Topic: exhaust flange screw removal, final report!

[Don R]

  Does anyone have a good procedure for removing the exhaust flange screws? I asked once years ago and the thread turned into a JIS lecture so let me say the screws heads aren't stripping out, but my snap-on impact bits are shattering. One in my battery impact and one in my hand impact.
  I have not gotten oxy-acetylene out yet but that might be next, maap gas didn't help nor has blaster or acetone/ATF.
  Maybe a different impact bit? Worst case, I can drill the heads off and mig weld nuts to the screws but I don't want to go nuclear just yet.

[scottly]

It's the tapered underside of the screw heads that makes them so hard to get out, just like the taper on the end of the crank that locks the alternator rotor in place. Have you tried any sort of penetrate to help loosen the bond, perhaps along with heat? I think the hand impact is the best for this job. Have you tried tightening first before loosening?

[Don R]

 Maybe a blunt punch around the screw rather than on the screw? I did use blaster and a maap gas turbo torch. I just mixed a fresh batch of acetone and ATF with a touch of seafoam for a eh, why not additive. I use mix loosely, it wants to stay unmixed.
 This unsuspecting K5 750 engine is getting a turbo to see if it works before I build an 836F2 for it.

[PeWe]

Possible to drill the head off. Take out the spigot and enough of the screw  left for a strong plier?
The countersunc screw might not have much left to grip after head is gone and spigot off. Maybe the thickness of the spigot flange only.

[pjlogue]

  Does anyone have a good procedure for removing the exhaust flange screws? I asked once years ago and the thread turned into a JIS lecture so let me say the screws heads aren't stripping out, but my snap-on impact bits are shattering. One in my battery impact and one in my hand impact.
  I have not gotten oxy-acetylene out yet but that might be next, maap gas didn't help nor has blaster or acetone/ATF.
  Maybe a different impact bit? Worst case, I can drill the heads off and mig weld nuts to the screws but I don't want to go nuclear just yet.

I have had good luck using a hand impact driver, good sized mallet, #3 JIS bit and PB blaster.  I let the PB blaster do its thing for a few  days giving a shot of spray 2x a day.  I then pre-load the impact driver to take up any slack by twisting counter-clockwise and give it a good blow with the mallet.  A couple of screws are hard to get at so I use an extension and try to get the impact driver as close to centered on the screw shaft.  I have never had an exhaust flange screw not come out using this method.  Harbor freight's hand impact tool works well for this.  I have had bits shatter in the past.  They were not tempered enough after hardening.  (Dewalt bits seem to shatter on me)  I don't think I ever had a HF bit shatter.

-P.

[jgger]

Don, have you ever tried the crayon and heat trick. I never have but the videos look promising.

[Don R]

 Crayons and heat are now on the list, I tried a new batch of Acetone and ATF in a WD40 pump can with a flat nose punch big ball peen and working around the screw head, no joy yet.
  I'll go by harbor freight and Lowes to see if I can buy some of their bits. I've collected 3 hand impacts over the years but if I have to buy #4 I will.

[jgger]

Keep us posted, it would be great to have a trusted source,  such as yourself  to verify this approach.

[BenelliSEI]

I’ve had good results with an expensive backwards drill bit (about 3/16” diameter). A couple on the Sandcast motor screws just wouldn’t budge with my hand impact tool. After the engine was out of the frame, I decided to try and drill the head off the screw, but both came loose before I finished drilling the head off. Maybe the focused heat the bit generated made the difference?

I replaced them all with some excellent hardware I found at a local “Bolts Plus” store. They were the identical size, but have an Allen head socket hole. Coated them with lots of anti seize and they seem a better solution….. Good Luck.

[piefairy]

Loctite used to make a product call Freeze and Release, it was for screws that had been put in with loctite red. Its the exact opposite theory of the torch. You hit the bolt with it in hopes of it shrinking slightly in size. Not sure it would work for this application, the cold would dissipate fast on the exhaust. But I did have luck some luck with it on work stuff that was smaller in size compared to the exhaust.
https://www.fastenal.com/product/details/0607066

[Don R]

  My report,
 I got the #1 and #2 spigots off, they were the ones I worked on first. A combination of PB blaster, bumping the flanges with a flat punch and a big hammer and lastly acetone/atf soaking overnight. I used my trusty craftsman impact on two screws, a hand impact on two other screws and an old #3 bit after breaking two snap-on bits off. Snap off?
 Tonight, I used maap gas from a turbo torch, ATF and acetone, an orange crayon twice, bumping the flanges with the big hammer and punch, hammering the bit into the screw, rinsed and repeated. No joy but one screw can be welded to or drilled because it no longer grips any screwdriver JIS or #3 phillips. My MIG has stainless wire in it at the moment so welding will wait.

 Freeze-off comes next, I have a can that I forgot about, I kept it in the racecar trailer but took it out for winter.

 Edit: freeze off zero, screws one.

[Don R]

Possible to drill the head off. Take out the spigot and enough of the screw  left for a strong plier?
The countersunk screw might not have much left to grip after head is gone and spigot off. Maybe the thickness of the spigot flange only.

Yes, but I didn't want to drill all of them, lol. Now I got half of them loose, I'm soaking the other half.

[Don R]

 The final 4 screws weren't coming possibly because I wore out all of my bits, both jis and #3. I did everything that worked on cylinders one and two plus freeze-off, which smells good except it's strong.
 The final 4 screws came off by drilling the heads, on #4 I used a slightly oversize drill which didn't leave much screw, and needed to use a left-hand drill to spin them out. On #3, I used a smaller bit and pried the flange off to pop the screw heads and save as much threaded screw as possible. Those two unscrewed with pliers and fingers.
  My can of blaster leaked the remaining half of the can out from under the spray nozzle and made a mess. The poor unsuspecting K5 can get exhaust studs now, I'll see how many I can spare from other heads.
  The moral of the story is that Scott is correct, it's the friction under the screw head that makes them stick not the thread itself.
  What's the answer? Try everything and when it doesn't work drill baby, drill.

[BenelliSEI]

And butter up the replacements with anti-seize.

[jgger]

Congratulations Don. Nothing like a 4 day 10 minute job, ya know what I mean!

[piefairy]

And butter up the replacements with anti-seize.

+2 on the anti-seize. Glad you got it.

[Don R]

 I was hoping to discover the magic bullet, it's still possible there is a JIS bit indestructible enough to spin them out in a hand impact driver or battery impact. It just isn't the ones I had. The #3 snap on bits had the ability to grip the screws but they are too brittle. Neither one had slipped when it exploded. My Craftsman bit didn't grip enough, neither did my JIS bits from an impact set. 
 A good drill made short work of the offenders, and I'm still puzzled why the #1- and #2-cylinder screws finally unscrewed when the others fought to the death.

[low-side]

Last time I did that job I drilled all 8 and turned the threaded portion out with vice grips after a good heat and oil soak.

[BenelliSEI]

I was hoping to discover the magic bullet, it's still possible there is a JIS bit indestructible enough to spin them out in a hand impact driver or battery impact. It just isn't the ones I had. The #3 snap on bits had the ability to grip the screws but they are too brittle. Neither one had slipped when it exploded. My Craftsman bit didn't grip enough, neither did my JIS bits from an impact set. 
 A good drill made short work of the offenders, and I'm still puzzled why the #1- and #2-cylinder screws finally unscrewed when the others fought to the death.

Don…. If you ever order anything from vintagecb750.com, add a set of their impact bits. They’re not expensive, and don’t look special, but the ones I got a few years ago have taken the usual abuse surprisingly well!