Lower heat shield question Options

[technicalninja]

I've got the beginnings of a performance T4.
I bought a decent 73 2.0 core complete from 914Sixer.
I got a set of 1.8 SSI aftermarket heat exchangers from another member that are also pretty nice.

What I am missing is the bottom tins that go between the heat exchangers and the engine case.

Anytime folks put dedicated headers on a T4 these are left off...

How important are they?

I'm thinking "not much" but I would like insight from others.

Thanks

Rick

[rhodyguy]

They really stiffen up/help support the heat exchangers. Just puny 8mm ex studs and nuts and a rear hanger makes for a good sized unconnected space. They provide some cover for the pushrod tubes too. Pretty sure the bean counters would have omitted the WAGs if the engineers would have let them.

[wonkipop]

They really stiffen up/help support the heat exchangers. Just puny 8mm ex studs and nuts and a rear hanger makes for a good sized unconnected space. They provide some cover for the pushrod tubes too. Pretty sure the bean counters would have omitted the WAGs if the engineers would have let them.

maybe.

but the heat exchangers are hung at both ends so there is no twisting.
its really just a span and the heat exchangers are plenty stiff enough as a bridge element. don't think they are stressing the head studs.

consider your standard VW. the whole exhaust system is cantilevered off the head studs.
muffler and all. (admittedly not anywhere near the length but it is just hung there).
no muffler hanger. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif)

those acclaimed engineers were definitely struggling with something on the 914 and they did not crack it from day 1 - good as they were. i give you the little rubber flaps that hang down either side just in front of the engine bay. not on early cars. they definitely do do something and not while the car is standing still either. heated cooling air exhaust was not fully cracked and maybe never fully cracked on a 914. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif)
the whole thing is pretty hairy when you think about it - jamming an engine that was designed to go in the rear end of a car and sticking it in the middle. at least they did a better job of it than all the italian supercar manufacturers back then who stuck substandard sized radiators into the pencil noses of their over engined wedges!. (IMG:style_emoticons/default/biggrin.gif)

[87m491]

[/quote]

maybe.

but the heat exchangers are hung at both ends so there is no twisting.
its really just a span and the heat exchangers are plenty stiff enough as a bridge element. don't think they are stressing the head studs.

consider your standard VW. the whole exhaust system is cantilevered off the head studs.
muffler and all. (admittedly not anywhere near the length but it is just hung there).
no muffler hanger. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif)


[/quote]

Data point, in dropping my system last week I found there was no rear muffler/HE hanger installed on my car and indeed the whole system was held up with lust the 8 exhaust manifold nuts and studs! (no lower tins) I can say the muffler was pretty rock solid before removal and some how 7 of the 8 manifold nuts came off and the one stud that followed the nut out left a very clean helicoil behind so it will be reused. Very surprised given the weight and leverage on the HE's. Probably why I can't even begin to get the manifold gaskets to budge!