RebekahsZ Posted August 23, 2011 Share Posted August 23, 2011 I'm considering the potential benefits of changing my motor mounts(the stock left side LS mount and the rubber JCI-provided right side engine mount) for polyurethane while I have the engine out (getting close to putting it in for the "final" time). Poly mounts for the right side are easily available in my AutoZone for $23. However, the F-body LS mount is a clam shell arrangement - I seem to be only able to find poly "guts" replacements that require me to take the "clam shell" apart and replace the guts. Summitt has a pair of Prothane LS1 mounts for $49. So my basic question is: how much do these engines move around with the stock JCI system? Would I actually gain anything in terms of reduced engine movement (which translates into exhaust system movement and banging around) by going ahead andd getting poly mounts? I'm thinking that I'd be fine with the JCI soft rubber tranny mount since it is in the center of the car(?) I'm hoping to hear from someone in the drag racing crowd with actual experience with either or both the "stock" rubber and poly setups. Quote Link to comment Share on other sites More sharing options...
Bigdeezs Posted August 26, 2011 Share Posted August 26, 2011 I've used both on my Cammed LS6/T56 280Z and currently have Poly in there now. When I first did the swap I had the stock rubber mounts and the motor went in without much issue. After putting in the Energy poly mounts (both sides) it was a PITA to get the motor lined up and back in the car. I dont know if the mounts caused the issue or if installing my roll bar and seats caused some chassis flex while the motor was out. On a side note I changed to Prothane poly mounts in my LS1 swapped Blazer (uses clamshell on both sides) and had the same alignment/installment problems. Either way I like them being in there since I drive this car pretty hard (drag and auto-x). There is a bit more noise/vibration transferred but I like the thought and feel of that motor being locked in there tight. I plan to switch to a poly trans mount to complete the set on my next Summit order. Also be careful to get the correct passenger side mount. I think I recall there being two different thickness mounts that appear identical. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted August 26, 2011 Author Share Posted August 26, 2011 Thanks so much for the reply-you are the first! Great advice. Since it was such a PITA, can you really tell a noticeable difference in engine movement when you drive the car? I was just thinking that some of the installation clearances between the header and the JCI mount and the exhaust and the crossmembers are pretty tight and I wanted to avoid a lot of exhaust contact with other things. If the motor really doesn't move that much I might just stick with stock mounts - any thoughts? My L24 was in rubber and didn't really move that much except the exhaust rattled on the rear crossmember; and on this install I will be using at least one flex section in my exhaust system. By the way, look at LS1tech forum on trans mount. There is a lot of chatter on there that is negative about using a poly trans mount-I guess it gave a few guys a lot of trouble. Quote Link to comment Share on other sites More sharing options...
Bigdeezs Posted August 27, 2011 Share Posted August 27, 2011 Thanks so much for the reply-you are the first! Great advice. Since it was such a PITA, can you really tell a noticeable difference in engine movement when you drive the car? I was just thinking that some of the installation clearances between the header and the JCI mount and the exhaust and the crossmembers are pretty tight and I wanted to avoid a lot of exhaust contact with other things. If the motor really doesn't move that much I might just stick with stock mounts - any thoughts? My L24 was in rubber and didn't really move that much except the exhaust rattled on the rear crossmember; and on this install I will be using at least one flex section in my exhaust system. By the way, look at LS1tech forum on trans mount. There is a lot of chatter on there that is negative about using a poly trans mount-I guess it gave a few guys a lot of trouble. I difference is slight but noticeable. I never had a problem with the rubber mounts but I think they wear more quickly and I have seen some pretty loose ones on less than 100k mile LS1s (beaten on pretty hard I'm sure)Mine needed replacement so I figured poly was a cheap upgrade. As for the trans mount, are you referring to the extra noise?...I believe that's all I ever saw on tech about it. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted August 28, 2011 Author Share Posted August 28, 2011 I saw several posts from guys who said that they couldn't wait to get them back out for vibrations. I'm not getting much feedback on this thread, so it must not be an issue. Will stick with rubber mounts because they are paid for. Gonna table this thread. Quote Link to comment Share on other sites More sharing options...
SUNNY Z Posted August 31, 2011 Share Posted August 31, 2011 I've been told by a couple people that the engine moves around quite a bit. If you have a cammed engine, you'll want poly mounts IMO. But stick with rubber on your trans mount. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted September 2, 2011 Author Share Posted September 2, 2011 Did you go poly? Quote Link to comment Share on other sites More sharing options...
SUNNY Z Posted September 5, 2011 Share Posted September 5, 2011 If you're referring to me, then no I have not. My car is "on hold" right now. I also don't like the bulky clamshell motor mount design, so I'm going to be modifying mine eventually. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted September 6, 2011 Author Share Posted September 6, 2011 Well, I just couldn't take it, I had some money in my wallet that just wanted out: I ordered Prothane LS1 motor mounts yesterday from Summitt. I only need the one, but I could only find a pair for sale ($50). So, if anybody needs it, I could sell off the second Prothane LS1 motor mount for $25 shipped. I can get the other side from Autozone since it is a universal small block mount. I do plan to cam the car next winter (this winter will be for R200). Thanks for loaning your car to the long tube header group buy. Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted October 15, 2011 Author Share Posted October 15, 2011 Poly motor mounts installed. Left side (clamshell) is Prothane from Summitt, right side is Energy Suspensions from AutoZone. Right side went in easy. Left side requires drilling out rivets in Camaro clamshell mount and swapping all the rubber stuffing. That went pretty easy. Putting the poly stuffing into the clamshell required trimming the poly a little because some of the rubber indentions do not exactly align, but after that it went together fine with the bolts supplied in the Prothane kit. The wings on the right side had to be bent out a bit, and the length of the metal tube in the Prothane mount had to be shortened a bit with a grinder. I had go take my oil pressure sender off to get the engine mount bolt in on the left side and it took a bit of pounding and loosening of the mount-to block bolts to get it all lined up, but it went together pretty well. I am glad I am making this change now-it would have been hell with a header in place to work around. Quote Link to comment Share on other sites More sharing options...
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