PT422 engine swap completed (with pics)

[KMA]

Success!

For those of you who read my previous thread you'll know I had my previous Robin EH65 engine die on me. I will most likely fix it back up and use it for something else, but I took the opportunity to replace the original 22HP motor (that refused to start if the temperature dropped below 50 degrees) with something more powerful and hopefully better running overall. I decided to go with a 28HP Robin EH72 FI. The biggest reason for choosing this engine was that it is the same dimensions as the original so there no low risk regarding fitment.The engine was ordered from Equipatron.com and it was a very pleasant experience. I promised to post a thread with pictures of the installation, so here we go.

 

[KMA]

To help with removing the engine, I took off one hinge so the cover could be set behind the tractor on some buckets without having to remove the hoses and cooler. With the gas tank , muffler and heat shield removed, there is more room to work as seen in the following pics.

 

[KMA]

I disconnected everything, unbolted the pump and lifted the engine being careful not to catch the wiring or fuel lines on the sides of the tub. Once lifted up several inches, I propped the pump assembly up using a small bottle jack. You can see the lovejoy style coupler on the EH65's shaft. The bore on the coupler is 1 1/8" but the new shaft was 1 7/16" I chose this size shaft when ordering based on a recommended EH72 part number Terry gave me last year. Luckily, I called Terry again he told me PT custom machines a coupler in the right size. I ordered it for $40 and received it on Friday.

 

[KMA]

The shaft on the new engine comes much longer than necessary and needs to be cut down. Since the new coupler is them same size and shape as the old one (other than bore), I measure the old motor's shaft and cut the new one the same length. I used a metal cutting disk on my 4 1/2" grinder which worked pretty well. The key way on the new shaft shallowed out towards the end and after cutting it only about half the key stock would fit. I ground down and shaped the key stock until it fit.

 

[KMA]

While I had the engine removed I did some cleaning inside the tub since it is so hard to get at when all put together. The fuel injected engine needs a return fuel line which I added to the top of the gas tank. I bought some fittings and more fuel line and plumbed it into the side of the tank such that it wouldn't interfere with the cover when lowered. I put the new engine in but did not connect it to the pump. I also had to add some oil, but the engine was ready to go otherwise. To break it in, the service manual recommends running the motor for 10 minutes at low rpms unloaded, then increase the rpms for another 10 minutes, and so on for 30 minutes total. There is t��ick tick tick sound coming from fuel injector area when I turn the key on (not starting) and I didn't know if it was expected or not. I rechecked the wiring and all was good. I turned it over for about 20 seconds and it ran pretty well.

 

[KMA]

I let the engine cool a while, then lifted it up again so I could mount the pump. I found it was easiest to mount the couplers and housing to the engine and angle the pump upwards (I held it temporarily with bungie cords). I slowly lowered the engine while trying to line up the splined shaft of the pump. Once the pump was attached, the block needed to be bolted to the bottom of the tub. It was tight and a little bit difficult to get at the nuts/bolts (my knuckles are pretty banged up), but it got done.

The new engine has the oil dipstick up high causing the heat shield not to fit. I had to cut the angled top portion of the shield. I'm going to wrap the exhaust pipe in the very near future which should keep a little more heat out of the bay.

I drove it around the yard and it definitely seemed more powerful. The engine didn't show any hesitation or struggling going up steep hills. So far so good and I'm happy with the result. I think it might get slightly better gas mileage too because of the fuel injection. I don't think it can be any worse than my EH65 was.

Thanks for all the advice and input!

 

[MossRoad]

Great job! Glad it worked out for you. :thumbsup:

 

[BobRip]

Good job. Thanks for the post and pictures. When you get a chance can you post a picture of the gas tank return connection? Also the fitting you used?

Does anyone have a concern about the shorter key and keyway?

 

[KMA]

Great job! Glad it worked out for you. :thumbsup:

Thanks!

Good job. Thanks for the post and pictures. When you get a chance can you post a picture of the gas tank return connection? Also the fitting you used?

Does anyone have a concern about the shorter key and keyway?

There is a picture of the gas tank and return line in my 5th post above. Is that what you were looking for? Also, in the very last pic I posted you can see the return line wrapping around the back of the engine under the air filter cover. That's where is starts and then is routed along the same path as my main fuel line back to the tank.

Regarding the key way. I was a little concerned too, so I ground down the key stock to match up with shaft as much as possible. About 2/3 of the key stock is untouched, and the back side of it tapers in an arc mimicking the key way. While grinding, I would stop and test fit over and over until it was right, and it was still over half its original thickness at its thinnest point. I'm pretty certain it will hold. Plus, the original coupler used much smaller key stock even compared to the one I modified.

Thanks for everyone's input! :thumbsup:

 

[ponytug]

Great job! Thanks for the many pictures. It really helps understanding the details. It makes me wonder how clean my coupler is...

Given how close the dipstick is, I think that your idea of wrapping and insulating the exhaust manifold is a great idea.

All the best,

Peter

 

[BobRip]

Thanks!


There is a picture of the gas tank and return line in my 5th post above. Is that what you were looking for? Also, in the very last pic I posted you can see the return line wrapping around the back of the engine under the air filter cover. That's where is starts and then is routed along the same path as my main fuel line back to the tank.

Regarding the key way. I was a little concerned too, so I ground down the key stock to match up with shaft as much as possible. About 2/3 of the key stock is untouched, and the back side of it tapers in an arc mimicking the key way. While grinding, I would stop and test fit over and over until it was right, and it was still over half its original thickness at its thinnest point. I'm pretty certain it will hold. Plus, the original coupler used much smaller key stock even compared to the one I modified.

Thanks for everyone's input! :thumbsup:

I see it now. Thanks. Sounds like you did a good job on the keyway. Good technique on fitting it.

 

[PTWannaHave]

Great job on the engine swap and documentation for the rest of us; thx!!

When you decide to replace this EFI engine, you can show us how to put the 2cyl. Kohler diesel in...

Cheers,

 

[KMA]

Thanks PTWannaHave! The diesel swap may be quite a ways off (or at least I hope so).

It hasn't been particularly cold here lately, but it was in the low 40's this morning. I tried starting the tractor and it fired right up. My previous '06 EH65 would have struggled at this temperature.

It's not a great test for cold weather starting, but it's definitely better so far.

 

[KMA]

Okay, so the new engine has been running fine except I've been experiencing vapor lock when mowing on warmer days. After 45 min or so it will stall out and I have to let it cool down. I re-routed the new fuel lines and installed a new gas cap hoping it would help. I think it did a bit, such that it takes a little longer before it happens but it isn't fixed. I was finishing up mowing one night in between rain storms and noticed the muffler glowing orange right where the stock manifold mates up with the PT muffler. Like most owners on here, I never liked the stock exhaust setup and wanted to replace it. With the new vapor lock issue, I figured I'd bite the bullet and see if swapping it out for something better would help.

Today I bought a new muffler kit for the Subraru V-twin series of engines. The part number is 92630044, and can be found online for just under $150. There is a fancier kit available for a bit more money, but this one looks like it's easier to modify to fit my tractor. I got lucky and found an old Ebay listing for this kit that didn't sell. I contacted the guy and he re-listed it for me. I ended up getting it for $58 shipped and it should arrive next week. If nothing else, I'll feel better having an OEM exhaust on this engine.

I'll try to post some pics of the installation. I've attached a pic from the Ebay auction.

 

[woodlandfarms]

So when a muffler is running red hot it might be a sign of running too rich. At least that applies to muscle cars that I have had. I don't know anything about Subaru v-twins so take this all with a grain of salt.

 

[KMA]

So when a muffler is running red hot it might be a sign of running too rich. At least that applies to muscle cars that I have had. I don't know anything about Subaru v-twins so take this all with a grain of salt.

Really? I always equated "hot" with running lean... running rich should cool things down, no?

Anyway, I think the hotness is due to poor design more than anything. The stock PT muffler just isn't very good. I've already had to drill out the manifold for better flow since some of the tubing wasn't lined up correctly and overlapped the holes. My new engine is fuel injected, so I don't think there is a lot I can do regarding fuel mixture.

 

[woodlandfarms]

Sorry.. lean.. Lean Yes lean. need to lay off the drugs....

 

[KMA]

I've attached pics of the new muffler kit installed. I added a short piece of pipe between the manifold and muffler. I cut down a section from a pole lying around that was once used in a large tent made for parking cars under, etc... The manifold diameter is much smaller than what's used for autos, so it was harder to find parts. I got a bit lucky. I also had to cut the bonnet since the manifold sits much higher than the PT unit. I still have to reinforce it around the cut, but haven't gotten to it yet. I only bolted the bottom portion of the muffler mount to give it a bit of flexibility when the engine is idling and vibrating side to side. It is definitely quieter, but not an enormous difference. It may be in my head, or the different sound signature, but it seems to runs "smoother" too.

Regarding the vapor lock, I removed the elbow on the bottom of the tank and found a large chunk of plastic blocking it up. When draining the tank, it went really, really slow so I wasn't surprised to find a blockage. I haven't mowed the lawn yet, but I'd be shocked if the vapor lock occurred again, especially with the new muffler arrangement.

 

[BobRip]

It looks like you connected the muffler to the power trac body. Since the engine is on flex mounts I think you need a flexible mount to the body. This is the way cars do it. Please correct me if I am wrong.

 

[KMA]

It looks like you connected the muffler to the power trac body. Since the engine is on flex mounts I think you need a flexible mount to the body. This is the way cars do it. Please correct me if I am wrong.

Hi Bob,

Yeah, I only bolted the very bottom part of the muffler mount (which was bent to fit the application). It allows the top portion where the manifold connects to flex back and forth slightly. I watched how it moved before mounting it, and the engine mostly shakes side to side a bit (particularly at idle). I may also add a rubber "washer" in between the mount and tractor body.

I'll keep an eye on it either way. :thumbsup:

Thanks!