K Frame Polyurethane Isolators from ESPO

Hello All,

I order a set of polyurethane K frame isolators (no, I don't want solid mounts), from ESPO (aka Springs n Things). These are made by Prothane but came without installation instructions. I found the Prothane ones but they are too generic to be useful and although the ones from Energy Suspension are much better, are not applicable.

The challenge (problem?), I have is twofold. One is the fit of the 'insert' section of the isolator that goes through the hole in the K frame. The factory isolator has a metal band around that section so it is a tight fit in the K frame hole. However, the ESPO item has a gap of ~0.5mm between the insert and the hole in the K frame. To me it should be tight to prevent and potential movement. The factory torque specification for the through bolt is 80 lb. ft. which, to me, would not be enough to 'crush' or 'spread' the isolator to prevent any movement. Pictures below; first image shows the lower front polyurethane isolator in place (notice the gap), the second image is original lower front isolator in place.

The second concern is the orientation of the isolators. From the factory the front isolator has the insert piece as part of the lower isolator and the rear has it in the upper isolator. The factory must have done this for a reason??? Pictures below; the third image shows the original front with the upper isolator on the left, the fourth image shows the original rear with the upper isolator on the left.

According to ESPO; 'in 20 years no one has questioned the insert gap or the orientation and no issues have arisen'.

Questions;
1. Has anyone used these isolators?
2. Did you notice the 'gap'?
3. How did you orientate them?
4. Did you have any issues after the install?



Looking forward to the feedback.

This won't necessairly give you all the details you're looking for...but way back when I used the POLY pucks (don't remember where I got them from, could have been Springs'n'Things though).

The package I got had these large thick washers that were to be placed against the K-frame (at the top) and at the bottom they were used for the big bolt to press against as it 'captured' the poly puck.

OK, so take a look at the photo that shows the PASS side install. You can roughtly see how they came together.

You are right, they certainly were not spot-on, there was movemement. I also glued the washer onto the POLY puck first so as to move positively locate that thing and worry less about stuff moving around on me as I proceeded to assemble the whole thing.

With 80 ft-lbs of torque those pucks did compress!

Probably the more important piece in all of this is the chassis alignment chart that will show you the measuring distances from key locating points. That is in the FSM book, I can dig that up for you and post it on here.

You would use these to correctly center the K-frame between the frame-rails and fwd/back location. There is not that much room to flop things around, but hey, even a 0.5" will show up, and the last thing you want is to have the alignment shop struggle afterwards trying to correct for a crooked K-Frame install.

Hello M_Body_Coupe,

THANK YOU SO MUCH!!!! Forums are SO valuable!

I have been going back and forth with ESPO (Spring n Things), for days seeking clarification was told no one has mentioned this in 20 years.

Your feedback has helped a great deal especially the photo. DOH! Never thought about 'alignment' of the K frame. I have a FSM for my '88 Plymouth, will check to see what it states. If I can't find it, I'll let you know.

BTW nice rotors - which brand?

And to think I was just going to use a pile of old hockey pucks... I'd didn't know anyone made new ones for these cars anymore

I wrote a whole lot then re read your post. So I noticed you only really asked this below. Sorry to go way off.

Questions;
1. Has anyone used these isolators? YES, Many times over but bought from a diff prothane dealer and they had instructions for the ones who need it.
2. Did you notice the 'gap'? Yep, I just set it all to the rear and then checked for square.
3. How did you orientate them? Like in the picture above if thats what your asking.
4. Did you have any issues after the install?

No issues, just rechecked them a a couple times to be sure the bolts were tight.

Fresh Air Inspector said:

Your feedback has helped a great deal especially the photo. DOH! Never thought about 'alignment' of the K frame. I have a FSM for my '88 Plymouth, will check to see what it states. If I can't find it, I'll let you know.

BTW nice rotors - which brand?

Click to expand...

1) I am sure your '88 FSM has the same chart, but here is the scan out of my '80 FSM book, for the 2dr. crowd this will help

Specifically I would use the 'TRANSMISSION CROSSMEMBER GAUGE HOLE' to 'ISOLATED CROSSMEMBER GAUGE HOLE' measurement, which is 55-7/8" (1419mm) on my chart.

That would pretty much take care of the K-Frame to chassis alignment in all four directions (front/back & left/right).

2) Rotors...my man, it's been forever that that photo was actually taken (2005 is what the image EXIF tells me LOL). My parts tracker though say I have:

#5311, QBS, 11.75" HD rotor (which crosses to Raybestos 7038)

Yup, when you could still find these goodies on eBay for like $40/set...lol, I see a bunch listed now, but that's normally a $90/ea expense these days.

RockAuto shows them at $47 right now, find a 10% discount coupon and that's a much better price!

Hello XfbodyX,

Appreciate the feedback. Having a 'second' confirmation of the issues I experienced is comforting.

Hello M_Body_Coupe,

As always, appreciate the info. I checked my FSM and I have the same diagram. My diagram references the same 'transmission cross member gauge hole' for the 3 reference measurements. I'll keep the rotors in mind, the ones on my '88 are original and in surprisingly good condition.
================
As for my K frame I'm planning an experiment with the gap between the insert and the hole in the K frame. I'll either cut a strip of aluminium about 1/8" tall and about 0.12" or 0.15" thick or use two hoops of copper wire about the same thickness as the aluminium but stacked to match the ~1/8" thickness. I'm hoping the metal will help 'lock' the isolator in the K frame opening. The unknown in this is whether or not the insert 'spreads' when the bolt is torqued negating the need for a 'gap filler'. Still running the pros and cons around in my head.

Fingers crossed.

0.5mm gap between the isolator and the hole in the K? Whatever you do, don't start laser measuring the chassis for squareness. If this has you worried then the tolerances of the rest of the car will give you cold sweats at night.

I'm with Coupe on this. Just crank it down and even poly will compress under that load enough.

If you're ordering rotors then look at the options on Rock Auto. I can't recommend a brand, but grab one that is zinc plated. It does a great job keeping the rotor for rusting.

Not that I had a issue with them but I do like the original mopar mounts better. Much better fit.

Hello All,

I realize that I'm probably being anal about the gap, I just dislike after market parts that don't fit properly. Unfortunately this is an issue with many after market parts these days.

I'll install the isolators as is, take the K frame to body measurements and torque the bolts. Out of curiosity I may try to get some before and after measurements of the isolators to see if there is a 'compression' factor.

Once again, thanks for all the feedback.