Ok, now I’ve got your attention I suppose you’re wondering why on earth changing camshafts on a Twin Cam engine would need a sump gasket ? It's a sorry tale so read on my friends…..
This all started when I decided a couple of years ago that I would like to have a touch more power in the car. Nothing dramatic, something like Lotus sprint cams with an improved exhaust system and matching carburettor settings would do fine. So with that plan in mind I did the easy job and made up a matched 4-2-1 header system in anticipation.
Then there was a relapse into apathy followed eventually with a book to learn a bit about cams and how they worked. Even after reading it twice I’m still no brighter, so when some Vegantune cams came up on Ebay I decided to follow someone else’s path and bought them.
As an aside the seller, another Europa owner, was very helpful and passed on quite a lot of useful background info which made the transition that much easier. Sometimes Ebay really does work well when you deal with good people !
For reference, the cams are reground to a Vegantune VJ5 profile which seems to be a slight improvement on the Lotus sprint profile. It’s purely my supposition but from what I can read I wouldn’t be surprised if this is a “standard” profile offered by many tuners as a modest boost for TC BV/Sprint owners. These particular regrinds were done some time ago by Twincam Techniques and stamped "TT36" but when you think about it anyone with a machine shop can re-create a known profile.
As you can see from the first image, the VJ5 profile has a faster opening/closing ramp with longer time at full lift. I think (note “think) it’s fractionally higher but the main benefit I can see comes from the open/close ramps and fully open period. It reminds me very much of the sprint cams I have in the Elan and I’m hoping for similar performance.
So let’s get started. It’s only a few nuts and bolts, we’ll have this lot sorted, back and running before lunchtime.
Set engine to TDC, remove old cams & replace with new ones. This is made even easier because the previous owner had used an offset dowel which, for the first time in over 40yrs of Lotus ownership, has given me timing sprockets which line up exactly as they look in the manual. Yep, not a millimetre out of place, it’s clearly magic !
The next step is slightly more tricky, what carb settings should I use ? It will start and run on the OEM 30mm chokes/jets of the standard TC but surely there’s more to be had ? From info passed on by the seller there were comments from Ed Winter that VJ5 profiles work well with OEM B/V Sprint settings and from research the QED360 cam profile uses only a slight variation from the same settings.
This journey isn’t yet complete because I’ve only messed around with it but the starting point has been the 33mm chokes of the TCS B/V Europa and fractionally richer main jets; it may (probably will) change when I get the AFR meter rigged up properly.
And here is where it all falls apart…….
I pay more attention to the valve clearances and decide to get them “spot on”. Much tinkering goes on, several goes until I finally shuffle my collection of shim stock around, buy a few new shims and end up with everything looking good. I replace the cam cover without sealant in case it needs to come off again and fire up the engine expecting for a powerful roar….
Well, it did fire up and run, but then it stopped. No warning, spluttering or coughing, just “nope, not going”. I try the starter again and it just clunks. Ah well, it has been standing around a while, the battery must need charging. Shove it on charge and… er…. it’s pretty much fully charged
Check earths and other connections – all good. Try it again and...
“clunk, clunk – I’ve told you before, I’m not starting”.
Remove cam cover and…..hey, that chain looks tight, so much so it’s obviously wrong - surely I didn’t adjust it that tightly ?
Slacken the adjustment screw, (which takes far too much effort to move) but the chain is still rock solid and more like a steel bar than a chain. Oh dear….. this looks like bad news.
USB borescope out, poke it around and it’s either my eyes or that chain tensioner looks bent. Remove cam sprockets to get rid of that chain tension and yep, it’s bent. Fortunately I had a spare in the box so I had something to work with and managed to remove & straighten the brass arm.
But why ? And more importantly, how ?
The answer is in the second image, the humble half moon plugs used in the front cover and rear of the head. At that point I realised one was missing, there's no sign of the AWOL plug in the front cover or on the floor under the engine so it must be in the sump, and this is where the sump gasket comes in !
As you can see from the second image, I have gone in for some customisation and decoration of my own with some nifty patterns on the plug.
What seems to have happened is that when I replaced the cam cover for the last time I must have dislodged one of the plugs and with double bad luck not only did it fall inside but also on the tensioner side. For those familiar with the TC engine that’s some achievement because there’s very little clearance between the bolt holding the cam sprocket in place and that front half moon plug. In fact I’d guess it’s not much more than the width of the plug.
Running the engine moved it until it managed to get itself trapped between the either the jackshaft or tensioner sprockets and because I tend to run the chain tight anyway, there simply wasn’t enough space for it to fit.
So the little rubber plug got peevish and bent the tensioner arm, locking the engine at the same time.
Crazy though it sounds I was actually relieved when I found it because at least I had an answer as to why the engine locked up. And more importantly the only cost was a £2 plug and not something like a broken camshaft. So all ended happily ever after…..
except it didn’t.
Replacing the sump was easy enough and looking up at the water pump belt I thought “heck, I might as well replace that while I’m down here.”
And that was when I realised there’s a touch of play in the water pump bearings. Not enough to leak, but enough to feel when rotating the pump. Because by then it was all back together I thought I’d run the engine for a while but heck, now I can hear it grumbling...… grrrrr……
to be continued……..
