from a 65 impala This boss is on the passenger side between the timing cover and fuel pump. The hole needs to be 1/2” to 3/4” deep at the most.

Any tips or advice before I start drilling?

On blocks with pre-drilled holes, the upper hole opens up into the passage for the fuel pump pushrod.. remove the fuel pump and rod before drilling.. THEN, be absolutely sure you remove all debris from the passage.. The upper end of the rod passage opens up onto the camshaft.. Left over debris could wreak havoc to your engine.

**MySons68C20** · 01-26-2023, 05:48 PM

Quote:

Originally Posted by RustyPile

On blocks with pre-drilled holes, the upper hole opens up into the passage for the fuel pump pushrod.. remove the fuel pump and rod before drilling.. THEN, be absolutely sure you remove all debris from the passage.. The upper end of the rod passage opens up onto the camshaft.. Left over debris could wreak havoc to your engine.

This!!!^^^^^^^
Well done Rusty!

**Getter-Done** · 01-26-2023, 06:46 PM

If you are not in a hurry I can make you a jig.

**chev-obsession** · 01-27-2023, 03:30 AM

Thanks for everyone’s advice! I got it drilled and tapped successfully. Only went in about 1/2”-5/8”. It never went into the fuel pump pushrod hole.

**MySons68C20** · 01-27-2023, 11:44 AM

Quote:

Originally Posted by chev-obsession

Thanks for everyone’s advice! I got it drilled and tapped successfully. Only went in about 1/2”-5/8”. It never went into the fuel pump pushrod hole.

I was wondering how deep that boss is.
Thanks for the update!

**chev-obsession** · 01-27-2023, 01:45 PM

Quote:

Originally Posted by MySons68C20

I was wondering how deep that boss is.
Thanks for the update!

You bet. I have a bare bow tie block, it was drilled about 1” and still wasn’t into the pushrod hole either. I posted this since the block I had to drill is a different casting and wanted to hear from people who have done it.

**The Rocknrod** · 01-27-2023, 04:43 PM

My roller cam 350 was drilled but not all the way through. Pain in the keester to install a fuel pump.

01-25-2023, 11:29 PM	#1
chev-obsession Senior Member Join Date: Jul 2008 Location: kennewick, WA Posts: 1,466	Drill / Tap front engine mount hole I am needing to drill and tap this hole to add a factory GM serpentine belt system. Block is a 327 from a 65 impala This boss is on the passenger side between the timing cover and fuel pump. The hole needs to be 1/2” to 3/4” deep at the most. Any tips or advice before I start drilling? Attached Images __________________ 1965 c/10 swb 1969 c/10 lwb

01-25-2023, 11:44 PM	#2
Getter-Done Senior Member Join Date: Dec 2009 Location: TN. Posts: 7,726	Re: Drill / Tap front engine mount hole Yes, I have Advice I would make a drill template plate/ jig. One that you can use the timing cover bolt holes that are beside to Bosses. Then use a Drill stop on the drilling process. __________________ ________________________________________________________________________________________ ____________________________________________ 84 Chevy K-20 63 Impala (my high school car) http://67-72chevytrucks.com/vboard/s...Crew Cab Build

01-26-2023, 06:46 PM	#5
Getter-Done Senior Member Join Date: Dec 2009 Location: TN. Posts: 7,726	Re: Drill / Tap front engine mount hole If you are not in a hurry I can make you a jig. __________________ ________________________________________________________________________________________ ____________________________________________ 84 Chevy K-20 63 Impala (my high school car) http://67-72chevytrucks.com/vboard/s...Crew Cab Build

01-27-2023, 03:30 AM	#6
chev-obsession Senior Member Join Date: Jul 2008 Location: kennewick, WA Posts: 1,466	Re: Drill / Tap front engine mount hole Thanks for everyone’s advice! I got it drilled and tapped successfully. Only went in about 1/2”-5/8”. It never went into the fuel pump pushrod hole. __________________ 1965 c/10 swb 1969 c/10 lwb

01-27-2023, 04:43 PM	#9
The Rocknrod Moderator Join Date: Aug 2011 Location: China Spring, TX Posts: 7,280	Re: Drill / Tap front engine mount hole My roller cam 350 was drilled but not all the way through. Pain in the keester to install a fuel pump. __________________ Master Chief, US Navy, Retired 1964 C10 Step-side Short Bed - In Progress 2009 2500HD Duramax LTZ 1948 GMC Panel 1956 Big Window Stepside 1953 5 Window Chevy Stepside 1932 Coupe New Seat Foam for Bench Seats?



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