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> What Motor and Transmission mounts to use, What motor and transmission mounts to use
Ken Mikos
post Oct 28 2018, 07:32 PM
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Replacing motor and transmission mounts in a original 1973 1.7. Any suggestion on the type and where to purchase? Thanks,

Ken
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Dave_Darling
post Oct 31 2018, 12:05 PM
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For a track-only car? Solid all the way around. Keeps the drivetrain more positively located.

May cause loosening issues with some fasteners on the engine; I seem to recall some kind of issue with Webers being blamed on solid mounts?

--DD
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sithot
post Oct 31 2018, 08:14 PM
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QUOTE(Dave_Darling @ Oct 31 2018, 02:05 PM) *


I seem to recall some kind of issue with Webers being blamed on solid mounts?

--DD



Richard Parr does not recommend them for use with PMO's.
5. Solid Motor and Transmission Mounts

I've noticed a proliferation of advertisements for solid motor-transmission mounts for Porsche 911 race cars. I'm sure they sell well because they are CNC machined out of solid aluminum and they look "cool". They are also considered "hardcore". My opinion is that any practical advantage they possess is vastly outweighed by a myriad of disadvantages.

The basic problem with solid mounts in internal combustion reciprocating engines is that they introduce destructive harmonics into the body of the race car and also back into the engine. Everyone has heard the true stories of cracked sheet metal, loosened nuts and bolts, sheared-off exhaust systems and broken engine cases.

The excessive vibration often sticks the float needle valves in carburetors causing flooding and other times aerates the fuel in the float bowls causing a lean condition.

The intense vibration also can knock out components in EFI systems leading to the common full-lean-at-full-tilt-equals-fried-engine syndrome. The additional tooth- rattling vibration and noise increases driver fatigue and the possibility of a crash. And if there is a hard crash, the solid mounts increase the likelihood of catastrophic damage to the engine and transmission.

Given these well known facts, why would anyone use solid mounts? It is because they stop the engine-transaxle unit from twisting, thereby improving shifting. This condition is substantially improved by using the Porsche sport mounts and is totally cured by using a WEVO shifter along with the sport mounts. Frank Eibell in Florida has made and installed anti-torque bars on the transaxle to cure this problem. Jim Patrick in Arizona makes urethane dampened 914-6 conversion mounts. WEVO urethane engine-transmission mounts are available now.

An interesting theory is that solid mounts actually decrease horsepower by forcing the engine to absorb vibrations that would normally be absorbed by cushion mounts. For every power pulse in an internal combustion reciprocating engine there is a reactive pulse responding to inertia, operating in a counterrotational plane. Containing this reactive pulse with solid mounts diminishes the power pulse by adding secondary vibrations. Greg Edmunds utilized this theory in designing motor mounts for his .4cc x 3.75 HP model airplane engines. By trial and error, Greg was able to tune out the unwanted vibrations by adjusting the durometer of the rubber in his composite motor mounts. His engines put out more horsepower and the airplanes flew faster with the cushion mounts! Full size aircraft never have solid motor mounts



As a footnote, not even the viton valves will hold the fuel level in some cases where solid motor and transmission mounts are used. For race cars, we recommend the Clubsport mounts which can be stiffened by modification. WEVO recently developed urethane motor mounts which should be the best of both worlds.
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Posts in this topic
Ken Mikos   What Motor and Transmission mounts to use   Oct 28 2018, 07:32 PM
Dave_Darling   The 73 uses solid outboard mounts between the bar ...   Oct 28 2018, 08:22 PM
914Sixer   Buy stock and be done.   Oct 29 2018, 07:46 AM
UROpartsman   For a '73-'76, engine mount 039 199 231 is...   Oct 29 2018, 10:51 AM
DRPHIL914   For transmission most of us have been using the 91...   Oct 29 2018, 11:00 AM
troth   Very happy with my wevo semi-solid trans mounts. K...   Oct 29 2018, 11:01 AM
DRPHIL914   Very happy with my wevo semi-solid trans mounts. ...   Oct 29 2018, 11:24 AM
troth   Very happy with my wevo semi-solid trans mounts....   Oct 29 2018, 12:08 PM
DRPHIL914   here is a picture of a 911 motor mount used on the...   Oct 29 2018, 11:02 AM
DRPHIL914   stock motor mount   Oct 29 2018, 11:08 AM
Ken Mikos   Thanks for all the follow up. You guys are a great...   Oct 29 2018, 02:52 PM
GregAmy   What's the right combo for a '74 track-onl...   Oct 31 2018, 06:44 AM
pete000   I have been running the Wevo blue Trans mounts fo...   Oct 31 2018, 10:00 AM
Dave_Darling   For a track-only car? Solid all the way around. ...   Oct 31 2018, 12:05 PM
sithot   I seem to recall some kind of issue with Webers ...   Oct 31 2018, 08:14 PM
GregAmy   For a track-only car? Solid all the way around. ...   Nov 1 2018, 07:54 AM
GregAmy   For a track-only car? Solid all the way around....   Nov 4 2018, 12:04 PM
GregAmy   "Solid" as in aluminum-solid? I don...   Oct 31 2018, 12:18 PM
Literati914   *Modified 911 mounts do not have the proper anti...   Oct 31 2018, 06:09 PM
UROpartsman   So, are you saying that either of the engine mount...   Nov 1 2018, 09:53 AM
GeorgeRud   I think either the 914-6, 911, or WEVO mounts will...   Oct 31 2018, 06:39 PM
Literati914   I think either the 914-6, 911, or WEVO mounts wil...   Oct 31 2018, 07:49 PM
mepstein   [quote name='GeorgeRud' post='2661903' date='Oct ...   Oct 31 2018, 07:52 PM
DRPHIL914   [quote name='GeorgeRud' post='2661903' date='Oct ...   Oct 31 2018, 08:03 PM
Larmo63   I'm going to change out my solid aluminum/delr...   Oct 31 2018, 10:27 PM
ConeDodger   I was seduced early on by solid mounts. My car is ...   Nov 1 2018, 08:28 AM
Dave_Darling   My contention is that on a race car, you nut-and-b...   Nov 4 2018, 01:45 PM
GregAmy   Thank you, Dave, I appreciate the advice.   Nov 4 2018, 03:48 PM
Ken Mikos   First drive today after installation of New Motor ...   Mar 17 2019, 07:18 PM
UROpartsman   Excellent Ken, which motor and transmission mounts...   Mar 18 2019, 11:11 AM
Ken Mikos   Excellent Ken, which motor and transmission mount...   Mar 18 2019, 02:39 PM


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