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peteyg

S2 Engine Mount Dimensions

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Could someone with access to their engine mounts give me the lengths of the left and right side please. For years I've had an issue with the engine seemingly sitting too high and fouling the cover which I have butchered to stop the carbs, cam covers and water bottle rubbing. Somethings not right and it needs to be sorted.

Cheers,

Pete

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Hi Pete,

At the moment I think my OEM mounts are fitted to a mock-up rig over at a buddy's shop, not readily accessible. Out in my garage there are the bits in the SJ uprate kit (poly) which, though differing in form, might provide something helpful. Not necessarily easy to get at though as I've had to tuck the lot into every open space of the body and shove aside to make room for the bleeding home reno work !!  If/when I can haul them out I'll try to derive something approximating the  c-c distance between chassis and engine block bosses. Meantime, perhaps some other good soul may chime in with the required measurements?

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Pete,

Do you mean , the hight of the standard rubber blocks? And I think left and right are the same.

The block , I have in the garage measures 4.5 cm t That is the one I send a picture in the other topic

Geert

Edited by gvy

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@gvy @drdoom

Hi Geert/Steve,

I'm after the length of the arms, not the rubber. I think one side is longer than the other.

Thanks Steve. Might be hempful if you get a chance but don't bust a gut.

Pete

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I do know that the exhaust side leg is indeed shorter than is the intake side. The reach to chassis is obviously shorter on the X side owing to the motor leaning over onto that side. Your situation is interesting, Pete, as it puts the focus squarely on the broader aspects concerning early series' engine mount performance.

To recap, the early powertrain locating is done very simply by way of the legs/biscuits (legs/bushes on the earliest) up front and the transaxle hangers from which the aft end dangles, with a minor role played by the trailing arm mounts. That's it. Next point to consider: what movement is to be expected as the forces are applied. The first set would be the result of engine rotation, no load as at idle or otherwise out of gear. That would be the set of vibrations innate to an inline 4 banger, roughly termed as shaking/rocking in 2 planes 1 set aligned on a fore/aft plane described by the cylinder centerlines/crank axis and the other set at 90 degrees across that plane. These are the motor related source of the directly applied NVH concerns addressed by way of compliant mounts in all conventional motor cars. I've written elsewhere on the also very intriguing aspects of acoustic excitement of the car structure, but that's off topic here.

Seat time as passenger in 2 early Esprits running on biscuits, all mounts in fine nick, engine cover absent, well demonstrated the nature of containing the driving related forces. Hard on throttle: the motor front end rises smartly; hard drop throttle, overrun in gear: the motor front drops down smartly. That's the visible expression of powertrain torques, forward and reverse under load, resolving to equilibrium through containment by all related mounts versus tyre contact traction. To my eye it seems there's a comparatively small role for the trans hangers to contribute in this aspect, as they are an assembly from which the powertrain should have liberty to swing a fair ways fore and aft. That said, failed motor mounts must ultimately result in the hanger bushes being drawn out of healthy form (failed) as a consequence of excess load/displacement. There are also the torque reactions rotationally aligned with the crankshaft axis and the hangers must be vital, along with the primary M/M's, in resolving those. Failed mounts might result in some vertical engine movement due to those forces as well. Back with the fore/aft thrusting forces in terms of the present discussion, it seems that while the M/M's are primary in the task of restraining those one must remember that the trailing arm mounts are also tasked, to a lesser degree I would think, in this regard. So what to expect if the trailing arm mounts are failed? One would hope there to be some sense of squiffy handling perceived, however the very broad stability inherent in all Esprit chassis seems to do quite the job of concealing component defects. Just review how many have reported utterly shot dampers discovered upon disassembly, nary a hint of it while driving. So it's not clear to me how far shot the T/A mounts would have to be in order to effect engine to cover clash.

One of the most appealing aspects of Lotus ownership is the way in which the sublime simplicity of chassis design leads the curious (Guilty !!) to explore the pertinent science in depth. In summary, Pete, you will want to review the state of M/M's as you already have, then also take stock of the trailing arm mounts just in case failure there might have taken away the margin to clash between bits. Most interesting thread.

Cheers   

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