348 Power Steering Brkt. Holes - Impala Tech
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post #1 of 4 (permalink) Old 03-22-2016, 08:51 PM Thread Starter
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348 Power Steering Brkt. Holes

Has anyone drilled and tapped the 2 lower bosses next to the crankshaft to add the power steering bracket on a 348 W engine? I'm needing to know how deep I can drill. Thanks in advance for any help.
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post #2 of 4 (permalink) Old 03-23-2016, 12:57 AM
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Not sure on a W-Engine, but we used to drill and tap our Small Blocks for the Mounts to fit in our '55 to '57 Chevys years ago. Best I can remember we would drill deep enough for about a 3/4 Inch Long 3/8ths Bolt to fit into it.

To be sure, if no one jumps in, I would check with the boys over at 348-409.com

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post #3 of 4 (permalink) Old 05-31-2016, 11:04 PM
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If it's a 60-61 348 the holes are already drilled and tapped. 58-59 348s aren't.

EDIT: bolts are 7/16-14 x 3/4.

Last edited by Jalapeno; 06-17-2016 at 12:35 PM.
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post #4 of 4 (permalink) Old 06-01-2016, 09:44 AM
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I walked outside to measure a scrap block lying outside the garage door but decided flipping it over to run a caliper depth gauge into the hole was more trouble than it was worth (I woke up with a sore back and don't need the additional aggravation to my back this morning).

Without wishing to sound heartless to your problem I can say that the bolts that go into the hole are 3/8-16x5/8th inch long. This includes an eighth of an inch for the thickness of metal of the stamped steel motor mounts that allow you to bolt a 348 or a SBC into a 1939-57 Chevy car or light truck. So the bolt only feeds into the hole a half an inch. That is the most it should be taped with a flat bottom tap (you can start the thread with a pointed tap but you need to switch over once you get the threads started). Similarly you could start the hole with a twist drill bit but it should be finished with a flat mill tool to prevent hitting water. (If you do the bolt threads will require sealer to prevent a leak).

The lower hole on the passenger side enters the push rod drive shaft cavity. That rod that powers the fuel pump needs to be removed before you drill the hole. That hole will also be putting chips and filings into the oil pan as it is open from top to bottom to allow oil to drain back from the timing chain. Magnets and lots of grease on the tap can minimize the amount of metal that gets inside the motor, but the only way I would do this is to a bare block in a machine shop.

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