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Infamy Infamy they've got it in for me!
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jensen541



Joined: 03 Dec 2007
Posts: 56

PostPosted: Sat Jan 31, 2009 5:02 pm    Post subject: Infamy Infamy they've got it in for me! Reply with quote

As you might have read in other threads I've had some small problems with my Jensen engine, not as much as Peter but I'm getting there!

I'd earmarked today to dip the block in Deox-C and to protect the bores as a precaution using petroleum jelly. You can see from the attached picture that as I was doing this I could feel something sharp and on inspection could see that part of the liner and casting on two pots had at some stage broken away. The picture is not clear but there looks to be a small piece more ready to break away on one of the pots too!
I have measured the bores previously and they have had a rebore at some time hence the +.030" piston (to which my new one's arrived yesterday). The maximum allowed is +.040".

Where to go from here.

Option 1. Reline this block. Would the cast iron around where the pieces have broken away need repairing. I should imagine so.

Option 2. I have a spare engine. Quickly removing the head today shows that the pistons are standard and a rudimentary check with a vernier confirms no rebore. Alas the head on this one has been welded or brazed.

I have just bought new shells which may fit and new pistons that wont (without a rebore). This just gets better and better.

Advice and opinions gratefully accepted please.

Brian


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peter scott



Joined: 18 Dec 2007
Posts: 6221
Location: Edinburgh

PostPosted: Sat Jan 31, 2009 5:41 pm    Post subject: Reply with quote

Hi Brian,

Sorry to hear of your further woes. Your situation with your spare engine and its different sizes sounds horribly familiar.

The chunks out of your cylinder skirts look kind of like the con rods managed to hit them. Can you see any evidence of contact on the other bores? If this is the explanation then it is a bit odd that there aren't "official"
cut-outs for clearance. I suppose that it's possible that very slack bearings could have permitted contact in the past. Assuming your rings don't have to pass over the broken parts in their normal travel then I'd be inclined to ignore the problem.

Peter
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jensen541



Joined: 03 Dec 2007
Posts: 56

PostPosted: Sat Jan 31, 2009 6:37 pm    Post subject: Reply with quote

Thanks for the prompt reply Peter.

I cant see any other problems with the other pots.

Measuring up I reckon the bottom ring will be between .250" and .375" above the damage. Seems pretty close to me as thats measuring to the top of the oil ring. Now here's the rub. The piston's I took out didn't have the very bottom fifth oil ring which the new ones received yesterday did!

Brian
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47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Sat Jan 31, 2009 6:52 pm    Post subject: Reply with quote

Brian

I would agree with Peter in that there has been contact with the con-rods. There is an obvious relief in the block to allow for con-rod travel. The fact that the other bores are undamaged indicates that the overtravel into the relief must be quite small. Have you checked the rods for contact damage? I would be inclined to grind the other liners back at the relief to allow for the rods. As for the lower oil ring, on older engine I think these were designed in to combat excessive oil consumption. Personally i would leave them out.

Art
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peter scott



Joined: 18 Dec 2007
Posts: 6221
Location: Edinburgh

PostPosted: Sat Jan 31, 2009 6:55 pm    Post subject: Reply with quote

Hi Brian,

The sectioned drawing I have for your engine doesn't show a skirt ring but I don't think there will be a problem in having one. 0.25" sounds a fair distance from the damage. Can you see any evidence of collision on the shanks of the con rods that correspond to the broken bores?

If you can confirm that the rods caused the damage and that with your new bearings there is no possibility of further collisions then I can't see a problem with using your block.

Peter
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jensen541



Joined: 03 Dec 2007
Posts: 56

PostPosted: Sat Jan 31, 2009 8:22 pm    Post subject: Reply with quote

Thanks fellas

I was certain and I've just double checked (boy it's cold out there) that there was no damage to any of the conrods. Small nicks and dents that are probably more to do with the casting process than anything.

What is your reference for the sectional drawing Peter? All I have is the Austin Sheerline service manual. That too doesn't show the skirt ring.
So leaving it off, as before, would leave the bottom oil ring miles away from the damage. But I am tempted to use the skirt rings.

I am certainly inclined to tidy up the jagged edges of the damage and grinding a similar relief away from the others sounds like a good idea.

Think you might have talked me into keep on keeping on!

Brian
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47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Sat Jan 31, 2009 9:34 pm    Post subject: Reply with quote

Brian,

I'm being a bit pedantic here but the con-rods are drop forged. There shouldn't be any nicks or dents as these would cause stress areas. Nicks and dents suggest to me damage and I would be inclined to remove any sharp areas with a smooth file.

ArtBrian

I would agree with Peter in that there has been contact with the con-rods. There is an obvious relief in the block to allow for con-rod travel. The fact that the other bores are undamaged indicates that the overtravel into the relief must be quite small. Have you checked the rods for contact damage? I would be inclined to grind the other liners back at the relief to allow for the rods. As for the lower oil ring, on older engine I think these were designed in to combat excessive oil consumption. Personally I would leave them out.

Art
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pigtin



Joined: 23 Nov 2007
Posts: 1882
Location: Herne Bay

PostPosted: Sat Jan 31, 2009 9:35 pm    Post subject: Reply with quote

Ran my brothers BSA A10 for ages with a larger lump out of the skirt, never gave any sort of trouble. Slipper pistons work after all. Wink
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47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Sat Jan 31, 2009 9:38 pm    Post subject: Reply with quote

Brian,

I'm being a bit pedantic here but the con-rods are drop forged. There shouldn't be any nicks or dents as these would cause stress areas. Nicks and dents suggest to me damage and I would be inclined to remove any sharp areas with a smooth file.

Art
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jensen541



Joined: 03 Dec 2007
Posts: 56

PostPosted: Sat Jan 31, 2009 10:33 pm    Post subject: Reply with quote

Art
Not pedantic at all. Of course you are quite right drop forged not cast and I should have known better Embarassed

If you look on my other thread 'stuck' you can see the rods assembled I have already removed sharp edges from around the big end. Before I attach the new pistons I'll fettle all the rods too.

Ding!!
I've just had a thought. When I removed cleaned the pistons All the rods and caps are marked 1/1, 2/2 etc and also had random numbers stamped on each ie. 442/442 and 132/132 etc
BUT the last two were wrong which were 5/6 and 6/5 also there random numbers were wrong. In other words the wrong caps were on the the wrong rods. I have now put them right ie 5/5 and 6/6 and the random numbers now match. The only explanation I could think of was the 6 on the cap was not stamped squarely and could have possibly been misread as a 5. That doesn't explain the random numbers being wrong though. Now 5 and 6 rods ran in the damaged pots in question.

Would any misalignment of rod and cap like this cause the damage? Surely it would have to be a large error or they run very close to the skirt normally.

Pigtin
Cheers mate feeling better all ready!

Brian
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47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Sat Jan 31, 2009 11:39 pm    Post subject: Reply with quote

Brian,

Try 'miss fitting' the big end caps and feel the joint with your finger. There should be no discernable ridge. I was thinking that perhaps the liners were inserted at different depths, 5 & 6 being deeper than the others thus allowing contact with the con-rods. The fact remains that there is a relief in the block casting there for a reason.

Art
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jensen541



Joined: 03 Dec 2007
Posts: 56

PostPosted: Sun Feb 01, 2009 5:36 pm    Post subject: Reply with quote

Art

Ok I have 'miss fitted' the caps and rods as you suggested on one there seems to be no difference and the another a very small ridge. I might stand corrected here but I can't see how that would make much difference.
The liner length theory seems a reasonable explanation but all the liners seem to be the same length so one would expect damage to them all.

It's rather academic really now I suppose,the damage has already happened. I'll tidy up the ragged edges and maybe grind back the others and check carefully when the piston are back on the crankshaft.

Brian
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47p2



Joined: 24 Nov 2007
Posts: 2002
Location: Glasgow

PostPosted: Sun Feb 01, 2009 5:52 pm    Post subject: Reply with quote

When conrods are made at the factory they are bored out as a single item, ie. the endcap is in place on the conrod when it is being bored, this means that every single conrod is matched only to the conrod it was made with.
If the caps get mixed up it will not be the correct fit when the shells are fitted to the crankshaft and the caps tightened. they could be either too loose or too tight, and we are talking only fractions of a thou. Can you look at the machine markings inside the endcaps and conrods and match them that way as they should have corresponding machine markings per conrod and endcap.

It could be that someone has already bodged the endcaps and had to fit one from another engine....
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47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Sun Feb 01, 2009 6:33 pm    Post subject: Reply with quote

Brian,

The small ridge you feel is the amount that the bearing shell would be offset from 'true'. As John says they are machined as a pair and should not have been mixed. As a matter of interest, what were the shells that came out of these two con-rods like (condition-wise). If you felt a ridge I would have expected some wear where they join. As you say it's all academeic now that you have corrected it.

Art
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jensen541



Joined: 03 Dec 2007
Posts: 56

PostPosted: Sun Feb 01, 2009 6:36 pm    Post subject: Reply with quote

Quote:
It could be that someone has already bodged the endcaps and had to fit one from another engine....


Now that seems to be a sound explanation. I know the block was rebored in the early 80's and not run hardly at all since Maybe on rebuilding something happened that crashed the skirts!?
I understand the manufacturing process and have checked the machine marks in the conrods and there corresponding endcaps. There is certainly a match up inside the bores and the chamfered edges. Some tool marks are clearly visible.
Regarding the manufacturers marks, my only concern would be number 6. The endcap is clearly stamped 6 on a ground section and stamped alongside into the forging is 04, which is a random number. The corresponding conrod has stamped what looks like 6 but has not been stamped squarely BUT the random number is the same 04. Both halves appear to have matching tooling marks. I am reasonably confident that these are correct now. Whether they are the original ones remains a mystery.

Yes I've just looked at the shells again although I'm not sure which are which, four of them have scored to my mind unacceptably.

Brian
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