PT422 engine swap completed (with pics)

[woodlandfarms]

Yeah, Kevin. That metal will break rather quickly. A rubber mount is needed.

Bad example, that 737 that had it rough ripped off. just a little bit of play and the metal fatigued from vibration.

Carl

 

[KMA]

I added some rubber "washers" between the mount and the body, and replaced the bolt with a pin that allows more movement. We'll see how it goes...

Thanks.

 

[BobRip]

I added some rubber "washers" between the mount and the body, and replaced the bolt with a pin that allows more movement. We'll see how it goes...

Thanks.

Thanks for listening. Sorry if I am being too pushy. Have you looked at how they hang exhaust systems under cars. It gives some lift, but is flexible. Look at the tail pipe on a car and trace it back to a hanger. Just another idea.

 

[KMA]

Thanks for listening. Sorry if I am being too pushy. Have you looked at how they hang exhaust systems under cars. It gives some lift, but is flexible. Look at the tail pipe on a car and trace it back to a hanger. Just another idea.

Yeah, unfortunately I'm somewhat limited in my options. I'll keep thinking about it and monitoring the fitment as I go along. Maybe I'll come up with something better if needed.

 

[BobRip]

Yeah, unfortunately I'm somewhat limited in my options. I'll keep thinking about it and monitoring the fitment as I go along. Maybe I'll come up with something better if needed.

My engine is close to 1000 hours, so I am not to far behind you in engine replacement. Please keep us updated.

 

[KMA]

Quick update that I've been meaning to post to this thread...

I eventually went back to the PT OEM exhaust. The replacement muffler I discussed in this thread wasn't really meant to handle the type of installation necessary on the PT. The tubing is too thin and doesn't support itself well enough. It was really meant to be mounted right to the engine block itself with the attached bracket. The main problem I had with the stock exhaust was heat. I felt the squared off tubing in the manifold inhibited flow. Since upgrading to the Robin EH72FI, there is even more heat in the engine bay. Between the increase in horsepower and now having an oil cooler on the exhaust side (EH65 didn't have this), I was getting vapor lock pretty badly when it was warm outside and I was working the machine pretty hard (e.g. digging or mowing). I decided to move the fuel supply line to the other side of the tub. It runs above the battery to the back of the tractor and up to the top of the engine. The fuel pump is inline, and there is already a bolt on that side to hold a bracket for the wiring. I used it to also mount the pump. Since the line is no longer next to the oil cooler fins and muffler, I think I should be okay. I also have a fan mounted to the engine compartment cover that blows air across the engine and out the muffler side, which should help further with avoiding vapor lock. I haven't really worked the machine as hard as I'd like and the weather has been a bit cooler too, so I may not know for sure that it is completely fixed until middle of next summer. I have a one of those laser temp meters that I will shoot into the tub and see if I can find a difference in temperature on one side or the other. I'm fairly confident there will be and I should have less of an issue with the new routing.

Overall, the EH72FI is running great and I still love my little PT. I don't put as many hours on it now since I picked up a 61" Ferris ZTR mower. The PT wasn't a terrible mower, but it definitely doesn't have anything on a commercial ZTR when comparing speed and quality of cut.

 

[KMA]

Okay. Another update regarding the exhaust. As I mentioned above, the Robin kit wasn't meant for the layout of the PT. The tubing is thin and needed to be brought out of the engine bay. Recently, I decided to take another run at using the Robin muffler. The PT muffler got way too hot (glowed brightly at night) where the square exhaust manifold comes into the muffler. I couldn't help but think there was some type of restriction there, causing me to have heat issues. This time around, I took some black iron pipe and fabricated a new exhaust that incorporated the Robin muffler. I welded it up, added bracing so it wouldn't "shake" apart over time, and painted it with VHT Flame Proof. I also wrapped the pipe inside the engine bay to try and keep heat away. It seems to work well, but I haven't had a chance to really work the machine and check for overheating. The new muffler is a little bit quieter too, which is a nice bonus.

 

[woodlandfarms]

Nicely done.

Just a side note, red hot exhaust can also mean bad valves or a fuel mixture issue.

 

[KMA]

Nicely done.

Just a side note, red hot exhaust can also mean bad valves or a fuel mixture issue.

Thanks Woodlandfarms. When I run with the Robin muffler, you can't really notice it's hot except when it's really dark you can see a faint red glow that's even across the entire unit. Contrast that with the PT muffler that gets bright red only where the pipe mates up. It really seems like a flow issue, and I hope it's fixed now because I don't want to deal with it any longer.

Here's a pic of the almost stock PT muffler in case anyone needs a comparison:

 

[Marks481]

looks nice.

did you weld the exhaust flanges onto the pipe that you have threaded onto that iron exhaust manifold you put together, or did you find a source for an exhaust flange with a stub tube that you could screw into the iron exhaust manifold?

 

[KMA]

Tim,

I welded the flanges. I actually cut them from the Robin pipe to re-purpose for my custom one.

I'm going to see how this one works for a while. If for some reason I don't think it's the right solution, I might make another one using larger diameter pipe, overall shorter length, and a different muffler.

 

[Marks481]

Anyone know if the flanges on the Kohler Command pro engine exhaust manifolds are the same dimensions as the Robin? You can buy flanges with stub tubes on them for the kohler, which woul dbe an easy way to start building your own exhaust manifold.

 

[KMA]

Tim, I can't recall with 100% certainty, but when I was looking at re-doing my exhaust a few years ago I saw the Kohler "stub" flanges and felt like they would work. I might have even mentioned it in one of my threads. Sorry I can't be more definitive.

 

[KMA]

Quick year #3 update:

EH72FI is still going strong. The latest exhaust update is working out nicely, and it seems to running much better after modifying the engine shroud for easy access and removing some mice nests. I don't know if I mentioned this in an earlier post, but I moved the fuel line, filter and pump to the opposite site of the tub to avoid the heat from the muffler and oil filter/cooler assembly. That, along with wrapping the exhaust manifold, seems to have cured my vapor lock issues. Yesterday I used the forks, bucket, brush mower and mini-hoe to clean out and extend a swale on my property to try to fix up some wet areas that have been forming. The whole thing probably took me about an hour... and I can't imagine doing without the help of something like my PT. I really need this machine to stay running this well for a long, long time.

One more thing; the new engine does start a bit better in the cold compared to my EH65, but it's not an enormous improvement (maybe 10-15 degrees lower or so). The next biggest issue is the load from the pump trying to push cold, heavy oil through the system. I'm convinced that other engines (i.e. the older Kohler models) start better in the cold, but I'm hoping to build a large barn in the next few months with electricity available making this a non-issue moving forward.