Front damper striped threads

[Dougal]

Hi All
I found that my front dampers, were attached using a mixture of BSF and UNF bolts. Not good you all say, worse one of the bolts was crossthreaded at some time and the thread is stripped.

My proposed solution to the 7 unstripped holes is to use new UNF bolts.

For the stripped thread I intend to drill out and tap to 7/16 BSF (next available size). I will have to open out the hole on the damper a bit as well.

I would be grateful for any comments on the above.
Dougal

 

[pan]

Unfortunately this is a common Healey problem. The best solution is the replacement of the tower top plate that damper is bolted to. This is quite a big job involving removing the old top plate welding the new plates accurately.
Repainting of the tower will be required to complete the job.

 

[zblu]

Might be able to drill, tap and fit a helicoil though

 

[stevebn2bj7]

I had the exact proplem you describe and fixed it in the manner you propose. It has worked well for over 6000 miles. It is a shame to have to modify the shock base to fit the 7/16" bolt but is much easier fix than replacing the shock mount.

 

[Patrick67BJ8]

I had the same problem several years ago.
I opened the shock tower plate from the side(made 3 cust like a hinged door) and carefully ground the welds off the stripped nuts and popped them out with a hammer and socket that was the same size as the nuts

I had a friend of mine make me new nuts that had the step down fit like the old ones did and even made them 1/8" longer. I reinstalled them and carefully welded them in 3 places on the top of the tower plate and ground the welds flush. I had extra of these special nuts made in case they ever messed up again and I have not had to redo this repair!! I've put lots of miles on them and no problems.

I used a Dremmel tool with a cutting disc to cut the access hole in the side of the shouck tower plates.
Patrick

 

[steveg]

I bought my car in 1999--it had 3 of the shock bolts replaced with 10mm metric bolts. They are only slightly larger .3937" vs .375" and have worked fine without any loosening. I haven't looked at these in a while and couldn't say if they're coarse or fine. Fine is stronger.

I would advocate using 10mm because if they strip later you have the option of going to 7/16 at that point.

 

[Dougal]

Cheers all, good to hear that i'm not alone with this problem. I'm not keen to cut off the mount, seems quite a big job to fix this problem. However although I have been driving the car quite happily with dodgy bolts holding the damper on I think I should try to fix the problem properly.
So... I'm now looking at drilling out all the holes and fitting inserts. I think I can do this for 3/8 UNF, which will give me solid mounts and no need to enlarge the holes in the damper.

 

[Bob_Spidell]

I just repaired a stripped captured nut with an insert. Worked great. You'll need a 90deg drill adapter and a "stubby" drill bit to work in the confined area. The insert kit was about $35.

 

[Hedgehog]

Perfect timing on this topic. As the 100/4 is stripped to the chassis I best check this now before paint.

Thanks.

 

[Cutlass]

I drilled and tapped a 1/2 inch steel plate, conformed to the pattern of the shock, and, after opening what was left of the top of the shock tower, placed it in the tower, welded in a new top cover with slightly oversized holes, letting the plate float a bit.

 

[pan]

1.zblu,
Helicoiling these captive nuts will not last! Remember, the weight of the
front of the car is hanging on this part.
2.Cutlass,
Re: "letting the plate float a bit", how do you make sure that the wheel
camber is correct?
Repairing this fault properly is worth doing. Once done (and the bush mechanics kept away from the car) you will never need to do it again. The problem is caused by neglect. Early in the cars life these bolts will have loosened, and were not checked. The movement thus allowed will have damaged the thread nut threads.
Our friends at Kilmartin Sheetmetal can supply a modified top plate featuring a clever device allowing camber adjustment.
On my pre-trip checklist, one of the items is: Check tension on front shocker bolts.

 

[Dougal]

"The insert kit was about $35"
Hi Bob can you let me know the name of the kit you used.

Hi Pan Why do you say the helicoiled threads will not last, I would have thought that they would be at least as strong as the original.

 

[Randy Forbes]

"The insert kit was about $35"
Hi Bob can you let me know the name of the kit you used.

Hi Pan Why do you say the helicoiled threads will not last, I would have thought that they would be at least as strong as the original.

The thing I would be most concerned about, is how little base-material would be left of the original threaded insert after being drilled & tapped for the repair's coiled thread.

Generally, Heli-Coil and Recoil inserts are for repairs where there is more surface area than a "nut" has; parts like engine blocks, cylinder heads and pump casings will have a much greater area of "solid" material (be it cast-iron, cast or billet aluminum).

Don't get me wrong; I use them when I have to...

 

[steveg]

Have to strongly urge going with the 10mm bolts--the hole is a tiny bit larger and mine have been going strong for the 9 years I've owned the car with no loosening--ever. I don't even know how many years they were on the car before that.

If I were doing the work I would do a trial run with an aluminum plate--drill & tap a 3/8" fine hole, then drill thru it with the proper tap drill size for the 10mm, then tap the hole with the 10mm tap. That way you can observe the difference and whether it's even necessary to drill out the holes in the shock base to 10mm.

This is the most conservative fix because it's the easiest to do and removes the least amount of metal from the car.

Some of the fixes described above are overkill--however the helicoil or 7/16" bolt are always an option if the 10mm doesn't work--but you can't go back.

If one of the forum members has his car apart, the captive nuts can be seen thru holes in the area where the coil spring seats--someone could estimate how large the captive nuts are.

Just my .02

 

[steveg]

pan--helicoils are stronger than the original threads given enough surrounding support because they have a larger diameter--more thread gripping area--and are made of very high quality stainless which is no doubt superior to the plain steel captive nuts.

 

[Patrick67BJ8]

1.zblu,
Helicoiling these captive nuts will not last! Remember, the weight of the
front of the car is hanging on this part.
2.Cutlass,
Re: "letting the plate float a bit", how do you make sure that the wheel
camber is correct?
Repairing this fault properly is worth doing. Once done (and the bush mechanics kept away from the car) you will never need to do it again. The problem is caused by neglect. Early in the cars life these bolts will have loosened, and were not checked. The movement thus allowed will have damaged the thread nut threads.
Our friends at Kilmartin Sheetmetal can supply a modified top plate featuring a clever device allowing camber adjustment.
On my pre-trip checklist, one of the items is: Check tension on front shocker bolts.

I'm not sure about helicoils and their strength on cars, but I hope the ones used in aircraft are much better than the ones in cars because the 747 uses over 350,000 of them.

 

[pan]

Well, I stand corrected......again!
I still reckon replacing the plate is the safest option.

 

[Dougal]

Well fellas I have made my choice, I'm going for the inserts. At great expense, have bought the kit a drill and a attachment for my 'Black and Decker' that will let me drill round corners.... well almost. Now the inserts with the kit are unfortunately 2D (2x diameter length) my guess is that i only need 1D, so will have to cut them down. Anyone with a chassis in bits know the thickness of the captive nuts?

 

[zblu]

Dougal,
Read very very carefully on how to install, ie getting yourself truly vertical to face of nut, correst drill size and how to ensure tangs are not proud of nut face etc, maybe read the info on the insert sites if it doesnt come in the kit

 

[Dougal]

Thanks Zblu, have done what you suggest, I must admit I have done a few before. One of my first jobs was in a precision engineering shop, we put thousands of inserts into aluminum castings for "secret squirrel projects". I have just never done one in something I owned or in steel before.