Aaron Cake
03-29-2026, 11:46 AM
https://www.aaroncake.net/delorean/5637/engine_cover_latch/1 - Latch Catch Pulled Out.jpg
Sigh. As we all know, the engine cover latch catch is weak point. Rather, the threaded insert molded into the fiberglass engine cover is the weak point. It was just never going to be reliable long term due to the weak retention of the threaded insert. If only they had molded a reinforcement plate with a bung attached into the cover. Mine had obviously been repaired at least once in the past and judging by the cracks in the fiberglass, probably more than once. It let go the second or third time I opened the engine cover.
I decided that I would fix it permanently instead of just repeating the factory mistake and bonding in a new threaded insert.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/2 - Tracing The Shape On 0.125 Stainless Plate.jpg
The first step was to establish the basic shape on some 1/8" 304 stainless plate. I started with the stock rubber louver latch washer and traced out the shape to locate the mounting holes. Then turned it 90 degrees to for a dimensionally pleasing triangle.
The resulting shape is vaguely rude looking.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/3 - Final Shape.jpg
Tangents drawn between the curved areas complete the pattern. On the first attempt I went from center to center but clearly that cuts off the curved area but a 2nd attempt got the result I was looking for.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/4 - Cutting Out Flange On Band Saw.jpg
After some time on the band saw, the flange was cut out. Going around the curves is a slow process of wiggling to give the blade room to follow the curve. There's no margin with stainless; it will bind.
Then I drilled the holes for the stock louver latch catch. The louver latch catch seems to be an obvious part to reproduce in stainless however I can't find anyone doing so. I'm going to look into making a die for my press so I can brake some stainless rod to the correct dimensions. Should be easy to stamp out replacements. For a one off, just a regular brake or even bending one up in a vice would do the job.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/5 - Flange Drilled For The Catch.jpg
A quick test fit on the engine cover. Seems to work.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/6 - Flange Test Fit.jpg
Now drill a hole through the engine cover! I started with a small bit which fit the existing hole left by the pulled-out threaded insert. Then gradually increased the size to about 15MM which was about as large as I could go without leaving razor thin walls in the existing fiberglass. Unfortunately that plan didn't work out as you will see later on. Turns out that the whole area must have been cracked for a while, so bits if fiberglass fell of as I drilled.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/7 - Hole Drilled In Engine Cover.jpg
The next part to create is the bung to hold the latch catch. I started buy turning some stainless rod down to about 15MM on the lathe.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/8 - Turning Down Rod.jpg
Actually, that's not quite true. I had originally intended to just bore a hole through some 1/2" stainless rod then tap it to M5. Making the hole in easy, because I ended up doing it 3 times. Because 3 bloody broken taps later, I gave up on that. The only taps I have are HSS plug taps which are not great for tapping deep holes in stainless. The first one I broke being too aggressive. It was jammed into the part, so I drilled out bung number 2. The 2nd one broke I think because it was just too dull. I was being very gentle and got about 5 - 6 MM into the hole before "snap!". And the 3rd was about the same as the 2nd. Well, there go all my 5MM taps. Realistically a taper tap is needed for this process however at that point I wasn't going to waste more time risking breaking more taps.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/9 - Nut Hole Bored.jpg
I enlarged the hole enough to fit a 5MM nut.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/10 - Nut In Bung Hole (Giggity).jpg
A 5MM nut was then pressed into the hole, making sure it was nice and level with the surface of the bung.
Some delicate TIG welding secured the nut into the hole. During a stainless steel bathroom vanity project, I got very practiced welding nuts into stainless runners as that's how I secured all the inner panels. Start the puddle on the thicker metal with the filler rod laying between the nut and the substrate. Then roll the puddle onto the nut. Pause to let everything cool because the nut will easily overheat then just continue around the circumference.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/11 - Nut TIG Welded.jpg
The bung was faced on the lathe to remove the weld bead, then a little bevel added. After cleaning up the threads a bit with a tap, test fitting the latch catch showed everything fit as intended.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/12 - Bung With Latch Catch Test Fit.jpg
The matching hole in the flange turned out to be much more of a pain in the ass due to a silly mistake on my part. I accidentally drilled the final hole to about 1MM less then it should have been. Not a big deal right? Just drill it out to the final size? On steel, no problem. On stainless...problem. Drill bits are meant to cut on their face, not their corners/sides. You can get away with some bit abuse on softer materials. Unfortunately when I tried on stainless, the material work hardened almost immediately and broke off the corners of the bit. Re-sharpening the bit and trying again was met with the same result. Sigh. So, I chucked a carbide rasp into my Dremel and just went around and around in the hole until it was the correct size. Not elegant.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/13 - Hole In Flange.jog
Bevels were added to the bung and flange so I could sink the weld bead deep into the material. I chucked the bung in a drill and spun it against the bench grinder wheel, while I used a countersink bit to create the bevel on the flange. Note also the flange is clamped securely to a thick metal plate. There's a hole drilled through the plate to accommodate the bung and 3rd hand adjustable arm holes it in from below. Clamping stainless is extremely important when welding because it will warp in an extreme amount. Without the clamps, the flange would become concave.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/14 - Bung and Flange Ready To Weld.jpg/img]
[img]https://www.aaroncake.net/delorean/5637/engine_cover_latch/15 - Bung Welded To Flange.jpg
30 seconds of TIG and the parts were as one.
Once everything was fully cooled (and that is naturally cooled, not blasted with air or water) I blended the top of the flange with a small belt sander. Now it doesn't match the grain pattern of the car perfectly so I will have to try again with a different grit later on.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/16 - Smooth Flange.jpg
The completed part. Countersunk the louver catch holes a little. You can see the gross uneven bung hole (that's what she said) I had to clearance with the Dremel. At least it will never be visible when the part is installed on the car.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/17 - Completed Part.jpg/img]
I will admit that it took a little filing of the hole I drilled in the engine cover before I could bolt the completed part down evenly. Whether my drilling was a bit uneven, or whether the louver latch holes aren't centered to the engine cover latch will forever be a mystery as I didn't feel like measuring.
[img]https://www.aaroncake.net/delorean/5637/engine_cover_latch/18 - Installed To Engine Cover.jpg
The rusty stock hardware as replaced with stainless.
With the engine cover back on the car, I installed the latch catch and adjusted. Took a few closing/opening cycles before it would operate smoothly and unlatch on command. Once done, the stainless jam nut was tightened.
You can see the condition the molded fiberglass was in due to 45 years of stresses from the threaded insert. It was cracked quite thoroughly and fell to pieces as I drilled it out to accommodate the new bung. This is going to have to be repaired because aesthetically it looks terrible. That's a problem for future me when I feel like getting messy with some fiberglass. I may also simply create a small stainless cap instead of having to deal with the fiberglass repair.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/19 - Engine Cover With Latch Catch Installed.jpg
Woo freaking hoo! My engine cover is now capable of latching securely! Maybe that will get rid of some rattles in the area. Also keep the curious away from lifting the engine cover.
Next time I have access to a laser cutter I may engrave a flux capacitor into the flange for shits and giggles. I considered making the flange into a DMC "D" but that seemed a little tacky.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/20 - Engine Cover Latched.jpg
If there is enough interest in these, I will see about producing them. Need to draw up the flange in CAD and get a quote on having them laser/water jet cut because that's the most time consuming and fiddley part of making these. Plus it would be nice to have the flange dimensionally accurate without a lot of hand finishing. This one was also built specifically for my car so the louver latch holes will probably only fit #5637. To fit other cars, slots would be needed to allow adjustment.
Sigh. As we all know, the engine cover latch catch is weak point. Rather, the threaded insert molded into the fiberglass engine cover is the weak point. It was just never going to be reliable long term due to the weak retention of the threaded insert. If only they had molded a reinforcement plate with a bung attached into the cover. Mine had obviously been repaired at least once in the past and judging by the cracks in the fiberglass, probably more than once. It let go the second or third time I opened the engine cover.
I decided that I would fix it permanently instead of just repeating the factory mistake and bonding in a new threaded insert.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/2 - Tracing The Shape On 0.125 Stainless Plate.jpg
The first step was to establish the basic shape on some 1/8" 304 stainless plate. I started with the stock rubber louver latch washer and traced out the shape to locate the mounting holes. Then turned it 90 degrees to for a dimensionally pleasing triangle.
The resulting shape is vaguely rude looking.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/3 - Final Shape.jpg
Tangents drawn between the curved areas complete the pattern. On the first attempt I went from center to center but clearly that cuts off the curved area but a 2nd attempt got the result I was looking for.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/4 - Cutting Out Flange On Band Saw.jpg
After some time on the band saw, the flange was cut out. Going around the curves is a slow process of wiggling to give the blade room to follow the curve. There's no margin with stainless; it will bind.
Then I drilled the holes for the stock louver latch catch. The louver latch catch seems to be an obvious part to reproduce in stainless however I can't find anyone doing so. I'm going to look into making a die for my press so I can brake some stainless rod to the correct dimensions. Should be easy to stamp out replacements. For a one off, just a regular brake or even bending one up in a vice would do the job.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/5 - Flange Drilled For The Catch.jpg
A quick test fit on the engine cover. Seems to work.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/6 - Flange Test Fit.jpg
Now drill a hole through the engine cover! I started with a small bit which fit the existing hole left by the pulled-out threaded insert. Then gradually increased the size to about 15MM which was about as large as I could go without leaving razor thin walls in the existing fiberglass. Unfortunately that plan didn't work out as you will see later on. Turns out that the whole area must have been cracked for a while, so bits if fiberglass fell of as I drilled.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/7 - Hole Drilled In Engine Cover.jpg
The next part to create is the bung to hold the latch catch. I started buy turning some stainless rod down to about 15MM on the lathe.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/8 - Turning Down Rod.jpg
Actually, that's not quite true. I had originally intended to just bore a hole through some 1/2" stainless rod then tap it to M5. Making the hole in easy, because I ended up doing it 3 times. Because 3 bloody broken taps later, I gave up on that. The only taps I have are HSS plug taps which are not great for tapping deep holes in stainless. The first one I broke being too aggressive. It was jammed into the part, so I drilled out bung number 2. The 2nd one broke I think because it was just too dull. I was being very gentle and got about 5 - 6 MM into the hole before "snap!". And the 3rd was about the same as the 2nd. Well, there go all my 5MM taps. Realistically a taper tap is needed for this process however at that point I wasn't going to waste more time risking breaking more taps.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/9 - Nut Hole Bored.jpg
I enlarged the hole enough to fit a 5MM nut.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/10 - Nut In Bung Hole (Giggity).jpg
A 5MM nut was then pressed into the hole, making sure it was nice and level with the surface of the bung.
Some delicate TIG welding secured the nut into the hole. During a stainless steel bathroom vanity project, I got very practiced welding nuts into stainless runners as that's how I secured all the inner panels. Start the puddle on the thicker metal with the filler rod laying between the nut and the substrate. Then roll the puddle onto the nut. Pause to let everything cool because the nut will easily overheat then just continue around the circumference.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/11 - Nut TIG Welded.jpg
The bung was faced on the lathe to remove the weld bead, then a little bevel added. After cleaning up the threads a bit with a tap, test fitting the latch catch showed everything fit as intended.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/12 - Bung With Latch Catch Test Fit.jpg
The matching hole in the flange turned out to be much more of a pain in the ass due to a silly mistake on my part. I accidentally drilled the final hole to about 1MM less then it should have been. Not a big deal right? Just drill it out to the final size? On steel, no problem. On stainless...problem. Drill bits are meant to cut on their face, not their corners/sides. You can get away with some bit abuse on softer materials. Unfortunately when I tried on stainless, the material work hardened almost immediately and broke off the corners of the bit. Re-sharpening the bit and trying again was met with the same result. Sigh. So, I chucked a carbide rasp into my Dremel and just went around and around in the hole until it was the correct size. Not elegant.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/13 - Hole In Flange.jog
Bevels were added to the bung and flange so I could sink the weld bead deep into the material. I chucked the bung in a drill and spun it against the bench grinder wheel, while I used a countersink bit to create the bevel on the flange. Note also the flange is clamped securely to a thick metal plate. There's a hole drilled through the plate to accommodate the bung and 3rd hand adjustable arm holes it in from below. Clamping stainless is extremely important when welding because it will warp in an extreme amount. Without the clamps, the flange would become concave.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/14 - Bung and Flange Ready To Weld.jpg/img]
[img]https://www.aaroncake.net/delorean/5637/engine_cover_latch/15 - Bung Welded To Flange.jpg
30 seconds of TIG and the parts were as one.
Once everything was fully cooled (and that is naturally cooled, not blasted with air or water) I blended the top of the flange with a small belt sander. Now it doesn't match the grain pattern of the car perfectly so I will have to try again with a different grit later on.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/16 - Smooth Flange.jpg
The completed part. Countersunk the louver catch holes a little. You can see the gross uneven bung hole (that's what she said) I had to clearance with the Dremel. At least it will never be visible when the part is installed on the car.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/17 - Completed Part.jpg/img]
I will admit that it took a little filing of the hole I drilled in the engine cover before I could bolt the completed part down evenly. Whether my drilling was a bit uneven, or whether the louver latch holes aren't centered to the engine cover latch will forever be a mystery as I didn't feel like measuring.
[img]https://www.aaroncake.net/delorean/5637/engine_cover_latch/18 - Installed To Engine Cover.jpg
The rusty stock hardware as replaced with stainless.
With the engine cover back on the car, I installed the latch catch and adjusted. Took a few closing/opening cycles before it would operate smoothly and unlatch on command. Once done, the stainless jam nut was tightened.
You can see the condition the molded fiberglass was in due to 45 years of stresses from the threaded insert. It was cracked quite thoroughly and fell to pieces as I drilled it out to accommodate the new bung. This is going to have to be repaired because aesthetically it looks terrible. That's a problem for future me when I feel like getting messy with some fiberglass. I may also simply create a small stainless cap instead of having to deal with the fiberglass repair.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/19 - Engine Cover With Latch Catch Installed.jpg
Woo freaking hoo! My engine cover is now capable of latching securely! Maybe that will get rid of some rattles in the area. Also keep the curious away from lifting the engine cover.
Next time I have access to a laser cutter I may engrave a flux capacitor into the flange for shits and giggles. I considered making the flange into a DMC "D" but that seemed a little tacky.
https://www.aaroncake.net/delorean/5637/engine_cover_latch/20 - Engine Cover Latched.jpg
If there is enough interest in these, I will see about producing them. Need to draw up the flange in CAD and get a quote on having them laser/water jet cut because that's the most time consuming and fiddley part of making these. Plus it would be nice to have the flange dimensionally accurate without a lot of hand finishing. This one was also built specifically for my car so the louver latch holes will probably only fit #5637. To fit other cars, slots would be needed to allow adjustment.