Modifying a sidevalve engine

[ian judd]

Has anyone any experience of a tuned/ modified sidevalve engine. I'm thinking of the kinds of things done to Austin 7 engines - larger valves, higher compression, hot camshaft, twin carbs, etc. Do the crankshafts in the sidevalve have the same reputation for cracking as the one in the OHC engine?

Ian

[Ian Grace]

Hi Ian,

Well, my McEvoy 70 has a mildly tuned engine - downdraught car - 1 1/4", polished/skimmed head, finned manifold. There was some talk here a while ago about having some better cams made, which should do some good. The cranks are basically the same as the OHC cranks, except the bearings are back to front. of course.

I agree that we should be able to learn lot about what works and what doesn't from the Sevenists. At least our crank is more solid than theirs!

[ian judd]

Thanks Ian,

Was McEvoy the only company that tuned sv engines? Has anyone ever come across any special parts, ie. alloy heads, fancy manifolds, etc.?
I suppose a normal sv car is flat out at 50?

Ian

[ashford]

I have seen Morris 8 'Alta' heads but Im not sure if they did one for the minor. However, there were many special heads for austin sevens yet many still believe that the standard Ruby is the best. Somewhere I have read (I think in an autocar article about a pre-war trials minor) that the late s.v. head is much better than the early one for performance. The same article talks about plating the head with bronze. I don't know the reason for this but it is intresting that so many prewar competition engines used cast bronze heads. Does any one know what the reasoning for this was?

[Ian Grace]

David Brown once told me that he had an ali head for a Minor, but I never actually saw it ...

I think that maybe other special builders did some mild tuning - maybe King Brothers? I'd have to check.

If top speed is the requirement, then I guess I'd put in a 9/44 OHC diff. for starters, and a 4-speed crash box would be a good idea too. Otherwise, its all down to the horses up front. I'd be interested to know of any practical valve mods.

[Toby]

Whaddayamean, 50 flat out! I have sent Ian an advert for the £100 minor with a quote from a satisfied customer claiming he motored along at 65. Mind you that could be a bit scary! Trevor Wilkinson is your racing mods man, his 34 minor zips along and I think Gren once quoted 55 as a cruising speed, both cars would have had a 34 head, maybe these are somehow better than the 33?

[Highlander]

My 1932 two seater sv goes like the wind but I am sure it does not go over 50mph. I have new valves, pistons and rings and run a bit rich but anything over 50mph is scarey. I still belong to the Humber Register and in todays Mag there is an article on making 1930s cars go faster - all the usual stuff but mention is made of:' What pprice a 'specially tuned; side valve Morris Minor, with polished head and 'spreamlined; exhaust maniforld , which ensembled was pleased to style itself @Le Mans?' Has anyone heard of a Le Mans Morris Minor? By the way the article was reproduced from Motor Sport April, 1954. Keep tuning, Highlander.

[Ian Grace]

My experience of SV Minors is also that they can go very well - particulary in that wonderful phase of their life where everything is nice and loose and frictionless - i.e. a few hundred miles before they run a bid end!

[ian judd]

How much space is there between the valve heads on a sv ? I'm wondering if larger inlet valves could be fitted, shortened MG J type perhaps. The cams could be backed off to increase valve lift, and I expect the compression could be raised to around 6:1 without disaster to the crankshaft.
There is lots of scope for lightening the flywheel which would improve acceleration.

The manifold looks as though it could be improved, and it would be simple enough to fit a larger carb. or twins.

It seems to me that it would all be fairly easy and relatively inexpensive. 99.9% of sv engines are apparently just as they left the factory - all made to run on 70 octane fuel and with an enormous flywheel for people who hated changing gear.

Ian

[Highlander]

Ian, Looking at an old Automobile Mag, August 2005, there is an article on Copper Heads and mention is made of an advertisment in 1936 fromm V>W> Derrington. I quote ' Copperised Cylinder Heads - Existing cast iron heads can be copperised, giving truly remarkable results. Max speeds have been increased by 12.5% hill climbing by 30% and acceleration by 30% All for 25 shillings per head. The copper plating is a decided inprovement not only for smoothness and accelaration but also in petrol consumption. end of quote. Go for it Ian but this is not my scene - why buy a morris minor sv if you want speed? Why not buy something that was made to go faster in the first place? Tune on, Highlander.

[Toby]

What about the block, is there scope for any vague gasflow improvements in this and the manifold. Personally, with the 3 speed crash box, the flywheel weight saves on over revving and gearchanges, although the 4 speed has no extra gearing it would make a lighter engine more useful.