Moparts
New spring perches, larger hole size
Posted By: Suregrip391
New spring perches, larger hole size - 03/30/20 11:15 PM
Is it important to get a new spring pin to match the larger hole that comes on new spring perches? Someone told me that it’s not necessary because it’s the u-bolts that place the rear where it needs to be and don’t worry about it. Bolt er’ in and forget about it.
Thoughts?
Posted By: moparmarks
Re: New spring perches, larger hole size - 03/30/20 11:51 PM
I just went through this on my Dart. I like them to be centered. I cut a couple spacers out of 3/8 pipe, I think it was. Got lucky as it fit great over the pin and in the hole. They centered the perches up on the springs.
Posted By: mopars4ever
Re: New spring perches, larger hole size - 03/31/20 12:00 AM
How big is the hole??
Posted By: topside
Re: New spring perches, larger hole size - 03/31/20 12:24 AM
I'd want to drop the rearend on there, bolt it up, measure the wheelbase.
Get that right & equal both sides.
If the holes are concentric, I'd want to sleeve the locating pins for race use so the axle can't re-locate itself.
If not concentric, double-check measurements, break out a die grinder & bit, make them concentric, and sleeve 'em.
For street use, sleeving is probably not necessary, depends on power/shock loads/grip.
Posted By: Neil
Re: New spring perches, larger hole size - 03/31/20 12:36 AM
I bought the next size up bolt with a larger head to fill the hole in the spring pads, and then had to drill out the register holes in the springs to fit the bigger bolt diameter. Spring steel does not drill very fast!
Posted By: hemi-itis
Re: New spring perches, larger hole size - 03/31/20 04:11 AM
So who is reinventing the wheel??? We been stickin it in the same hole for over 50 years
Posted By: moparmarks
Re: New spring perches, larger hole size - 03/31/20 04:29 AM
Seems some of the replacement perches have a larger hole. I have inboard springs with new perches. There was a lot of slop. I wanted it all centered up so it didn't go down the road sideways like an old Chevy truck.
Posted By: moparmarks
Re: New spring perches, larger hole size - 03/31/20 04:31 AM
Posted By: Cab_Burge
Re: New spring perches, larger hole size - 03/31/20 05:30 AM
Posted By: BANDIT
Re: New spring perches, larger hole size - 03/31/20 04:15 PM
Yup, that’s what I do on all the street car rears I narrow, you can buy the tubing by the foot and just tack weld a 3/4 “ on inside of perch. Moroso or Competition Engineering make em with 1/2” hole, but they used to be spendy. That is by far the quickest and most cost effective way to do it. Jim
Posted By: Neil
Re: New spring perches, larger hole size - 03/31/20 05:13 PM
So who is reinventing the wheel??? We been stickin it in the same hole for over 50 years
I bought new springs from Eaton and the register bolt was smaller than the stock one for some reason. I just went up a bolt size and drilled the holes in each leaf bigger.
Aftermarket parts always have to have at least one thing not quite right about them.
Posted By: Suregrip391
Re: New spring perches, larger hole size - 03/31/20 08:54 PM
Thanks guys. I think I’ll try the 3/8 black pipe trick to keep things in line. Makes you wonder why something as simple as a hole can’t be made right after all these years. Always something.
Posted By: BDW
Re: New spring perches, larger hole size - 03/31/20 09:14 PM
I don’t understand the concern?
Once the U-bolts are tightened, where’s it going to go?
I highly doubt the 1/16” is going to make a difference.
Posted By: UCUDANT
Re: New spring perches, larger hole size - 03/31/20 09:40 PM
Posted By: jb500
Re: New spring perches, larger hole size - 03/31/20 09:55 PM
The nut on the bottom of the leaf spring pin will/should center itself to the mounting plate.
Posted By: hp383
Re: New spring perches, larger hole size - 04/01/20 12:28 PM
I stopped buying the Mopar perches and switched to the Moroso for that reason. On the several spring, and axle swaps I have done I have never once had the Mopar perch sized centering pin. It hasn't mattered if the springs were stock 30yr old or brand new aftermarket, the locating pin has always been the smaller diameter.
Posted By: moparmarks
Re: New spring perches, larger hole size - 04/01/20 03:22 PM
Those Mopar perches look like they are for the 73-up B Isolation setup.
Posted By: 1969ronnie
Re: New spring perches, larger hole size - 04/02/20 11:14 PM
hi , the P4120074 mopar spring seats have a .625 or 5/8" center hole . the ones you want are mopar P5007857 with the .500 or 1/2" center hole .
ronnie
Posted By: Magnum
Re: New spring perches, larger hole size - 04/11/20 11:46 PM
The bigger hole perches from Mopar are from their truck parts bin, resold as Performance Parts.
I love the cut pipe spacer idea. Why build a car and allow the rear housing not to be accurately located? No wonder some of the Mopars out there are crapboxes.
As much precision that can be controlled by me, gets the go ahead.
Posted By: dvw
Re: New spring perches, larger hole size - 04/12/20 12:17 PM
The large hole perches are for the isolator type attachment. They are later production, therefore probably more common. I've been using the 3/8" pipe as a spacer for years.
Doug
Posted By: DoctorDiff
Re: New spring perches, larger hole size - 04/12/20 05:14 PM
Iso spring perches were made with a 1 1/2" center hole.
The MP perch with a 5/8" center hole was originally a Dakota application (3/8" spring center bolt). Installing them on a passenger car 5/16" center bolt is a non-issue because this bolt locates the shock plate, and the shock plate locates the rearend housing via U-bolts tight against both sides of the spring perch.
I carry special 5/16" center bolt spacers, however.
Posted By: dvw
Re: New spring perches, larger hole size - 04/12/20 09:11 PM
Ya, I missed the Iso diameter by a ton.
Doug
Posted By: 572B1
Re: New spring perches, larger hole size - 04/13/20 12:04 AM
I purchased a relocation kit in the nineties and it came with the large holes in the perches. we used two drill a 1/2'' hole in a flat plate and fully weld it to the perch. this lowered the car and fixed the large hole problem.