Query about gearing...

[Duncan Grimmond]

As promised. the Yorkshire Spannermen arrived yesterday, fully armed with parts and weaponry. A test-drive  drew the conclusion that there might be something we could do....
After testing ignition(fine) compression(fine)  the manifold c/w Solex carb was removed and preparations to fit a side-draught Zenith began. Of course it's never as simple as that.... the downdraught manifold had a vacuum fitting which, naturally, was oversize and completely stymied any attempt to remove the central nut. Much cursing and general  fannying about then showed the manifold studs were 5/16" rather than 1/4" and  the replacement manifold needed drilling to suit. You can guess the rest and then I had to rush off to an appointment with a hypodermic and 'flu shot.
 On my return the throttle linkage was now misaligned, bending it actually broke it, repair required, swear, swear, where are the right Allen keys, more swear, eventually it's all fitted, lined up and running. So, off for a second test drive and with much attempted buckling of the floor below the gas pedal the magnificent 51mph was achieved!
We all agreed that the only conclusion we could make was that  he Solex ran rich, the Zenith gave a squirt more and the Cherry bomb exhaust needs a longer tail pipe with some restriction to give a bit of back-pressure to help the engine breathe correctly....

I'll be down to the local garage later to look through their skip for suitable test lengths of pipe! Watch this space (or not as the fancy takes you!)

Many thanks to Malcolm and Steve who gave up the best part of a day to help get to the bottom of the problem.

[Malcolm Parker]

Both Steve and myself passengered as Duncan did his stuff on the long straight roads alongside the A1.  We both think that the car goes pretty well given that the engine appears to be bog standard apart from (ostensibly) a Phoenix crank.  With around 17bhp and a full windscreen a true 51mph is probably about right.  With minor tuning the output could be increased to around 25bhp and it might nudge 60mph.   
The engine was happier on the Zenith 26VA.  It started immediately and idled nicely.
The important thing at this stage is that the engine does not need to be taken out and stripped for further investigation. 
It will be interesting to see if a longer exhaust  makes a difference.

[Renaud]

This is all very interesting of course. Thanks for sharing.

[JonE]

All sounds good. Did you ever work out what the Solex choke was?
You keep mentioning the putative Phoenix. I removed the screw oil filler and got a cameraphone up close to the hole to get some pictures of the crank turning to likely confirm identification.

[andrew34ruby]

All to do with breathing then. and yes, a longer exhaust will be interesting.

[Steve Jones]

Yes, we agreed that there doesn't appear to be anything fundamentally wrong with the engine. As Malc says, given it's bog standard then the sort of performance it gives, two up with a full screen doesn't seem far off. That it's nearly as fast in third as it is in top isn't that unusual and it certainly accelerates up through the gears well. As we've all said so many times, the factor holding back standard spec A7 engines tends to be breathing and, to a degree, the change to a S/D 26VA has improved that a little from the Solex that was fitted. The planned revisions to the exhaust should help but after that, it'll be manifolding and further carburation changes that'll make a difference but I know Duncan doesn't want to go that far.

It is a very pretty car though with those little tweeks to the style and fittings that Duncan with his excellent eye specialises in. He really is a very skilful chap when it comes to body and sheet metal work.

Steve

[Nick Turley]

Well done chaps