Cams

[nickspeed]

The cork gasket in the attached pic is leaking, so the head needs to come off. Will take the opportunity to think about cams and ignition. The car is a 1969 S4 SE on Strombergs. Assuming - may not be the case - that the cams are SE, is it worth upgrading to Sprint, or QED Q360 or Q420? Do the 360 or 420 require head work, or are they straight replacements? Ignition - am thinking of https://www.heritagepartscentre.com/uk/ ... -volt.html providing they do one compatible with the twin cam. Any other jobs worth doing while the head is off? All thoughts appreciated. Many thanks, Nick

[JonB]

To identify your cams, count the grooves on the sprocket end of one of them. You have to remove the sprocket to do this. So called “Sprint cams” are more formally known as “D type cams” and have two grooves. 1 groove and it’s C type, no grooves indicates B type.

My 1970 S4 S/E has D cams, and AFAIK is untouched since leaving the factory. So there’s a chance you already have them. The other thing to look at is the ID stamp on the head, by No.1 spark plug on a raised boss: H = high compression head, N = Big Valve / high compression head, S = standard compression. Given you have Strombergs and it’s a SE, you ought to have high compression. This, along with D cams, would mean your car is very close to a Sprint in power output (those “big valves” are only ~1mm more in diameter than standard, so add only marginally to the power. An excellent marketing gimmick that still works today.). You get a bit more power for having Webbers or Dellortos but disproportionately higher fuel consumption, and I believe the torque curve is less advantageous, but I’m sure an expert will be along in due course to disagree with me!

Get a copy of Miles Wilkins’ book on the Twin Cam. It’s all in there. He differentiates between SE and “Super SE” spec. SE=C type cam, Super SE (and Sprint)=D type cam.

Other jobs? Check the valves for lateral play, you may need new guides. Check cam follower clearance on reassembly. Clean & decoke. Lap in the valves. Check condition of cam bearing shims, sprockets. Check condition of cam chain, can tensioner sprocket and friction pad. Check piston - block clearance. Check bore diameter and ovality. Don’t think you can do much more without pulling the block (to check condition of the rings, pistons, big and little end bearings).

Like I said, buy the book, it’s not expensive and covers all of this and much more.

If you choose electronic ignition, carry a set of points and condenser in the glovebox, just in case. The Hall effect types are known to fail due to the extreme conditions inside the distributor. My car has a Lumenition Optronic ignition (so uses an optical sensor and a chopper rather than a magnet and Hall effect switch) which is at least 35 years old and still working.

Cheers
JonB

[vstibbard]

+1 Jon my first Elan was same as yours H stamped head D type cams, when I rebuilt it we added big valves and 10.3 compression and porting done by Ed Winter back in 80’s. Ken at QED dyno’d the engine and key change was needles. It produced sprint like power and torque with 40mpg at motorway speed, only down side was lack of intake roar!!

[nickspeed]

Thank you very much for the info and advice. Really helpful. Await with interest what is revealed when the cam cover comes off! Will get the Miles Wilkins book too. With thanks again, Nick

[alan.barker]

Hi Nick,
the first thing how many miles has the Engine done and has it been rebored in the past.
If original bores and no ridges you can deglaze and buy a set of original Pistons.
It's no good improving the Head if it has a lot of miles you will just kill off the Engine.
In the past SJS have sold original bore Pistons for a good price.
If you do this it will mean new set of Vandervell Bearings + new Oil Pump.
If it's done about 70,000 or 80,000 miles it's a good time for a refresh.
cheers
Alan

[JonB]

Alan makes a good point.

You can see if the engine is rebored by looking at the tops of the pistons. They are normally marked in some way to identify what they are. For example, "+20" would indicate a 20 thou overbore. My car has 65 thousand miles and there were slight ridges at the bottom of the bores, almost imperceptible at the top. I thought this meant I might get away with a hone and new rings, but wiser minds prevailed (thanks to 512BB) and the block is in for a rebore. It had standard pistons, most likely they were factory fitted.

You'd really need to pull the pistons out to determine bore wear reliably, and to check them and the bearings for wear. Again, on my engine the big end and main bearings were worn through to the copper (that is, shot). Although Leslie (BB512) thought it hadn't had regular enough oil changes which has contributed greatly to the wear.

I'm sure you can see where this is going. Down a rabbit hole! Once you get Miles's book you will get a good idea how deep it is.

[alan.barker]

+1 JonB,
Sounds like a bit of spending but will be cheaper in the long run and no heart aches.
If the Cams are Sprint in good condition keep them spot on for road driving, soo sweet. The music of a Twink "on song", who needs a Radio.
Alan