Motor Mounts?
12-30-2017, 03:12 PM
#22
Race Director
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?
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?
I had the exact 'out of balance' missing feeling when i gapped my spark plugs too tight (less than .030").I would get that miss on the highway. Ingapped them tighter when i added supercharger. When i put my gap to .035" the miss went away. I also run an msd 6al.Id look at gap and wires just to rule those out
01-27-2018, 05:30 PM
#24
Instructor
https://www.summitracing.com/parts/ens-3-1116g
02-02-2018, 03:43 AM
#25
02-02-2018, 08:10 AM
#26
I would like to update the information posted here before in case someone is considering this option for their mounts:
I had to mill down about 1/2" from the protruding tab on the drivers side motor mount because there was some interference with my Melrose headers.
No problem with the passenger side.
This is what it looked like after milling:
I had to mill down about 1/2" from the protruding tab on the drivers side motor mount because there was some interference with my Melrose headers.
No problem with the passenger side.
This is what it looked like after milling:
Last edited by RicardoG; 02-02-2018 at 08:12 AM.
02-02-2018, 12:49 PM
#27
Melting Slicks
and it looks like some how some way the whole front end of the engine / drivetrain is gonna depend on two little allen head bolts (per side)
05-31-2018, 04:38 AM
#29
Just to follow up. Ordered some of the Prothane mounts. Solid quality piece. See how well they do in a race application.
05-31-2018, 07:35 AM
#30
Race Director
IMHO solid mounts are the only option.
churchkey makes good stuff.
the only drawback is that my side view mirror had a slight rattle to it at idle and sometimes stuff in glovebox rattles if its all hard stuff.
no changes at anything other than idle
churchkey makes good stuff.
the only drawback is that my side view mirror had a slight rattle to it at idle and sometimes stuff in glovebox rattles if its all hard stuff.
no changes at anything other than idle
05-31-2018, 07:57 AM
#31
Melting Slicks
Member Since: Jun 1999
Location: Bowling Green KY
Posts: 2,948
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Bump for Churchkey's solid mounts.
I love em'.
I may have missed it up above, but just in case, keep in mind L98's and LT1's have totally different mounts.
I love em'.
I may have missed it up above, but just in case, keep in mind L98's and LT1's have totally different mounts.
Last edited by DVNCI; 05-31-2018 at 07:57 AM.
05-31-2018, 01:37 PM
#32
