[Updated] Help me, machinists of Oppo!

"MoCamino" (mocamino)
10/29/2020 at 16:54 • Filed to: None

Update : I was finally able to get back to this project this past weekend. (Why does life always get in the way of the projects I actually want to do?) As was suggested by Rusty and JawzX2, the tapped holes were nowhere near clean. Embarrassingly so. After copious amounts of chlorine-containing brake cleaner and many cotton swabs, I think they’re clean enough now that threadlocker would work a lot better. With that said, I also followed advice from just-a-scratch and called the local Fastenal store so I could talk to a human. They can sell me the drive screws by the each rather than a box of 5000. I was able to order 30 of them (more than I need, but adds a buffer) for less than $8. I should have called them in the first place! I won’t have them until Monday, but then I can make an educated decision about which fastener I feel better about. Thanks everyone for your suggestions on this. Hopefully I will be able to update again in the middle of next week.

[Original post] I am working to reassemble the engine for our Suzuki Grand Vitara after replacing the timing chains, gears, and chain tensioners. These engines (the Suzuki H25a, if you’re interested) are notorious for sludge build up, leading to chain tensioner failure and eventual destruction of the engine. While I have the engine out and partially disassembled, I’ve done quite a bit of cleaning to eliminate as much of the sludge as I could. That includes disassembling, cleaning, and reassembling the valve covers.

The covers have an internal baffle that is supposed to keep the PCV from sucking oil out into the intake manifold. The baffles are held in by what I believe are a series of drive screws. One is indicated by the arrow in the picture. Because the covers were so nasty under the baffles, I was concerned that having a shop boil them out would leave me wondering if anything was still underneath. So I drilled the top of the drive screws to remove the baffles and proceeded with the cleaning. They were disgusting underneath. I truly don’t believe any amount of time in the parts washer would have gotten them completely clean, especially given the maze of walls under the baffle plates. They weren’t draining properly, exacerbating the very problem they were supposed to prevent.

I thought I’d reattach them using 6 mm machine screws, along with some red threadlocker. All the instructions on the threadlocker liquid say it will take significant heat to remove a bolt held in by the red stuff. I must have done something wrong, because it took very little effort (and no heat at all) to remove them after the 24 hour cure time. I even used their surface prep spray since the valve covers are cast aluminum and the bolts were stainless steel.

So that gets me back to the drive screws. (Also referred to as u-drive screws or type u drive screws.) The machinists out there (and other folks smarter than me) will already know this, but a drive screw is essentially a self-threading screw that you hammer into a pre-drilled pilot hole like a nail. As an interference fit, they have to be drilled out to remove and are considered a permanent fastener. My problem is this: I drilled and tapped the holes for 6 mm machine screws. Now that plan has failed and I need to use drive screws. From what I can see, the largest ones normally available are #14 drive screws, but the specified pilot hole for those is 0.221". The 6 mm holes already in place are 0.236", so I don’t know if the #14 drive screws would hold properly. I have seen reference to 5/16" drive screws, but the pilot hole size jumps significantly - up to 0.295". I’m not sure I have room for that size pilot hole without risking splitting the boss that they would be driven into.

TL;DR: Would the #14 drive screws work? And where in the world do you buy small quantities of these things? The only suppliers I have been able to find want to sell them in boxes of 1000 and up. I only need 24 of them! Is there a different/better fastener I could use?

Sorry for the long post, but in this case the details kinda matter. Any advice will be greatly appreciated.

DISCUSSION (34)

Rusty Vandura - www.tinyurl.com/keepoppo > MoCamino
10/21/2020 at 16:04

This is an interesting case. Are the threads that you tapped still lining the holes that you drilled? My initial thought is that the thread locking glue failed because the threads were not clean. My inclination would be to hose out the holes using Brake Clean -- the non-environmentally friendly stuff -- and trying that method again.

MoCamino > Rusty Vandura - www.tinyurl.com/keepoppo
10/21/2020 at 16:14

Yep, the threads are still there. I *thought* I got them good and clean, but I can’t swear I did. I’ll give that a shot.

Rusty Vandura - www.tinyurl.com/keepoppo > MoCamino
10/21/2020 at 16:20

I’d almost be willing to wager a sandwich that this will work. Make sure both the holes and the screws themselves are scrupulously clean.

just-a-scratch > MoCamino
10/21/2020 at 16:21

I’m not going to weigh in on using drive screws. The Machinery’s Handbook doesn’t cover them, I haven’t used them, and interference did are tricky. I wish you luck.

You can buy stuff like that at

McMaster-Carr

Grainger

Fastenal

And your local fastene r specialty shop. I like Tacoma Screw around here.

I wonder if a through hole and rivet would work as well.

BTW, consider how much a new valve cover will cost of all goes wrong.

My bird IS the word > MoCamino
10/21/2020 at 16:49

As far as fasteners, I can feel your pain. There is a chain called "fastenal" that has stores that you can sometimes get small quantities of obscure bolts or nuts. But that's generally been my experience rebuilding my trans am. Maddening.

MoCamino > just-a-scratch
10/21/2020 at 16:52

Yeah, I already looked at new valve covers. $270. EACH. If all goes wrong here, I’ll get another set from a junk yard and try another route cleaning them. :)

MoCamino > Rusty Vandura - www.tinyurl.com/keepoppo
10/21/2020 at 16:54

Thanks. Since the bolts are stainless and the covers are cast aluminum, do you think I should have to use the surface prep spray?

SBA Thanks You For All The Fish > MoCamino
10/21/2020 at 16:54

Sorry for your pain... But this is outstanding, weapons-grade, OPPO.

Thanks for sharing an unusual dilemma. I thought I was the only one who managed to get boxed in on a project gone pear-shaped in a hard-to-fix way.

MoCamino > My bird IS the word
10/21/2020 at 16:55

I’ve tried Fastenal and McMaster. They have #14 drive screws, but the shortest they have are 1/2" and 3/4" long - too long for my application. :(

You can tell a Finn but you can't tell him much > MoCamino
10/21/2020 at 17:14

Loctite also makes a product rated for oily surfaces that may give you better lu ck. We use it at work, but it’s medium strength not red. I can’t remember the temp that blue loctite is rated for, but seems like it may be an option on valve covers. I think the usual blue is 242 and the oil resistant is 243, but check McMaster or the loctite website to verify.

MoCamino > SBA Thanks You For All The Fish
10/21/2020 at 17:25

This has gone so very pear-shaped. I’m an old-school Chevy guy. We bought the truck knowing it needed the timing chain work. My thought was “even with pulling the engine to make it easier to replace the water pump and oil pump while I’m at it, I should be done in a few weeks”. As if. It has been an exercise in frustration. Every bolt I’ve turned on this thing has fought me. The upside is when we’re done, it will be a great vehicle for my wife that should go 300,000 miles.

MoCamino > You can tell a Finn but you can't tell him much
10/21/2020 at 17:27

I thought about using that stuff. But I’m paranoid that the bolts will vibrate loose and drop out, landing among the camshafts. (DOHC!) I figure a bolt bouncing around in the valve train would be what we call un-good.

just-a-scratch > MoCamino
10/21/2020 at 17:30

Have you talked with them on the phone? In my experience, the humans can find stuff I cannot get through the website. That's probably more true for local Fastenal and other local stores than the web only outfits.

JawzX2, Boost Addict. 1.6t, 2.7tt, 4.2t > MoCamino
10/21/2020 at 17:33

I agree with Rusty: clean those holes and the screws with the non-friendly brakeclean and try the red again. Barring that, see if you can find some tri-lobe thread forming screws. Metric ones can be tough to find, but they will bind better in loose fit holes. If it were me, and I had the metric gears for my lathe (I don’t, it’s a 1940's vintage South Bend. M etric gearsets were rare for those 70 years ago, now they’re pretty much unobtainium ) I’d turn down some m7 bolts to oversized m6.

SBA Thanks You For All The Fish > MoCamino
10/21/2020 at 17:36

I should post on my Audi dilemma sometime. My son’s 4.2L V8 was really gummed up... great car... but “oil vapor in humid climates” did a number on the oil passages. I thought I’d gotten it all cleared out... but... damn... I think there must have been a clogged oil galley I never found. The assembly-disassembly was a nightmare.

MoCamino > JawzX2, Boost Addict. 1.6t, 2.7tt, 4.2t
10/21/2020 at 17:39

I will admit I’m not confident in my tapping job. They could just be too loose to seal properly. Since the locker is anaerobic , I know that bit is important.

MoCamino > just-a-scratch
10/21/2020 at 17:40

I will admit I have not done that yet. That is a good idea. I’ve become spoiled by online shopping. :)

Rusty Vandura - www.tinyurl.com/keepoppo > MoCamino
10/21/2020 at 18:57

I wouldn’t be able to speculate about that, but I know that in my own experience, dissimilar metals like that would tend to stick together, rather than come loose. But I think if they’re clean and then doused with the Loc-tite, you’d be good. How many miles on the car before you did this service? Did the car receive an oil change diligently every 5k miles prior to this service? I bet the answers are >100k, and no.

MoCamino > Rusty Vandura - www.tinyurl.com/keepoppo
10/21/2020 at 19:45

It has 116k on it. While it was purported to have had regular changes, I don’t believe it for a minute.

MiniGTI - now with XJ6 > MoCamino
10/21/2020 at 20:53

I don’t know about yours but according to the internet newish SAABS are also a little prone to sludge as the manuals said it was OK to run d ino oil for 10k in a turbo engine . An important place to check on SAABs is the pickup screen in the oil pan.

A bit of a PITA son I paid my SAAB mechanic to do it when I bought my 98 so I wouldn’t have to worry about it.

MoCamino > MiniGTI - now with XJ6
10/21/2020 at 21:36

Oh definitely. The pickup and screen (and the pan, and whatever part of the lower end I could reach) have all been cleaned thoroughly. :)

MiniGTI - now with XJ6 > MoCamino
10/21/2020 at 23:33

Excellent

gmporschenut also a fan of hondas > MoCamino
10/21/2020 at 23:46

I have never used drive screws so i can’t say how they will perform.

However for work I went down a deep rabbit hole regarding screws backing out. Most come with a fine oil mist to prevent corrosion, and loctite will not stick if there is oil. I would recommend brake clean, and some qtips to get in there. get the stronger chlorinated stuff.

I would recommend repeating this 3 or 4 times till the qtip comes out spotless. Spraying is good but wont work out all the gunk still in the thread area. Also soak the 6m screws.

also wear gloves and eye protection

brianbrannon > MoCamino
10/22/2020 at 16:05

You can use JB weld epoxy to hold the screws in permanently

MoCamino > brianbrannon
10/22/2020 at 16:49

I hadn’t thought about JBW. I wonder how it would handle the vibrations/oil/heat... I’ll have to investigate that.

Rusty Vandura - www.tinyurl.com/keepoppo > brianbrannon
10/29/2020 at 18:51

I have a thing for adhesives and I play with them whenever I get the chance and JBW has been a consistent disappointment. I’d definitely argue against using it inside an engine, or anyplace else the really mattered.

Rusty Vandura - www.tinyurl.com/keepoppo > MoCamino
10/29/2020 at 18:52

Rusty Vandura - www.tinyurl.com/keepoppo > MoCamino
10/29/2020 at 18:55

Does the Loc-tite have a high-temperature flavor? I predict that once you clean the holes and use new screws, they’ll want to stay put.

Rusty Vandura - www.tinyurl.com/keepoppo > JawzX2, Boost Addict. 1.6t, 2.7tt, 4.2t
10/29/2020 at 18:56

Showoff.

Rusty Vandura - www.tinyurl.com/keepoppo > MoCamino
10/29/2020 at 18:58

What about drilling straight through and having locknuts on top of the valve cover? The loveliest, maybe not, but you’d not have to worry about anything dropping inside. As I think about it, that’s probably what I’d look at. Then metric or standard becomes a non-issue and you can probably buy hardened machine screws.

MoCamino > Rusty Vandura - www.tinyurl.com/keepoppo
10/29/2020 at 19:31

The way the covers are built I don’t think it would work. I will take another look though.

brianbrannon > Rusty Vandura - www.tinyurl.com/keepoppo
11/10/2020 at 00:34

I’ve used Jb weld in a coolant jacket to fix a cracked block and to seal passages in carburetors I modified. Honda has a tsb to use it on blocks. Maybe you weren’t using it right?

Rusty Vandura - www.tinyurl.com/keepoppo > brianbrannon
11/10/2020 at 08:38

It makes a great sandable filler...

Rusty Vandura - www.tinyurl.com/keepoppo > brianbrannon
11/10/2020 at 08:38

Did you see this?