Joined: 18 Dec 2007 Posts: 2935 Location: Edinburgh
Posted: Wed Jan 07, 2009 1:25 pm Post subject:
Oh dear! I tried altering the timing of the Mark V camshaft in the Lotus Engineering simulation and if I advance the overall timing from 10,50,50,10 to 20,40,60,0 I get a small increase in torque.
Now should I reassemble the engine with the revised timing?
Joined: 18 Dec 2007 Posts: 2935 Location: Edinburgh
Posted: Thu Jan 29, 2009 8:25 pm Post subject:
I think the last thing I reported on was stripping out the dural rods from the old engine so that I could rebuild using its crankcase but with shaft and rods from the new engine. I also intended to use the cylinder head from the new engine.
The rod swap went without incident and unusually for me, I managed this without breaking any rings. Not easy as the +60 thou pistons don't easily get past the main bearing housings without coaxing the rings over an obstacle course.
Here all the nice steel rods are in place and showing off half my new bearing shells.
This crankcase is designed to use a flanged rear main bearing whereas the later engines use separate thrust washers, but there is no provision for retaining these so to allow me to use the later crank and bearings I've
drilled into the rear main bearing cap and inserted roll pins and a further one in the upper part of the housing. Although not shown here,I had to cut newspigot grooves for the rear main shells.
There is not enough metal to do the same on the inside so it has to rely simply on the lower thrust washer. Not as bad as it seems as the only real thrust is on the other side due to clutch disengagement.
Thanks again to Ed, my Australian mentor for suggesting the adaption.
And here all the bearings have been fitted and oil pump and end plates re-installed.
After fitting the sump I then sat the engine vertical again and took off the old cylinder head. Fortunately this revealed (as expected) a much happier looking top deck, free from horrible inserts and cracks.
The new cylinder head appeared to be in good condition so I gave its valves a light grind in and cleaned it up prior to fitting. I had one or two Corrujoint head gaskets (These are a single sheet of copper with embossed rings around the aperatures that get compressed almost flat when tightened down.) and selected the best one. I fitted it before lunch and was slightly puzzled by a mismatch between gasket and a couple of water passges. Anyway, I tightened it down and went for lunch. Then sitting there looking at my engine photos a horrible memory came back to me.
The last time I had fitted the head I had made the same mistake. The gasket is almost symetrical but confusingly the side that looks like it should be the top is if fact the bottom. The last time I sorted the problem before tightening down the head but senility levels must be greater now and I had to take the head off and discard my best, now flattened, gasket and refit using my second best.
With a very strong sense of deja vu here I am with the new bits built into the old crankcase.
It's now installed in the car although I still have a fair amount of work to reassemble the exhaust systems, carbs, distributor, starter motor, radiator, prop shaft etc etc but hopefully will have her in good running order again very soon.
p.s. I chickened out of experimenting with the valve timing. It's not changeable without taking the engine out. _________________ http://tinyurl.com/ssjaguar
Joined: 18 Dec 2007 Posts: 2935 Location: Edinburgh
Posted: Fri Jan 30, 2009 10:50 am Post subject:
Thanks 47ers, I sincerely hope it doesn't, but this could so easily turn into yet another saga if for example my thurst washer pinning just gets swept away by the crank.
My first press on the clutch is going to be an anxious moment.
Joined: 18 Dec 2007 Posts: 2935 Location: Edinburgh
Posted: Fri Jan 30, 2009 9:21 pm Post subject:
I'm afraid the saga hasn't ended yet but maybe is a little nearer.
On the good side the engine has really good compressions and my fears for the thrust washers when I first pressed the clutch have, so far, proved unfounded.
On the bad side I discovered I had an exhaust blow at the front manifold, an oil leak from a bolt that goes through the main oil gallery and a water leak at the thermometer bulb. None of these involves much effort but I also discovered a small weep at the one rear corner of the head. This is me paying the penalty for wrecking my best gasket and having to use second best. Annoyingly I discovered I had an immaculate gasket on another shelf that I'd forgotten about.
Anyway, I took the rocker shaft off and torqued the head down again. This didn't stop the weep but it does appear to have stopped now the engine has cooled down. I'll wait to see what happens before whipping the head off again.
Joined: 23 Nov 2007 Posts: 1815 Location: Herne Bay
Posted: Fri Jan 30, 2009 11:45 pm Post subject:
Things are looking a little better this time, fingers crossed _________________ If you tie a piece of buttered toast to a cat's back, then drop it off a high building. It will hover just above the ground rotating slowly.
Joined: 18 Dec 2007 Posts: 2935 Location: Edinburgh
Posted: Sun Feb 08, 2009 2:51 pm Post subject:
Hi Rick,
I think the oil pressure is ok but I am going to strip the engine yet again.
When I drove the car with the engine with the cracked block I did notice some imbalance between 2000 and 3000 rpm but I had fitted an old flywheel that had some rust pitting on one side and I thought this was probably the cause.
When I rebuilt it in my old block I fitted the flywheel that I've been using for years. I could have checked the steel rods for static balance but I thought that as these were obviously a factory set and unmodified that I wouldn't need to check them.
Then there was the question of the crankshaft. Although I couldn't read the part number on the shaft that I fitted, it was the one that came with the rods. There was a change of crankshaft part number when the rods changed from dural to steel and it just so happens that my old engine was running with dural rods and a steel rod crank. So when I fitted the steel rods I compared the two shafts which appeared to be identical so I thought I was safe to fit the shaft that came with the steel rods.
Anyway the bottom line is that the engine still has vibration between 2000 and 3000 rpm and I suspect this is beyond my tool kit to fix so I'll make enquiries about engineering shops that can do static and dynamic balancing and find out what I need to give them. Then I'll strip the engine
and out of curiousity check the static balance of the rods but I'm fairly sure that will be ok and then I'll pass it to the experts.
Joined: 18 Dec 2007 Posts: 2935 Location: Edinburgh
Posted: Sun Apr 05, 2009 7:08 pm Post subject:
Having now returned home after 6 weeks away I visited JEM Engines, Falkirk to enquire about balancing my rough running Jag. They suggested that 99% of all balance problems are caused by rods and pistons as opposed to crankshafts. This encouraged me a little and so today I took the engine out yet again and stripped it. That said my enthusiasm turned to gloom when I found that weighing pairs of pistons and rods on the kitchen scales showed no significant imbalance. I also mounted the crankshaft with only the front and rear main fitted but I couldn't see anything bent about it. I was also able to confirm the correct 45659 part number is embossed on the crankshaft.
I've ordered up a precision scale for a more detailed look at the balances.
Joined: 18 Dec 2007 Posts: 2935 Location: Edinburgh
Posted: Thu Aug 19, 2010 10:24 pm Post subject:
When I left off this saga over a year ago I had vibration problems. The engine as rebuilt had the same block, pistons and flywheel as my original engine (which didn't have vibrations) but it now had the steel rods and crankshaft taken from my other engine. I decided to strip it once again and noticed that the crankshaft balance weights were very different in size to each other so I abandoned this shaft and was fortunate to be able to buy another one from a friend. The new shaft was from a Mark V and required a little modification and regrinding to remove pitting corrosion and to fit my bearing sizes.
The balance weights on this shaft looked nice and symetrical. I asked the machine shop who did the regrind to dynamically balance the shaft and flywheel and clutch cover.
Whilst this was happening I proceeded to grind off some of the big end bearing caps on the heavy rods so that they matched my lightest one.
The small ends also need to be balanced and after pairing up the heavy rods with light pistons, so as to minimise the material that I needed to grind off, I balanced the small ends by selecting gudgeon pins and grinding the ends where needed.
The picture shows the 0 to 1000gm postal scale that I bought supporting the big end of a rod balanced horizontally on knife edges. (The little scale has a resolution of 0.1gm.)
After fitting the new balanced crank and rods the engine was much smoother especially above 3000 rpm although I was still left with a little vibration at 1600 rpm which is apparent when rev'ing out of gear.
The strange thing about this was that I could feel it sitting in the driver's seat but not if I put my hand on the engine. I then connected up a microphone to my laptop and with the aid of a very nice little freebee spectrum analyser program I noticed that the frequency of the vibration peak didn't change when I changed the engine speed. Clearly I had a resonance at 1600 rpm. I haven't been able to track this down but earlier this week I thought I might experiment with the flywheel and clutch.
I took the gearbox out and supported the engine on a pile of bricks with a rubber engine mounting on the top.
I wondered whether the dynamic balancing had been less than perfect and that perhaps I had mounted either the flywheel and/or clutch cover with a different orientation to that used by the machine shop.
Firstly I ran the engine with the flywheel but no clutch but I couldn't really detect any vibration. Then I mounted the clutch in its two possible positions and tried to compare the vibration levels. Unfortunately I couldn't really tell the difference but opted to refit the clutch 180 degrees out from its previous configuration.
Apart from vibrations I had also not been very impressed with the hot oil pressure readings that I was getting. I believe I've now resolved this issue but I'll wait until I've completed a few more miles before reporting my findings on this. _________________ http://tinyurl.com/ssjaguar
Last edited by peter scott on Fri Aug 20, 2010 9:46 am; edited 2 times in total
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