1973 Exhaust manifold changing problems

[ghhatley]

My '73 has a leak from the driver side exhaust manifold. Its obviously coming from the manifold gasket that is deteriorated and now here is my question... has anyone changed the exhaust manifold on these cars? how difficult is it? do you have to jack up the motor and cast wizard spells over it for easy removal?

[Jeff Rosansky CLC #28373]

Soak the bolts with 50/50 mix of acetone and ATF. Soak it for a couple of days. Keep away from paint. Be sure socket/wrench is squarely on the bolt. You don't want to round the bolts off.

[ghhatley]

ATF, I assume automatic trans fluid?
Manual ratchet or air impact?
I have an oxi-accyteline torch should I heat them then after they cool soak them?

[Bob Hoffmann CLC#96]

That subject has been discussed in GREAT detail in the past months/years. I suggest a search.
HTH, Bob

[nanaimogene]

Graham, I noticed you have a fine collection of luxury cars. When I see a classic on line Im interested in I always ask the seller...any exhaust leaks? When my 62 Continental developed  exhaust manifold leak, I noticed no space for wrenches. I took the  Lincoln to a Ford dealer who had a mechanic there for 40 years. When I got the car back I asked them how the did it (bill was low), pull the engine No they unbolted lower pipe and pulled the head. I don't think you have to do that on your Caddy.Gene

[Scot Minesinger]

Provided that the bolts do not break it is easy.  It is all about removing the bolts without breaking them and if you do a search you will see that is the main problem and their are suggestions  The ones toward the firewall seem to be the worst, and if you break one, the head will have to come off.

[beastly beauties]

Soak, soak, soak, and soak some more and apply plenty of patients. If the left side is leaking it is very common for that side to be cracked and not just the gasket failure. Brand new ones are readily available at several vendors for that very reason.  Good Luck, David Symonds

[ghhatley]

So I soaked the bolts with P-B Blaster and let them sit for 20 min then got a whim and went to it. Within 15min I had everything off without a single problem. The worst thing was keeping the exhaust pipe out of my way! I'll be reinstalling the gasket tomorrow, any suggestions or recommendations?

[Scot Minesinger]

Those copper crush gaskets are super nice, I would use those. 

[TJ Hopland]

I would take a close look at it with a straight edge.   If it does not look perfect (they usually don't) I would look into getting the manifold 'surfaced'.   That is where they basically take it to a belt sander to make sure its flat.   Its usually not expensive and does not take long, you just need the right size shop with the right people where you can walk in and they just take it back and do it.

My 73 used to eat gaskets.   I think for a while I was doing them almost every year.  At one point I installed a rebuilt engine and used the manifolds that came with the other engine so everything was different and same problem.  I had to pull the rebuilt because of an oil problem and when I did that I had the manifolds surfaced again and put em back with no gaskets (apparently the factory way) and its been good now for 5+ years.   I don't remember any copper looking gaskets, I'm guessing I was using felpro and or victor.   I remember them all being the sort of layered tin foil sort of things.   Who makes the copper ones?

I have heard the bolt type is critical for exhaust manifolds.  On my Cads I have had decent original bolts to use so I don't think the bolts were my problem.   Apparently because of all the expanding that has to go on there has to be just the right amount of tension on the bolts.   If you use the wrong type of bolt they could be too tight or too loose and that is when you get leaks or cracks.   An example is apparently standard grade 8 bolts are too hard for most applications.

[Scot Minesinger]

The copper gaskets will likely take up the slack in an exhaust manifold that needs machining.  I install them with no issues routinely and no re-surfacing.

The exhaust manifold bolts are critical, I think grade 5, plus they have a bigger shoulder than standard.

I bought the copper gaskets and bolts from MTS in CA and they cut off the ID in the packaging for the copper gaskets so you don't know where they come from.

[Gene Beaird]

I would take a close look at it with a straight edge.   If it does not look perfect (they usually don't) I would look into getting the manifold 'surfaced'.   That is where they basically take it to a belt sander to make sure its flat.   Its usually not expensive and does not take long, you just need the right size shop with the right people where you can walk in and they just take it back and do it.
<SNIP>

^^This!  I broke an exhaust manifold on a Pontiac 455HO engine once because it was 1. warped, and 2. using a gasket.  It was at a time when I could get factory new manifolds, so I got one from the dealer.  That brand-spanking new manifold was also warped.  Took it to the shop at the hangar my Dad flew out of, and we put it on a big benchtop belt sander. A couple of minutes later, we had a perfectly-flat mounting surface.  That manifold went on with NO manifold, and we never had any more trouble out of it.  Additionally, it's the kind of manifold that's held on with 3 bolts. 

Flat mounting surface and I recommend an anti-seize compound....  just in case.

You were lucky things came off as easily as they do.  Some days chickens, some days feathers.   

[TJ Hopland]

Are the copper gaskets like solid copper or like the typical silver ones were its some sort of layered material?

[ghhatley]

I'm in NC so where do I get these Copper gaskets? we have O'reilly auto, Auto zone, Advanced auto, and NAPA
So I need to have my manifold sanded flat? I think that wont be a problem
Anti-seize got it
I bought from Oreilly and got gaskets that look like layers of cork and tin.
I want to make sure to " Do this once and DO IT RIGHT!"

[TJ Hopland]

Here is where Scott said he got his.  Links didn't used to work from his site but looks like they may now.     Not cheap at $50 but likely decent quality.

http://www.500cid.com/#!product/prd1/3520123691/copper-exhaust-gasket-set-8-individual

[ghhatley]

i have the original nuts off the manifold, do i need to replace them with new grade 5 nuts?

[TJ Hopland]

IF the choice was decent looking originals vs hardware store hardware I would go with originals.   I'm not sure about this model but one issue I remember running into with a Chev one time was 1/4 inch increments in length were not enough.  You have to make sure they don't bottom out but also you need enough threads to engage.   

Unless the cost is an issue I would not hesitate to buy those from MTS.   They seem like good people that sell good stuff.

[Roadmaster75]

I believe that ARP is now producing exhaust manifold bolt sets for 472,500,425

[ghhatley]

Reused the originals and they worked great.
Anyone put dual exhaust on their '73?
I assume it wont be a problem.

[Scot Minesinger]

I put dual exhaust on my 1970 and it was not a problem.  The 73 should be no issue.  Many compliments received on how nice it sounds.  Dual exhaust help during high use of air and fuel, such as on the highway, so I get about 1 or 2 mpg better with duals.  The other advantage is that there is no "Y" pipe so if you ever want to drop the oil pan or flywheel cover it is much easier. 

You do need to plan ahead a little around the gas tank.  One side has room for resonator the other does not.  I used Atlantic Tube resonators, which are less diameter than conventional resonators.  Be sure and use the GM angle cut exhaust pipes so it looks factory, rather than the straight out can see the dual exhausts a mile away install (which is of course easier).  I can send you pictures of mine if you want.