Oxygen sensor thread? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**smitty62** · 02-22-2005, 09:27 PM

I need to drill & tap an exhaust manifold for an oxygen sensor--does anyone know what thread these are? Thanks

gmc67swb · 02-22-2005, 09:31 PM

I believe 18mm

71swb4x4 · 02-22-2005, 09:32 PM

I think they are metric
M18 x 1.50mm
Not positive, I googled it.

71swb4x4 · 02-22-2005, 09:34 PM

The Bosch LSU 4 sensor is a pump cell sensor like the NTK L1H1. The sensor requires a bung with an 18 mm diameter hole with 1.5 threads/mm pitch (this is one of the standard lambda sensor & sparkplug base sizes).

Here is some more support, everything I have found says 18mm x 1.5mm

**smitty62** · 02-23-2005, 01:53 AM

Thanks guys! I believe 18 X 1.5 is correct. Now to find a tap??

EROC · 02-23-2005, 07:56 AM

Drilling and tapping cast iron can be a real PITA. Your local muffler shop can probably sell you a steel oxygen sensor bung for a couple bucks. Just drill a hole in the pipe just past the manifold and weld the bung to the pipe. If you decide to get a tap most auto parts store sell taps to repair spark plug holes, which I think are 18mm.

tom hand · 02-23-2005, 08:07 AM

http://www.needboost.com/part/holley..._sensor_bungs/

neonlarry · 02-23-2005, 08:45 AM

You would be better off with a bung vs tapping unless you also want to machine a flat surface around the hole for the sensor to seal against.

**smitty62** · 02-23-2005, 11:14 AM

Wow Tom!--$13 plus shipping for a 39 cent bung?? I don't think so! Those guys don't even use a gun!
The reason I wanted to tap it is that welding old cast iron (ramshorn) can be a disaster--even using TIG.. The bung don't expand/shrink at the same rate as the cast. It can last a year or so before cracking, but you've still lost a manifold. Thought I'd try tapping with welding as a last resort.

**'70_402** · 02-23-2005, 06:40 PM

You Can Go The Parts Store And Get A Spark Plug Anti-fouler And Cut It Apart And Use It For The Threads...thats What I Did....

krue · 02-23-2005, 08:10 PM

I don't know jack about FI but couldn't you just put the sensor in the exhaust pipe instead of the manifold? Seems like it would be a heck of a lot easier.

smokekiki · 02-23-2005, 08:15 PM

Weld it into the exhaust pipe below the manifold.

neonlarry · 02-23-2005, 09:53 PM

^ Good sugestion if the sensor doesn't work right there, i.e. too cold use a heated sensor.

02-22-2005, 09:27 PM	#1
smitty62 Registered User Join Date: May 2002 Location: North Carolina Posts: 1,234	Oxygen sensor thread? I need to drill & tap an exhaust manifold for an oxygen sensor--does anyone know what thread these are? Thanks __________________ Stepsides look like real trucks! Smitty

02-22-2005, 09:31 PM	#2
gmc67swb Registered User Join Date: Feb 2003 Location: Mesquite, Tx Posts: 396	I believe 18mm __________________ GM 330HP/350, Magnuson 122HH, Tremec TKO 5spd

02-22-2005, 09:32 PM	#3
71swb4x4 Senior Member Join Date: Nov 2003 Location: Brookings, SD Posts: 10,497	I think they are metric M18 x 1.50mm Not positive, I googled it. __________________ Some people are like slinkies, they aren't good for anything, but you can't help but smile when you see one tumble down the stairs.

02-22-2005, 09:34 PM	#4
71swb4x4 Senior Member Join Date: Nov 2003 Location: Brookings, SD Posts: 10,497	The Bosch LSU 4 sensor is a pump cell sensor like the NTK L1H1. The sensor requires a bung with an 18 mm diameter hole with 1.5 threads/mm pitch (this is one of the standard lambda sensor & sparkplug base sizes). Here is some more support, everything I have found says 18mm x 1.5mm __________________ Some people are like slinkies, they aren't good for anything, but you can't help but smile when you see one tumble down the stairs.

02-23-2005, 01:53 AM	#5
smitty62 Registered User Join Date: May 2002 Location: North Carolina Posts: 1,234	Thanks guys! I believe 18 X 1.5 is correct. Now to find a tap?? __________________ Stepsides look like real trucks! Smitty

02-23-2005, 07:56 AM	#6
EROC Active Member Join Date: Jan 2005 Location: Salem,Virginia Posts: 123	Drilling and tapping cast iron can be a real PITA. Your local muffler shop can probably sell you a steel oxygen sensor bung for a couple bucks. Just drill a hole in the pipe just past the manifold and weld the bung to the pipe. If you decide to get a tap most auto parts store sell taps to repair spark plug holes, which I think are 18mm. __________________ 69 GMC 2500 Camper Special 88 S10 Pickup 04 Impala I ship UPS from 24153

02-23-2005, 08:07 AM	#7
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	http://www.needboost.com/part/holley..._sensor_bungs/ __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

02-23-2005, 08:45 AM	#8
neonlarry Registered User Join Date: Feb 2002 Location: Vacaville, CA Posts: 2,746	You would be better off with a bung vs tapping unless you also want to machine a flat surface around the hole for the sensor to seal against. __________________ 70 C/10 Light Red 350/TH350, HEI, Duals w/40 series Flows, 91 seat, LED taillights 99 Pontiac S/C GTP, SLP Ram Air hood, GMPP Konis & springs 95 Neon ACR, MP PCM, AFX UDP, 3.0 CAI

02-23-2005, 11:14 AM	#9
smitty62 Registered User Join Date: May 2002 Location: North Carolina Posts: 1,234	Wow Tom!--$13 plus shipping for a 39 cent bung?? I don't think so! Those guys don't even use a gun! The reason I wanted to tap it is that welding old cast iron (ramshorn) can be a disaster--even using TIG.. The bung don't expand/shrink at the same rate as the cast. It can last a year or so before cracking, but you've still lost a manifold. Thought I'd try tapping with welding as a last resort. __________________ Stepsides look like real trucks! Smitty

02-23-2005, 06:40 PM	#10
'70_402 Senior Member Join Date: Dec 2003 Location: Pampa, Texas Posts: 1,554	You Can Go The Parts Store And Get A Spark Plug Anti-fouler And Cut It Apart And Use It For The Threads...thats What I Did.... __________________ https://www.ebay.com/itm/29620574751...mis&media=COPY

02-23-2005, 08:10 PM	#11
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,450	I don't know jack about FI but couldn't you just put the sensor in the exhaust pipe instead of the manifold? Seems like it would be a heck of a lot easier. __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck" Last edited by krue; 02-23-2005 at 08:13 PM.

02-23-2005, 08:15 PM	#12
smokekiki Mike Join Date: Jan 2003 Location: west chester pa Posts: 2,474	Weld it into the exhaust pipe below the manifold. __________________ 70'c/10, 71 suburban4x4 402bb, 72suburban 4/6 drop, 72k/5 4x4 blazer 4" lift 35 tires

02-23-2005, 09:53 PM	#13
neonlarry Registered User Join Date: Feb 2002 Location: Vacaville, CA Posts: 2,746	^ Good sugestion if the sensor doesn't work right there, i.e. too cold use a heated sensor. __________________ 70 C/10 Light Red 350/TH350, HEI, Duals w/40 series Flows, 91 seat, LED taillights 99 Pontiac S/C GTP, SLP Ram Air hood, GMPP Konis & springs 95 Neon ACR, MP PCM, AFX UDP, 3.0 CAI

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