520H engine blew out valve seat

[mustangken 0]

My 520H blow out a valve seat.  Any suggestions on a new motor or should I have the seat repaired?

Edited February 12, 2018 by mustangken

[Sarge 3,464]

Repair it if possible , not a lot of choices out there for other engines that will last long.

 

Sarge

[mustangken 0]

Thanks Sarge - that was my dad's nickname.

 

I'm looking into have the seat fixed.  Just wondering what other solutions might be out there.

 

Think I also want to replace the lifters while in there as they kept losing adjustment.

[lynnmor 7,537]

1 hour ago, mustangken said:

 

Think I also want to replace the lifters while in there as they kept losing adjustment.

 

If the lifters are rough where they contact the cam, the cam is bad as well.  If the adjustment threads are loose that would require replacement.  Perhaps the adjustment issue was due to loose or worn seats.

[mustangken 0]

So now my problem is that the engine shop says the opposing cylinders will not fit on his table for him to work on the valve seat.

 

Any suggestions? 

 

Any rebuilt used 520H's out there?

[WNYPCRepair 1,923]

I found this while searching for specs. I know nothing about them

http://shop.kustomlawnandgarden.com/Rebuilt-ONAN-P220-20HP-engine-remanufactured-core-required-ReboP220.htm

[mikeeyre74 289]

2 hours ago, mustangken said:

So now my problem is that the engine shop says the opposing cylinders will not fit on his table for him to work on the valve seat.

 

Any suggestions? 

 

Any rebuilt used 520H's out there?

 

Find another engine shop. He's probably using a Serdi machine that has to have the head (in this case the whole block, chichis the problem) bolted into the fixture.. but most reputable places should have hand held equipment that can grind those seats. It's not really a big deal, unless you're stuck using certain pieces of equipment, like that guy ^^^.

[mustangken 0]

4 hours ago, mikeeyre74 said:

 

Find another engine shop. He's probably using a Serdi machine that has to have the head (in this case the whole block, chichis the problem) bolted into the fixture.. but most reputable places should have hand held equipment that can grind those seats. It's not really a big deal, unless you're stuck using certain pieces of equipment, like that guy ^^^.

The seat fell out of the head.  It has to be pressed back in.  Likely going to need an oversize seat.

[lynnmor 7,537]

Any machine shop with a turret (Bridgeport) type of a mill, can rotate the head to a horizontal position and do the boring with the block laid down.  It would take a lot more setup time and that would add to the cost, but it can be done.  Other automotive machine shops might have specialty machines that will accommodate the block. The block needs bored for the oversize seat and, depending on the blank, the seat ID needs bored to the original size.  Normal valve grinding equipment can then be used to shape the seating area.  Way oversize seats are available here: https://www.onanparts.com/index.php?main_page=product_info&cPath=1_6&products_id=14  I had to make an exception for their outdated security certificate.  These seats may need turned on a lathe as well, and might be regarded as simply raw material.  Automotive machine shops might be able to get a seat that will work as well.  The stock Onan seats may not be oversize enough to do the repair.  Be sure to have plenty of press fit on the seats, without looking it up, I believe it is around .005"

[mustangken 0]

Thanks.  I spoke with the engine shop and he is willing to try if I strip the motor down to a bare block.  So it looks like she will be getting new rings as well.

[mustangken 0]

Ok so the valve seat in the block was damaged and had to be machined.  The seat has been repaired.  Now I need to rebuild the motor.  Can someone help me locate rings, cam bearings and crank bearings and a full gasket set.???

[littleredrider 409]

X2...gonna be doing same to mine I think

[520HC 208]

onanparts.com

[Shynon 7,475]

2 hours ago, mustangken said:

Ok so the valve seat in the block was damaged and had to be machined.  The seat has been repaired.  Now I need to rebuild the motor.  Can someone help me locate rings, cam bearings and crank bearings and a full gasket set.???

@boomers_influence

 

[littleredrider 409]

$1200 for a gasket set?!? Is it made of platinum?? Wow.....

[lynnmor 7,537]

2 hours ago, littleredrider said:

$1200 for a gasket set?!? Is it made of platinum?? Wow.....

Where did that come from?

[littleredrider 409]

Onanparts.com. No wonder people say rebuilding these takes ur first born. If that’s the case I’ll prolly put the 16 horse twin from the g/f’s tractor on it...

[littleredrider 409]

Wait, looked at wrong one lol. Something I looked at was $1200, but gasket set was $130 I think. Still pricey, last 454 I built were cheaper.

[WVHillbilly520H 10,376]

8 hours ago, littleredrider said:

Still pricey, last 454 I built were cheaper.

That lil 406 SBC I built a couple years set me back $6-7k...and that was supposed to be cheap ...

[mustangken 0]

He's talking about just the gaskets.

 

And the guy at onanparts isn't helping much.

 

I need main bearings. Any other places to order them?

[boomers_influence 106]

ken

I DID send you a pm yesterday at 10:21 AM.

i gave my phone# and e/mail.

i stated that i have any and all parts that you will need.

 

thank you. boomer ( the used onan engine parts guy, also NOS and new )

[richmondred01 2,287]

I stopped Rebuilding onans because the cost of the parts.