The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Superflash on 28.01. 2020 10:35
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Hey y'all. Have a conundrum on my hands. The piston set arrived today so I pulled the motor apart after doing a dry run. After splitting the cases I noticed a crack around one of the oil pump stud holes. Gave it a tap and a big chunk fell out. Now, these aren't matched cases. So...is it ok to use or should I get a new timing case....or, there's another option. One of the suppliers here has got a matched pair of std A10 cases. Just means I'll park the SF case.....
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Clean it up.
weld a lump of metal there the reface & redrill the hole.
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Yes, build up the case with weld to restore the pump mating suface, but in fact there looks to be enough material for the gasket to give an oil tight joint, but this is marginal.
You may find there is sufficient depth of metal to extend the stud hole deeper, and make a longer custom stud. Original threads... Case Thread is 1/4 Whit, nut end 1/4 Cycle. As mis -matched cases,only the drive side carries any true identity, so the basic choice is to use the matched A10 cases (easy), swap the timing side case or repair existing, both entail more work but easy success really depends on how well the castings line up, as regards sump plate, gearbox mount and cylinder base faces.
Line boring just the blind camshaft bush is the cheap way of sorting that area, then a custom timing side bush line bored to match the drive side case is the usual trick.
Swarfy.
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I had a similar issue at my sump plate. You can see a picture of the weld here:
https://www.a7a10.net/forum/index.php?topic=14370.msg119450#msg119450
Richard L.
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Would that have been caused by not using a washer on the nose of the pump?
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GB Unlikely. Accidentally dropping the case on the oil pump stud is more probable. A tight on the studs oilpump is usually down to bent or bowed studs. The result of a missing washer will distort a pump body, but not fracture a sound casting. Always the possibility of some fella forcing a stud down an oil filled blind hole, and hydraulic pressure fracturing the casting. However the stud needs to go to the bottom of the hole to get maximum support from the soft alloy case. Too short a stud puts the load just on the first few threads.
Swarfy
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Hey y'all. Have a conundrum on my hands. The piston set arrived today so I pulled the motor apart after doing a dry run. After splitting the cases I noticed a crack around one of the oil pump stud holes. Gave it a tap and a big chunk fell out. Now, these aren't matched cases. So...is it ok to use or should I get a new timing case....or, there's another option. One of the suppliers here has got a matched pair of std A10 cases. Just means I'll park the SF case.....
JB weld “plastic metal” will fix that, instead of welding, it’s amazing stuff, it looks like there is enough thread left in the case anyway, so no need to rely on a thread cut in the JB weld.
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Well I've had a good look with a torch and magnifying glass. The missing bit stopped before it reached the thread, so I'm thinking that there shouldn't be any issues with getting the stud fixed in. My only worry was the potential for oil to seep past the washer and gasket even though the top stud hole is quite a bit apart from the oil passages, (unlike the bottom stud hole which is almost in line with the oil holes). I had bought a set of pump studs with the idea of doing up an old pump that I had picked up. After reading a thread on here about the SRM pumps, I forked out the dosh and bought one of them instead of using the old one. As you know, they supply allen bolts to fix the pump in with, but I'm thinking, if I use the std studs instead, then I could build up the mating surface with some of that plastic steel that KiwiGF suggested.
Even though the cases aren't matching, they do seem to bolt up together quite well. Again, used a magnifying glass right around the seam looking for dips or bumps, and couldn't see any. The sump plate plopped straight on no problems, and the cases go together quite snuggly with a bit of encouragement with a rubber mallet...is that usual, or should they just more or less plop together as well? Cheers
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Well I've had a good look with a torch and magnifying glass. The missing bit stopped before it reached the thread, so I'm thinking that there shouldn't be any issues with getting the stud fixed in. My only worry was the potential for oil to seep past the washer and gasket even though the top stud hole is quite a bit apart from the oil passages, (unlike the bottom stud hole which is almost in line with the oil holes). I had bought a set of pump studs with the idea of doing up an old pump that I had picked up. After reading a thread on here about the SRM pumps, I forked out the dosh and bought one of them instead of using the old one. As you know, they supply allen bolts to fix the pump in with, but I'm thinking, if I use the std studs instead, then I could build up the mating surface with some of that plastic steel that KiwiGF suggested.
Even though the cases aren't matching, they do seem to bolt up together quite well. Again, used a magnifying glass right around the seam looking for dips or bumps, and couldn't see any. The sump plate plopped straight on no problems, and the cases go together quite snuggly with a bit of encouragement with a rubber mallet...is that usual, or should they just more or less plop together as well? Cheers
It’s encouraging the sump mating faces “match” but I don’t think there is any option but to check the camshaft bushes are aligned, and of course the mains. My engineer reckoned the mains generally align but not the cam shaft.
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Superflash, The thread starts at the joint face, not halfway down the hole, so looks to have been a pulled thread at some stage. The front stud is shorter.....possibly put in this hole by mistake, (maybe?) and without a full length of supporting thread the load was too much.
SRM use cap screws, but the stud arrangement is better for soft castings, as the alloy thread is undisturbed no matter how many times the pump is on and off.
If the camshaft turns freely, any cases are a good reasonable match. So try the cam first to get an idea. The cases usually require a light tap here and there to get them square to align. Camshaft binding (check its not bowed by trying it in the matched cases or turn between centres) means bushes and line boring. All three bushes...expensive, cheap way, just the one as I suggested earlier.
Swarfy
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Hi Swarfy. Well just tried putting the cam in as you suggested. Solid as a rock... not even interested in turning. I think at this stage given I've only got the drive side case that is genuine SF, I'm going to wrap it up and stash it away. As I mentioned Mike's classics have a matched pair of plunger cases so will put all the internals into them. Over time I'll revisit the whole SF thing and do the job properly. Once I've paid the credit card off... *eek* Cheers.
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the cases should come together without tapping / bashing them they just glide down the studs if they are matching cases and a hand clap on the cases seats them. matching cases that don't glide together have studs that over the years have been stressed a little and end up a tiny bit out of line.
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A couple of things to look for when chasing plunger crankcases.
If you are lucky to have a choice, go for cases from the BA engine number series. These cases have a proper crankshaft oilseal on the drive side and an oil feed from the PRV to the camshaft trough. These features were an improvement over the earlier design, but whether they make any real difference.......
Matching cases have identical numbers stamped in the crankcase halves, on the front just below the dynamo cradle. If out and about looking at cases, take the camshaft to check it turns without binding.
Swarfy.
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Hi. The ones he has are stamped ZA10 6603. Cheers
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Hi, That number dates from 1951-'52, and are the early design. They use a slightly different crankshaft primary drive sleeve, with a scroll edge. Over time whether by rationalisation, design, or substitution, early engines without a seal are found with a smooth edged drive sleeve, according to findings by Forum members, so any sleeve you have will fit.
Design and part applications for the drive sleeve, oil slinger and later oilseal are all covered extensively within previous forum posts. There is no difference in the basic crankcase castings for A7 or A10 variants.
The condition of the anti drain ball valve in the oilway between pump and timing side bush is often overlooked, as is the integrity, operation and oil tightness of the sump pick up pipe. Problems with either can only be fixed by splitting the cases, once more extensively covered on the Forum so plenty of information available to consider.
Cheers, Swarfy.
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Thanks Swarfy. After much gnashing of teeth I've come to a decision. I think the SF is a unique beast and it would be a pity to chuck in the towel. Have sourced a decent timing side engine case on fleabay for a reasonable price. Tomorrow I'll grab the last 2 cam bushes from our local supplier. Have also spoken to an engineering shop just up the road. They have all the gear to machine the cases and line bore the cam and crank bushes. I already have a new anti drain ball and spring along with a scavenger pipe. So now I'm going to have to be patient and do some heavy duty saving to pay for it all. *eek*. Watch this space. Cheers
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Next trap (in more ways than one)....The Crankshaft. Read the posts about the crank, the types, the differences and the most important single factor for good engine performance, bearing life and the abilty to ride home rather than on a tow truck, with a rod through the case.
I will step aside to allow a fanfare to sound, the curtains open, and the spotlights shine on........an important announcement from an esteemed member.
Additional... Accepted practice these days is to grind the crank main bearing journal just to clean up, rather than sticking to standard undersizes, thus increasing the number of possible crankshaft main bearing regrinds. Choose a smaller undersize solid one piece bush and fit to the case, then line bore the bush to the running clearance. All detailed on the Forum. The bush housing sometimes suffers damage and ovality, remedy here is line boring the case and a custom bush. Leakage here, between bush OD and case, obviously lowers oil pressure on the pump delivery side.
Camshaft and other simple plain Bronze bushes should be of commercially available standard types. Possibly just needing drilling an oil hole as required. Some pattern parts come with internal scroll oilways, most don't. Heat the cases, as usual practice, bushes should come out easily. Blind camshaft bush removal can be a conundrum.
Check assets and arrange finance while interest rates are low.
Cheers.
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I think I have a matched set of BA10 cases stored away along with a spare set of Super Flash cases. The big problem is the cost shipping from the U.S.
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Next trap (in more ways than one)....The Crankshaft. Read the posts about the crank, the types, the differences and the most important single factor for good engine performance, bearing life and the abilty to ride home rather than on a tow truck, with a rod through the case.
I will step aside to allow a fanfare to sound, the curtains open, and the spotlights shine on........an important announcement from an esteemed member.
[Cough] I think that may be a queue for me to repeat the mantra "Clean the sludge-trap!". *smile*
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Yes, GB, Thanks once more for drawing attention to our old friend the sludge trap. Right on cue with a timely reminder.
To anyone doing a rebuild.
Your friendly crank grinder will not mention the vital attention that should be paid to the sludge trap. This is located between the big end journals, and is sealed at each end by screw-in plugs, and on later cranks also located by a radial bolt. So get those plugs out and clean away the accumulated mix of carbonised oil, sludge and bearing metal from previous mishaps. Early crank has just a plain drilled oilway, later crank has a removable tube, which may require violence to extract. All the replacement parts needed are available.
The forum comes to your aid showing how to do it, with detailed and worked examples together with vivid pictures of what lurks within. Neglecting this has brought many an owner to tears, as their newly rebuilt engine tightens, locks and sometimes goes bang within a few hundred yards of the first triumphant (until then) test run. You get the crank done again, and guess what? So, no if's, but's or excuses. Clean out that trap. Thereafter regular oil changes, plus fitting a modern filter in the return line to the tank to keep the oil clean, will give long engine life.
Swarfy.
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Hi all. Well I found a timing case that's in pretty decent condition other than the dirt/oxidisation etc....
Now the bloke I bought it off claimed it was an A10 and looking at the photo's this appeared to be the case (pun intended...).
It arrived today, and when I placed it next to the broken case that came as part of the motor, there were differences. So am wondering you gents can identify why the changes in the castings, and will it make any difference?
First difference is what looks like a stud tube under where the magneto sits, but above the gearbox mount.
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Hmmm. still trying perfect the art of attachments here...
So, 2nd difference is inside the timing chest itself. The new one has a raised bump running horizontally across the top of the timing bush hole more or less from one side to the other, whereas the old one hasn't. I'm wondering if the new case is actually older than the one I had. Case number on the new one is 178, the original case was 231.
Had a good long chat with the guy who is currently boring the cylinders, and he has agreed to machine the cases and line bore the crank and cam bushes.
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And my favourite wheel barrow to push
Whenever a crank is out get it CARBO-NITRIDED.
An by preference find some one who does it in an ammonia furnace.
Note I did bot sat Nitrided
Note I did not Carbonised.
The process goes under the trade name of TuffCoat or Tuffride.
If the heat treater starts talking about hardness increases he is talking about the wrong process.
Basically it introduces both Carbon atoms and Nitrogen atoms into the crystal structure, but not enough to chemically react as would be the case with case hardening.
What the process does is substantially toughen the crank and makes it very hard for cracks to propergate to a size where they are big enough to cause failure.
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Amazingly enough, we have a nitriding oven at work for doing aluminium extrusion dies. It's used for hardening the die bearings where the aluminium flows over. Same thing you're talking about? With regards to a few of the earlier posts, yes, I have taken the sludge trap plugs out and cleaning the whole thing out. Have new plugs, and am wondering if loctite will do rather than swinging a hammer and centre punch? Cheers
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Yeh, me again... *smile* I think I've answered my own question. Looks like the "new" timing case is a pre BA10 model. So assuming the engineer can match them etc, will this case go together with the SF drive side case? Cheers.
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Whenever a crank is out get it CARBO-NITRIDED.
.......
Basically it introduces both Carbon atoms and Nitrogen atoms into the crystal structure, but not enough to chemically react as would be the case with case hardening.
What the process does is substantially toughen the crank and makes it very hard for cracks to propergate to a size where they are big enough to cause failure.
Well , that is a piece of useful info! Thanks *good3*
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Looks like you struck lucky.
The basic casting is the same, so should fit. The locating dowel positions the web above the camshaft trough. This narrow drilling is the breather, running across the engine, exits above the gearbox sprocket.
Have a look in the PRV cavity. Early case has a drilling leading DOWN to exit below the oilpump. Later case drilling goes UP, to connect with a gallery running back, over the timing bush area (the bump) and up to the camshaft trough. There is a small drilling visible to feed oil to the timing gears. Often neglected, worth cleaning out. Originally this later casting could be from a BA Series motor. So for once, you done good.
Look carefully at the parts. Some have a date stamp below the dynamo cradle, and near/under the primary chain tensioner. The actual casting number is not the part number, as the same casting may be machined in different ways as engine development proceeded. Also an "assembly" complete with fittings eg timing side crankcase with pick up pipe and bushes, will have a part number sometimes closely, but not necessarily, related to the casting number.
Best buy a Lottery ticket while you have a winning streak.
Swarfy.
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The case type with the raised bump and feed to the cam trough was introduced after engine ZA10 4712, which is about September/October 1950. The first ones after the change did not have the cam trough drilling plugged at the crankcase joint and some leaks happened so the recessed plug at the end of the drilling was introduced.
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BSA55 - nitriding and tuftriding are two different processes. Most steel / iron can be tuftrided but only a few nitrided.
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Which is why I emphasied CARBO _ Niriding.
Strait nitriding will add some toughness but is basically an alternative to case hardening.
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BSA 54 – apologies if it seemed I was stepping on your toes, but I do get concerned that queries about nitriding BSA cranks keeps coming up, when that would not be a good choice. You did indeed state ‘not nitriding’ but I felt that using the term carbo-nitriding was possibly unfortunate as it could plant the ‘nitriding’ thought back into some peoples’ minds.
In that regard I was merely raising the fact tufftriding and nitriding are different, without going into all the details. Sure, the effects are very similar (fatigue resistance etc) but there are critical differences as you are aware. It’s bad enough that even some firms advertising such services don’t know what they’re talking about - I saw one stating that ‘nitriding, unlike tufftriding, is very shallow and if not careful could be polished out’! They went on to state that tufftriding causes less distortion. Best avoid that firm methinks.
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RD,
Never worry about challenging anything that I post.
We have now had some chit chat and hopefully enough too & fro to make it stick in peoples mints.
It was easy 20 years ago when you could just say Tuffride or tuffcoat & every one knew what you were reffering to but now days those prpritory names are fairly meaningless.
A member had his crank done decades ago & when doing a major rebuild was horrified when the grinder sent it back with full circumference deep cracks around all journals.
But the crank was running strong & true & he was running 10.5:1's
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Hi all. I've cleaned up the new timing case and discovered something that doesn't make a whole lot of sense. I thought the plunger motors stopped being made in 1957. Yet I've found a date stamp saying 21.5.61....? Had a good look and it's definitely 61.
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What does the date stamp on the drive side say? Should be close to the top of the chain adjuster
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22.5.52. Cheers
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G'Day.
It may have been part of a Service Exchange Unit. Page 37 of the 49-53 parts Catalogue has a note that a damaged crankcase half could be replaced with a new casting, and by all accounts factory matched to the existing used good half. But from experience, it is the timing side that usually survives, a rod through the drive side case being the usual malady.
So that's a possibility, but halfway round the world hardly likely, however the stamp font used looks BSA factory style. Maybe they just kept making spasmodic batches?
Date on the Drive Side Case is from a time of change and case may have the early crankshaft oil slinger or the later proper oilseal. The only difference is the size of the hole, early case can be opened up to take a seal. If the drive side outer race is still in place, and no seal fitted, the slinger should be found still in place between race and case. I mentioned this difference in design with an earlier post.
Cheers
Swarfy.