Stripped intake bolt holes, help!

[LSUfan71]

I was installing my intake when I stripped the two bolt holes indicated by the arrows (below pic). It looked like the bolt holes had previously been drilled out just a bit, or is that normal? Anyway, those two were the only ones that gave me any trouble when I cleaned them with a tap. I think I partially stripped the first few threads trying to insert the tap but I finally got them done and it seemed like there was enough there to get the install done. I got the intake on and got the bolts finger tight. Then started tightening using the correct sequence. I first torqued the bolts to 20lbs with no problems before going up to the listed 35lbs. Both of these bolts stripped when I attempted to torque to 35lbs. All other bolts are fine.

My question is: Do I remove the intake, drill/tap the holes? Or is there the slightest possibility that this engine will be fine as is?

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[98slv]

remove the intake and use a helicoil, this way you'll be able to reuse the same bolts. If they are stripped then you'd have to drill them bigger and tap them and end up using a bigger bolt...

 

[someotherguy]

And since both of those go all the way through back into the intake valley, you'll want to cover up everything you possibly can so you don't get chips in the engine from drilling those holes out for the helicoil inserts. Tape up all the holes, temporarily drop the valve covers back on, and use a shop vac to suck out the chips before uncovering anything. Even just a chip or two can be disaster for your bearings.

If you were tapping those holes as part of just cleaning them up for the hell of it, you should have been using a thread chasing tap, which is very different from a thread cutting tap. Regular thread cutting taps remove material in order to make threads. If you use them to merely clean an already threaded hole, you remove more material and weaken the holding power of the threads.

All the bolts need to be able to be torqued to the correct value or your intake gaskets are likely to leak.

Richard

 

[454ss]

if the they were drilled/tapped to the correct size originally you are not going to be removing any material by chasing them with a tap as long as the tap is the same size as the spec for the thread, g1,g2,g3, ect. you need to drill the holes out, tap and install a heli-coil insert. be sure to keep the drill centered/straight in the existing hole and when you tap fill the flutes with grease to catch the chips and use a quality cutting fluid.

 

[LSUfan71]

remove the intake and use a helicoil, this way you'll be able to reuse the same bolts. If they are stripped then you'd have to drill them bigger and tap them and end up using a bigger bolt...

I guess I was hoping someone would tell me that it would be fine as is, no such luck tho. I bought a coil repair set today. I'll try to get it done this weekend.

...you should have been using a thread chasing tap, which is very different from a thread cutting tap. Regular thread cutting taps remove material in order to make threads. If you use them to merely clean an already threaded hole, you remove more material and weaken the holding power of the threads.

I didn't know there was a difference. I'll have to check.

if the they were drilled/tapped to the correct size originally you are not going to be removing any material by chasing them with a tap as long as the tap is the same size as the spec for the thread, g1,g2,g3, ect. you need to drill the holes out, tap and install a heli-coil insert. be sure to keep the drill centered/straight in the existing hole and when you tap fill the flutes with grease to catch the chips and use a quality cutting fluid.

I don't recall removing any metal, just some rust and gunk. I'll make the repair this weekend and let you guys know how it went. Thanks for the replies.

 

[Silverick]

I saw a demonstration on TV using this stuff... I can't remember the show. Muscle Car Garage?

http://www.youtube.com/watch?v=FqpStMLTE6E

 

[ernjohn]

I hate to say it at this point, but I'd recommend drilling out the heads and using a threaded insert. but if the the thread size of the intake bolts isn't a common size - say m8x1.5 vs the common m8x1.25 - a heli-coil may be better.

lightly placing the intake on, may help as a guide if you'll be needing to drill, provided you won't be drilling the intake.

A slotted insert is what I'd recommend w/ high-strength loctite on the outer threads

http://www.mcmaster.com/#standard-threaded-inserts/

 

[Silverstang84]

Heli coil may be the only way to go

 

[LSUfan71]

I saw a demonstration on TV using this stuff... I can't remember the show. Muscle Car Garage?

http://www.youtube.com/watch?v=FqpStMLTE6E

I got a Fix-A-Thred kit at Advance Auto. I just finished drilling & tapping the holes, been busy this week. I'm about to go out now and get the intake back on.

I hate to say it at this point, but I'd recommend drilling out the heads and using a threaded insert. but if the the thread size of the intake bolts isn't a common size - say m8x1.5 vs the common m8x1.25 - a heli-coil may be better.

lightly placing the intake on, may help as a guide if you'll be needing to drill, provided you won't be drilling the intake.

A slotted insert is what I'd recommend w/ high-strength loctite on the outer threads

http://www.mcmaster.com/#standard-threaded-inserts/

I wanted an easier way out but I finally realized I just needed to do it right the first time.

Heli coil may be the only way to go

It is. No sense in chancing it.

 

[LSUfan71]

Using this: http://afs-fix.com/fix-a-thred/06.htm