exhaust manifold

[garrywlh]

Some advice please. Never done this before.
Hedley's exhaust manifold has this fissure. Is this a problem? Serious enough to seek out a replacement manifold?

http://www.aulro.com/afvb/attachment.php?attachmentid=68371&d=1384044189

Many thanks,
Garry

[chazza]

There is no soot around it so I presume it isn't leaking; however; because it is cracked it will only get worse, so a good second-hand one is a good idea.

If you can't get a replacement, it can be welded by: chasing the crack with a grinder; drilling a hole at the end of it; and pre-heating it to a dull-red before welding; followed by post-heating and very slow cooling,

Cheers Charlie

[garrywlh]

thanks Charlie.

No soot might be because it has been in molasses for a week and then scrubbed down before examining it! Who knows how much soot may have been there. Note to self: examine components before thoroughly cleaning them to get an idea what their operating condition might reveal!

Anyway, as I have a new gasket and as there is no hurry, I will hold off reinstalling it until I see if I can obtain a better specimen.

:)

[Cannon]

Are you interested in extractors or do you want to keep it original?

I got extractors for DaOot delivered the same day for about $320 from a supplier in one of the stickies in this forum.

[Lotz-A-Landies]

Just be a little careful with replacement after market exhausts, some products sold as extractors are only headers with poor flow dynamics and many that don't have mandril bends so you get a reduction of flow caused by the waisting in the bends. On the inside some even have the pipes assembled in a design better suited to the oposite flow.

Make sure you have a look at the headers/extractors before you buy.

http://www.aulro.com/afvb/attachments/series-ii-iia/68508d1384219884-exhaust-manifold-header-flow.jpg

[Cannon]

Just be a little careful with replacement after market exhausts, some products sold as extractors are only headers with poor flow dynamics and many that don't have mandril bends so you get a reduction of flow caused by the waisting in the bends. On the inside some even have the pipes assembled in a design better suited to the oposite flow.

Make sure you have a look at the headers/extractors before you buy.

well i'm glad i got the ones you linked to in your aftermarket generic parts thread. :) :P :angel:

they seem pretty good to me :)

[Lotz-A-Landies]

They had two different types when I bought mine, so I don't know which ones you got or even if they were the same. But when a mechanic mate had a look at them recently he started pointing out all the deficiencies. At the end of the discussion he did state, that no matter how bad they were they still flow better than the original manifold.

(He is currently doing some performance work on a customer's 2 1/4 litre. One smart cookey, I love looking over his shoulder to see his latest creations.)

[garrywlh]

Are you interested in extractors or do you want to keep it original?

I got extractors for DaOot delivered the same day for about $320 from a supplier in one of the stickies in this forum.

Prefer to keep original if possible; though I know extractors would provide a performance improvement. I've got a second manifold here that looks to be in better shape - that is, I have one good inlet manifold and one good exhaust manifold, so I think they are about to get married. :)

[garrywlh]

Right! Set screw that holds the counterweight to the spindle. Trying to be firm, but gentle, but managed to break it off! :mad:

http://www.aulro.com/afvb/attachment.php?attachmentid=68782&d=1384601544

The 'hot-spot' mechanism is a mystery to me. I mean I read in the manual that the bimetal spring opens as the exhaust gases heat up, causing the flap to close. I sort of get WHAT it does, but have no idea WHY it does it. :eek:

Anyway, the spring seems ok, but the whole assembly is a bit loose, causing the adjusting plate to slip off the stop pin and just turn freely. So I was trying to tidy it up.

How serious a problem is this, considering that I doubt it has been working properly for a very long time?

Thanks for the help,

Garry

[Ozdunc]

I'd say not serious at all as it was deleted from later models.
It's there to heat the incoming air in the intake manifold when the engine is cold. Maybe warmer air/ fuel mixture combusts more easily, maybe it's a sort of automatic choke. Do you have a choke cable to your carb?

[JDNSW]

The hot spot in the manifold is to prevent drops of fuel (the fuel leaves the carburetter as a spray, not a gas) from pooling where they hit the bottom of the manifold and causing mixture to vary between the inner and outer cylinders.

The thermostatic variation of this hot spot was dropped in later production, so it presumably was found to be not necessary. The bimetal strip adjusts the position of a flap allowing the exhaust to hit the hot spot directly when cold but deflects it when warmed up so that the hot spot warms up more quickly - probably not a significant improvement except in very cold climates.

John

[garrywlh]

Thanks chaps.

So nice to know that the bit that broke off wasn't really necessary anyway! :)

And thanks for the explanation of the hot spot. As someone who has never really had an opportunity to 'get down and dirty' with a project like this, I am fascinated by all these little gems of information along the way.

cheers,

Garry

[JFD]

If you are not going to repair flap so that it operates properly it is important to make sure it is fixed in the open position,ie exhaust deflected away from the hot spot as it will slow exhaust gases leaving the ehaust chamber area and can cause burning of exhaust valves. Regards John