Lotus Elan

Front engine mount height differences

PostPost by: mr.vman » Sat Sep 25, 2010 7:19 pm

Trying give the +2 engine the correct engine compartment clearances, air box and cam cover. What is the height difference between the standard Twin Cam, left hand engine mount and the, "Weber" right hand mount? I cannot find the difference in any of the listings. On a +2, how much clearance is there normally between the front of the cam cover and hood (bonnet?) bottom? Trying to get this sorted before I drill and tap the chassis. By the way, I have a Spyder chassis, "inverting" the engine mounts, puts the engine too high and too much spacing of the body is needed. I will try "inverting" the front mounts and lowering the body again on the chassis. Curious about the front mount differences.
Thanks in advance, Steve V. +2 in Arizona
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PostPost by: garyeanderson » Sat Sep 25, 2010 10:27 pm

I think Spyder uses the same mount on both sides, the less expensive mount is the used. Please read the following topics.

elan-plus-f13/tilted-engine-t16110.html

elan-f14/tall-block-twin-cam-spyder-chassis-t18132.html

elan-plus-f13/engine-sitting-too-high-t18036.html

found with google search engine
http://www.google.com/search?hl=en&q=%2 ... =&gs_rfai=

and elan.net search of "engine mount"

http://www.lotuselan.net/cgi-bin/search ... oom_sort=0

Seems like Russ and I have discussed this along with the rest of the crew. If this doesn't help ask again and we'll run it again.

Gary
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PostPost by: mr.vman » Sat Sep 25, 2010 11:13 pm

Gary, Thanks for the quick reply. Is there a measurement, number, in height between the Weber (right) and standard left front engine mount? Spyder does want the front engine mounts "inverted". The +2 does use the standard left mount on both sides. I have been considering the future, if, I install a "tall block", there would be ample cam cover to bottom of the hood clearance. Perhaps I could use the, Weber mounts or mounts, to get the front crankshaft pulley off the front cross-member and leave space for a "tall block" later. There is about, .650 inch, clearance, front cam cover to hood bottom. This is with the front mounts in the standard position, not inverted. Tomorrow I will try 'inverting the mounts as Spyder wants, take measurements on clearance. I have been searching past posts, can find no measurements, numbers. Sorry on the number thing, it is my training.
Thanks for the information, Steve V. +2 in Arizona
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PostPost by: garyeanderson » Sat Sep 25, 2010 11:28 pm

Engine mounts are failsafe, in that if the rubber fails the U section catches the engine and prevents it from falling. Inverting will defeat this safety feature. You post said nothing about tall deck, pleanty of posts on that. The tall deck is 7/16 inch taller than stock Twin Cam block. if you have .650 inch clearance, thats nearly 1/4 inch of free space with a tall deck, slot the engine mounts a bit if you need more. I have no experiance with Plus2's, only Elans and full height tall deck twin cams have enough clearance. I have a tall deck 1700 in a S2 with Spyder chassis. can't help on specific plus2 stuff. Someone else will have to help.

Gary
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PostPost by: stugilmour » Sun Sep 26, 2010 3:11 am

mr.vman wrote:Gary, Thanks for the quick reply. Is there a measurement, number, in height between the Weber (right) and standard left front engine mount? Spyder does want the front engine mounts "inverted". The +2 does use the standard left mount on both sides. I have been considering the future, if, I install a "tall block", there would be ample cam cover to bottom of the hood clearance. Perhaps I could use the, Weber mounts or mounts, to get the front crankshaft pulley off the front cross-member and leave space for a "tall block" later. There is about, .650 inch, clearance, front cam cover to hood bottom. This is with the front mounts in the standard position, not inverted. Tomorrow I will try 'inverting the mounts as Spyder wants, take measurements on clearance. I have been searching past posts, can find no measurements, numbers. Sorry on the number thing, it is my training.
Thanks for the information, Steve V. +2 in Arizona



Steve:

Sounds like the car is proceeding well. I have new mounts of both dimensions here. A rough difference in the height for them is 1/2" to 5/8". I just measured these crudely; let me know if you need something more exact.


I was considering a similar idea; using the Weber mount to lower the engine due to minor fouling of my non-stock SU carbs, which are slightly higher than the Stromberg's.

Note that the Weber mount is the taller of the two if it is in the correct fail safe position. If you want to use the Weber mount to lower the engine you will loose the fail safe feature. This is the same for the Spyder or stock chassis; the fail safe feature works when the manufacturer's mounting direction recommendation is followed.

I was advised by listers not to do this, rather as Gary says oval the mount holes slightly to gain any required clearance. On looking things over I think this will work in my case; plan to get things right over the winter. I figure I can get ~1/4" in this way by ovaling both sides of the mount. Edit to add on a second look I think I can get an additional 1/4" of adjustment if required by slotting the Spyder engine mount struts at the lower end, which should be plenty in my case. Max lowering I can go with is going to be limited by the crank pulley, so thanks to Steve for pointing this out.

If you decide to proceed with the Weber mount or stock mount in non-fail safe positions to lower the motor, I would recommend the reinforced ones that Ray has on his site now. The rubber goes right down into the U on the mount, so I expect they would be less likely to fail.

In order to relieve the clearance issues, I inserted a couple of packing washers under the front tunnel body mounting bolts and ~3 washers on the steering rack body bolts. I am currently just running the hood a bit high until I get to the motor mount fix. I think the engine has settled slightly in the first 1000 miles of use. I cannot accurately estimate how much, but it would be 1/16" to 1/8" tops at a guess. Also suggest checking clearance on the brake boosters and radiator cap carefully before drilling; they were causing issues in my case. My non-stock air filter is presently rubbing the hood slightly, so that will be the dimension I have to clear up with the recommended motor mount mods.

HTH
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