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> 'C' Series Engine Rebuild, Cyl.Head
Fred Oldham
post 3 Sep 2015, 22:02
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I decided to start a new thread dedicated to the rebuilding of my A90 engine. So, after a lot of delays and distractions, I have finally started to put it back together.

Today I started cleaning the cyl. head. I blasted out all the 'holes' to clear any loose debris with the air-line. Then I got ready to grind the valves in. First thing I noticed with all the clean shiny parts was that the inlet valves were shrouded by the side of the combustion chamber. I looked at the spare head that came with the new car and that had a good even gap all round. Close examination of my head showed that the chamber was cut away below the head face leaving an overhang above. I got the Dremel-a-like on the job and removed this lip and smoothed the edge of the chamber. This should improve the gas flow and let the engine breathe. I then lightly tickled the edge of the combustion chamber all the way around to take off the sharp edge left by the head-skimming. The valve grinding should not be too tedious with everything freshly machined. It's been years since I last did a head job. There was a tool you could buy that fitted an electric drill and gave an oscillating action for valve grinding. I don't plan on making a habit of this, so I'll get by with the 'swizzle stick'.
I will sort some pictures of the story so far.
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Fred Oldham
post 23 Nov 2015, 16:50
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I forgot that I have started a new thread for the rebuild. So, a quick update:-

Washed out all the oilways in the block and the crank with long thin brushes and diesel. Then blew them through with the airline.
Bolted on the engine end-plates.
Fitted the new Healey, fast-road cam, liberally plastering the lobes with assembly goo.
Fitted the re-ground crank with new main bearing shells and thrust bearings.
Fitted the flywheel. This will fit any way, but there is a ref. mark, presumably to do with balance.
Assembled the new timing gears, chain and refitted the cleaned tensioner. On this engine this is hydraulically operated by oil pressure, rather than just a spring.
Assembled the pistons and con-rods. Then did it again, because I had mis-interpreted the direction of the off-set!
Fitted the piston rings. Five on these pistons.
Inserted the oil pump drive shaft and discovered that it didn't engage with the cam.
Measured the gear diameters of the oil pump and distributor drives on the old cam. Both the same at 44mm.
Looking at the new one, the pump gear looked smaller. Rang Austin Healey Spares and explained the problem. They checked the cam and said that the pump gear is 39mm. So, I have ordered a new shaft with a larger gear that is a standard Healey part. Why the difference? they don't know either.
The new shaft is £80+vat. It had better fit.

I won't do anything else until the cam / pump thing is resolved.
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Danny
post 24 Nov 2015, 01:44
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QUOTE
Why the difference?


Simply that there were changes to cam and distributor drive early in the 2.6 C series' life...probably before they were used in Healeys.

Danny

I'll just amend the above to say that the cam and drive change was more of a later change to the 2.6 about 1956 I should think. Whether the early cams were in the first big Healeys I'm not sure but Healey specialists notoriously have little knowledge of the 2.6. Danny

EDIT to say distributor drive should be oil pump...

Danny

This post has been edited by Danny: 28 Nov 2015, 01:49
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Fred Oldham
post 24 Nov 2015, 09:30
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Thanks for that Danny. The shaft is carried at the cam end by a machined hole in the block. The block is also machined out to give a pocket that surrounds the gear. AH Spares assure me that with the thick thrust washer and the stepped gear, the new shaft will not foul the sides of this pocket. I just hope they are right.
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Fred Oldham
post 27 Nov 2015, 15:34
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Well, after much assembling and disassembling and a lot of measuring, I have come to the reluctant conclusion that the machined pocket is not wide enough to clear the larger shaft gear. This is what is stopping the shaft from going all the way down and preventing the oil pump from fitting properly.
The pocket is going to have to be machined or ground out. This means stripping the engine again, one, for the space and two to allow the swarf and debris to be washed out.
What a swine !! I really don't need this, but I don't think I have a choice. Well wrapped-up, I think the crank can stay in, but the pistons, cam and timing gear will have to come off.

Any bright and constructive ideas welcome.
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enigmas
post 27 Nov 2015, 22:33
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Fred if I recall correctly the camshaft you're fitting is not the one that you removed from the block but an alternative one from an Austin Healey specialist. Can't you simply return the camshaft (as not fit for service...for your model engine...i.e., refund) and have your original camshaft lobe profiles reground by a camshaft specialist. (Nothing new in this procedure. I've probably had 3 or 4 camshafts done this way by reputable companies.) They carry all sorts of master profiles and would easily find one that will accommodate your requirements. They don't build up the lobe by welding but regrind the original lobe removing material from the heel to gain extra lift. The camshaft is then re-hardened. Since your engine has adjustable tappets there's no issue with getting the correct clearances. I've done this with several V8s (hydraulic self adjusting lifters) and there's never been an issue. In many ways it's better on an old engine with an unknown history as the block has often been decked and the head surfaced...reducing operating clearances. This is probably more an issue with engines using non adjustable hydraulic lifters that rely on OEM factory tolerances. A bit of a ramble, but I hope you get the gist of it!

PS. Don't forget to have your lifters refaced by the camshaft company or you'll chop out your new camshaft and run it in with plenty of camshaft lube and an oil with the correct quantities of ZDDP ((Penrite)

This post has been edited by enigmas: 27 Nov 2015, 22:38
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Danny
post 28 Nov 2015, 01:45
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I am surprised that this is the case but can't throw any light on it unless it's to do with being an early 2.6 block..but as I said earlier the 2.6 6/90 has used the old & new cam & drive with, as far as I can tell, no alteration to the block.

I was going to suggest more or less as Vince has ie get the dosh back on the cam... but if your original isn't damaged (you said the lifters/tappets are OK?) just bung it back in it'll go lovely with the standard grind.

Roadability might be better served with diff ratio and advance curve work.

I've amended my post #3 (again) as I wrote dizzie drive instead of oil pump (IMG:style_emoticons/default/wacko.gif)

Danny
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Fred Oldham
post 28 Nov 2015, 13:02
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Thanks for your input Danny, Vince. Problem is, even I refitted the original cam without any mods, I would still have strip the engine and take the block for reworking because new camshaft bearings were fitted and reamed to suit the new cam. They won't be right for the old one in all probability. If I am a going to that trouble I might as well mod the block to suit the new bits. At least by doing it myself I only lose time and not cash. I'm sure I don't have to tell you that a full rebuild costs serious money.
As to parts suppliers, I think it's fair to say that mine is the earliest engine to get this treatment and they have no experience of this problem before. I emailed some pictures to show the difference, but it's difficult to see the size difference just looking into the bowels of the engine block.
A chap on the Austin website suggested chain drilling all round the 'pocket' and chipping the pieces out. With the crank well wrapped up and everywhere else stuffed with rags to catch the drillings, a good flush-out afterwards should see things ok. All the debris should be relatively large and readily contained, unlike grinding.
Me thinks it is bite the bullet time.
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enigmas
post 28 Nov 2015, 19:37
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Hi Fred, I've never heard of any one reaming cam bearings to size. They are usually a standard size and a press fit into the block. They are also tapered down in size front to rear. If you have a set of verniers it's a quick process to check the journals of one camshaft against the other for commonality of journal size.
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Fred Oldham
post 28 Nov 2015, 23:42
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All I can tell you is that the bearings were sized to match the cam. Anyway, the engine is now stripped and the pocket is going to be opened up to accept the new cam and shaft. Nuisance it may be, but I won't be beaten.
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Danny
post 29 Nov 2015, 02:33
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Here's the (very grubby) way BMC/Nuffield claim that cam bearings should be fitted to the C Series.


Attached File  cam.jpg ( 1.06MB ) Number of downloads: 0


And they used this tackle to do it with.

Attached File  reamer.jpg ( 630.31K ) Number of downloads: 0




Danny

This post has been edited by Danny: 29 Nov 2015, 02:58
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enigmas
post 29 Nov 2015, 10:14
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Well that makes for a lot of extra work Danny...but I assume (perhaps wrongly) that the journals are all standardized for size on the camshafts. Has anyone measured the journal sizes for comparison on these engines?
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Fred Oldham
post 29 Nov 2015, 13:25
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Thanks for the pictures Danny, that's exactly as per my workshop manual and I believe exactly what the reconditioners did with my engine block. I supplied the cam so they could check and match the bearing sizes.

I have ordered some rotary files ( burrs ) to carefully open up the block. The engine is stripped and ready. Familiarity and freshly fitted parts meant that it came apart many times quicker than the first time around.
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Danny
post 30 Nov 2015, 13:30
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I don't know this for a fact but I am assuming that the reaming of the cam bearings is not to suit each individual cam but rather to make sure they are to size and inline after fitting.... (Do the bearings go out of round after fitting?)

The reason I say this is that many moons ago I acquired a NOS 3 litre C series block. I didn't build it up untill many years later (1997) and was uncertain what to do about the cam/bearing situation. The new cam shot wasn't on the board, so I selected a used one to have reground...long story short it fitted perfectly and has been running for 18 odd years with no problem.

So it seems that a replacement block's cam bearings were reamed in the factory with no regard to the particular cam that was going to be used.

Danny
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enigmas
post 30 Nov 2015, 13:58
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Line boring an engine block is the usual procedure when some sort of distortion has taken place or when first establishing correct alignment on a fresh block. New or green blocks can shift so an older 'seasoned' block is often more stable. Blocks that have been given time to stabilise after coming from the foundry are also more likely to remain true after machining tasks have been completed. Hence old blocks that have seen a lifetimes service are very stable.

Reaming cam bearings on these blocks may be more to do with the the quality of finish of the replacement bearings than with any variations in journal sizes, as these are usually standardized in mass produced engines. Swapping camshafts is generally a straight forward process. So fitting an alternate camshaft as you did Danny, should be an afternoons work.

I also imagine the reaming tool's cutters for the various journals are standardized so that there are no variations in clearances. This would have been especially important during initial assembly at the factory.

This post has been edited by enigmas: 30 Nov 2015, 14:00
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Fred Oldham
post 1 Dec 2015, 13:30
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[img]http://https://www.flickr.com/gp/135282773@N08/61JJ8u[/

If it works, this is the 'pocket' that needs opening up.
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Fred Oldham
post 1 Dec 2015, 14:05
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So much for that idea. Anybody want to buy an iPad? Poxy object is the most frustrating user unfriendly gadget I've ever seen.
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enigmas
post 1 Dec 2015, 20:48
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It's not the IPad Fred, the forum doesn't like the [img] tags.


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Penguin45
post 1 Dec 2015, 23:49
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Yes. Had a little look - not sure that Fred's picked up the entire Flickr link. The Photobucket ones work OK and it's the same basic system - copy and paste.

p45.
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Fred Oldham
post 2 Dec 2015, 09:09
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Well I've decided to give Photobucket a try sometime. Meanwhile I'll go back to loading my pictures onto the laptop. Having said that, since I was persuaded to upgrade to Windows 10, the picture file resizing facility has vanished. I am getting heartily sick of technology lately. Grumpy old man, me? You bl*#%y bet I am.
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