[6t5gto]

Which hardware is correct to attach the head pipe to the exhaust manifold?A stud with a nut or a bolt with a washer? If a stud with a nut is correct, then is the wide nut correct or a standard nut?

[b-man]

Bolt with a washer.

[6t5gto]

The hardware in question is for a 1965.

[hobbygto65]

Should be a stud with a brass nut.

[G.T.O.boy]

Stud with a steel nut was factory, brass is the common replacement nut (better but not oem) stud would have been blackened zinc plated, and nut was zinc with a blue hue. If it is not concours restoration use the brass nut it is better to get off if it ever needs service.

[6t5gto]

It is a no excuse concourse restoration so I am trying to get every clip oem correct.

[bill ryder]

MPC shows 1" NC cad bolts.

"Bill"!

[60sstuff]

Originally Posted by b-man

Bolt with a washer.

b-man is correct.

Just some simple research with the proper book (1965 Pontiac Tempest Chassis Shop Manual).

More examples,
Scott Tiemann’s concourse restored ‘65 GTO.
A pair of mint condition ‘65 exhaust manifolds I have on the shelf with OEM Bolts.

Plus both of my Survivors came with the Bolt and Washer.

[bill ryder]

I do see the bolt and washer on Scott's engine but not in the other 4 examples plus MPC.

"Bill"!

[6t5gto]

As Bill stated, the 4 examples that 60sstuff posted does not have the washer and neither does Scott Tiemann's motor. His motor does have the bolt locks on the outer bolts but no washers at all. Interesting enough almost all the unrestored exhaust manifolds that are for sale on Ebay have a stud with a nut. I purchased a mint condition set of exhaust manifolds from a member that stated the manifolds have been sitting on the shelf for 30 years and they even have a stud with a nut.

[elefantrider]

My all original survivor '65 Lemans also had a bolt on the downpipes. Don't remember if a washer or not.
My GTO has studs. (factory bolts likely replaced, came to me with a rebuilt engine).

Now for the follow up question, is it worth keeping the bolts or changing to stud.
Seeing how difficult the bolt was to get loose, I am likely to think studs and nuts are better.... less thread engagement means less likely to snap them off.

[elefantrider]

I think with a stud and nut it makes it easier to install the pipes. As long as the studs aren't too long.

My original bolts did not have a washer.

These have been heat cycled countless times. I think it is better to replace these. Looks like they were grade 5.


Originals manifold to head bolts were of the thin-head type, unsure of the grade. Most replacement bolts have thicker heads.

[Tom Vaught]

Originally Posted by 6t5gto

As Bill stated, the 4 examples that 60sstuff posted does not have the washer and neither does Scott Tiemann's motor. His motor does have the bolt locks on the outer bolts but no washers at all. Interesting enough almost all the unrestored exhaust manifolds that are for sale on Ebay have a stud with a nut. I purchased a mint condition set of exhaust manifolds from a member that stated the manifolds have been sitting on the shelf for 30 years and they even have a stud with a nut.

MPC and advertising literature (especially) have known to be wrong occasionally.

My 64 GTO: Bolt locks, no washer, BUT not the same as 65 for sure.
PIA to remove those Bolt Locks on the manifolds when in the chassis.
Only thing I remember.

Headers came sometime later, so not a good question for me.

Also different plants have different installations at times as John V has pointed out many times.

Tom V.

[geeteeohguy]

Not correct but practical: studs with brass nuts. No more broken or frozen fasteners on the exhaust.

[elefantrider]

Looks like the factory bolt length was about 1.25" long?

[Sirrotica]

FWIW, speaking from actual experience working on those cars when they were just a few years old, I took a ton of OEM exhaust off back in the late 60s-70s. A 3/8"x11/4" bolt with no washer is what came from the factory. That's my experience from working at a Pontiac dealer, a muffler shop, and also when I worked for myself, and I specialized in working on Pontiacs. I started working on cars as my job in 1969, 65 GTOs , and all Pontiacs were right at the beginning of needing new exhaust at 4 years old in the rust belt. In that time period I also owned 3, 65 GTOs with manifolds, because in PA headers at that time were illegal, in 1977 they changed the law so that headers were legal.

If you look at the third picture in my signature, the background is my garage, and service station. You'll notice most every car in the parking lot behind the race car is a Pontiac. The picture was taken in 1978.

[elefantrider]

https://www.inlinetube.com/products/inl12316

https://www.inlinetube.com/products/inl10179

These guys sell a black oxide kit. Unsure what changed in '68, perhaps the length.

[elefantrider]

https://www.inlinetube.com/products/inl10855

They also sell a manifold to head kit, with the correct lock tabs.

Looks like their bolt heads are the correct size as per my originals.
They don't mention the grade.