Erik,
Norm has some good points. I'd just like to make a couple of comments from several thousand miles away and as someone who has no particular knowledge of this engine, but is well versed in fundamentals
.
(1) I looked at the video. As I understand it this motor was designed to be run hard, yet you don't advance it much beyond idle, have you actually tried it under load with throttle up? Is it possible that it always ran like this at idle?
(2) There have been various comments around timing, and I think at one stage you seemed uncertain about whether the advance lever was reversed over a standard T. It's easy to determine this - in a motor with a distributor such as yours you would ordinarily turn the distributor body in the direction of rotation to retard the ignition. Given that, it should be possible to determine if your lever is 'standard' in operation, or reversed.
(3) As you appear to have reasonable compression, and have had the head worked on (I assume it been crack/pressure tested etc), you're essentially left with timing and carburetion to determine how well it will run. While your motor is heavily modified it will still work according to the usual laws surrounding ICE operation, thus I suggest for timing you:
(a) first check/set the valve timing (which you can do when you put the cam back in - having first determined the position of the lobes etc).
(b) set the ignition timing using a degree wheel (you'll need to find TDC) such that with the lever fully retarded (normally UP) the points just open on #1 when the timing is around 15 deg ADC.
(c) consider the use of a simple dwell meter to set the points. Apart from the greater accuracy, in the absence of more sophisticated equipment this may show if you've any issues with the distributor.
(d) better still use a 'scope to look at various aspects of the timing, including the EHT output to each plug - this would show if there are any intermittent or off-time events. BTW, have you replaced your coil (it's a quick thing to do to eliminate it as an issue)?
(4) Once you've got the timing sorted from first principles it
may run a little better, and just need a little fettling from there. If however it doesn't then that leaves fuel. To some extent it's difficult to advise here, I don't want to get into stoichiometric mixture ratios etc, but maybe the simplest thing to do, if possible, would be to make an adapter plate to fit a standard carburetor. From what I see (bear in mind I've never come close to one of these in real life) it looks as if that shouldn't be too hard, and I seem to recollect from your earlier thread that you have another motor laying around? Note that I wouldn't necessarily expect it to run perfectly with a standard carb, just that may well show whether or not you have an issue with the present carburetor - and it may be easier to mess with mixture etc. I realise this appears quite a drastic measure, however it could be the quickest in the long run.
Finally, with the original intent of the vehicle in mind, and given that your mum wants to use it in shows, it could be that some 'de-tuning' is advisable (or possibly even fitting a more standard engine and keeping this one for display)? I totally get the desire to keep the history intact, and I'm mindful of how special this machine clearly is, however in terms of practicality for driving on modern roads I wonder how it would go?
In this regard there are clearly others here who will have real experience of motors equipped such as yours, and may be able to advise whether I'm talking rubbish and it should be as docile as needed from day one, or if it may need a little work to claw it back from a 97mph beast to something that will putter along neatly at a parade...
Luke.
