Lotus Elan and Lotus Elan Plus 2 Forums

Colsibro Guides for the Cosworth Head arrived today.

Initial set up

Plasticene check with all the pistons in equals a clash on #3 Inlet - drat!!!

Hopefully I'll go better doing it the ISKENDARIAN WAY!

"Many years ago a standard height was sought after by ISKENDERIAN engineers where all racing camshafts could be timed to give accurate results and in 1958 it was decided and later published in our top tuner's manual, "Valve Timing for Maximum Output" that .050" lifter rise off the base circle would be the accepted standard for our camshafts. This figure was ideal because it was not far enough off the base circle to confuse the engine builder when timing the camshaft, and it was high enough to show effective valve timing (a point where the valve is far enough open to pass an effective air flow). Also, the velocity (rate of cam lift) of most camshafts is approximately .004" per cam degree at .050' lifter rise. Therefore, a .002" error in checking height would only affect the degree wheel reading about 1 crank degree. The ISKENDERIAN .050" lifter rise check has now become a standard in the racing cam industry. "

I shall have to give myself a good lashing!

rgh0 wrote:QED, Burtons or Dave Bean plus the other usual suppliers should ll be able to supply all the sprockets and offset dowels. I recently got a vernier sprocket set from Burtons just to try it verus offset dowels that I have always used.

The standard sprockets work fine at 8500 rpm

cheers
Rohan

John McCoy recommends the QED vernier sprockets at the moment. (Hopefully a pair will be winging their way to Oz from Quorn later on tonight!!)

Got 'em on the money at 50 thou "opening" figures.

Next stop, clearance check.

Having a quick lunch break. Plasticene is in and looks like it will measure up OK, Am tempted to put it together without lowering the compression ratio (It's at 12.7) or coating the pistons as am running out of time to get it in the car!

12.7 should be fine with the cams your using

cheers
Rohan

I've got plenty of engagement on the shaft with the pump pulley - but it's still 5mm proud of being flush with the end of the shaft, so I may shorten the crank pulley so I can get the whole lot a bit closer to the front cover (even if the pump pulley were flush with the end of the shaft it would still be 2 mm away from butting into the snout of the cover).

Pistons are back after spending a week in an overnight bag!

Keeping dry sump pan happy by shortening the studs to be no longer than they need to be to hold the nuts.

CBUEB1771 wrote:

SJ Lambert wrote:Steel or standard for "1/2 length" jack shaft?

Have you compared the thickness of the two thrust plates? I thought Cosworth made a steel version slightly thicker than the standard Ford item. The intent was to reduce axial motion of the jackshaft and thereby reduce scatter in spark timing.

The steel one is three quarters of a thou thicker than the Ford one!