I am replacing my 115 000 mile engine with freshly built forged 383 with LE heads and intake.

I have oly had this C4 for about a year and am not very familiar with the hydraulic engine mounts.
My question is: how often do they wear out or break in order to need replacement? Would it be a good idea to replace them now or should I rather keep the OEM mounts?
There are not many spare motor mount brands availiable. Makes me wonder if they dont brake that often.

Opinions welcome.
Thanks for looking.

 

If it were me, I'd replace them just for the hell of it as there is no better opportunity than now.

I put Polyurethane in when I changed mine.

 

Solid mounts are an option.

 

looking into my crystal ball I see ... worn out motor mounts...

Stock hydraulic units are going to be hard to find and expensive

However, solid rubber mounts are available and quite reasonable. For performance use, the euro and Asian racers consider replacing their stock hydraulic mounts with solid rubber to be a performance upgrade.

And its not that the stockers aren't rubber, its just that the rubber eventually leaks.

As mentioned above, solid mounts are available...I'm going to try a set

 

for reasons I don't understand polyurethane mounts aren't available for the 92 - 96 LT based engines...for earlier engines, polyurethane is an excellent option.

 

I have only found OEM and aftermarket hydraulic mounts sofar.
No solid rubber.
Do you have a lead for the solid rubber or the poly mounts?

I tink solid motor mounts are a bit too much for a street car, but that is just my opinion.

Thanks

 

Wow, used to be that the local parts stores only had solid rubber mounts and no hydraulics...now it's just the opposite....but not all is lost:

Summit Racing, solid rubber motor mount (at least for my 96 and should be the same for all for LT engines): Anchor Industries # 2902SR $30.97 good luck

 

engine move so much the blower pulley was ground down from hitting an a-arm bolt

 

Who is currently making the solid mounts?

 

Sent PM

Installed pic
jpg.gif leftmount.jpg (317.2 KB)
jpg.gif rightmount installed.jpg (506.5 KB)

 

I should get a set myself

 

So, I got my new solid rubber motor mounts.
Is it necessary to have them wrapped in heat shielding material?

 

.

On my 93 they were wrapped by GM.

I'm now running the ones Churchkey listed above.

Never had a problem and they take up less space and provide rigidity.

When I had a rough tune the car would shake but with a better tune you dont know they are solid. With a very aggressive cam it would be different.

 

I certainly would

 

As you all know, I also have a 383...though with (what I consider to be) a super small cam.

214/214 .550/.550 lift 112LSA

When I built it, I bought "white-box" stock replacement mounts. For one thing, I figured the thing would idle like OEM and it's close. But maybe not?

Occasionally...especially light loads or decel, I'm convinced I feel the engine. By that, I mean a mild trembling that's not unlike imbalanced tires. Oddly, it's more apt to occur during warm-up but I don't get why there'd be a difference.

It doesn't help that I've also had some mild tire imbalance issues, the need to rebuild/replace suspension bushings, been the victim of a side-swipe (hwy speeds), have ZR1 rears, use less expensive Sumitomos, and have even questioned the method of RA balance in my engine. IOW, I've been reluctant to conclude I'm actually FEELING a mild tremble/shake in the motor. As everyone knows, a tremor through a C4 can be quite annoying. (That's why we talk about frame strengthening, look at cross-braces, and/or V2V heim bars.)

I feel like I have a mild miss on top of it. I don't consider it's the nature of the cam...though I don't know anyone else (locally) with a single-pattern cam. A hotcam (for example), has a pronounced, rhythmic "bubba-la, bubba-la" to it. Mine cam seems less rhythmic -- more even. That is, except for the mild sensation of a miss. And, this annoying mild body tremble (only in the hwy).

Because I've bought a couple of sets of tires now AND have had them road-forced, AND even had one set checked/double-checked, I'm getting more convinced I'm feeling the motor from time-to-time. It's seems more clear that's what it is by holding my speed (say 70mph) and downshifting.

Kicking it out of gear or shifting can immediately eliminate the phenomenon. I think the main reason I've been reluctant to believe I'm actually feeling the motor is it's not more obvious in my manual shifter handle. I feel it more in the body/frame. And, again, it's ONLY on the hwy above 65mph.

You'd THINK I'd feel it from time-to-time at lower rpms too. The only thing I notice is the mild miss below 2k rpms. (I can't say I'm totally thrilled with the "isolation" above 4k rpms either.)

I can't say I remember noticing it during the first 6mos or so...but maybe I was having too much fun to notice? I've talked to Jon Banner about it (a couple of times). He considered the possibility the NEW SVO injectors I used for the build could have been contaminated with debris from the gas tank...since it DID sit quite a while (3 yrs). As such, I've considered pulling them and have them cleaned/flow checked. (It's been 7yrs and 25k miles).

I've also considered I have more than one issue... For example, a less-than-perfect RA balance where too much material was removed from the crank...or partially clogged injector...or something "still not right" after refurb/repairs were done to the suspension...or even drive-shaft orientation (since I didn't know to mark it BEFORE I pulled the motor for the rebuild.

I've tried some things here/there including new plugs, spraying propane to check for vacuum leak, etc... One of the things I never considered were the mounts!

If it IS the mounts, I suppose the reason I only feel the engine on the hwy has something to do with the low rpms and gearing. If there IS some engine shudder due to cam profile, maybe I only feel it during light loads in 5th or 6th due to rpms AND chassis load on the motor?

Since it appears (by this thread) that mount TYPE is something to be considered, please give me some feedback on the options (alternative diagnoses I gave) versus the OEM mount-type I installed during the build. Is the occasional hwy tremble/shudder normal for the config I'm running AND the mounts I used?

Or...should I pull the injectors and check them next?

 

FYI: Prothane makes a poly motor mount insert for 84-96 corvettes, pn 7-522.

 

Those mounts don't do LT style applications. Lt5 and LT1 mounts are very different.

 

Ended up having to make my own mounts.
One of the solid rubber mounts shipped was defective and had to send them back.
Then I ordered from Summit the Anchor solid rubber ones and after waiting and waiting finally got a shipping date around Feb 2018, so I cancelled.

I am going to use these tall and narrow POLY mounts instead of the engine brackets in combination with the fabricated pedestal mounts instead of the OEM combo:

 

..... I wonder if true solid motor mounts would affect knock sensors ? .....

 

My first thought is no -- since the KS is mounted INSIDE the engine anyway. I suppose it's possible vibration transmitted throughout the car could act as an amplifier to make is more possible for the KS to "hear" pre-detonation. Still...it seems a stretch....unless the motor vibrates/rattles IN the mount?