Door latch mods for greater reliability and function

[Gumball]

UPDATED - 7/5/16: This one is an oldie but a goodie and certainly has as much relevance today as it did back in 2013. Don't risk having the little ball snap off in your hand (or more likely, a passenger's hand) or having the doors only latch on the first catch and not fully, only to spring open while rounding a corner.

Original post follows......

As I'm working through body fitting (doors are my current project), I did a bit of research and found that the FFR supplied latches have two weak points - 1) the lever arm is only swagged onto the latch release assembly, causing it so come loose; and 2) the chrome-plated brass knob on the end of the lever arm tends to snap off. I followed the two known fixes for these issues when installing my latches to reduce the risk of failures on the road.

I also did a few other things to ensure that the latches operate smoothly and are reliable.

One very important step is to also ensure that you lubricate the latches very well using white lithium grease and work the mechanism until it operates smoothly and the lubrication is evenly distributed.

For the lever arm issue, all you need is a 5/16" carriage bolt, a washer, and a nylock nut. The square hole in the latch mechanism may have a bit of flashing, so a little filing may be necessary for the bolt head to fit all the way. If your washer is not thick enough to apply pressure, you'll need to grind down a bit of the cast area that the bolt protrudes up through. If you're not using the FFR supplied spacers behind the latch mechanisms, you'll also need to either grind the head of the carriage bolt or relieve the door behind it to ensure smooth movement.

Here are a few pics:

http://i845.photobucket.com/albums/ab15/CCRsAC/LatchwithCarriageBolt_zpsa5c1c6ef.jpg

http://i845.photobucket.com/albums/ab15/CCRsAC/CarriageBoltComparison_zpsf45f89fc.jpg

http://i845.photobucket.com/albums/ab15/CCRsAC/CarriageBoltHeadProfile_zpsdea88789.jpg

I also noticed that the latch shaft wasn't retracting completely into the mechanism when the lever was moved the the farthest point of travel, so I filed a bit of material off of the stop tab that is cast into the latch, which gave just a bit more travel and allowed the pin to completely retract - goal of this was to ensure smooth opening and closing. The stop is just to the left of the lever arm in this picture - note the flat spot where the arm contacts the stop:

http://i845.photobucket.com/albums/ab15/CCRsAC/Latchwithfiledstop_zps2b947b02.jpg

Another suggestion was to chamfer the hole for the pin in the striker post, so here's a shot that shows that mod, as well as the spacer I made using some of the FFR supplied aluminum spacer material - I'll give the spacer a good polishing before final assembly so that it matches the striker. I did this mod using a conical grinding stone on a Dremel.

http://i845.photobucket.com/albums/ab15/CCRsAC/StrikerwithSpacer_zps1ad3fa36.jpg

Finally, I also did the mod to ensure that the knobs don't break off the levers by drilling the back of the knobs with a #36 bit (after marking it with a spring loaded punch) and then tapping the holes for 6-32 machine screws. The knobs are brass, so this was really easy to do. Just make sure that you keep the holes clean when drilling (remove the bit regularly to get the shavings out as it gets deep) and that you drill deep enough to account for the end of the tap that doesn't cut threads. I used 3/8" long screws, so the holes are drilled nearly 1/2" into the knobs.

http://i845.photobucket.com/albums/ab15/CCRsAC/KnobFix_zps0d0cbc7a.jpg

[SCFFR]

Great job Chris. One of my latches broke just the third time I opened the door so ended up doing the carriage bolt fix also. Definitely the latch could use a little re-engineering.

Keep up the good work!!

Ron

[skullandbones]

I think the filing of the stop tab is a great idea. Also, I had not seen the tapping of the latch knob before but I hadn't heard of it falling off either. That's worth a little time for some added peice of mind. This reminds me of the gun shows where the gun smith details the trigger mechanisms and files the trigger and firing pins to get a smoother action. So we'll have the fastest latches in the west!!! Thanks, Chris. WEK.

[Jester]

My DS door latch failed today while some distance for home. I need to make the carriage bolt fix as outlined above. I am glad there is an easy fix.

I highly recommend others consider this fix to avoid a similar failure. Mine failed just into the second season - I estimate less than 100 open-close cycles of the latch before it failed. This is a definite design deficiency in the door latches.

Thanks for posting the fix Chris!

[skullandbones]

I'd just like to add that now that I have gotten a chance to see and operate the doors of a lot of other cars besides mine, I have noticed that the latches may experience a lot more stress on them due to alignment and adjustment from car to car and from side to side. If the latch gets in a bind, it is possible to stress it and break the "weak points" much faster than by hundreds of openings and closings. That could explain the very early failure mentioned above. The upgrades should be included in the manual as necessary upgrades. IMO, WEK.

[Jeff Kleiner]

One thing to add--- I always remove the little coil spring (shown in Chris' first photo). Doing so makes the latches move easier reducing the stress on the weak lever. This spring to me is kind of redundant as there is another in the barrel behind the latch pin that is more than sufficient to keep it engaged.

Jeff

[CraigS]

I agree w/ Jeff, toss that spring. Mine have been gone since 07. I tossed the springs and lubed the latches well w/ gear oil and have had no problems. Maybe once per year I drip a little more gear oil in there. I also agree w/ WEK, perfect alignment is important. It is not easy to get but well worth it. As bad as these things are, w/ a little effort they can be made to work as easily and smoothly as your daily driver.

[j.miller]

One more. If you do a bench fit you will find that the pin does not drop all the way into the hole (50 percent pass side-95percent driver) chamfering helps get it started but it stops half way. The handle still returns because of the spring but the pin is not seated. We drill the holes a bit oversize. This does two things. Lets the pin seat fully and gives you just a little wiggle room for not having everything in perfect alignment. I like to shoot everything with Tri Flow for penetration followed by spray Lithium for lasting lube. Filing the stop is a great idea. I prefer to retract the pin with the handle then file the exposed tip of the pin and re-bevel. If you do everything talked about in this thred you should have latches that give good service for a long time...da Bat

[MPTech]

I did all of these mods last year before my car was licensed and they have been VERY beneficial to a smooth operating mechanism. HIGHLY recommend these modifications. I strongly believe the not making these improvements will almost certainly result in failure / damage to the latches (it's only a matter of time).
These are all simple improvements that can be done without specialized tools / equipment.

Don't overlook these improvements!


ok, with that said, the only issue I have had (and it's not really covered in these mods) is my latches have come loose from the doors a couple times. I applied blue loc-tite and re-tightened, but they loosened up again over time. I keep an eye on them, but would like to permanently resolve this.
Any suggestions? I'm concerned about stripping them out if I keep re-tightening them.

Thanks!

[skullandbones]

X2 on the same issue of loose latch body after driving a while. I have not focused on it as I am still not finished with body but have thought a lot about it. Thought about going in from below and thru bolting with lock washers (the flat kind). Also, rivnuts of some kink might work but haven't found the perfect combination. Like I said I haven't really focused on it yet. I may have to move mine a little anyway when I mount the other piece of the latch that you don't normally use for FFR. I like it and must have that as an interior detail. The FFR way just looks "kit car like". I want to remove as many of those obvious cheap looking solutions as possible. Therefore, it is only a matter of time that I will have to discover a better solution than screws. I think the thru bolt way is more permanent and also will allow some adjustment for fine tuning the latch if necessary. I'm very happy with the mods suggested so far.

Thanks, WEK.

[Jester]

Door latches are fixed and good to go. Very easy fix. The PS latch was fine but I installed a modified cartridge bolt to eliminate a possible failure. I also removed the outer latch spring as suggested.

Thx

[Gumball]

Today's TTT on a 2013 thread that is sure to help keep your door shut and the latches operating as they should.

[JIMOCO]

I am having trouble with my DS door opening while driving. I have tried to follow this thread and am a bit confused. I understand the suggestions about using a carriage bolt, removing the spring and tapping the lever knob. I can see where these improve the structural integrity of the latch. I do not see that those fixes will solve unexpected door opening. There is discussion about chamfering the hole on the striker post. I do not understand the benefit of that recommendation. Also, there is discussion about modifying the pin to fit better in the hole. Can someone please explain in more detail the steps related to resolving the unlatching issue? I tried filing the grove on the latching post so that the latch goes in deeper but that has not helped. Someone also mentioned that there should be a double click when the door latches. Is there an internal second latch the should be engaging?

[Chris @ Forma]

Several years ago, we were also frustrated with the door latch system that was vintage in appearance as well as reliability. So we developed a solution that incorporates a modern automotive latch and is easily retrofit-able to in process as well as completed Mark IV's. We haven't looked at earlier FFR cobra replicas, but it may work there as well. The instruction manual is available here if you are interested: https://www.dropbox.com/sh/42caex67ki4gysh/AABnyh2_qqqTBFfixfOX8CtOa?dl=0

[frankeeski]

I am having trouble with my DS door opening while driving. I have tried to follow this thread and am a bit confused. I understand the suggestions about using a carriage bolt, removing the spring and tapping the lever knob. I can see where these improve the structural integrity of the latch. I do not see that those fixes will solve unexpected door opening. There is discussion about chamfering the hole on the striker post. I do not understand the benefit of that recommendation. Also, there is discussion about modifying the pin to fit better in the hole. Can someone please explain in more detail the steps related to resolving the unlatching issue? I tried filing the grove on the latching post so that the latch goes in deeper but that has not helped. Someone also mentioned that there should be a double click when the door latches. Is there an internal second latch the should be engaging?

There is a hole in the striker and the pin of your latch is not fully seating inside the hole (or at all). Chamfering the outside of the pin will sometimes help but enlarging the hole in the strike will insure it. As it is now, the pin is just latching on the indent in the striker post.

[phileas_fogg]

Like Frank says, enlarge the hole just a skosh. Jeff Miller has some excellent tips for smooth operation of the latch pin (Post #7 at https://www.ffcars.com/forums/17-factory-five-roadsters/567009-driver-door-fitment.html). Also, check the rotation of the latch post. A small tweak with a crescent wrench (using a rag to protect the chrome) is often all that is needed.


John

[JIMOCO]

Thanks guys. The light finally went on and I now see the issue. I did not do the original installation and hope that I can make these mods and get the proper result.