SB Motor Mount Bolt - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Bram · 02-23-2004, 12:21 PM

Ok everyone, I need some help.
Here is the problem, I have the small block motor mounts mounted on the engine right, well my problem is the single bolt that goes up through the middle of the tower into the motor mount, (By the way this is a 72 4x4). I need to know the length of the bolt and any other hardware that goes with it, lock washer ...etc?
The problem is I can't find the original hardware I pulled out, since I cleaned out my shed, so I’m relying on my memory which is gone. The tower hole where the bolt goes is pretty large, and I can't remember if there was a rubber piece or just a washer, or what?
Can anyone help me out, it sure would be appreciated.

*rage'nrat638* · 02-23-2004, 02:28 PM

9/16 X 1" WASHER AND A LOCK WASHER WILL BE FINE

Bram · 02-23-2004, 02:44 PM

I don't understand? The bolt goes through the tower, and threads into the motor mount, is there room to get behind the mount to put on a lock nut?
Also when I put a bolt in, the only thing that keeps it from going through the tower is the washer. When I tighten it down the washer starts to bend in? This is why I thought I was doing something wrong?

*rage'nrat638* · 02-23-2004, 03:02 PM

a lock washer sorry

try a smaller washer...how big of a washer are you using?

Bram · 02-23-2004, 03:25 PM

That's the problem, if I use the correct size washer it goes right through the hole. I tried using an oversized washer but then it bends.
Does anyone have any pictures of the 72 4x4 motor towers? I want to check and see if mine are the same.

Tx Firefighter · 02-23-2004, 08:24 PM

WHOA! I'm calling foul on this one!

That isn't a 9/16 bolt. It's a 3/8 x 1 inch long bolt. Yes, a 9/16 wrench or socket fits it, but that don't make it a 9/16 bolt.

For the washer, I use old harmonic balancer bolt washers on mine. They are thick as hell, have the right 3/8 size hole in them, and they are real big around so they don't go into the hole.

tom hand · 02-23-2004, 10:36 PM

Hmmmm..mine has a 7/16 14 x 1 bolts...pretty sure it's factory...anyone else?

Bram · 02-24-2004, 12:56 AM

I guess I don't understand why they made the hole so big in the first place? Wouldn’t it be stronger to have the correct size hole? Or does it give it enough slack with the bigger hole that when the engine moves forward or backwards a little it's less likely to break? I don't know, I guess I'll find the toughest washer I can, and torque the SOB down so my Big Block won’t rip them out.

**kwmech** · 02-24-2004, 02:38 AM

I have used 7/16-14 x 1.25'' long with the harmonic washers and a lock washer.

Tx Firefighter · 02-24-2004, 07:44 AM

I am a moron. I just put my big block in on Saturday and yes, they are 7/16 bolts. I have no idea why I said they were 3/8 inch. But, never the less, I used the harmonic balancer washers to compensate for the big holes.

JimKshortstep4x4 · 02-24-2004, 10:00 AM

The factory ones are 7/16-14x1 1/4" (not positive on the length, 1" will work). The were set up with extra thick washers and lock nuts. Harmonic balancer washers will work fine but you may have to compensate for length since the balancer washers are very thick.

Jim

02-23-2004, 12:21 PM	#1
Bram Broke Join Date: Aug 2001 Location: West Plains,MO Posts: 385	SB Motor Mount Bolt Ok everyone, I need some help. Here is the problem, I have the small block motor mounts mounted on the engine right, well my problem is the single bolt that goes up through the middle of the tower into the motor mount, (By the way this is a 72 4x4). I need to know the length of the bolt and any other hardware that goes with it, lock washer ...etc? The problem is I can't find the original hardware I pulled out, since I cleaned out my shed, so I’m relying on my memory which is gone. The tower hole where the bolt goes is pretty large, and I can't remember if there was a rubber piece or just a washer, or what? Can anyone help me out, it sure would be appreciated. __________________ 72CheyenneSuper1ton4x4BigBlock

02-23-2004, 02:28 PM	#2
rage'nrat638 Account Suspended Join Date: Mar 2003 Location: THE FALL GUY CHICAGO IL Posts: 5,883	9/16 X 1" WASHER AND A LOCK WASHER WILL BE FINE Last edited by rage'nrat638; 02-23-2004 at 03:02 PM.

02-23-2004, 02:44 PM	#3
Bram Broke Join Date: Aug 2001 Location: West Plains,MO Posts: 385	I don't understand? The bolt goes through the tower, and threads into the motor mount, is there room to get behind the mount to put on a lock nut? Also when I put a bolt in, the only thing that keeps it from going through the tower is the washer. When I tighten it down the washer starts to bend in? This is why I thought I was doing something wrong? __________________ 72CheyenneSuper1ton4x4BigBlock

02-23-2004, 03:25 PM	#5
Bram Broke Join Date: Aug 2001 Location: West Plains,MO Posts: 385	That's the problem, if I use the correct size washer it goes right through the hole. I tried using an oversized washer but then it bends. Does anyone have any pictures of the 72 4x4 motor towers? I want to check and see if mine are the same. __________________ 72CheyenneSuper1ton4x4BigBlock Last edited by Bram; 02-23-2004 at 03:45 PM.

02-23-2004, 08:24 PM	#6
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	WHOA! I'm calling foul on this one! That isn't a 9/16 bolt. It's a 3/8 x 1 inch long bolt. Yes, a 9/16 wrench or socket fits it, but that don't make it a 9/16 bolt. For the washer, I use old harmonic balancer bolt washers on mine. They are thick as hell, have the right 3/8 size hole in them, and they are real big around so they don't go into the hole. __________________ I'm on the Instagram- @Gearhead_Kevin

02-23-2004, 03:02 PM	#4
rage'nrat638 Account Suspended Join Date: Mar 2003 Location: THE FALL GUY CHICAGO IL Posts: 5,883	a lock washer sorry try a smaller washer...how big of a washer are you using?

02-23-2004, 10:36 PM	#7
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	Hmmmm..mine has a 7/16 14 x 1 bolts...pretty sure it's factory...anyone else? __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

02-24-2004, 12:56 AM	#8
Bram Broke Join Date: Aug 2001 Location: West Plains,MO Posts: 385	I guess I don't understand why they made the hole so big in the first place? Wouldn’t it be stronger to have the correct size hole? Or does it give it enough slack with the bigger hole that when the engine moves forward or backwards a little it's less likely to break? I don't know, I guess I'll find the toughest washer I can, and torque the SOB down so my Big Block won’t rip them out. __________________ 72CheyenneSuper1ton4x4BigBlock

02-24-2004, 02:38 AM	#9
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,499	I have used 7/16-14 x 1.25'' long with the harmonic washers and a lock washer.

02-24-2004, 07:44 AM	#10
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	I am a moron. I just put my big block in on Saturday and yes, they are 7/16 bolts. I have no idea why I said they were 3/8 inch. But, never the less, I used the harmonic balancer washers to compensate for the big holes. __________________ I'm on the Instagram- @Gearhead_Kevin

02-24-2004, 10:00 AM	#11
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	The factory ones are 7/16-14x1 1/4" (not positive on the length, 1" will work). The were set up with extra thick washers and lock nuts. Harmonic balancer washers will work fine but you may have to compensate for length since the balancer washers are very thick. Jim



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