speedwell_alloy

Speedwell Alloy Heads

First, lets kill a few myths off!

These alloy heads are not the "bees knees" One in good condition is usable, it is certainly an improvement over an 850 or 998cc A series head, but compared to even an bog standard 12G 295 998 Cooper head it is rubbish! Remember things have moved on in 40 years. If you are determined to use one of these heads, there are a few things worth bearing in mind.

First, if you are lucky enough to find one at all, it is probably well used and a bit tatty looking, if it looks mint BEWARE! it is probably porous and has been from new, a lot of these heads suffered from casting porosity thanks to the Italian company that originally cast them. Oil and burns are a good sign, it ran once therefore it might run again.

The most common area of damage on any Speedwell head is the tapped holes. These will invariably have been fixed with helicoils in the past, in most areas this is not a problem. On the rocker post mounting it can be.

The picture at the top shows the typical damage done by over tightening the nut that connects with this hole. As you can see the casting has broken and the helicoil has begin to pull out., this example is (just about) livable with. If it is any worse than this a repair will have to be made, entire area is ground out, new alloy is welded into place and the head is then remachined, this can get expensive if more than one need doing!

Speedwell valve guides were of a particularly shocking design, they were prevented from moving by circlips, the groove for this clip was of a square profile creating a beautiful stress point for guide breakage. About 80% of the heads I have seen have one or more broken guide! To cure this the valve guide holes need reaming out and oversize valve guides must be made to fit the bigger holes, at the same time round section grooves are machined in them for round wire circlips.

The final thing you need to worry about is the Compression ratio that you could end up running, these heads are notorious for being skimmed to within an inch of their lives. if the chambers are very small it is easier to machine a chunk of your pistons than it is to increase the combustion chamber size.

If you have a very good condition head or have carried out the above procedures and a few more probably, you are ready to get the head modified! I would recommend passing this work on to a competent head tuner who will be able to turn your Speedwell head into a relatively good performance item. If you are thinking about resurrecting a Speedwell head I am happy to advise on the practicalities of this and can undertake the work if necessary.

To see a completed restoration click on the links below.

CLUBMAN1, CLUBMAN 2, CLUBMAN 3.

	First, lets kill a few myths off! These alloy heads are not the "bees knees" One in good condition is usable, it is certainly an improvement over an 850 or 998cc A series head, but compared to even an bog standard 12G 295 998 Cooper head it is rubbish! Remember things have moved on in 40 years. If you are determined to use one of these heads, there are a few things worth bearing in mind.
First, if you are lucky enough to find one at all, it is probably well used and a bit tatty looking, if it looks mint BEWARE! it is probably porous and has been from new, a lot of these heads suffered from casting porosity thanks to the Italian company that originally cast them. Oil and burns are a good sign, it ran once therefore it might run again.
	The most common area of damage on any Speedwell head is the tapped holes. These will invariably have been fixed with helicoils in the past, in most areas this is not a problem. On the rocker post mounting it can be. The picture at the top shows the typical damage done by over tightening the nut that connects with this hole. As you can see the casting has broken and the helicoil has begin to pull out., this example is (just about) livable with. If it is any worse than this a repair will have to be made, entire area is ground out, new alloy is welded into place and the head is then remachined, this can get expensive if more than one need doing!
Speedwell valve guides were of a particularly shocking design, they were prevented from moving by circlips, the groove for this clip was of a square profile creating a beautiful stress point for guide breakage. About 80% of the heads I have seen have one or more broken guide! To cure this the valve guide holes need reaming out and oversize valve guides must be made to fit the bigger holes, at the same time round section grooves are machined in them for round wire circlips.