Exhaust sealing issues

MadMax78 · Posted: Mon Apr 07, 2008 3:36 pm Post subject: Exhaust sealing issues

I've been working the entire day to get my new (Dansk) heater boxes (72-74) to fit my heads (2.0l heads, AMC casting)

I have read Ratwell's write up on this subject which was very helpfull and pretty much every related forum post. I'm still having problems to get a good seal.

I have two questions;
1. When the exhaust is seated do to the 2 flanges have to be seated aswell? Or is is ok to have a little space between the head and the flanges?

2. I put the exhaust studs into the heads with the indicated torque value. However, the lower threads aren't completely in the head. Since the lower thread is a bit wider, this could pose a problem if the holes in the heater box flanges are too small, here's a picture:

Image may have been reduced in size. Click image to view fullscreen.

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VDubTech · Posted: Mon Apr 07, 2008 3:42 pm Post subject:

If there is any space, you will have an exhaust leak. That stud should be flush with the surface of the head. I would think the heater box isn't seating because it's hitting the shoulder of that stud before it hits the head. I would try to get it flush with the head, or maybe just open up the holes in the heater boxes just at the end so it will sit flush.

Ritter · Posted: Mon Apr 07, 2008 3:42 pm Post subject: Re: Exhaust sealing issues

busdaddy · Posted: Mon Apr 07, 2008 4:20 pm Post subject:

The outer bosses on the heat exchanger flanges don't meet up tight with the head but could be hanging up on the stud. Have you ran it and heard a leak or are you still assembling?

You may need to grind a bit off the head end of that stud to get it down flush if you think it's hanging up.
Anneal the gaskets with a propane torch (blue heat, air cool) before installing as well.
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MadMax78 · Posted: Mon Apr 07, 2008 4:21 pm Post subject: Re: Exhaust sealing issues

[quote="Ritter"]

Ritter · Posted: Mon Apr 07, 2008 4:35 pm Post subject: Re: Exhaust sealing issues

MadMax78 · Posted: Mon Apr 07, 2008 4:47 pm Post subject:

CarlSpackler · Posted: Tue Apr 08, 2008 8:18 am Post subject:

Drill your flanges larger on the side where the interference is occuring so they'll clear the threads. You can run it all the way through too, if you wish, but at the very least, drill them out to 9mm for a cm or so into the flange.
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busman78 · Posted: Tue Apr 08, 2008 9:12 am Post subject:

Busdaddy is right about the gaskets needing annealed, but you must heat it beyond blue, copper requires being heated to a dull red, then either air cooled or dropped it in water if you are in a hurry, it makes no difference how you cool it.

Randy in Maine · Posted: Tue Apr 08, 2008 9:26 am Post subject:

Also this may be of help to you.....

http://www.bostonengine.com/articles/hbmanifold.htm

Bursch · Posted: Tue Apr 08, 2008 5:16 pm Post subject:

Spent another day on the HE's...

The Dansk repro is a bitch. The bend in the exhaustpipe of the 1/2 HE was way off, creating a mismatch on my header and engine tin and hitting the mustache. Spent a few hours carefully filing the sealing area 2mm down on one side to compensate.

Anyway, gone through the whole process of filing/marking/filing/marking/filing/etc. I'm still in the fase of test fitting with the un-annealed seals. When torqued to spec it's still leaking noticeably. Is it even possible to obtain a proper seal without annealing and using locktite 518?
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VDubTech · Posted: Tue Apr 08, 2008 5:27 pm Post subject:

You do realize having more than one account is against the Forum Rules don't you??

Wildthings · Samba Member Joined: March 13, 2005 Posts: 50352

Why don't you pull your offending studs and measure the depth of the bore verses the length of the threads on the studs. You should be able to determine is it would be better to run bottom tap into the hole or the grind off the end of the stud a little.

Sorry you are having so much trouble with the aftermarket exchangers. I wish Bus Depot or someone would find a company to manufacture new shells for the old exchangers, a SS or at least a more corrosion resistant shell would be nice.

nebe · Posted: Tue Apr 08, 2008 7:31 pm Post subject:

busdaddy · Posted: Tue Apr 08, 2008 8:22 pm Post subject:

Don't feel bad, I had to go at a set of OG "F" tubes today with a pipe wrench, vice and portapower, didn't take much tweeking but once the twist was gone and they were spread out a bit they fit soooo much nicer.
Do yours slide down the studs nicely or are they a battle from the first thread?

You're right Busman, dull red is the right heat but I've always been taught to allow to air cool unless you want to harden it, at least for non ferrous metals.
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busman78 · Posted: Tue Apr 08, 2008 8:56 pm Post subject:

Copper does not react the same as ferrous metals, a water quench does not harden the copper after annealing.

VDubTech · Posted: Tue Apr 08, 2008 9:57 pm Post subject:

Bursch · Posted: Wed Apr 09, 2008 4:25 am Post subject:

Drilled a large hole in the bottom of the flange, making room for the studs. They slide on pretty nice, only need a gentle tap when almost seated. Gonna work on that a little more, so they'll just slide into place with the gasket being the fist thing they hit. Grinded down the flanges so that there is over 1mm of play before the flange hits the head. This should give enough room for the gasket to crush.

Need to do some more clearance work where the HE's meet up with the fan shroud. Did all the fitting with the fan shroud removed.

82-T/A · Posted: Wed Apr 09, 2008 5:50 am Post subject:

Just a thought, but have you checked to make sure that the flanges are flush with eachother? If they're slightly off, it would cause a leak. This is usually corrected by taking it to a machine shop where they put it on a belt sander, or a sanding disk and make the mating surface of both flanges completely flush.
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Bursch · Posted: Wed Apr 09, 2008 6:49 am Post subject:


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