Exhaust thread size

[Doppleganger]

Whats the thread-pitch of the exhaust bolts? I see some listed as 3/8-16 and others as a M8x1.25

Would imagine the SAE is for the earlier heads. Dunno.

Thx.

 

[wanderinthru]

All I've ever ran into is 3/8-16?

 

[Doppleganger]

All I've ever ran into is 3/8-16?

Me too.....but always had older blocks/heads too. Maybe new stuff is metric?

 

[PrairieDrifter]

As far as I know it was all sae until the late 90's, the engine im pretty sure at least. The rest of the trucks had metric scattered around.

 

[wanderinthru]

Me too.....but always had older blocks/heads too. Maybe new stuff is metric?

Hell I'm sure it is, the newest I've delt with would be on TBI heads, they were in an 81? and 3/8. Could see the LS's being meteric.

 

[Vbb199]

73 marked the first year of introduction of metric bolts in GM products

 

[Vbb199]

Hell I'm sure it is, the newest I've delt with would be on TBI heads, they were in an 81? and 3/8. Could see the LS's being meteric.

TBI started in gm trucks in 87

Alot of **** on it put together with 10mm and 8mm

 

[wanderinthru]

TBI started in gm trucks in 87

Alot of **** on it put together with 10mm and 8mm

I'm aware of that. Doesn't change the fact the heads were in an 81, point being **** can and does get changed around, so put your tongue back in your mouth........Grin

 

[Vbb199]

I'm aware of that. Doesn't change the fact the heads were in an 81, point being **** can and does get changed around, so put your tongue back in your mouth........Grin

Weird someone put tbi heads on an 81, factory tbi heads are junk IMO

 

[wanderinthru]

Weird someone put tbi heads on an 81, factory tbi heads are junk IMO

Seen alot weirder ****! Nobody said they are factory heads.....they do have 3/8 exhaust manifold threads in them.

 

[Frankenchevy]

I can confirm that my new vortec from GM is still 3/8-16.

 

[Poppy 87]

My 87 tbi heads have 3/8" exhaust manifold bolts and are original equipment

 

[80BrownK10]

Weird someone put tbi heads on an 81, factory tbi heads are junk IMO

Probably had a ruined set of heads on or in something they wanted to fix. And a junk tbi motor sitting around and were able to get them free or traded or paid next to nothing for them so they put them on the older motor not knowing there junk or just didn't care just wanted it running.

 

[wanderinthru]

Probably had a ruined set of heads on or in something they wanted to fix. And a junk tbi motor sitting around and were able to get them free or traded or paid next to nothing for them so they put them on the older motor not knowing there junk or just didn't care just wanted it running.

Really? See that you and @Vbb199 know everything and all but, here is another idea. Back in 81 an old farmer in the western Texas panhandle bought him a brand spankin new half ton 4 wheel drive 6.2 liter diesel (put tractor fuel in it) automatic shift, with air condition. Will still use the old 60's something around the farm, park the 50's something. That's what happens till somewhere in the 90's, when the 81 is wanting to lay down. So said farmer takes said 81 to a shop little west of him, and ask can he get said truck going and reliable? Said mechanic is a friend of mine, and known for doing real quality work. Said mechanic tells Mr Farmer " ain't much I can do, other than make it what it was?" Mr Farmer says, I just need a good truck I can use on the farm, and don't care much for this auto tranny thing. Said mechanic says "yes Sir, we can fix you up" and does, builds Mr. Farmer a 350, with TBI heads on it, puts him a 4 speed granny in it, Mr Farmer takes it back to the farm uses it daily, parks it in the shed every night, always has clean oil, and air filters. I wound up with it in 2018, and it runs fine and still wears it's 1981 paint with pride! And! And! The holes drilled and tapped in the heads to accept the exhaust manifolds, are By Gawd 3/8 by 16!!

 

[80BrownK10]

Really? See that you and @Vbb199 know everything and all but, here is another idea. Back in 81 an old farmer in the western Texas panhandle bought him a brand spankin new half ton 4 wheel drive 6.2 liter diesel (put tractor fuel in it) automatic shift, with air condition. Will still use the old 60's something around the farm, park the 50's something. That's what happens till somewhere in the 90's, when the 81 is wanting to lay down. So said farmer takes said 81 to a shop little west of him, and ask can he get said truck going and reliable? Said mechanic is a friend of mine, and known for doing real quality work. Said mechanic tells Mr Farmer " ain't much I can do, other than make it what it was?" Mr Farmer says, I just need a good truck I can use on the farm, and don't care much for this auto tranny thing. Said mechanic says "yes Sir, we can fix you up" and does, builds Mr. Farmer a 350, with TBI heads on it, puts him a 4 speed granny in it, Mr Farmer takes it back to the farm uses it daily, parks it in the shed every night, always has clean oil, and air filters. I wound up with it in 2018, and it runs fine and still wears it's 1981 paint with pride! And! And! The holes drilled and tapped in the heads to accept the exhaust manifolds, are By Gawd 3/8 by 16!!

That's a very similar story as to what I said. Except some guy building his truck back with a junk motor, said guy goes to a shop and says make it work for a good price. Guy builds it to run and that's what you have.

I know I can't list every possible scenario but my point was that someone just made it work.

I don't know everything, most people here know way more than me and have way more experience than me.