0-300 tear down.

[Tom-D]

In by 10:00 out by 14:00.
Ready for shipping containers.

 

[SCCutler]

Cool.

I remember watching the tear-down of an IO520 at Lucky Louque's shop a few years back.

It was being torn down for overhaul, and from mounting on the stand to the "crankshaft on a stand" stage was, maybe, 2 hours? No rushing involved, either. Very impressive.

Lucky measured everything, said it still measured out to new limits, and that, "...if it was a prop-strike inspection, I'd say put it together and fly another 1,000 hours." Engine had 2,700 SMOH at that time.

 

[Tom-D]

With this one we are not that fortunate, crank is going to be re-worked .010" under, cam will be reground. 12 new lifters/hydraulic units & cups, case will go out to be reworked, (lapped and line bored) 6 new cylinders, sump will go get a liner put in, and all new common hardware.
This is an owner assisted rebuild. He is doing all the boxing/shipping/paying
He will be back when all the parts are here, and we'll put it back together, starter upgrade, alternator up graded, new mounts, prop gets IRAN and refinished then turned down to 80/40.

 

[455 Bravo Uniform]

Questions:

1-are the cam and crank on an airplane engine connected by gear rather than chain?

2-if gear, do they make undersized gears to make up for the closer cam-crank centerline from the line boring?

3-the wierdest thing to me is that airplane cams are reground (the one in my IO-470 was when I bought my plane). How common is this? I guess there is no real difference in cam/lifter failure rates between new vs reground?

4-are airplane engine cams “degreed” before the final close-up of the engine (to confirm the proper cam was ground and proper installed timing)?

And if anyone derails this thread by starting an argument while I’m trying to learn, **** you in advance

 

[Tom-D]

Questions:

1-are the cam and crank on an airplane engine connected by gear rather than chain?
gear

2-if gear, do they make undersized gears to make up for the closer cam-crank centerline from the line boring?
Line boring shrinks the case horizontally not vertically the gears remain the same distance apart. Center line of the case is vertical,
3-the wierdest thing to me is that airplane cams are reground (the one in my IO-470 was when I bought my plane). How common is this? I guess there is no real difference in cam/lifter failure rates between new vs reground?
Very common new cam and lifter kit for the 0-300 is over $2100 resurfacing less than a $1000

4-are airplane engine cams “degreed” before the final close-up of the engine (to confirm the proper cam was ground and proper installed timing)?
Changing the cam lift or duration would be a major modification for the engine, I've never seen it done, lobes are the same, just smaller. lifters the same, they just become shorter by .001"-.003"

And if anyone derails this thread by starting an argument while I’m trying to learn, **** you in advance

The case becomes narrower, cams become smaller, lifters become shorter, so it all equals out, The crank gets smaller diameter journals , but that effects nothing, but when the case gets narrower the pistons will travel higher in the cylinders, but the rods get reworked they become shorter which equals out on the deck hight.

 

[455 Bravo Uniform]

Thanks!

On the line bore - if the case halves are surfaced, and the boring bar opens the hole back up, the machinist is still removing material from the entire circumference, no? If so, doesn’t the crank-cam centerline get closer?

I am clueless about these goofy flat engines. Who puts an engine on its end to work on it, lol (and spins the “block” - case, whatever - to bring something up to TDC or BDC...you guys are wierd).

 

[Tom-D]

Thanks!

On the line bore - if the case halves are surfaced, and the boring bar opens the hole back up, the machinist is still removing material from the entire circumference, no? If so, doesn’t the crank-cam centerline get closer?

I am clueless about these goofy flat engines. Who puts an engine on its end to work on it, lol (and spins the “block” - case, whatever - to bring something up to TDC or BDC...you guys are wierd).

It's just easier to turn the engine on the stand than turn the stand.

think about it.

 

[Tom-D]

On the line bore - if the case halves are surfaced, and the boring bar opens the hole back up, the machinist is still removing material from the entire circumference, no? .

The amount removed at the 12:00 and 6:00 is virtually .000" but is usually made up by wear of the gears. we do have a min/max backlash check after case installation. Even with new gears and a reworked case, I've never seen one too tight.

 

[455 Bravo Uniform]

Gotcha, thanks. Looking forward to following along on this one if you guys will be posting progress.

 

[Salty]

Thanks!

On the line bore - if the case halves are surfaced, and the boring bar opens the hole back up, the machinist is still removing material from the entire circumference, no? If so, doesn’t the crank-cam centerline get closer?

I am clueless about these goofy flat engines. Who puts an engine on its end to work on it, lol (and spins the “block” - case, whatever - to bring something up to TDC or BDC...you guys are wierd).

Everyone would if they could. Only works because of the nice prop attachement on the end of the crankshaft. It makes assembly so much easier.

 

[Stewartb]

Case halves are milled to true the meeting surfaces. That allows the shop to align bore the cam and crank journals, important since an aircraft engine’s cam rides directly in the journals milled into the case without bearings. If the crank is milled the material loss compensated for by using oversized bearings for mains and rods. We’re talking about thousandths of an inch of material removed. If cam and/or followers are ground the rocker arm clearances are adjusted/maintained by changing push rod length to achieve the proper clearance. Rod caps are milled and the crank attach ends rebored. Piston ends are repaired by repacing the bushings.

 

[455 Bravo Uniform]

Did not realize there were no cam bearings. Wierd (to me).

You said journal rather than saddle, but I knew what you meant...before the pedants (NOT @timwinters) come out, lol.

Thanks guys.

 

[Tom-D]

Gotcha, thanks. Looking forward to following along on this one if you guys will be posting progress.

That will be a while, all depends on machine shop backlog and shipping time.

 

[Tom-D]

Case halves are milled to true the meeting surfaces. That allows the shop to align bore the cam and crank journals, important since an aircraft engine’s cam rides directly in the journals milled into the case without bearings. If the crank is milled the material loss compensated for by using oversized bearings for mains and rods. We’re talking about thousandths of an inch of material removed. If cam and/or followers are ground the rocker arm clearances are adjusted/maintained by changing push rod length to achieve the proper clearance. Rod caps are milled and the crank attach ends rebored. Piston ends are repaired by repacing the bushings.

Push rod length is changed in Lycomings, not in the 0-200/0-300. they have enough hydraulic clearance in the lifter to make up and deviance in the valve train.
Plus when a crank is reworked, they make the bearing journals smaller, requiring the bearings to be " undersize " That's why we call it 10 under.
Years long gone by they lapped the cases on a huge flat plate and lapping fluid. and the amount taken off the mating surface varied from side to side top to bottom, now it is done on a surface mill and the amount taken off is carefully controlled to remove only what is necessary.

 

[455 Bravo Uniform]

The 2nd engine I ever built (in 1983) was a big block Buick. I had the heads milled 0.045 (wierd how you can remember crap like that). On the Buicks, valve train is non adjustable. I figured the hydraulic lifters had enough room.

I had a heck of a time figuring out why my rpms topped out at 4500. When I finally got to make the mental connection, I ordered a set of adjustable pushrods. I set them so the lifters had very little preload, like 0.015. Reved up to 6k under load no problem.

That engine went on to win the Regal Modified class at the GS Nats one year and runner upped the next year. Stock heads, tiny carb, pump gas, and crazy cam. It’s still running today (bro in law owns it now).

 

[Tom-D]

a different engine going together, just as an example

 

[455 Bravo Uniform]

That’s fricken awesome. Does that second gear on the crank drive the mags?

 

[455 Bravo Uniform]

What do airplane engines sound like without the prop? Can you hear the timing gear whining?

Glory days (cue up Bruce Springsteen):

 

[455 Bravo Uniform]

And it looks like the thrust bearing is right on the snout? That makes sense.

 

[455 Bravo Uniform]

And what’s this cylindrical thing?



Sorry for the questions, I know you’re probably busy.

 

[Stan Cooper]

When we replaced the TCM cylinders on our O-300 with ECi Cerminil "Titan" cylinders, we had to order new pushrods because the new cylinders required different length pushrods than the TCM cylinders. While we were at it we installed the "Real Gaskets" pushrod tubes with spring loaded seals. No oil leaks a decade later! (The OEM pushrod tubes leaked like sieves.)

 

[BiffJ]

I don't think I've ever seen an aircooled airplane engine with a chain drive for the cam....at least nothing still in use and not 100 years old. I think the Wrights used a chain to drive the prop? Centerlines of the cam, crank and gears don't change even if you grind the journals down to nothing so no need for odd gears. I think its been covered already though.

Frank

 

[455 Bravo Uniform]

I don't think I've ever seen an aircooled airplane engine with a chain drive for the cam....at least nothing still in use and not 100 years old. I think the Wrights used a chain to drive the prop? Centerlines of the cam, crank and gears don't change even if you grind the journals down to nothing so no need for odd gears. I think its been covered already though.

Frank

Frank- it’s not journals (not the cam, not the crank) it’s the saddles (the case where the cam and crank and/or bearings sit) that when align (line) bored (honed) brings the cam and crank closer.

 

[Gary Austin]

Thanks!

On the line bore - if the case halves are surfaced, and the boring bar opens the hole back up, the machinist is still removing material from the entire circumference, no? If so, doesn’t the crank-cam centerline get closer?

I am clueless about these goofy flat engines. Who puts an engine on its end to work on it, lol (and spins the “block” - case, whatever - to bring something up to TDC or BDC...you guys are wierd).

That reminds me of a drawing when the first Ryan STA was designed and the enginnear ( i cant even spell it), wrote on the paper, of course the engine is inline, you won't fire a bullet sideways!!. It had a Menasco inline engine in it, a very pretty airplane, It was in some Ryan files in the San Diego Museum before the fire

 

[Tom-D]

And what’s this cylindrical thing?

View attachment 61687

Sorry for the questions, I know you’re probably busy.

I'll get to them eventually,, that is a modified starter support, we modify it to except a new light weight starter.
I just did one today I should have taken before and after pictures, I'll search my spare parts box, see If I can find a before example.
The old pull start starters needed a support to slide in and out on. the new ones do not.

 

[Tom-D]

When we replaced the TCM cylinders on our O-300 with ECi Cerminil "Titan" cylinders, we had to order new pushrods because the new cylinders required different length pushrods than the TCM cylinders.

Who ever told you that lied, and got in your wallet for nothing.
I've done hundreds of that swap, never needed new push rods. If the cylinders were not a direct replacement, they would require an STC to cover the change, ECI does have a STC to cover the exhaust valve rotator, but that is the extent of it.

 

[Tom-D]

Frank- it’s not journals (not the cam, not the crank) it’s the saddles (the case where the cam and crank and/or bearings sit) that when align (line) bored (honed) brings the cam and crank closer.

What the hell is a saddle ?

 

[Tom-D]

That’s fricken awesome. Does that second gear on the crank drive the mags?

No, it is the starter gear, notice the bevel where the spinning starter engages ?

 

[Tom-D]

What do airplane engines sound like without the prop? Can you hear the timing gear whining?

No gear whine but the 0-200 sounds like a big lawn mower. I run with a counter weight for short runs. they won't run with out some counter balance prop is best.

 

[Stan Cooper]

Who ever told you that lied, and got in your wallet for nothing.
I've done hundreds of that swap, never needed new push rods. If the cylinders were not a direct replacement, they would require an STC to cover the change, ECI does have a STC to cover the exhaust valve rotator, but that is the extent of it.

Tom, it was a number of people who told me that including at least three IAs, and I don't believe they were all lying. This is a 2005 post from a very long thread on the CPA forums about my cylinder replacement project.

 

[Checkout_my_Six]

probably have hydraulic lifters....they are self adjusting....within an operating range (~0.01-0.2).

 

[Stan Cooper]

probably have hydraulic lifters....they are self adjusting....within an operating range (~0.01-0.2).

Right, and based on Kent Felkins' recollection and the O-300 overhaul manual table of limits, that range is .030" to .110".

The clearance with the original pushrods and rockers collapsed after installing the ECi cylinders was ~.120", so I needed a longer pushrod to get the clearance in the spec'd range. I'm not saying the original pushrods wouldn't have worked, but having that extra slop when the specs say it's too much isn't my idea of doing the job right. YMMV.

O-300 Overhaul Manual Table of Limits

 

[Dan Thomas]

Frank- it’s not journals (not the cam, not the crank) it’s the saddles (the case where the cam and crank and/or bearings sit) that when align (line) bored (honed) brings the cam and crank closer.

The crank and cam don't get closer together. The case halves are machined laterally, 90 degrees to the vertical centerline that the cam and crank are on, and line-boring just makes the now-somewhat-egg-shaped cam and crank holes round again. They don't move closer together or father apart. Here is the backside view of an O-300 case:

The crank sits in the big hole in the middle. The cam sits in the small hole near the bottom. The case is milled on the two surfaces where the right and left halves join; the case is a half-inch apart in this photo. Milling those surfaces and reboring the holes does nothing to cam and crank spacing.

 

[455 Bravo Uniform]

What the hell is a saddle ?

I’ll see your “what the hell” and raise you “wtf”- wtf do you call that which the bearing half sits in?

 

[455 Bravo Uniform]

The crank and cam don't get closer together. The case halves are machined laterally, 90 degrees to the vertical centerline that the cam and crank are on, and line-boring just makes the now-somewhat-egg-shaped cam and crank holes round again. They don't move closer together or father apart. Here is the backside view of an O-300 case:

The crank sits in the big hole in the middle. The cam sits in the small hole near the bottom. The case is milled on the two surfaces where the right and left halves join; the case is a half-inch apart in this photo. Milling those surfaces and reboring the holes does nothing to cam and crank spacing.

I get it now, thx. Did not realize the cam bore needed to be rebored as well.

 

[Checkout_my_Six]

If you have too much slop....the valves won't open all the way....and you'll lose power.

Right, and based on Kent Felkins' recollection and the O-300 overhaul manual table of limits, that range is .030" to .110".

The clearance with the original pushrods and rockers collapsed after installing the ECi cylinders was ~.120", so I needed a longer pushrod to get the clearance in the spec'd range. I'm not saying the original pushrods wouldn't have worked, but having that extra slop when the specs say it's too much isn't my idea of doing the job right. YMMV.

O-300 Overhaul Manual Table of Limits

 

[Tom-D]

I’ll see your “what the hell” and raise you “wtf”- wtf do you call that which the bearing half sits in?

The case.

 

[455 Bravo Uniform]

The case.

That works. Auto vs aero differences.

This was great, I learned a lot guys.

 

[Tom-D]

I get it now, thx. Did not realize the cam bore needed to be rebored as well.

As does the starter support hole.
Modified and unmodified. one is for the new light weight starters, the other is for the old pull start.

 

[Omalley1537]

The case.

In auto circles, the semicircle that the bearing sits in on the engine block is called the saddle. The crank has half the bearing surface in the block and the other half in the caps (like a connecting rod).

455-If memory serves the reason a shorter cam chain is needed is that when they align-bore, they take most of the material out of the block side of the journal and not the caps, thus moving the crank centerline higher (closer to the cam). On the flat aircraft engine with the case split vertically, the issue is not present.