Calling All Machinists - Valve Cover Gasket Bolt Size (1 Viewer)
- Thread starter GremlinMobile
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
I have tried it and they fit with no issues whatsoever, along with pretty much any grade of JIS or normal/cheap M6x1.00 boltI'm just saying before you invalidate what I'm saying I'm seeing, and before you discredit everyone on this thread whom theorized that the treads are JIS class, try it out for yourself. Don't take a video if you don't want want
. I re-read the thread and actually didn't notice anyone concluding that JIS bolts are substantially different than normal/ISO metric bolts, or that they had come across this problem before. This is consistent with my experience (of them being totally interchangeable).My rig is probably a lot less corroded than a NY rig. I would wager than a Irwin M6x1.00 tap from Ace with a good tap handle and some Tap Magic would clean it out just fine, with you going very slow and back and forth.
Last edited:
- Thread starter
- #23
I see you have a GX470. Is that what you're basing your advice on? I have a GX and an LX. And while I agree both probably have the same thread type, perhaps Toyota switched to Ace Hardware taps when they started building their GX's in 2007..I have tried it and they fit with no issues whatsoever, along with pretty much any grade of JIS or normal/cheap M6x1.00 bolt
I would wager that an Irwin M6x1.00 tap from Ace would take a lot of torque to "clean out" the threads on any nut on this vehicle. "Clean out" because it would be cutting deeper threads than factory, thereby creating a much looser fit. The issue with your theory that galvanic corrosion between steel/aluminum left bits of the steel bolt in the aluminum threads, making it a tight fit is that the tap doesn't fit in any steel/steel bolt-nut configuration anywhere else on the vehicle either. Also, wouldn't the aluminum be more likely to get removed from the threads and be stuck to the bolt, rather than steel coming off the bolt and getting stuck to the aluminum threads?
Take any other places where the bolt came out shiny and uncorroded, mated with fresh steel. Try the horn bracket bolt for example. Or any other places that required torque to break the original stretch of the threads and later required just a finger to unthread it - those same threads were still too tight for the tap. This all points to what others here have said about a different class of threads being used on these vehicles.
TBH I think you are way-over thinking this. And this is coming from someone who is an engineer . I would have re-tapped the hole with the Irwin tap and moved on, probably in less time than I've spent responding to this thread. It's a valve cover bolt, after all, which is a very non-critical item subjected to low torque (7 ft-lb spec).
. I would have re-tapped the hole with the Irwin tap and moved on, probably in less time than I've spent responding to this thread. It's a valve cover bolt, after all, which is a very non-critical item subjected to low torque (7 ft-lb spec).
2001LC
SILVER Star
I avoid using tap or die, when I can. As they easily cut new threads.
I've used, thread chase to clean-up many threads. Mostly of corrosion, but even damaged thread correction or old thread remains removal. A chase is designed, to NOT cut new threads. But they do take some patient. The test is, in the end. Will it hold the torque after chasing. They do!
Many times, I've drilled out a busted bolt. Only removing center shaft of bolt, leaving the capture threads. This leaves some of bolts threads, in the capture nut/casting. If enough removed, the remainder can be chased out.
There is a few threads. Where some of the back bolts of head cover, were busted. They used a angle drill chuck, to get in the confined space. Another thread where a clamp was used to hold head cover to head.
I've used, thread chase to clean-up many threads. Mostly of corrosion, but even damaged thread correction or old thread remains removal. A chase is designed, to NOT cut new threads. But they do take some patient. The test is, in the end. Will it hold the torque after chasing. They do!
Many times, I've drilled out a busted bolt. Only removing center shaft of bolt, leaving the capture threads. This leaves some of bolts threads, in the capture nut/casting. If enough removed, the remainder can be chased out.
There is a few threads. Where some of the back bolts of head cover, were busted. They used a angle drill chuck, to get in the confined space. Another thread where a clamp was used to hold head cover to head.
- Thread starter
- #26
Now that's interesting. Like one of those tiny C-clamps?
For the ones I've had to re-tap they've generally been on suspension/frame/underbody components and I've been able to drill them out re-tap them from M6x1.00 to M8x1.25, which seems to be much more sturdy and less breakage-prone. A perfect example are the front skidplate bolts which break off on every 120 platform. In my experience the M6 threads can get pretty mangled easily and can be too far gone to restore, at least when they are in steel, and have been cross-threaded already by others.
I have broken off some bolts (exhaust manifold studs) and successfully extracted them by welding a nut on to the remaining stub. They came right out and the threads did not require a clean or tap at all. That's probably the way to go for a broken valve cover bolt - unless it's broken off really deep. Steel weld won't stick to aluminum and the heat from welding will loosen things. I bought my first welder ($200 HF flux core) for that exact purpose. Much easier than trying to drill out a broken bolt.
I honestly need to buy a better tap/die kit. I have an assortment of name-brand taps and a cheap HF kit I bought in an emergency situation. There is a difference in quality.
Last edited:
You sound just like my wife! JK. Your advice wasn't offensive at all. Your theory about part of the bolt's threads being left in the aluminum, making the aluminum hole harder to tap is a fair theory, but it is just a theory. This issue exists with every M6 bolt/nut on this rig, steel/aluminum and steel/steel interfaces. A lot of the bolts are perfectly easy to get out, but the tap still doesn't fit the holes.
I'm just saying before you invalidate what I'm saying I'm seeing, and before you discredit everyone on this thread whom theorized that the treads are JIS class, try it out for yourself. Don't take a video if you don't want want
I've redone some threading on my 100's, but I've done hundreds of holes on old Supras. Almost all were done with a plain M6 Craftsman tap. I believe the JIS fitment of threads means that taps and dies of the plain hardware store variety will cut into the JIS threads where they don't necessarily need to, but by no means does that mean the generic ones can't accomplish the same task.I see you have a GX470. Is that what you're basing your advice on? I have a GX and an LX. And while I agree both probably have the same thread type, perhaps Toyota switched to Ace Hardware taps when they started building their GX's in 2007..
I would wager that an Irwin M6x1.00 tap from Ace would take a lot of torque to "clean out" the threads on any nut on this vehicle. "Clean out" because it would be cutting deeper threads than factory, thereby creating a much looser fit. The issue with your theory that galvanic corrosion between steel/aluminum left bits of the steel bolt in the aluminum threads, making it a tight fit is that the tap doesn't fit in any steel/steel bolt-nut configuration anywhere else on the vehicle either. Also, wouldn't the aluminum be more likely to get removed from the threads and be stuck to the bolt, rather than steel coming off the bolt and getting stuck to the aluminum threads?
Take any other places where the bolt came out shiny and uncorroded, mated with fresh steel. Try the horn bracket bolt for example. Or any other places that required torque to break the original stretch of the threads and later required just a finger to unthread it - those same threads were still too tight for the tap. This all points to what others here have said about a different class of threads being used on these vehicles.
On the Supras, a lot was engine work and I was trying to build something to reliably run DOUBLE or TRIPLE the factory power. The details mattered, at least a little. Conversely the 100 is so overbuilt and redundant in most things that you need not sweat a little slop in the threads - even on something as sensitive as the valve cover. If you strips those threads out completely it will not be because you cut a little bit of new thread with a generic tap of the right pitch.
The thread chasers are ideal. If you don't have that and don't want to wait for it, use that generic tap. Albeit with caution not to snap a tap or crossthread new threads. Corrosion is a complete game changer. Me working on my southwest cars vs some of my client's cars from all over the country has shown some huge differences due to climate. It's a totally different ball game. Things that work on normal cars do not always work on the rust buckets from west of the Mississippi. NY and PA are brutal on metal fasteners.
