SBC engine mounting

[dyeager535]

I'm kind of revisiting my thread on my engine mount that went bad, except that this is more specific. Summary: Poly motor mount was damaged beyond reuse, motor mount through bolt broke, and I noticed the hat/mount/frame don't line up right.

After half-disassembling the engine bay, I was able to take off the driver side motor mount "hat" (stamped piece that bolts to the block with three bolts) and the engine mount, and shift things around. Here is a pic of the frame side mount piece (not mine):

On the drivers side, the bottom edge of the motor mount is up above the bottom of this frame piece lip when in the motor mount hat, maybe 1/2". On the passenger side, the motor mount edge is lined up with the bottom edge of this piece. Obviously this causes a real problem trying to get the bolts lined up to bolt the motor mount to the frame piece. As in, not possible.

I loosened up the passenger side, and lifted the engine, hoping to get enough play to line it up, but to no avail. As you can see, if anything the upper two bolt holes are for fore/aft adjustment, not vertical. The motor mount bolt holes are easily 1/2" higher than they need to be. No amount of prying is going to fix the offset. And yes, the poly inserts are in correctly, and I'm inserting the complete mounts the proper orientation.

I do not believe there is any frame damage, I had no issue with mounting the springs or anything else to indicate the frame was tweaked, but the frame was purchased by itself, and other than being told it was from an '81 K5, I don't know it's history.

In looking at the GM parts manuals from '73-91, I found at least six different part numbers for the motor mount hats JUST for the SBC in K10 trucks. I know a few things changed (oil cooler bracket hole, strut rods to t-case, etc), so that may be why, but was height ever one of the changes among the SBC differences?

The motor mount hats I have I'm pretty darn certain are right for this truck, since the drivers side has the oil cooler bracket bolted to it, but I can't guarantee. I have no idea why the motor mount hat height would have changed, but it's the only way I can see to drop the motor down far enough to fit. I have two pairs of motor mount hats from other trucks a buddy lent me, and I'm going to swap them in as sets, about the only thing I can think of to fix it. I'm going to try and keep from staying OCD on this, if the hat swap doesn't fix it, I'm going to drill new holes in the mounts.

 

[imiceman44]

I'm kind of revisiting my thread on my engine mount that went bad, except that this is more specific. Summary: Poly motor mount was damaged beyond reuse, motor mount through bolt broke, and I noticed the hat/mount/frame don't line up right.

After half-disassembling the engine bay, I was able to take off the driver side motor mount "hat" (stamped piece that bolts to the block with three bolts) and the engine mount, and shift things around. Here is a pic of the frame side mount piece (not mine):

On the drivers side, the bottom edge of the motor mount is up above the bottom of this frame piece lip when in the motor mount hat, maybe 1/2". On the passenger side, the motor mount edge is lined up with the bottom edge of this piece. Obviously this causes a real problem trying to get the bolts lined up to bolt the motor mount to the frame piece. As in, not possible.

I loosened up the passenger side, and lifted the engine, hoping to get enough play to line it up, but to no avail. As you can see, if anything the upper two bolt holes are for fore/aft adjustment, not vertical. The motor mount bolt holes are easily 1/2" higher than they need to be. No amount of prying is going to fix the offset. And yes, the poly inserts are in correctly, and I'm inserting the complete mounts the proper orientation.

I do not believe there is any frame damage, I had no issue with mounting the springs or anything else to indicate the frame was tweaked, but the frame was purchased by itself, and other than being told it was from an '81 K5, I don't know it's history.

In looking at the GM parts manuals from '73-91, I found at least six different part numbers for the motor mount hats JUST for the SBC in K10 trucks. I know a few things changed (oil cooler bracket hole, strut rods to t-case, etc), so that may be why, but was height ever one of the changes among the SBC differences?

The motor mount hats I have I'm pretty darn certain are right for this truck, since the drivers side has the oil cooler bracket bolted to it, but I can't guarantee. I have no idea why the motor mount hat height would have changed, but it's the only way I can see to drop the motor down far enough to fit. I have two pairs of motor mount hats from other trucks a buddy lent me, and I'm going to swap them in as sets, about the only thing I can think of to fix it. I'm going to try and keep from staying OCD on this, if the hat swap doesn't fix it, I'm going to drill new holes in the mounts.

If I understand correctly what you mean about hat, there are 2 different heights.
I want to say there is 1/2" difference.
I was told the taller one is for the 4wd.
When I got my blazer it had the short one and the balancer was rubbing on the cross member

 

[dyeager535]

Yeah, I can't help but get verbose.

GM lists at least 6 different "hat" part numbers for the K10 trucks with a SBC. What I have doesn't fit the frame.

Unfortunately the numbers stamped into the hats don't seem to be a part number, as the two different ones I ran didn't come up in the '73-91 parts manuals I checked.

Pretty sure cars used a different part number hat, and I'd assume they were shorter, but for trucks, I don't see why height would have changed...the frames were all the same (K10 of course), the bodies were all the same, etc.

 

[diesel4me]

From what I experienced doing a few engine swaps,the K series square bodies used a engine mount bracket that had the thru bolt hole about 1" further away from the block,than those used on 2WD trucks and passenger cars..(and I would not be surprised if there were variations among all of them,as far as the thru bolt hole location,depending on the year & model of the vehicle )..

I tried leaving the car style brackets on one engine I swapped into a 4x4 and was able to get the thru bolts in OK,but the engine was doing a nose dive towards the front,and the oil pan nearly touched the cross member..had to locate the right brackets and swap them in,a real pain with everything all bolted up..

Also one 4x4 truck I took apart,and a G-10 van at the salvage yard,had a steel plate sandwiched between the engine mount bracket and the block on only one side (passenger side)-,a factory "shim" I guess..not sure why it was needed,it had no provision for a strut bar or other things that might have bolted to it there,I assume it was required to level the engine ?..

 

[dyeager535]

This is definitely an interesting issue, but frustrating. Something that should take an hour or two takes weeks.

Think I'll loosen the poly trans mount as well, can't hurt to get a bit more slop in everything.

 

[dyeager535]

FWIW, here are pics of the hats that came out of the truck ("tall") and what I put in ("short").

FWIW the drivers side hat I took out was taller than the passenger side, I believe they used a plate on the passenger side in some apps for the transfer case support rod? But there are obviously different height hats used on the trucks. Had to drill the shorter one for the engine oil cooler line clamp. BTW, when you take the clamp out, weld the bolt to the cooler line clamp....so much faster to install when you don't have to fight with the small nut and bolt in tight confines.

Swapping both hats and using the engine hoist to level them, it went together without issue. There is still something messed up on the drivers side, as the engine mount puck ears aren't sitting on the hat correctly, but close enough. I'll watch it and if it starts to eat the ears up, will look at shimming the bottom of the motor mount up a bit.

 

[Blue85]

Look, the bracket is smiling.

Yes, I know I'm not helpful.

 

[dyeager535]

Look, the bracket is smiling.

Yes, I know I'm not helpful.

Guaranteed, if it was able to give me the middle finger, it would.

 

[diesel4me]

.....
Sorry,I know it's not funny......

Having been there myself and frustrated when it came to finding "the right parts" ,I know it can be very aggravating,especially when you had to scour junkyards and bust your nuts trying to remove a motor bracket with the engine still in the vehicle--then get home and find out its still "wrong"..

I remember the day my steering rag joint failed on my '77 GMC K2500--was lucky it came apart during a slow speed U turn,not while going 65 mph...then I spend the next 2 days bumming rides to where the truck died,to a junkyard 3 miles away,and I had to go there 3 times,before I got the right rag joint,my truck had the large splined steering colum,not the square "D" type,and the steering shaft was also different at the box end--the junkyard had like 50 square bodies to pick from then,but all but 2 of them had the "wrong" steering colum shaft & upper flex joint at the colum end..
..I had to put parts from 3 trucks together in order to make a shaft that fit it..

 

[Blue85]

So how were you able to install the poly mounts to begin with? Did you drop them in with the engine?

 

[dyeager535]

So how were you able to install the poly mounts to begin with? Did you drop them in with the engine?

I recall profuse amounts of vulgarity, a tide of anger, and a six foot two by four of leverage eventually. I suspect that I may have bent the ears on the puck on install, thus the need for all the leverage, and why the bolt broke.

Frustrating part is, the hats in the truck almost had to be the right parts, since the oil cooler line bracket was on them. As I recall BBC hats are a different height, but not sure by how much. Seems unlike my problem since I needed shorter which I assume would be what the BBC hats would be.