Looking for reasonably priced 531211 & 537466 through bolts

[an8pilot]

Good Morning,

Been looking for reasonably priced 7 each 531211 & 2 each 537466 through bolts for my O-300 since I got back from deployment.

Anyone seen any decently priced?

[GAHorn]

The overhaul instructions require replacement with New. Few (if any) field “overhauls” actually do that due to cost. (Another reason most so-called “overhauls” are actually “repairs”...so when folks shop for an airplane and see adverts stating “300 SMOH” it probably means “300 since major “repair”).

If you can accept “used” you’ll find some from one of our Members who is disassembling an engine. PM me if interested and I’ll send you his contact info.

[an8pilot]

Thank you, yes I wasn't really going to call it overhauled.

The cam followers or lifter bodies I'm using reconditioned ones, and the lifter plungers as in the hydraulic lifters inside the cam followers I am inspecting them per the manual. Lifter plungers meaning the internal units that pump up with pressure inside the lifter cam followers or lifter bodies, the actual hyd lifter plungers can be replaced without splitting the case and not really wanting to take a chance on new ones compared to my used ones that were working well and meet test spec, as I am not calling the engine overhauled, just calling it a repair inspect and replace as necessary on the 337.

At this point though, if the case (an overhauled case) is apart if I could get the new through bolts then I would.
But not at the listed price I'm seeing. Wow.

7 each 531211 (SB required) with o ring grooves, the bolts that clamp the main bearings

2 each 537466 (SB required) no orings, the two bolts that clamps on central part of cam

2 each 531212 2 EA ( not SB required) with o ring grooves,the 2 bolts that clamp the front main bearing just behind crank prop flange

2 ea 537465 (not SB required) no orings, goes through at front and rear bottom of the case and attach the eng mounts and clamping lower front corner split line and rear corner split line of case. Again not required but if they were cheap I would replace.

Those prices from aircraft specialties are just way over what I expected.

Nothing against them they can only sell them for what they have to sell them at and they have been a great shop.

Just the price for replacement is way over what I expected.

One 531211 of mine is nicked from someone pulling it out at some point and then burnished. Same on one 537466.

Hoping someone had a new old stock set on here they never used at the old prices.

Thank you Bruce

[c170b53]

I thought the through bolts were mag particle inspected on a overhaul.
From my experience (that’s certainly limited ) I think you’re in no mans land, almost knowing exactly what you have. Sounds like you have disassembled the engine but you’re hesitant of splitting the cases. Typically the lifters will begin to spall right in the middle and thats very hard to see when she’s assembled. Also it would be beneficial to polish the crankshaft and possibly regrind or replace the camshaft. More money, time and work but then you know. That know is the confidence you might like if you fly over water and mountains.

[an8pilot]

Thanks Jim,

I've overhauled flat engines, radials and jet engines.

This engine is one of my personal engines on my personal airplane so it's my money that I need to spend while home not working forced to be social distancing. This O-300 I have already had everything overhauled that can be overhauled, except replacing hydraulic lifters as required by the Continental overhaul list. The cam followers have been reconditioned/faced by Rick Romans, and I'm not calling the engine overhauled. I had originally taken it apart after I found evidence of previously polished off rust that a Continental SB said was ok as long as we inspect it I think I remember every 100 hours.

The overhaul replacement list says to replace the through bolts. They are expensive. Since the now overhauled case is apart, it would be nice to replace the through bolts. I can replace the lifters down the road if needed, but after I have checked the lifters, I will be happy to reuse them, which have been working well, compared to installing unknown new lifters. Just that's my experience with new bye lifters and sharp edges inside.

Sorry I didn't clarify as well as I should. I was looking for anyone possibly have a new old stock set of carry through bolts laying around they never used on an engine. Two of the carry through bolts I have were knicked by someone in the past. Yes if the bolts have been magnafluxed, I have faith in them not stretching and lasting if they have lasted this long compared to new ones stretching and possibly fretting the case mating faces, with people not rechecking through bolt torque after a while, and at every annual. A whole lot less stretch than some of the bolts we stretch on the jet engines which is scary.

[Arcticmayhem]

I'm also in the process of overhauling my engine and was planning on reusing the through bolts until I saw this thread. I haven't seen anywhere in the overhaul manual that says these must be replaced. My A&P couldn't find it either. Where is this published?

[n2582d]

Table C-1 “Mandatory Overhaul Replacement Parts” in Appendix C of the Maintenance Manual.

[c170b53]

Thanks Gary, i can see why the price of an overhaul has been a steady climb.

[counsellj]

[quote="an8pilot"]Thanks Jim,

I've overhauled flat engines, radials and jet engines.
I can replace the lifters down the road if needed, but after I have checked the lifters, I will be happy to reuse them, which have been working well, compared to installing unknown new lifters. Just that's my experience with new bye lifters and sharp edges inside.


I have a set of overhauled lifters from when I overhauled my engine if you are interested. I decided to put new ones in my engine.

Jon "Jughead" Counsell
850-723-2072

[Bruce Fenstermacher]

Table C-1 “Mandatory Overhaul Replacement Parts” in Appendix C of the Maintenance Manual.

The table has been around for a while but in the form of a Service Bulletin. Of course service bulletins are not mandatory. With the introduction by Continental of their Maintenance Manual (M-0) which incorporates all the individual engine overhaul manuals, the Table C-1 and everything else in M-0 is also part of the Overhaul Manuals.

Pretty tricky of Continental isn't it. Almost makes you want to buy a Lycoming.

[an8pilot]

I have a set of overhauled lifters from when I overhauled my engine if you are interested. I decided to put new ones in my engine.

Jon "Jughead" Counsell
850-723-2072

[/quote]

Hello there Jon, I also have a set of overhauled Lifter Bodies as in the Cam Follower.

Are you saying Lifter Bodies as in Cam Followers, or the internal parts as in the actual Hydraulic Lifters as in Plungers the units that pump up with oil with a spring and ball we test for leak down ?

The lobe face on my Lifter Bodies that I took out of the engine was thicker than the reworked units I have from Rick Romans ( the lifter body lobe faces will be milled down of course sending it to Aircraft Specialties to be ready to accept the overhauled cam) but the reworked set body I have, the o.d. after stone vibratory device is .7165 and Aircraft Specialties limit is .7162 . Mine taken out of the engine were averaging .7175 to .7178 so i sent them in to ASI telling them to leave my o.d. of the bodies alone and don't put them in the vibratory stoning device. That vibratory stone device make jet engine compressor blades pretty but I don't want to take a .0013 away for no reason when they fit perfect.

The 531211 o ring bolts that clamp the crank i can see replacing. I can also see replacing the 2 each 531212 short oring bolts because they go at the crank prop flange end but they are not required replacement under the SB, only the 7 each 531211 clamping the crank and the small non oring bottom center 537466 bolts are required SB replacement. The 2 each 537465 non o ring long bolts that are at the bottom forward and rear ends of the case that hold the engine mount arms are also not required replacement in the SB. But again, the small non o ring bolts, 537466, at the bottom below the two central main bearings and clamp the area below the two lower central cam bosses are require replacement per the SB.

You would think they all would be required replacement per the SB if a SB is not required. Especially the two forward 531212 crank prop flange o ring sealed bolts and the bottom forward and rear split line bolts that hold on all the engine mount arms. All other bolts on the engine mount arms are only screwed into the case.

My opinion which is only good for me is that any items not listed as mandatory replacement cancels any verbiage that someone wants to construe that the manual overrides. Unless the bolts are found no good after NDT or damage rust or threads show not to be ok for re-use.

[ghostflyer]

Have a talk with some of the big overhaul shops and see what they do at over haul. Bolts stretch when torqued and when heated and cooled over the life of the engine become brittle . There isn’t any cheap way of overhauling a engine and the cost will escalate if a bolt snaps in service and a bearing spins .

[an8pilot]

Thats a good thought. Although I had different thoughts today.

I write these thoughts for someone like me struggling with this decision in the future. Just my thoughts.

I've been involved with all sorts of engines over the years, engines where we RREEally stretched the bolts per manual.
Alot of the bolts that we stretched in the JT8D holding all the disks together didn't get replaced. And these engines were always continued time engines where everything had times and cycles, they didn't call them overhauled and they went thousands upon thousands of hours.

I've never seen or heard of a Continental tie bolt snapping. I've seen bolts, even one of them on mine galled and knicked. So I need a replacement. But I've never seen one break. I've seen jugs pop off. I've seen rods go through cases. I've seen oil pumps gall. I've seen mag impulse mechanisms break apart and stop an engine in flight. But not a broken tie bolt.

I've also been a structural sheet metal guy rebuilding aircraft both small and very large.
You know the bolts that hold our Cessna wings on. There is only one on the front and one on the back and I've not seen a requirement to change them. One breaks it means death. I've never seen one break. I've seen multiple wing removal and reinstalls and still never a break.
I have however seen a 170 lose a wing coming out of Tamiami years ago from lift struts being rusted.
I later bought new factory new lift struts for my 1950 C150 with a big engine kit and Taildragger and long range fuel kit but I've never heard of a Cessna 150 or 172 lift strut let go. And not wing bolts. Of course there is the Beech wing bolt inspections. Also not required. I've done a lot of Beech rebuilding. I've never seen a Beech wing bolt break. I think it's good to do though on the upper bolts due to being the bath tub drains get clogged and collect water if the aircraft sits outside.

But if we are following the Continental overhaul SB I think there would be more clout put to it if they had required the two 531212 o-ring bolts replaced right behind the prop flange and the 2ea 537465 non o-ring bolts that are at the bottom ends and hold the engine mounts on. The two 537466 bolts required by s.b. that go below the cam that are shorter than the 537465, are the same size in diameter as the 537465 but have a whole lot less stress under the cam than the two 537465 which hold the bottom front and rear of the case together as well as each one holds two engine mounts on for each one bolt and maintain all the gyroscopic stress of the prop and weight of the engine. It goes a long way against credibility. Neither of the not required 537465 or the required 537466 have a pinch fit.

I measured the o.d. of the main required 7 each 531211 and the not required but should be 2 each 531212 right behind the prop flange.
Both the 7 and the 2 have a interference fit at the center that basically keeps the case from the ability to shift.
That would be a reason they would need replacing if that interference fit is worn. The interference fit is to be a min loose .0005 to max .001 loose.
My o.d. is right at .418 to just a bit over as in .4182 and the case holes i.d. is .41887 to .419 so, I feel good in the required Tie bolts in crankcase new parts minimum of .0005 Tight to .001 Loose and my i.d. o.d. above meet that. There is no repair to make the case holes smaller and I have two overhauled cases from two good overhaulers and they are both the same on the i.d. of the tie bolt pinch area. The new tie bolts are minimum .418 on the ones that I have measured so even new tie bolts would not help in that arena. The only way three tie bolts would make a pinch fit better is if they were plated oversize and that would have to be done to even new bolts to get bigger than .418 and I don't know of an approved process for that. We could get something done like that with engineering and get an approval for that on jets but not heard of that here. But jet engines is a different world.

After all the thoughts above and the
prices below at cost discount... itvis $3472
220 times 7 each for 531211 SB required main crank bearings with pinch fit and o ring
618 times 2 each for 531212 Not SB required behind prop flange AND clamps main nose bearing front, AND pinch fit and o ringd
118 times 2 each for 537466 SB required under cam with light stress
230 times 2 each for 537465 Not SB required holds forward and rear bottom split line, same small size diameter as 537466 and each one bolt holes two engine mounts on and all engine weight and gyroscopic forces

It would not make sense only replacing the SB required bolts. If in a court of law what each bolt that is required does compared to the ones that are not required, the question would be why weren't they all replaced if I were a juror.

The answer would be it is obvious the 531212 and 537465 should be replaced as well, so I think it was salesmanship. Not based on pure safety. Sell sell sell when they were cheap. Now it's supply and demand.

Also the answer would be it's a service bulletin that if you are overhauling and want to meet Continental wants, in accordance with their overhaul manual, it would be time to see what an experienced lawyer thinks about the SB outside the overhaul manual without an AD applied.

Meanwhile, I'm not overhauling. I'm repairing with a 337. I've had everything overhauled. I sent the crank back twice because I didn't like the way they packed it and this is the best shop I've seen at machining. I send all my engine parts there. I am not replacing my hydraulic lifters because I've tested them and I don't want new machined edges cause problems compared to a known quantity where I can replace them later easily without splitting the case, and, I'm not calling it overhauled per a SB. I'm not calling it overhauled at all. And I'm not replacing these tie bolts.

$3472 goes a long way towards things I've seen more likey to cause problems. Like sending out my 10-3237 to become a 10-4895-1 and get my right exhaust/cabin heat exchanger rebuilt to new standards to ward off carbon monoxide and any left over towards adsb out.

This engine if I had not noticed a pit on the cam lobe lifter face interface would still be running really nice as it was and a Continental SB says that's OK!

[GAHorn]

There’s a huge difference in the Cessna wing attach bolts and the Beech wing attach bolts. The Beech bolts are in TENSION. And frankly, I’ve always thought that was just about the DUMBEST engineering design they could have produced. The Cessna bolts are in SHEAR.... a MUCH STRONGER method.
(And although I didn’t see the broken Beech bolt in-person I DID talk to the pilots who survived the incident. They were in downwind at Louisville when they heard a loud shotgun-like sound and their right wing began to “float”. After a few choice words they were veerrryyyyy gentle in turning final and getting onto dry land alive. It was the right, forward, lower attach bolt that snapped.)
Rather than concern with the upper Beech bolt, I am more concerned with the lower ones as they are the ones which undergo the majority of the stresses of that design. It’s true the upper “bath-tub” fittings can collect water. That’s why they have drain-holes in their design (and water/corrosion-resistant grease on the bolts, as well as an option for corrosion-resistant replacement bolts.) Pilots should include that drain-hole occasionally in their preflight inspections (but that’d require they know how to remove/reinstall the cover) and mx personnel should assure they’re open at each visit. Paint shops should be cautioned about them when they strip and paint Beechcrafts. So MANY of the BEECH airplanes have that particular design from the little Bonanza types thru the King Airs. I hate that design and have a hard time understanding why Beech has kept it alive. (Might be to avoid recognition of the previously-produced thousands of defectively-designed aircraft they’ve produced.)

The 170 strut that you described as rusted means it was a steel strut that was not properly inspected and/or maintained, and must have been on a ragwing which has very different issues than the more common streamlined, aluminum struts most Cessnas utilize. Steel struts have issues on all airplanes (The Piper Cubs lower attach ties come to mind just now.). Steel requires extra-special consideration, inspections, and mx.

[n2582d]

Mike,
I really appreciate the detailed write-up. It's been 40 years since I overhauled an O-300 in A&P school so forgive my ignorance with the following questions.

How is Continental using the term "through bolt" as listed in Table 1-C? In the generic sense of a bolt with male threads at either end that clamps the two case halves together or only with what it lists as through (or thru) bolts in the IPC? The IPC lists four "thru bolts", nine "crankcase tie bolts" and one "stud" (p/n 530950).
If the Service Bulletin (now table C-1 in the Maintenance Manual) is strictly referring to what the IPC lists as thru bolts then mandatory replacement would only apply to the two 537465 and two 537466 thru bolts. Where do you read that the seven 531211 and the two 531212 crankcase tie bolts need to be replaced in the Service Bulletin or that the two 537465 "thru bolts" do not have to be replaced? It seems logical to me that the seven crankcase tie bolts should be replaced as these would have the greatest stress on them but they are described as "tie bolts" rather than "through bolts". For those of us having a hard time following all these part numbers here is a picture. I found the IPC illustration for the location of these bolts hard to decipher. Have I depicted stud 530950 in the right position? As this bolt/stud is the only one shown to be available in .003", .006", and .009" oversize it seems to me that it is critical for case half alignment.

Click to Enlarge

Edit: It appears you are getting what is mandatory replacement from Aircraft Specialties Services. I just talked with Mark at TCM technical support and he said the bolts that need to be replaced are the cylinder hold down through bolts on either side of the crankshaft. Those would be "tie bolts" p/n 531211.