Broken Motor Mounts

[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?