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Phoenix crank location - John3528 - 27-02-2020
After 20 years without an Austin Seven, I recently acquired a long-mothballed 1932 3-speed Tourer with little known history. Having removed the engine to fix a clutch issue, to my amazement I discovered not only that it has a Phoenix crank but also that the engine has done virtually no work since (perhaps because of the clutch problems). Needless to say, I am delighted!
Then I noticed that the crank seems to be positioned too far back in the crankcase with two of the little ends only a fag paper away from the rear gudgeon pin bosses in their respective pistons and the other two little ends also heavily biassed towards the rear of the space between their gudgeon pin bosses.
From what I can deduce of the car's history, I guess that the crank was probably fitted around 2005. Is anyone aware of any possible dimensional problems with Phoenix cranks from that period? Could it be that the front main bearing journal should have been machined another 1/16" or so further back to allow the crank to sit further forward?
If is not the crank that is at fault, maybe it is the crankcase which has had the usual lip replacement repair carried out but possibly not in exactly the right place. But the timing gears are perfectly in alignment which suggests that the lip is in the right place.
I have one thing left to try and that is to rotate the conrods 180 degrees to see if the little end moves across the gudgeon pin towards the other boss. That would mean of course that the white metalling on the edges of the big end has not been machined symetrically.
Whatever the final outcome, I have two further questions:
First, is there any reason why I should not put a 1/16' shim behind the outer race of the rear front bearing to move the crank forward, so long as I take 1/16" off the back face of the crankshaft gear?
Second, how important is it that the little end is centred between the piston's gudgeon pin bosses?
Any thoughts or suggestions will be most gratefully received.
RE: Phoenix crank location - AustinWood - 27-02-2020
Two widths of front main bearing were fitted to The A7 engine. Fitting the narrower bearings in the 'wider' crankcase needs spacers to take up the gap. It could be that your engine has these spacers but fitted the wrong side of the bearings.
RE: Phoenix crank location - Chris KC - 27-02-2020
John,
There was an issue on early Phoenix cranks that the front web touched the lip - also they were very close to the centre cam web. This might have some bearing on your situation.
I would certainly urge you to check the front lip position is correct, irrespective of the gear mesh (which can be fudged).
In particular I would check clearances between big ends & cam lobes.
I think shimming the front bearing into the right position is a good way to go, but if it's moving forward you might do better to have the thing machined to the right depth and have done with it. I don't think I'd remove material from the gears though.
As for running with an offset, yes there is some precedent e.g. Reliant conversion and I can dig out the numbers for you if of interest. However better to sort it out if you can.
RE: Phoenix crank location - John3528 - 27-02-2020
Thank you so much for these two very prompt and most helpful replies.
Jim's brilliant thought of different bearing widths and the possibility of a shim in the wrong place had never occurred to me (despite lying awake at night for hours considering the problem from all angles!).
However, Chris' mention of the issue with early Phoenix cranks may indeed be what I am up against. I have had a quick look and the front web is so close to the new front lip that I doubt now that I would be able to move the crank forward even 1/16". Also, I can see that someone has removed some metal from the centre cam web which suggests that there was a clearance problem in that area too. My dream discovery of a Phoenix crank is fast becoming a nightmare!
I reckon that this must be an early crank and I may have to live with these issues, so long as there is indeed at least a fag paper's clearance between little ends and gudgeon pin bosses. If there isn't, I should have thought that I could safely remove enough metal from the two bosses at risk to provide a definite clearance without compromising the pistons' strength.
This in turn raises another question. Should I now drill the gudgeon pin bosses from below, as seems to have been done with earlier pistons, to improve gudgeon pin lubrication in case not enough oil is reaching the pins because of the small gap between little end and boss?
What a wonderful source of invaluable information Forums like this are.
Thank you both again,
John.
RE: Phoenix crank location - Chris KC - 27-02-2020
As nightmares go John it could be worse! I would persevere and try to get it to the correct position - must be someone here who has faced the same issue.
RE: Phoenix crank location - Tony Betts - 27-02-2020
hi john,
if the job is done right, you wont need shims. and will end up with a very nice engine.
ive seen plenty of home done flange repaires, were the old flange is NOT machined off. just the lip brocken out fully, and a new steel plate fitted. so the bearing can be pushed back further into the flange.
you should be able to measure the depth to the new flange with a vernier, and im sure someone will come up on here with the original depths for front bearings. from memory i have 1.611 thou full width bearing engines. and 1.555 for narrow bearing engines. BUT PLEASE CHECK.
turning the rods is a good way of checking white metal, like aways there are plenty who do this work, not so many who get it right.
kc is right pheonix cranks had early fitting problems, as far as i recall the problem with the web hitting front flange would have been corrected well before 1990. and is an easy fix, (grind and re-ballance). the centre hitting the cam however, only got worse. and wasnt corrected until 10 years ago. although that centre cutout is still out of shape today.
tony.
RE: Phoenix crank location - John Cornforth - 27-02-2020
Hi John
Back in winter 2003/2004 as a newcomer to A7s and following a broken crank in my 3 bearing engine, I built a replacement 2 bearing engine from all sorts of new and old parts, including a 1935 crankcase and a nice new Phoenix crank. One snapped crank was enough for me. I remember being a bit surprised that the con rods were rather offset sideways relative to the pistons, but as there was nothing I could do to adjust this and the engine seemed to turn over freely I put up with it.
To digress a bit, I had already been through the trauma of a crank assembly (no rods yet) which resulted in a crank very stiff to turn. This turned out to be due to a massive preload of about 12 thou in the front main. After learning belatedly about matched and unmatched bearings, I fashioned a suitable inner race shim which reduced the preload to a more reasonable 3 thou and things freed off remarkably.
This engine (my first and only Seven engine build) has now completed over 10,000 trouble-free miles in 16 years. So I would be inclined to leave yours alone unless of course you need to dismantle it for some other reason.
Cheers, John.
RE: Phoenix crank location - Chris KC - 27-02-2020
I'm working from memory here John but a Reliant crankshaft has big ends displaced 7/32" from the (A7) bore centerline; this is partly compensated by 0.18" offset built into the con rod; but still leaves the small end offset 39 thou from the bore centerline. You can certainly run a touring car in this condition without issues.
Tony is right, a bit of (careful!) work with a grinder and a re-balance would sort the issue out; but I like the idea of re-thinking the lip better. Most are probably thicker than necessary (check out Jack French's piece in the 750 companion) and could stand a bit of chamfering or trimming. Having one thing in the wrong place can so easily have unforeseen knock-on effects for other things.
RE: Phoenix crank location - Alan - 27-02-2020
It’s not a big deal. The way forward has been described. Only thing to add is I wouldn’t worry too much about disturbing the balance. Typically early Phoenix were not well balanced as supplied. Static only, which isn’t enough. First thing I’d do is sort out the clearances and then have it properly balanced on a dynamic machine.
RE: Phoenix crank location - John3528 - 27-02-2020
This has been a most enlightening day; thank you all so much for taking the trouble to pass on your thoughts and experiences. I now feel in possession of enough knowledge to press ahead and sort the problem. Obviously, I have got to completely strip everything down, make some measurements and go from there.
You might be interested to know that I can now see that someone has already taken an angle grinder to the crank to make it clear the front lip repair plate. It wasn't obvious at first but now I know what to look for and where to look! Balancing is therefore a must.
Also, for some reason, No.1 rod had been installed the wrong way round from all the others with the little end bolt head facing the nearside of the engine along with the split in the piston skirt. I reversed the rod to see what would happen and was pleased to find that it had moved the little end probably a 1/16" away from the gudgeon pin boss. So that is an encouraging result and only requires me now to reverse the piston on the rod.
Should I make any further unexpected discoveries, please bear with me if I raise them.
In the meantime, thank you all again,
John.