mba_mensan

I just bought my 92 red vette July 4th.....engine started running funny so I decided I needed to change the wires and plugs...so far so good....got the first 3 out and in with no problem. The 4th one (closest to firewall on passenger side) got cross-threaded and can't get the plug back in.

I tried buying a $6 dollar thread chaser from autozone but I don't have very much room to work and don't know if i'm lined up right or not.....

Also bough a KD back-tap for $50 but the darn thing is too long and I can't get it in the hole.....

I'm a computer nerd type and am really at a loss right now...any suggestions on how I might approach this short of "taking it to the dealer"?

Thanks.

kwd1

I'd try and get a look at the threads to see how far in the fouled thread is. Maybe a digital camera could get a pic.

Get a tap and tap wrench. Take a spark plug to a hardware store and find a nut that fits the threads, then you know what size threads you have. Then find the same sized tap.

With luck you should be able to start the tap in the existing threads. You'll know if you do it right. You'll feel the tap grab on the good threads. When it hits the fouled portion of the threads you'll feel resistance. In about a 1/4 turn or so, the resistance should ease.

deerra

I think you should also place a good amount of grease on the threads to catch any shards from falling into the cylinder.

nitronick

When I do any kind of work like this, where something might fall into the cylinder, I turn the engine over until the piston is at the top of it's stroke. Then I stuff a clean rag in through the spark plug hole.
I know there isn't a lot of room to work. You might want to pull the motormount bolts and use a jack to lift on the engine. That might get you a little more room...

Pete K

You have 1 shot at fixing the threads. If I were you, I would find someone who has been down this path before and let him do it. No substitute for a pro.

rightofway

kwd1 would this method work for a brake caliper too :bb

Big_John

While its not that difficult a fix, if you haven't done anything like that before, it might be time to have someone else do the job.

That said, chances are, if the thread is that messed up, you really need to start thinking about heli-coiling the hole. Re-tapping the hole won't put threads back that have been stripped out.

grayml

Save yourself a lot of time and hassle and take it to the dealer. Sometimes trying to save money just isn't worth it and usually there will be a mechanic there who has done this more than once.

The end result of failing to fix this right on your next attempt will cost you more than letting the dealer do it.

My dealer isn't cheap, but they have a very experienced vette mechanic. I know not all dealers are the same though.

Good luck

dndrsn

Where do you live? Maybe a local member would volunteer to help or could point you in the direction of a Corvette shop or knowledgeable mechanic.

kwd1

yes but you would need to take the caliper off and clean out the shavings real well. Wouldn't want shavings to get in the brake fluid.

rightofway

The problem (big problem) with simply attempting to rethread the spark plug hole is that whatever filings are created during the process will ultimately find their way into the combustion chamber scoring the cylinder wall. I know it is not what you want to hear, but, the safest way to do this would be to pull the head and have the hole retapped at a machine shop.

mba_mensan

Got a guy to come out to my home and couldn't do it with the tools he had so he was to come back (he's a hot rod mechanic)...that was 2 weeks ago so I'm now taking my baby to the dealer. Made 2 car payments and don't even get to drive.

Any ideas on what this should cost me? I live in Birmingham, Alabama. I would appreciate local members letting me know where I can find a trustworthy mechanic.

Thanks for all your advice.

scranage

I'm in nearly the same boat. That !$#@* #8 plug is just about impossible to replace. I spent the entire day yesterday trying to get the threads to catch on the replacement plug with no luck at all. I also tried to get a thread chaser to catch with no luck, and the threads were fine when the old plug came out.

I guess I'll try to get a 14X1.25 tap in the hole today so I can clean the threads and get a feel for the proper angle of approach, but am really afraid of accidentally cutting a cross thread in the process. I've got the wheel well out, and the tire off, so I can see everything, except of course when I squeeze a hand in to try to install the !@#$!* plug, 3 of which I've now dropped and tossed in the trash.

I'm about ready to vent the AC and remove the evaporator to save myself having to remove the head for repair. So far the threads are good, I just can't get them to start.

Tell me there is some simple trick I haven't tried to get this plug in? I've tried using a rubber hose, and a universal coming in from the side, and my fingers, 12 hours wasted on this one plug so far. I'm at my witts end.

scranage

Are you sure? Not to challange you, but I just can't see how aluminum filings could score cast iron, the latter being so much harder... Not that I like the idea of having those filings in there, but still, wouldn't they just get blown out once the engine starts?

If I manage to get the hole cleaned out with a tap on mine, I plan on dropping a 1/4 " ID hose into the cylinder an putting the other end on a blow gun. Maybe I'll do the rag thing too.

hippy

If you plan to stick a hose in there and blow thru it where are the shavings going to go? Unless the exhaust valve is open the shavings are just going to fly around like in a mini wind tunnel.

scranage

I expect them to blow by the hose and exit the cylinder.

hippy

Really? Good luck with that.

scranage

Can't see why it wouldn't work. All that compressed air has only one place to go, and that's exiting the spark plug hole. Why wouldn't it carry any filings left on the bore with it?

Anyway, I also ordered a bore scope so I'll be able to get a good look before I button it up and start the engine.

scranage

The other thing I was thinking about was replacing the injector with a barbed fitting and blowing air into the cylinder while running the tap, only problem is I hate pulling anything fuel related that's pressurized for fear of a leak and engine fire. Is there anything like a cooling system leak tester made for fuel injection systems?

EMBPILOT

I think a little compressed air in the hole will do just fine. But I see a heli-coil in your future.