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'10 Model 20 engine rebuild....


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As some of you know, last summer on the way TO the NE Brass & Gas tour, our '10 Hupp engine finally let us down with a bad rod bearing (or a few).  See pics HERE.  Finally got the engine out here to UT.....MAN that thing is heavy!  400 lbs for 20 hp.  Yikes. Anyway, I need to get going on this project and figured I'd start the thread to cover it, and start by asking a few questions to help my planning.  

 

First question is: Has anyone used a very light weight, "modern" piston design in their rebuild?  What I'm thinking is this: back in the day, OEM's used pistons w/huge skirts, that went all the way around the base of the piston.  Diesels still use a similar design.  The purpose is to increase the wear area of the piston, so it lasts longer.  

See the piston on the left and middle: (see pic)

 

The piston on the right (see same pic) is from a '06-'13 Corvette Z06.  It is designed to last past 100,000 miles and makes 505hp with a 7000 RPM redline....a far more abusive environment than a 20 hp Hupp motor.  Each piston in the Hupp is make 5 hp (at best) from ~450cc's.  Each of the Corvette's pistons is making 63 hp (net) from 875cc.  It's working way harder.   

 

Would a smaller/lighter "modern" piston combined with a light weight wrist pin...not reduce stress on the crank shaft?  I'd think that it would and by a substantial amount since loads increase by the square of the RPM.  I'd think that it would last "long enough", even w/less skirt, because of the massive advances in oil that we've seen in the past 110 years.    Has anyone, any experience with this? 

 

 

Second question is: does anyone know of a place that can regrind the stock cam....or are there places that make cams for Hupp's?   I believe that there are options for T's...but I don't know about for the Hupp?

 

That's about it for questions thus far.  I'm sure that more will come up as I get into the engine.  Thanks for reading.  

IMG_2846[1]-M.jpg

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I put a set of Egge pistons in my Model 20 back in 1977, they had good quality then. I wouldn't buy from them now, have had problems in two engines with their product within the last few years.  If I were to buy pistons for it now, I'd go to Aries pistons, they're beautifully made and infinitely functional.

 

As to the cam grinding, you'd best forget about that.  To grind the cam, you'd have to remove it.  The Hupmobile Model 20 engine has cam bearings cast in place, to remove cam you have to melt the Babbitt out, and replacing it is an ordeal at best.  It can be done, but in my case finding someone to do it and then paying the price was a lesson learned.

 

If your cam is already out of the housing, then you could do your grind, but if it's still in there and still turning well leave it alone.

 

How do I know this?  My magneto locked up and stripped the original gear, which was fiber between two sheets of metal.  New gears are available, but that's not the hard part.

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Hi Tom,

I think my pistons are Jahn’s,but not positive.I do think you want to go with new aluminum.

As David mentioned the cam could be a nightmare.Do you have a really good shop to do Babbitt? I think there are several places to have the cam done,but getting it back in the side plate is the big one.

How is the engine otherwise,crank,the cylinder bores,valve guides,the main,rods?

Ken

66020B99-CF40-4918-92C4-38DAE3536846.jpeg

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Thanks for the replies!
 

There is a guy local to me who rebuilds brass era engines -he's done a bunch and pours his own babbit.   He actually owns a '14 Hupp, so I feel that helps with his relating to my engine/situation.

 

I haven't torn the engine down yet.  The rod pins looked serviceable to me...in spite of the failed rod bearings.  I expect to find pretty heavy wear throughout; the engine was put together in the early 60's, I believe and it's probably averaged 500 miles/year or more.  It's been driven hard, many a-time.  One (of many) examples was a NE tour we were on, my Mom was driving it and the car got a flat tire.  She left it and hitched a ride.  For those who know him, John Lothrop came along and saw the Hupp.  He stopped, fixed the flat, and jumped in and headed for tour headquarters (had his rider drive his Corbin back).  John pushes all of his cars and he pushed the Hupp, that day too.  When it got back to us, the paint on the jugs was burn/chard black around/above the valves.  We'd never got it that hot in decades before that or since.  But that little engine has run hard for decades.  I've run it hard, my Mom broke the crank shaft once, my Dad ran it hard too. I expect to find a lot that needs attention.  And that is fine; it's put in it's time (nearly 60 years?) and mileage ~30,000 miles?

 

 

Trima:  

Quote

My magneto locked up and stripped the original gear, which was fiber between two sheets of metal.

Same thing happened to this Hupp in the late 70's; it got ran hard on a tour, mag got hot and melted the epoxy.  We parked it that night.  Next morning, my Dad grabbed the crank and gave it a yank...broke three teeth off that fiber gear. It was just my Mom, Dad and I touring in the Hupp.  No other car so I remember thinking that "the tour is over".   My dad went to an auto parts store and bought several small drill bits, epoxy and sand paper...maybe a file, I don't remember.  He drilled three (IIRC) drill bits into the spot for each broken tooth, toward the center of the gear, then broke the bits off, creating studs that would form the structure for a new tooth.  Then, he mixed up epoxy and laid it in around the drill bit/studs and let it set up. Finally, he hand filed/sanded the gears into the shape of teeth.  We finished the tour on that gear, and I believe that gear is still in the engine today.  

 

 

.

Edited by Tom400CFI (see edit history)
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That's a great story on rebuilding the cam gear!

 

My car had sat up during the winter, so I went out to start it.  Did all the normal things, cranked it and it tried to start and then died.   Did it again and same thing.  Realized that for some reason the timing seemed off, so I made sure mag was in the right place, same thing, would try to run then quit.

 

A friend came over who knows early cars well, we were fooling with it, had gear cover loose, and I just happened to look up and see stripped gears, all of the other times it had stopped with good teeth showing.  You cannot change the gear without taking the cam out of housing, and that means pouring Babbitt in place.  That means suspending the cam out in space while you pour a couple of bearings, then pouring the rest.  It's not a job for the faint of heart, regardless of how good a Babbitt man you guy might be.

 

Not impossible, just tough to do.  Reminds me of the joking motto we had when I ran a large maintenance shop for a food manufacturing plant, "We'll fix it immediately, no matter how long it takes!"...…..

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Good stories. Makes the hobby fun.I had a ride with John Lothrop in the Corbin,wow! Drove it like he was a teenager in a sports car.He was a very talented man,could build anything in his basement.

Please keep us posted Tom,and good luck.If you do have to get the cam out it was suggested to me to make a locating jig before removing the babbitt.Luckily,I did not have to do one.Also there has been some previous discussion on the cam babbitting on this forum.One of the gentlemen from down under.

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I had a cam made for  mine . Wasn't expensive  including manufacture Grinding and hardening  at about NZ$1000 ie about US$ 600  depending  on exchange  rate ,

Of course it would need shipping to  the States  from here which  would probably add another $60 to the cost -Karl 

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On 4/22/2020 at 10:26 AM, KenHupp20 said:

Good stories. Makes the hobby fun.I had a ride with John Lothrop in the Corbin,wow! Drove it like he was a teenager in a sports car.He was a very talented man,could build anything in his basement.

Please keep us posted Tom,and good luck.If you do have to get the cam out it was suggested to me to make a locating jig before removing the babbitt.Luckily,I did not have to do one.Also there has been some previous discussion on the cam babbitting on this forum.One of the gentlemen from down under.

Good suggestion, if you are going to work on the cam, have the person who is going to put it back in take it apart!  On mine, the shop put in threaded locating bolts on each end so that the cam could be suspended in correct place, middle bearings poured, then ends poured.  There was a long discussion on this forum once about doing this, and using newspaper around the cam bearing surface so that after Babbitt is poured there's correct clearance.

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  • 2 months later...

Finally started tearing the thing down....it's in a lot rougher shape than I was expecting, unfortunately.  I was expecting it to be "well worn" from ~4 decades of pretty hard use, but it's beyond that.  Here are some pics.  First one, this may have had something to do with why it'd run hot, climbing hills...

 

 

20200707_195032[1].jpg

 

Anyone know what that hole is for? 

20200707_201041[1].jpg

Edited by Tom400CFI (see edit history)
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I guess you can only have .977 mb per post?  I was thinking it was per pic....I guess there will be  a lot or posts.

 

 

EDIT:  DOH!   I guess it's 9.77 per thread??   That kind of sucks.  I'll have to resort to hosting them on the 'Vette forum again, I guess....

 

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Thanks for the tip on the pics.  I'll try linking it to the Corvette forum where I already posted the pics....

 

The pistons are total overkill....they look like pistons from a Caterpillar diesel.

20200707_200422_1__ca29a5ae998f12f881d26

 

 

 

This is a pic of one of the intake ports. The two cylinders' intake valves are in the same "port", which opens up into a big "box" essentially, which the two cylinders' valves, share. What I thought was odd about this and why I took the pic....what's up with the oily/carboned up intake port? Gas should clean it. There is no path for oil into the intake -no PCV, and there is not "reverberation" of the intake charge -the cam timing is way less than 180*.

 

20200708_181620_1__113e9b1aefab1894b21ee

 

 

 

 

This is apparently, the end of the valve stem? It actually threads on to the actual valve stem, and the cinching bolt keeps it from turning. That is your valve adjustment there. But look at the WEAR on that thing! It's crazy to me, that it's that worn when there is not lateral movement on it at all (like a rocker swiping on a valve stem)!

 

20200708_181719_1__91a41a9ab9b137bc9faf6

 

 

 

Here is the cam plate w/lifters. It's odd that the 4 lifters at the front of the engine have little holes in them.....

 

20200708_181746_1__06ac2270a0d74680b2831

 

 

 

 

....and the rear 4 don't?

 

20200708_181755_1__8cb709a74f22f1f0ea86d

 

 

 

 

Anyway, I unbolted the rear jug(s) and pulled it off, set it down on the bench and then....saw.....chit.....
And how about the wear on those stems ends?? The last one is worn clear through!....

 

20200708_223537_1__c751641dec245d3a59a26

 

 

 

 

 

I turned and looked back at the crank case, and there was the other piece, still sitting there....

 

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A little more looking and I found this, broken piston. How? Why? What??

 

20200708_223933_1__78b046883504279566b6c

 

 

 

 

 

And this is as far as I made it last night.....

 

20200708_223820_1__78ae880f58fabf85392a8

 

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Yes, aluminum pistons w/a 1/4" raised crown.  The engine was put together in the 60's.   In the 80's the crank broke and another used one was installed, but I believe everything else remained.  The crankshaft replacement was a "repair", not a "rebuild".  Maybe the valves were ground at that time, but I think that would be about it. 

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Quote

We found exactly the same thing  when we  stripped mine down to replace  the  stripped cam gear .  How  the finger tight rod  nuts  held on  and I  hadn't but  a leg out of bed  still amazes me -Karl 

 

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  • 4 weeks later...

Made some progress...took some pics....

They say that unhardened valve seats + unleaded gas = worn seat. Here....we have some pretty worn seats and sunken valves...

20200801_175447_2affa99132a5bab9225dc22f

20200801_175447_2affa99132a5bab9225dc22f


Here is another pic of the "adjuster" that goes on the end of the valve stem. Look at the wear! The lifter pushes straight up on this thing....I can't believe how worn it is...

 

20200801_180750_c261fc9a725be0f5bb16b6d5
20200801_180750_c261fc9a725be0f5bb16b6d5



Now this pic was intended to show a weird thing: all the valves aren't the same length. Note the heavy carbon build up on the valves. Where did that come from? Why isn't the gasoline keeping them clean? 

 

20200801_181955_28a2e26e2ec9e41133d2b3c2
20200801_181955_28a2e26e2ec9e41133d2b3c2



Here is one piston that is pretty representative. A weird thing here is the heavy wear....on the wrist pin end? NOT on the thrust side? How? Why? I THINK, that the piston may have been machine, round. As it heats, a piston expands more across the wrist pin dimension and less across the perpendicular dimension, due to more metal around the pin, less on the adjacent sides. I THINK, when the engine got hot, the piston expanded too much in that dimension and caused heavy wear....but I'm not really sure.  

 

20200807_203018_697871b87113915e361b9a13
20200807_203018_697871b87113915e361b9a13


Here is just a pic of one jug off, w/the pistons stuck back in. For you performance guys, check this out: 6" rods, stock!!  lol.gif

 

20200807_210605_33342162ca3d20621f0050c0
20200807_210605_33342162ca3d20621f0050c0

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The crank is supported in a very odd way in the Hupmobile;  
*There is a poured babbitt rear main bearing, in the rear of the crank case casting.  
*The center main is poured into a split casting, that is machined (round?) and fit rather loosely into a machined ID of the middle of the crank case. Then, two large studs pass all the way through the top of the case, the two split casting pieces and through the bottom of the case. Nuts on the top and bottom cinch it. I assume that you're deforming the crank case when you tighten them to "grab" the center main fixture?  
*The front main bearing is poured into the crank case front cover...which is "located" with exactly zero down pins or anything like that. You can see this casting in the bottom of the pic above^^.

To remove the crank, you remove the front cover, then remove two nuts on the center main bearing studs, and knock them out, then pull the crank out the front of the crank case. As you pull it out, the center main carrier, since it's two pieces, falls off the crank and lands in the front case area. Pull them out, then finish pulling the crank out of the case. It feels like pulling a cam from a push rod engine.

When I removed the front cover, and grabbed the crank snout, this was revealed....serious slop in the rear main bearing....

 

 

 

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Got the crank out. Guys...this is some serious race stuff here! 6" rods? Flat plane, forged crank? Raised dome pistons for higher compression? SICK! :lol:

20200807_211249_2bec0c4b98acbd6ee3401086d2852ce2f43a8c54.jpg




The following pics are just close ups of the journals, which don't look that great to me. I guess if I'm pouring new bearings, then the crank can be polised to whatever size, and the new bearing is custom fitted to that journal, whatever size it is. Here is the front main:

20200807_211338_a622bccc9a813a6aafba3bf2fb4732b38114f09e.jpg



Cylinder #1 rod journal....

20200807_211343_757612bff1f823a704ea2ac971694fad01fc94ce.jpg




Cylinder #2 Rod journal:

20200807_211348_55313d146666d9bcd8f58604e760eb4314ea1e41.jpg



Center main:

20200807_211354_e2cd6da87124e98df0c655750a28f85aa881acf4.jpg



#3 rod journal:

20200807_211358_8cb3dba4b5b5c763eb9d77e895fe123be92c0a34.jpg



#4 rod journal. This is the one with the smashed out/missing bearing.

20200807_211402_ed2df4729a56271de82e9a6f105fddd45e9ff2c0.jpg

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  • 1 month later...

^Thanks for the reminder about the clutch.  I'll have to get it shipped out here so that I have it.

 

Couple questions:

1. How did Hupmobile make the rod bearings?  Did they have a bronze insert with babbitt lining?  Or was it just all babbitt poured in place?  Or something else? 

2. Were the mains poured in place? Or are they shells? 

 

3. Finally, my crank needs to be turned.  Should I turn it, or weld it up and turn it?  I'm concerned about turning it and losing strength by making the pins smaller...

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The Hupmobile 20 had poured bearings, made of Parson's Bronze, whatever that might be.  The mains and rods in my Model 20 are still the original, and are holding up well, but I'm fairly positive there's no removable shell.

 

As to the crank, I don't think the danger is in having too small of a journal, but rather having too thick of Babbitt or whatever you use for rods and mains.  Babbitt can't dissipate heat very well, so the thicker it is the higher the chance of failure.

 

You need to be careful with the pistons in the jugs.  Not sure on the Hupp, but on some jugs there's a ridge at the top, if the rings go past that ridge it locks the piston in the cylinder.

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It might be best to start with measuring the crank and the bores to see if they have been machined before.I think there are places that can bring back to original size,but that may not be needed.

If the cylinders need boring I’ve been told it’s important to radius the top to relieve stress.

Good luck with the work.

Ken

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Thanks for all the replies.  They all help!

 

David, thanks for the tips on the bearings and bores.   I already "tested" the piston ring @ TDC by thoughtlessly ramming the piston all the way in to the bore....THEN thinking, "SOB....what if the top ring pops out into the combustion chamber?"  Fortunately, that didn't happen (with this engine) and the piston came right on back out. 

 

Andrew; we have a spare cylinder(s) at my Mom's house in Maine.  However, I'm going to try to weld/bore/surface the one that I have.  First, doing so is much cheaper than I'd thought.  Second, it's already been broken and welded in the past.  That repair has held up.  Third, I can keep that extra cylinders "in the bank" so to speak, for later. 

 

Ken, The cylinders will need to be bored.  There is some scoring and pretty visible wear.  I've not yet mic'd them for barrel and out of round, but I will.  I feel that the walls are thick enough for further boring regardless of what's already been done, but yes, I'll measure them for sure. Thanks for the tip on radius'ing the top of the bore job.   Good idea. 

 

I took the broken jug to the gentleman that I'd mentioned earlier.  He has a '14 Hupp and has built quite an impressive list of brass era engines: Cadillac, Locomobile, Packard, and others.  He was right on w/virtually everything we talked about which was awesome.  I'm glad that I found him.  One thing we both agree on is surfacing the bottom of the jugs and the top of the crank case....then assembling w/RTV and no paper gaskets.  This should put less bending on the jug's flange ears, IMO....and end up sealing better too.  

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Repairing the block sounds doable.You might look for someone who knows Muggy weld,it’s a brand of rod for cast iron and does away with all the heating,cooling issues.Those bottoms to the block are quite thin,maybe some gussets could be added to strengthen them.

Well good luck.

Ken

p.s. I think I used a very thin paper gasket and Hylomar anaerobic sealant.

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