Exhaust Manifold Heat Shield: More than one Shape?

[ricsix]

My exhaust manifold on my 1974 02 had a crack in it. I found one through a salvage yard in Florida that was to fit all 2002s, After installing  it with the remainder of the new exhaust, all seemed to fit just fine.  But... when it came time to attach my original exhaust manifold heat shield, it just didn't seem to fit right. The bolt holes lined up, but some of the heat shields geometry was really in the way of getting to the #1 spark plug, I don't remember that ever being a problem in the past with the original manifold. 

 

The photos below are the best of what I have of the old/ manifolds (the old is red). Researching the number stamped on the new one doesn't reveal anything.

 

Anyway, are there several types of heat shield geometries? Maybe I need to find one that fits this new manifold?

 

Cheers,

 

Ric 

[PaulTWinterton]

Can't really see what your problem is in the photos other than the stud should be (locktited) in the head, not forced through the manifold with the nut on it.  Remove the nut.  Put the stud in the head and attach the shield and manifold.   Does that help?

['76mintgrün'02]

1 hour ago, ricsix said:

Anyway, are there several types of heat shield geometries? Maybe I need to find one that fits this new manifold?

 

 

@John76 has posted some nice photos of how he installed an aluminum heat shield on his manifold.  I forget which manifold he used, (tii?) but it required some spacers under the shield where the little bolts go through.  Do you have the aluminum style heat shield, or the stamped sheet metal one?  (more photos is (almost) always better!)

Tom

[John76]

Although all factory exhaust manifolds will bolt onto a M10 head, there are differences in the connections for various emission plumbing.

'71 and '72 manifolds have air injection and EGR ports.

'73 and '74 manifolds have EGR only.

'75 and '76 California cars have thermal reactors, air injection and EGR.

'76 49-state manifolds have air injection only.

Tii manifolds are "naked"....no emission connections.

 

The heat shields for the various manifolds generally use the same mounting stud spacing (except for the thermal reactor) however provisions are made to allow clearance for the various smog connections.

 

This is the stock '76 Calif. (or '75) with thermal reactor and metal heat shield.

 

'76 49-state manifold with air injection and aluminum heat shield.

Tii manifold with heat shield

 

Tii manifold with '76 49-state aluminum heat shield.  Note: Warm air connection to the snorkel to prevent carb icing.

 

Spacers are needed on the 49-state heat shield when adapting to the Tii manifold to make up for the extra clearance neededfor the air injection pipe on the '76.  All the heat shield mounting holes are the same orientation. 

[Mike Self]

Regardless of whether you use the sheet steel or cast aluminum heat shield, suggest using stainless steel bolts (6x1mm) to secure it to the manifold, and some anti-seize paste for insurance.  That way you won't discover some time in the future that you'll have to remove the manifold to drill out/re-tap a mounting hole with a broken off steel bolt.  Ask me how I learned this!

 

mike

 

PS--before re-installing the steel heat shield, check around all the bolt holes carefully--rust forms under the bolt heads and washers and will enlarge the holes/start stress cracks.

[tech71]

A quick, inexpensive solution not mentioned is to install a readily available E30 M10 gasket with integrated heat shield.

[Son of Marty]

+1 on the one piece later gasket unless you building a show car.

[Conserv]

2 hours ago, John76 said:

Although all factory exhaust manifolds will bolt onto a M10 head, there are differences in the connections for various emission plumbing.

'71 and '72 manifolds have air injection and EGR ports.

'73 and '74 manifolds have EGR only.

'75 and '76 California cars have thermal reactors, air injection and EGR.

'76 49-state manifolds have air injection only.

Tii manifolds are "naked"....no emission connections.

 

The heat shields for the various manifolds generally use the same mounting stud spacing (except for the thermal reactor) however provisions are made to allow clearance for the various smog connections.

 

This is the stock '76 Calif. (or '75) with thermal reactor and metal heat shield.

 

'76 49-state manifold with air injection and aluminum heat shield.

Tii manifold with heat shield

 

Tii manifold with '76 49-state aluminum heat shield.  Note: Warm air connection to the snorkel to prevent carb icing.

 

Spacers are needed on the 49-state heat shield when adapting to the Tii manifold to make up for the extra clearance neededfor the air injection pipe on the '76.  All the heat shield mounting holes are the same orientation. 

Thank you, John: great explanation and photos! It feels like The Article on heat shields! ?

 

Best regards,

 

Steve

 

 

[dlacey]

3 hours ago, tech71 said:

gasket with integrated heat shield

This is likely the best solution... Minimalist to just protect the plug leads... Some say the original heat shield accelerates cracking of the manifold as the cast iron runs hotter under the heat shield.... It's better to allow the heat to radiate away to protect the cast iron....

[Conserv]

Of course, some of us are quite attached to our winter-summer boxes…??

 

?

 

Best regards,

 

Steve

 

 

[ricsix]

10 hours ago, PaulTWinterton said:

Can't really see what your problem is in the photos other than the stud should be (locktited) in the head, not forced through the manifold with the nut on it.  Remove the nut.  Put the stud in the head and attach the shield and manifold.   Does that help?

Thanks Paul, I did do that; I bought a bunch of extra studs before I got started as I heard that they can unthread from the head (as was the case for me too). 

[ricsix]

10 hours ago, '76mintgrün'02 said:

Do you have the aluminum style heat shield, or the stamped sheet metal one?  (more photos is (almost) always better!)

Interesting - it seems I have the aluminum style (from looking at John's photos below) 

[ricsix]

8 hours ago, John76 said:

Although all factory exhaust manifolds will bolt onto a M10 head, there are differences in the connections for various emission plumbing.

John, thank you! This is very helpful and a true masterclass on heat shields. I really appreciate it!