Exhaust manifolds - stainless as OE?

[itiejim]

Reading some old threads on here it seems that the OE manifolds were mild steel - can anyone confirm?

I've posted a picture of mine below which are definately stainless and therefore, I'm guessing aftermarket. Are they the same design as the OE ones, also I see that the 4.2 and 4.5 manifolds were different, my car is a 4.2 taken out to 4.5 - which manifolds are these?

That's the great thing about older cars (especially if they've been looked after) you just keep finding out new things about them

[newberry]

cant see any pics.

[itiejim]

Doh

Here it is:

[plumAJP]

mine looks like this, and I presumed it was mild steel and not stainless as the flanges were rusty.

all the pipes are discolured with an orangey rusty tint but no actual rusty flakes etc (bar the flanges to block) how can I tell if they are stainless or not. any home diy tests I can perform

[markh1]

The standard manifolds are low grade stainless I think and are prone to cracking.

[julian64]

The flanges will be rusty because they are welded. Weak point for rust I'm afraid. All my stainless welds end up rusting sooner or later

[Duke Thrust]

I have a set of 4.5 manifolds if anyone's interested? (Bigger bore than 4.2 but will fit straight on)

[brogenville]

Are they really bigger bore on the 4.5? I've heard from a few people now that thats just a myth. Be happy to be proved wrong though if someone wants to take some measurements.

[plumAJP]

so even with low grade staniless its still not adviseable to heat wrap them?

[ridds]

Flanges are mild steel and hence they look crap.

Manifolds are low grade but resist going proper rusty.

4.5's are bigger than 4.2's (I've measured them).

Neither are port matched and wreck the flow as it comes out of the head. Although it's not horrific due to the angles involved.

[Duke Thrust]

ridds said:

4.5's are bigger than 4.2's (I've measured them).

Likewise, definitely bigger

[itiejim]

So it looks like they're the original ones.

Can anyone confirm the outside diameter of (either 4.2 or 4.5) manifolds and I can see what I've got on mine.

[clive f]

I know the 4.2 is 1 1/2" pipe and think the 4.5 is 1 3/4", or 1 5/8"

[itiejim]

Thanks Clive, I'll check mine out later.

[caduceus]

Heres how the originals can look after shot blasting, welding and wire brush polishing:



They would come up better with a proper polish head, but I'll be wrapping mine, so theres no point.

[rev-erend]

The flange is usually 8mm mild .. so may have surface rust but with 8mm of steel - is never going to rust all the way thru.

Hope the wire brush was stainless and not mild steel or you will have rust deposites all over them soon.

[caduceus]

rev-erend said:

Hope the wire brush was stainless and not mild steel or you will have rust deposites all over them soon.

They're going to get a zinc phosphate coating before they go back on the car, which will kill any potential rust and prevent any occuring

[rev-erend]

caduceus said:

rev-erend said:

Hope the wire brush was stainless and not mild steel or you will have rust deposites all over them soon.

They're going to get a zinc phosphate coating before they go back on the car, which will kill any potential rust and prevent any occuring

Nice one.