Exhaust pipe stuck in old Briggs exhaust port- Need help

[creia]

Model- 100202
Type - 0232-02
Code - 6807266

I am hoping to (once again) tap into the collective wisdom and experience on this wonderful forum on a challenge I am having...
This is an old 1968 Briggs 4 Hp, horizontal shaft, "flathead" I am restoring. When I took the engine into inventory I noticed it had a 5" length of 3/4" water pipe screwed into the engine exhaust port threaded hole. I want to remove the pipe so I can eventually install an OEM Briggs "hot dog" style screw in muffler. This section of pipe is REALLY frozen in the block! I have ran into this situation before and have always been able to (eventually) remove these sections of pipe or old screw-in mufflers.NO-Go on this one!

Here is what I have tried so far with no success whatsoever:
1. Soaking that area in "Evaporust" for over 24 hours.
2. Spraying the junction of the pipe and threads with WD-40, PB Blaster, and Gibbs Penetrant and using a lot of "tap-taps" with a hammer to help jar it loose.
3. The "melted wax" technique where you heat the area with a propane torch just enough to melt candle wax and let molten wax be drawn into the junction/threads.
With all of these techniques I use a big pipe wrench and try to unscrew it. All I have done is start flattening the pipe- the pipe has not budged one bit. I am afraid about putting any more force with the wrench, or using any more leverage as I do not want to bust a section out of the engine block in the process.

Is it time to really put the heat on the area with the propane torch? If so, do I heat the pipe or the area around the threaded boss on the engine block? If the latter, should I have concerns about melting the aluminum engine block? I am wondering if the different metals in contact with each other (iron pipe, aluminum block) have resulted in galvanic corrosion over time and caused the two to fuse together? Does anybody else have any ideas on how to get this section of pipe out?
Thank you in advance for any help!
Michael

[bobodu]

Cut the thing close to the block....use a hacksaw blade to cut through the nipple perpendicular to the threads at 4 o'clockish...make another cut at 7 o"clockish....use a chisel to cave in the pipe. Ten minutes tops..
Ooooo...found a video....https://www.youtube.com/watch?v=uSoNXnJ1_j4

[bgsengine]

yeah what bobo said.. and if you have a big enough drill, it can help to simply drill out the bulk of the pipe , less cutting to do, might even get it in one cut and able to collapse the pipe from there..

[RoyM]

That is how I have done it. Just cut enough to weaken the pipe, try not to bugger the threads in the block.

[creia]

Update:
SUCCESS!!
A BIG "Thank you" to everyone and especially to forum member "bobodu" for providing the link to the Youtube video which was done very well and easy to understand. Mine took 3 cuts to get the remaining nipple out. Once I did I cleaned the threads in the block with a wire brush and chased the threads with a brand new 3/4" pipe nipple lubed with some cutting oil. Overall it is in good shape and will accept and secure a new Briggs muffler very nicely. You taught this old dog (68 years old) a new trick today. Very much appreciated (as always)...
Michael

[Skywatcher]

Hi Creia

One other trick that has worked for me, but only on an engine that can run. Find a piece of metal bar or an impact socket that will snuggly fit the inside of the pipe, do not insert into pipe yet. Start and run the engine to get the exhaust port hot, aluminum has twice the expansion coefficient as steel so the engine block will expand more than the exhaust pipe. Once hot, shut the engine down and insert the bar or socket into the pipe to prevent the pipe from collapsing in the jaws of the pipe wrench.

Hold a wax candle (beeswax if you have it) momentarily against the union of the pipe to the engine and some of the wax will wick into the threads. Next, pour cold water onto the pipe to chill it being careful not to get any onto the hot engine, chilling the pipe will cause it to contract a little. Now apply force to the pipe with the pipe wrench and the pipe should come out. Getting these pipes out can take a lot more force than you expect. All the best,

Sky

[Skywatcher]

Hi Again

We're all learning from each other all the time on this forum. You evidently got the pipe out while I was watching the video and typing up my response . All the best and Merry Christmas.

Sky

[creia]

Hi Again

We're all learning from each other all the time on this forum. You evidently got the pipe out while I was watching the video and typing up my response . All the best and Merry Christmas.
Sky

Skywatcher,
Thank you for taking the time to post an alternative method- duly noted and appreciated! I always look forward to and learn from your kind, caring, and informative posts on this forum.
Michael