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Help - messed up my plenum

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Old Jan 11, 2003 | 09:01 PM
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Larry Dunlap's Avatar
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From: Katy, Texas
Car: '91 Formula
Engine: 350
Transmission: TH350 built
Axle/Gears: 3.73
Help - messed up my plenum

Looks like I damages threads in two runners to plenum holes by cross threading. I am going to try a tap tomorrow. What else can I do besides taking it to machine shop and having them drill out and put inserts in and redrill and tap the holes. I hate screwing up. I always heard to start a bolt in aluminum by hand, but I took a chance here and lost.
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Old Jan 11, 2003 | 09:03 PM
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If the Tap Doesnt work for ya ( I belive its 8mmx1mm or is it 1.5mm Picth ?) Then just drill and helicoil.

No Big deal really.
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Old Jan 11, 2003 | 09:05 PM
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Larry Dunlap's Avatar
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From: Katy, Texas
Car: '91 Formula
Engine: 350
Transmission: TH350 built
Axle/Gears: 3.73
OK, helicoil, hhmm sorry to be so stupid but I guess thats a homemade way of doing what I said the machine shop would do. Could you explain how it works a little? where do you get it, the auto parts strore or hardware?
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Old Jan 11, 2003 | 09:07 PM
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From: concord New Hampshire
Car: 87 iroc and 88 k2500 tbi truck
Engine: l98 and lo5
Transmission: 700 r4's babby
dont you need a helicoil tap to put that thing in. i have never put one in my self havent had bad enough luck yet
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Old Jan 11, 2003 | 09:25 PM
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From: Aridzona
Car: `86 SS / `87 SS
Engine: L69 w/ TPI on top / 305 4bbl
Transmission: `95 T56 \ `88 200-4R
heli-coil kits come with a perfectly normal tap. It's just the correct thread & pitch for their insert to fit in there.

do a search on the internet for heli-coil etc. and you'll see what one is. They work GREAT. I did the 4 shifter bolt holes on a T5 tailhousing not too long ago and they're rock solid.

Matthew
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Old Jan 11, 2003 | 09:27 PM
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Larry Dunlap's Avatar
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From: Katy, Texas
Car: '91 Formula
Engine: 350
Transmission: TH350 built
Axle/Gears: 3.73
Thanks, Im starting to feel a little less bummed out. I thought I really f'd up this time. Can you get these kits at the local auto part store?
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Old Jan 11, 2003 | 09:30 PM
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From: Aridzona
Car: `86 SS / `87 SS
Engine: L69 w/ TPI on top / 305 4bbl
Transmission: `95 T56 \ `88 200-4R
I pick mine up at a place that specializes in bolts. Pep Boys has alternate brand thread inserts, but I have not tried those; just heli-coil brand.

Matthew
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Old Jan 11, 2003 | 10:06 PM
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You can get them At ACE.


About 15 Bucks For the Kit to do a few holes. Not too bad.
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Old Jan 11, 2003 | 10:06 PM
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You can get them At ACE.


About 15 Bucks For the Kit to do a few holes. Not too bad.
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Old Jan 11, 2003 | 10:06 PM
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You can get them At ACE.


About 15 Bucks For the Kit to do a few holes. Not too bad.
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Old Jan 11, 2003 | 10:06 PM
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You can get them At ACE.


About 15 Bucks For the Kit to do a few holes. Not too bad.
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Old Jan 11, 2003 | 10:13 PM
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From: Aridzona
Car: `86 SS / `87 SS
Engine: L69 w/ TPI on top / 305 4bbl
Transmission: `95 T56 \ `88 200-4R
Ian, you're now up to $60. Take it easy on the guy.
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Old Jan 11, 2003 | 11:21 PM
  #13  
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From: Oakdale, Ca
Car: 89 IrocZ
Engine: L98-ish
Transmission: 700R4
I don't think I'd spend the money for a helicoil, kinda pricy for such a low-torque bolt.

I'd drill it out a size larger in SAE, then tap...also drill out the runner hole as well.

Ofcourse, if the tap works, go for it. Use some WD40 on the tap to keep the Al. from galling
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Old Jan 12, 2003 | 04:05 AM
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From: pgh,pa,
advance auto also sells the heli-coil setup, i used it on a t-5 tailhousing as well , i think the size is 8mm x 1.25 for the TPi stuff.
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Old Jan 12, 2003 | 10:23 AM
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From: Savannah, GA
There is nothing "backyard" about heli-coils. You'll find that on alot of aluminum cylinder heads, every hole already has one in it. Its definatly the way to go.
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Old Jan 14, 2003 | 12:41 PM
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From: Katy, Texas
Car: '91 Formula
Engine: 350
Transmission: TH350 built
Axle/Gears: 3.73
Well I bought the helicoils at Orielly's auto parts, and yes they are proud of those, $28 for the tap, the tool to put the helicoils in and about 8 helicoils. And by the way it is 8mm 1.25 threads. Anyway, I bought a $3 tap too. Tried the tap, voila, worked perfect, I guess I didn't F them up as bad a I thought.
Took the helicoils back and traded them for a case of oil for my next oil change.

I was careful to start them all by hand this time. I think I had the plenum cocked to one side the first time. Live and learn. thanks for the help
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Old Jan 14, 2003 | 06:12 PM
  #17  
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From: Manassas VA
Car: 04 GTO
Engine: LS1
Transmission: M12 T56
As final verification: The runner bolts are all metric 8mm x 1.25 pitch.

Just wanted to pitch in since i saw 1.5 also offered as the pitch, which is wrong. I just pulled out my tap to verify. That and 3/8x16 are absolutely vital on these cars, only sizes i own, the rest i borrow when i need 'em. But those 2 are on probably 90% of the fasteners on these things.
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Old Jan 14, 2003 | 06:27 PM
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lol, How did that Happen ? hahaha

Yeah My bad ed, It was jus toff the top of my head.
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