Broken Motor Mounts

[gooffeyguy]

The jack lifting the engine up has 7" high of wood. The top 2 pieces are no more than 3" wide.

Where did you jack it up at?

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[Meccanoble]

Where did you jack it up at?

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The visible section of the engine in between a beam and the sway bar. There is a small window of opportunity. If your wood is too wide, it wont fit between that area and if your setup is not high enough, the jack can get in the way before you start lifting. I did majority of my work from driver side to pull and add mount. The top was useful for bolt install/removal on the sides closest to the front of the car, while the driver wheel area was most helpful with the bolts closest to rear. Since I'm 4WD, I had no good options from below, atleast for the part towards the rear. I'm sure I'm not alone in saying for 4WD, the bolt closest to passenger/rear is the worst. You dont have enough room for an extension and need a ratchet with an angle or adjuster/tilter.

I also took heat shield off to help with mount removal and moved a wire while pulling on the wheel well plastic to help maneuver mount out.

 

[iamdub]

I'm sure you're ok in this instance. But, going forward, just know that tighter does not always mean better. Too tight can be worse than not tight enough.

I almost learned that the hard way on some hub mounting bolts. It's only three bolts and they hold your hub and wheel on, so they're quite critical.

 

[Meccanoble]

I'm sure you're ok in this instance. But, going forward, just know that tighter does not always mean better. Too tight can be worse than not tight enough.

I almost learned that the hard way on some hub mounting bolts. It's only three bolts and they hold your hub and wheel on, so they're quite critical.

I agree with you. I think I took a frustration route as the only thing that made sense for these bolts to come loose in the first place (even the ones I know I tightened to spec successfully) is not tight enough. I will definitely use the right torques in all situations.

 

[iamdub]

I agree with you. I think I took a frustration route as the only thing that made sense for these bolts to come loose in the first place (even the ones I know I tightened to spec successfully) is not tight enough. I will definitely use the right torques in all situations.

I'm just glad it was an easy fix and that you didn't actually kill an H3 mount. That one was a mind boggler.

 

[Rocket Man]

That would have been the first H3 Mount to break on a mostly stock truck that I had heard of so I’m glad it wasn’t the case.

 

[iamdub]

That would have been the first H3 Mount to break on a mostly stock truck that I had heard of so I’m glad it wasn’t the case.

Word. Those of us running the H3s might be more relieved than he is. lol

 

[Luie]

These H3 mounts I assume are from the Hummer and are a better option for the Tahoe?

 

[Meccanoble]

LMAO! I promise you guys I'm way more relieved. I spent HOURS looking at different cars with solid mounts to compare vibration levels and I am a firm believer in stats and data. I hate to be the one off and was questioning my existance ever since i thought that mount was broken. Why me?

But the GREATEST relief was when I saw the mount partially off and what I thought were BOLTS still stuck on the mount (they were heads on the mount for something else, look totally different), I thought half the bolts were stuck in the engine. You know that feeling when you are royally FUXED so you are kind of calm but crying inside? I went from one project to a bigger project in my head. The relief of ONLY missing bolts. Things could always be worst and we always think the worst.

I have to look for all the threads and reviews where i bashed the H3 mounts and correct my feedback.

 

[Meccanoble]

On another note, the engine has been jumping up and slamming on that mount for who knows how long. Very dangerous situation on my part, even during the testing phase sitting in one spot. I think this speaks volumes on the quality of the H3 mount to still be fully functional.

 

[iamdub]

These H3 mounts I assume are from the Hummer and are a better option for the Tahoe?

Si. The original ones are hydraulic and are short-lived. The H3 mounts are the same as those used on the previous generation (GMT800) and easily last 150K miles with little to no increase in detectable vibrations.

 

[Meccanoble]

I have a before and after video of the truck showing vibration before the H3 was properly installed and after. I was going to compare with the solid mount but did not have to install. H3 highly recommended

 

[gooffeyguy]

So, as I said earlier, I really have limited experience with GM mounts and am just curious why so many bolts on each mount to the block? Because aluminum block?

I've done mounts in mustangs (2 bolts on block, 1 big bolt and locating pin on K member) and on the '33 Ford Sedan which has a GM Performance ZZ4 350 crate motor (3 bolts on block and 1 bolt through the frame plates). These are all iron blocks.

 

[iamdub]

So, as I said earlier, I really have limited experience with GM mounts and am just curious why so many bolts on each mount to the block? Because aluminum block?

I've done mounts in mustangs (2 bolts on block, 1 big bolt and locating pin on K member) and on the '33 Ford Sedan which has a GM Performance ZZ4 350 crate motor (3 bolts on block and 1 bolt through the frame plates). These are all iron blocks.

Maybe to spread the load more? The four on the block straddle a cylinder so why not make it a square with two fore and two aft of the cylinder? I'd rather four smaller bolts than two larger bolts. It could have been spawned from the aluminum block and, to keep manufacturing variaces/costs down, why go out of the way to redesign the block's structure to delete a bolt or two for the iron block?

 

[gooffeyguy]

Maybe to spread the load more? The four on the block straddle a cylinder so why not make it a square with two fore and two aft of the cylinder? I'd rather four smaller bolts than two larger bolts. It could have been spawned from the aluminum block and, to keep manufacturing variaces/costs down, why go out of the way to redesign the block's structure to delete a bolt or two for the iron block?

Iron block would've come first, so they added bolts. I was just asking if the additional bolts were due to the aluminum blocks or some other reason, because older blocks had fewer bolts. The ZZ4 is a 350 block with aluminum heads and has 355hp/405tq

 

[Rocket Man]

Iron block would've come first, so they added bolts. I was just asking if the additional bolts were due to the aluminum blocks or some other reason, because older blocks had fewer bolts. The ZZ4 is a 350 block with aluminum heads and has 355hp/405tq

You’re asking a question we can only speculate on. You would have to ask the engineer who designed them. But as far as what makes sense, yes it is most likely because you’re attaching to aluminum instead of iron and you can’t torque bolts in aluminum to near what you can in iron.

 

[iamdub]

Iron block would've come first, so they added bolts. I was just asking if the additional bolts were due to the aluminum blocks or some other reason, because older blocks had fewer bolts. The ZZ4 is a 350 block with aluminum heads and has 355hp/405tq

I thought the first was the aluminum LS1 in the '97 Corvette, then the iron 5.3 came about in the following year to be used in the '99 trucks.

The ZZ4 has two up top that appear to straddle a cylinder and a third that's lower and probably below the cylinder so it can be in the center. It looks like the block is much thicker for it's strength. The LS series was designed to get its strength from engineered gusseting and structural oil pan rather than from sheer metal thickness.

 

[gooffeyguy]

I thought the first was the aluminum LS1 in the '97 Corvette, then the iron 5.3 came about in the following year to be used in the '99 trucks.

The ZZ4 has two up top that appear to straddle a cylinder and a third that's lower and probably below the cylinder so it can be in the center. It looks like the block is much thicker for it's strength. The LS series was designed to get its strength from engineered gusseting and structural oil pan rather than from sheer metal thickness.

I don't know, and don't know the differences between LT, LS, etc. I do know 350's have been around a lot longer than '97 though.

 

[gooffeyguy]

You’re asking a question we can only speculate on. You would have to ask the engineer who designed them. But as far as what makes sense, yes it is most likely because you’re attaching to aluminum instead of iron and you can’t torque bolts in aluminum to near what you can in iron.

I just figured with the amount of knowledge on this site someone would know.

I don't know much about the newer GM engines, especially when it comes to LT or LS series. I'm more old school 350's and Ford 302's, have rebuilt several of each

 

[Luie]

Part number for said H3 mount?