[PontiacsForLife]

I am about to put a new exhaust system on my '62 Tempest (4cyl), and would like to install at least a 2-1/4" pipe. I have some questions regarding the exhaust manifold:
1. Will a 2-1/4" or 2-1/2" pipe bolt up to the stock 4cyl manifold?
2. If no, should I replace the exhaust manifold with a 350 or 400 log manifold? Will a 350 or 400 log match the (essentially) 389 head?
3. Is the 350 or 400 log a less-restrictive manifold?

If I keep the stock manifold, I plan on removing the butterfly valve and plug the shaft holes then block off the heat crossover underneath the carburetor. Is there any problem with that plan? The car will never be driven in sub-50 degree weather.

Thanks,
-Adam

[63Banshee]

You won't gain anything by going to another type of log manifold. 2.25" should fit as long as you "86" the slant 4 x-over tube adaptor. Double check the flange to manifold connection. I take the heat x-over out of play on all my Pontiacs. There are drawbacks, but if you drive in a warmer climate you'll be ok.

[PontiacsForLife]

Originally Posted by 63Banshee

...Double check the flange to manifold connection....

I noticed the crossover adapter is threaded, and the manifold has a thru-hole (non-threaded). I cannot see the bolt on the engine side clearly, but it appears the exhaust manifold may be threaded - perhapse due to accessibility. So this makes for an odd situation.

Assuming what I see in the picture is correct: Manifold is threaded on the inside (engine side) flange, and manifold has a thru-hole on the outside flange. Should I simply put a nut on the backside of the manifold's outside flange bolt hole? Will that endure the heat/cool/vibration cycles? Lock nut should ensure it does, huh? Just looking for some reassurance...

-Adam

[PontiacsForLife]

Here I am again - about 5 minutes after my previous post - I confirmed what I thought I saw, and that is the two different thread arrangements between the crossover adapter and exhaust manifold. The Chassis manual I just looked at showed it clearly. It also showed that the manifold end (once the crossover adapter is removed) is not a rounded 'ball' end that would fit in a typical exhaust head pipe 'socket'. I also am not looking forward to buying a pipe tap to plug the holes left after removing the butterfly valve shaft.

Instead, I'm going to go find a newer passenger side exhaust manifold that does not have the crossover butterfly valve, but does have the 'ball' formation and two (or three) threaded flanges. It sounds like one heckuva lot less work, and less chance of screwing up while modifying the original manifold.

I answered a previous question regarding exhaust manifold compatability: Headder manufacturers show the same part number for Pontiac 326/389/400/421/428/455 headers, so I am going to conclude that factory cast iron log manifolds are likewise interchangeable (except for round port RA or long branch manifolds).

-Adam (asking too many questions before actually researching!)

[SD421]

What I did on my 4 cylinder was to block the heat crossover pipe under the intake manifold. Im using a 1967 Ram Air factory manifold. Everything works great. I just had to have the muffler shop splice in a new header pipe.
Ram Air Restorations will sell you the right side manifold by itself.
-Don

[67SS&99SS]

I am also in the process of redoing my exhaust. I carried the car to the shop today as a matter of fact. However, when we took off the elbow the connects the exhaust to the manifold EVERY bolt broke. We heated them up with a torch and put penatrating oil on them. All to no avail. The reason for having to take it off was that one of the bolts that goes into the ear part of the flange on the exhaust side cracked. I have an NOS elbow, to replace my damaged one, however I don't want to have this problem with my exhaust manifold. How do you guys get the exhaust manifold bolts out without breaking them? I'm going to have to take mine off to drill out the broken bolts that are in the manifold flange. I also found out that the butterfly in the manifold was rusted in place. Luckily, I was able to turn it with a huge pair of channel locks. The tube that runs from the intake to the elbow, can I remove it from the car? I don't want to damage anything, so thats why i'm asking, lol. I also plan to remove the butterfly in the exhaust manifold due to it's poor condition. I live in Georgia, so a harsh climate really isn't a concern for me. I just want to fix the exhaust correctly and without it being a huge headache. Please help!

[PontiacsForLife]

I suggest getting an exhaust manifold without the butterfly valve, and install it in place of the factory manifold. The heat tube would be removed, and the hole under the carburetor would be blocked off with a simple plate and high-temp gasket.

Of course, there are several opportunities to run into stubborn bolts: Those 6 that go into the head, and the two that are under the intake.

I haven't answered your question about how to effectively remove the exhaust manifold bolts, but I do have a suggestion - despite my suspicion that you already know this tip, looking at your herd of cars: Bolts loosen up when there is a sudden torque applied - not a gradual torque. For example the whacking of an impact wrench is better than a constant torque with a breaker bar. Since we can't likely get an impact wrench on these bolts, maybe a hammer whack on a breaker bar.

The risk of breaking bolts, I feel, outweighs the potential for exhaust leaks under the hood due to the butterfly valve and the three extra exhaust connections you'd be eliminating.

...at least that's what I'm going to try...
-Adam